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Machinist Abbreviations You Need to Know
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From http://www.tec-ease.com/what-is-gdt.php
What Is GD&T?
View attachment 259596
GD&T stands for Geometric Dimensioning and Tolerancing. It is a system of symbols, rules and definitions used to define the geometry of mechanical parts.
GD&T is one of the most powerful tools available that can improve quality, reduce cost and shorten delivery time. All of this is possible when the concurrent engineering team is involved with the creation of the drawing. The drawing is a common thread that ties these groups together. They all are involved with the engineering drawing. GD&T on the drawing must first and foremost capture design intent. However, the best design in the world is worthless if it cannot be produced. That is why it is necessary for production/vendors and quality to be involved with the requirements that are placed on the drawing. When they are not involved, the drawings often have overly tight tolerances and result in non-producible parts. At least not producible at the quality level, cost and timeliness expected by industry.
Nearly every company in the United States and many companies around the world use the ASME Y14.5 standard on GD&T. There is an ISO standard but it is in a state of flux. Because of this the Y14.5 standard is recognized and used around the world.
In short, GD&T is:
View attachment 259594
GD&T Glossary and Resource Symbols and Terms
Use this quick reference to find definitions of common GD&T symbols and terms. Our full color Pocket Guide is a great resources for your desk, workbench or pocket. Be sure to check out our GD&T Tips!
View attachment 259597All Around Symbol - indicating that a tolerance applies to surfaces all around the part.
View attachment 259598All Over Specification [Y14.8 - 2009 R2014 (sections 3.14.1 & 3.14.2)] - In addition to a general profile of a surface tolerance there is the option of specifying that the tolerance applies all over on the field of the drawing. It is important to realize that this specification, whether in a general note or on the field of the drawing, applies UNLESS OTHERWISE SPECIFIED.
View attachment 259599All Around This Side of Parting Line [Y14.8 - 2009 R2014 (sections 3.14.1 & 3.14.2)] - To apply a requirement to all features all around one side of a parting line, the graphical symbol for all around this side of parting line is indicated on the leader line.
View attachment 259600All Over This Side of Parting Line [ ASME Y14.8-2009 Section 3.14.2] - To apply a requirement to all features all over one side of a parting line, the graphical symbol for all over this side of parting line is indicated on the leader line.
View attachment 259601Angularity - is the condition of a surface, axis, or centerplane, which is at a specified angle from a datum plane or axis.
View attachment 259602Arc Length - indicating that a dimension is an arc length measured on a curved outline. The symbol is placed above the dimension.
View attachment 259603Basic Dimension - used to describe the exact size, profile, orientation or location of a feature. A basic dimension is always associated with a feature control frame or datum target. (Theoretically exact dimension in ISO)
View attachment 259604Between - to indicate that a profile tolerance applies to several contiguous features, letters may designate where the profile tolerance begins and ends. These letters are referenced using the between symbol (since 1994) or the word between on drawings made to earlier versions of the Standard.
View attachment 259605Concentricity - describes a condition in which two or more features , in any combination, have a common axis.
View attachment 259606Conical Taper - is used to indicate taper for conical tapers. This symbol is always shown with the vertical leg to the left.
View attachment 259607Continuous Feature [ASME Y14.5-2009 Section 2.7.5] - The note CONTINUOUS FEATURE or the continuous feature symbol is used to identify a group of two or more features of size where there is a requirement that they be treated geometrically as a single feature of size. Although the definition only mentions features of size, there is an example of CF being applied to a pair of planar features.
View attachment 259608Controlled Radius - creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. Where a controlled radius is specified, the part contour within the crescent-shaped tolerance zone must be a fair curve without flats or reversals. Additionally, radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit.
View attachment 259609Counterbore/Spotface - is used to indicate a counterbore or a spotface. The symbol precedes the dimension of the counterbore or spotface, with no space.
View attachment 259610Countersink - is used to indicate a countersink. The symbol precedes the dimensions of the countersink with no space.
View attachment 259611Cylindricity - describes a condition of a surface of revolution in which all points of a surface are equidistant from a common axis.
View attachment 259612Datum Feature - is the actual component feature used to establish a datum.
View attachment 259613
Datum Target - is a specified point, line, or area on a part that is used to establish the Datum Reference Plane for manufacturing and inspection operations.
View attachment 259614Depth/Deep - is used to indicate that a dimension applies to the depth of a feature. This symbol precedes the depth value with no space in between.
View attachment 259615Diameter - indicates a circular feature when used on the field of a drawing or indicates that the tolerance is diametrical when used in a feature control frame.
View attachment 259616Dimension Origin - Signifies that the dimension originates from the plane established by the shorter surface and dimensional limits apply to the other surface.
View attachment 259617
Feature Control Frame - is a rectangular box containing the geometric characteristics symbol, and the form, runout or location tolerance. If necessary, datum references and modifiers applicable to the feature or the datums are also contained in the box.
View attachment 259618Flatness - is the condition of a surface having all elements in one plane.
View attachment 259619Free State Variations - is a term used to describe distortion of a part after removal of forces applied during manufacture.
View attachment 259620Least Material Condition (LMC) - implies that condition of a part feature of size wherein it contains the least (minimum) amount of material, examples, largest hole size and smallest shaft size. It is opposite to maximum material condition.
View attachment 259621Independency Symbol [ASME Y14.5-2009 Section 2.7.3] - The Independency symbol is applied to the size dimension in order to invoke the principle of independency to regular features of size and override Rule #1.
View attachment 259622Maximum Material Condition (MMC)- is that condition of a part feature wherein it contains the maximum amount of material within the stated limits of size. That is: minimum hole size and maximum shaft size.
View attachment 259623Movable Datum Targets [ASME Y14.5-2009 Section 4.24.6] - The movable datum target symbol may be used to indicate movement of the datum target datum feature simulator.
View attachment 259624Number of Places - the X is used along with a value to indicate the number of times a dimension or feature is repeated on the drawing.
View attachment 259625Parallelism - is the condition of a surface, line, or axis, which is equidistant at all points from a datum plane or axis.
View attachment 259626Parting Lines [ASME Y14.8-2009 Section 3.14] - are depicted on casting/forging/molded part drawings as a phantom line extending beyond the part in applicable views, with the parting line symbol added.
View attachment 259627Perpendicularity - is the condition of a surface, axis, or line, which is 90 deg. From a datum plane or a datum axis.
View attachment 259628Position Tolerance - defines a zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position.
View attachment 259629Profile of a Line - is the condition permitting a uniform amount of profile variation, ether unilaterally or bilaterally, along a line element of a feature.
View attachment 259630Profile of a Surface - is the condition permitting a uniform amount of profile variation, ether unilaterally or bilaterally, on a surface.
View attachment 259631Projected Tolerance Zone - applies to a hole in which a pin, stud, screw, etc., is to be inserted. It controls the perpendicularity of the hole to the extent of the projection from the hole and as it relates to the mating part clearance. The projected tolerance zone extends above the surface of the part to the functional length of the pin, stud, and screw relative to its assembly with the mating part.
View attachment 259632Radius - creates a zone defined by two arcs (the minimum and maximum radii). The part surface must lie within this zone.
View attachment 259633Reference Dimension - a dimension usually without tolerance, used for information purposes only. It does not govern production or inspection operations. (Auxiliary dimension in ISO)
Regardless Of Feature Size (RFS) - the condition where the tolerance of form, runout or location must be met irrespective of where the feature lies within its size tolerance.
View attachment 259634Roundness - describes the condition on a surface of revolution (cylinder, cone, sphere) where all points of the surface intersected by any plane.
View attachment 259635Runout - is the composite deviation from the desired form of a part surface of revolution through on full rotation (360 deg) of the part on a datum axis.
View attachment 259636Slope - is used to indicate slope for flat tapers. This symbol is always shown with the vertical leg to the left.
View attachment 259637Spherical Diameter - shall precede the tolerance value where the specified tolerance value represents spherical zone. Also, a positional tolerance may be used to control the location of a spherical feature relative to other features of a part. The symbol for spherical diameter precedes the size dimension of the feature and the positional tolerance value, to indicate a spherical tolerance zone.
View attachment 259638Spherical Radius - precedes the value of a dimension or tolerance.
View attachment 259639Spotface [ASME Y14.5-2009 Section 1.8.14] - Counterbore and spotface previously used the same symbol. A spotface now looks like the counterbore symbol with the addition of the letters SF.
View attachment 259640Square - is used to indicate that a single dimension applies to a square shape. The symbol precedes the dimension with no space between.
View attachment 259641Statistical Tolerance - is the assigning of tolerances to related components of an assembly on the basis of sound statistics (such as the assembly tolerance is equal to the square root of the sum of the squares of the individual tolerances). By applying statistical tolerancing, tolerances of individual components may be increased or clearances between mating parts may be reduced. The increased tolerance or improved fit may reduce manufacturing cost or improve the product's performance, but shall only be employed where the appropriate statistical process control will be used. Therefore, consideration should be given to specifying the required Cp and /or Cpk or other process performance indices.
View attachment 259642Straightness - a condition where an element of a surface or an axis is a straight line.
View attachment 259643Symmetry - is a condition in which a feature (or features) is symmetrically disposed about the center plane of a datum feature.
View attachment 259644Tangent Plane - indicating a tangent plane is shown. The symbol is placed in the feature control frame following the stated tolerance.
View attachment 259645Target Point - indicates where the datum target point is dimensionally located on the direct view of the surface.
View attachment 259646Total Runout - s the simultaneous composite control of all elements of a surface at all circular and profile measuring positions as the part is rotated through 360.
View attachment 259647Datum Translation Symbol [ASME Y14.5-2009 Section 3.3.26 ] - This symbol indicates that a datum feature simulator is not fixed at its basic location and shall be free to translate.
View attachment 259648Unilateral and Unequally Disposed Profile Tolerance [ASME Y14.5-2009 Section 8.3.1.2] - To indicate that a profile of a surface tolerance is not symmetrical about the true profile, this symbol is used. The first value in the feature control frame is the total width of the profile tolerance. The value following the symbol is the amount of the tolerance that is in the direction that would allow additional material to be added to the true profile.
Why Do I Need GD&T?
The craftsmen of old could fashion parts in a way that would allow them to slide together and give the impression that the parts fit "perfectly." Today, with the concept of interchangeable parts, credited to Eli Whitney, it is expected that parts will assemble the first time and perform their intended function. Interchangeability does not apply only to mass produced parts. Whenever two parts are expected to fit together and function without rework or adjustment, the parts must be clearly defined. Parts that have been made in other departments, plants, cities or even countries must consistently fit and function even though slight variation from the intended shape and size will exist in every part.
All parts go through a manufacturing process. There is variation in all manufacturing processes. These variations are reflected in the parts. In addition, there must be a way to inspect a part to assure that it was made to the required specifications. As Bob Traver says:
"You can't make what you can't measure because you don't know when you've got it made!"
Most importantly, the part must perform its intended task or function. To accomplish all of this, the part must be clearly and totally defined. In most cases, this definition is accomplished on a detail drawing or within a CAD file.
When used properly, GD&T will get the right questions asked early in the program, simplify the engineering drawing, and directly relate customer requirements to product specifications and process control.
Geometric dimensioning and tolerancing has been evolving for decades, and is now a crucial practice for manufacturers hoping to compete globally.
What geometric dimensioning and tolerancing (GD&T) is depends on one's discipline. To the designer it is a way to describe the design intent of individual parts. To someone in production it is the language of modern print reading. To someone working in metrology it is a guide to the inspection of parts. To management it is a concurrent engineering tool that provides clear communication across the enterprise.
View attachment 259649
GD&T has been developing during the past 80 to 100 years. It really started to be applied during World War II when the military realized the importance of defining parts with a document that had only one meaning to ensure interchangeability and part functionality. For many years companies, countries and the military published their own version of GD&T. This caused much confusion for suppliers trying to produce parts for multiple customers.
Tolerances on component and assembly dimensions are crucial to the success of a medical device.
Today most companies, from those that produce aircraft carriers to those that produce cell phones, satellites or sump pumps, have committed to following either the ASME Y14.5M-1994 standard or the collection of ISO standards on GD&T. The ASME Y14.5 standard has emerged as the preferred standard in the United States and several foreign countries, mainly because of its stability, emphasis on design intent, mathematical definition and translation to several languages.
In addition, there is now the ASME Y14.41-2003 standard, which sets forth the rules to applying the Y14.5 dimensioning and tolerancing concepts to digital data such as solid models. Dimensions and tolerances can now be embedded in the CAD model. Embedding tolerances in the solid (digital) model opens the door to reduced dimension drawings and automated analysis, which can include the expected variation which is bound to occur in production. GD&T enables this change in technology. According to ASME Y14.100 the word drawing now refers to the paper document or digital data.
View attachment 259650Directly Toleranced Dimensions
Dimensions may be directly or indirectly toleranced. Directly toleranced dimensions are those that are not basic. Directly toleranced dimensions may have a tolerance written next to the dimension, be limit dimensions or make use of a general title block tolerance. The drawing in Figure 1 illustrates common tolerancing methods. In addition to the tolerancing shown, tolerances may be unequal bilateral, or applied by using limits and fits tolerance symbols, or by referencing implied tolerances found in standards such as ISO 2768.
Basic Dimensions
Basic dimensions do not have a direct tolerance. The basic dimensions in Figure 1 are 076 and 40. By making these dimensions basic, the general tolerances no longer apply. Their tolerance is indirect. The tolerance is applied to the features on the part, not the dimensions. The basic dimension may be thought of as the goal and the geometric tolerance is the amount the feature may deviate from the goal.
Geometric Tolerances
Where geometric tolerances are used, they are applied to the feature rather than the dimension. The geometric tolerances are found in the feature control frames. In Figure 1 they are 00, 0, 0.1, 0.2 and three 00.3.
Even though there are 0s in some of the feature control frames, it does not mean that production must make perfect parts. The 0 tolerance applies only at one limit of size known as the maximum material condition (MMC) or the least material condition (LMC). Using 0 tolerancing actually provides production with more tolerance because it allows the acceptance of the best parts. This was not possible without GD&T.
Size Dimensions
The size dimensions in Figure 1 are 030, 0100, 050, 012 and 14.1/14.0. The 10 and 30 dimensions use the dimension origin symbol in place of an arrowhead to indicate which surface functions as a "local datum feature" for inspection.
View attachment 259651
Originally only direct tolerancing was used on drawings even though there never was a standard that could provide one clear meaning. Some of the problems with direct tolerancing include:
There are four categories of geometric tolerance characteristics: location, orientation, size (handled with direct tolerancing not shown in chart) and form. There is a hierarchy to these geometric characteristics. Location tolerances also control the orientation of features. Size also controls form.
View attachment 259652
Datum features are labeled using a letter in a box at one end of a line and a triangle at the other. The triangle is associated with the feature that will serve as a datum feature to establish origins of measurement. Figure 2 illustrates a drawing where this approach has been applied. The old general titleblock tolerance has been replaced by a note making the dimensions that do not have a tolerance specified basic and a general profile of a surface tolerance that applies to the entire part unless it is overridden by a tolerance that appears on the field of the drawing. All measurements should be made from the datum reference frame established by datum features A, B and C.
View attachment 259653
GD&T has been evolving for decades and an understanding of it is essential for anyone who reads today's drawings. There is no other standard for defining parts. GD&T is enabling the new technology in CAD, CNC software and automated inspection such as CMMs and 3-D scanners. Becoming educated in GD&T is an essential requirement for those who wish to compete on a global level.
What Is GD&T?
View attachment 259596
GD&T stands for Geometric Dimensioning and Tolerancing. It is a system of symbols, rules and definitions used to define the geometry of mechanical parts.
GD&T is one of the most powerful tools available that can improve quality, reduce cost and shorten delivery time. All of this is possible when the concurrent engineering team is involved with the creation of the drawing. The drawing is a common thread that ties these groups together. They all are involved with the engineering drawing. GD&T on the drawing must first and foremost capture design intent. However, the best design in the world is worthless if it cannot be produced. That is why it is necessary for production/vendors and quality to be involved with the requirements that are placed on the drawing. When they are not involved, the drawings often have overly tight tolerances and result in non-producible parts. At least not producible at the quality level, cost and timeliness expected by industry.
Nearly every company in the United States and many companies around the world use the ASME Y14.5 standard on GD&T. There is an ISO standard but it is in a state of flux. Because of this the Y14.5 standard is recognized and used around the world.
In short, GD&T is:
- Symbols
- Rules
- Vocabulary
- Mathematical definition (ASME Y14.5.1)
- Internationally recognized Standards - (ASME Y14.5 and ISO 1101)
View attachment 259594
GD&T Glossary and Resource Symbols and Terms
Use this quick reference to find definitions of common GD&T symbols and terms. Our full color Pocket Guide is a great resources for your desk, workbench or pocket. Be sure to check out our GD&T Tips!
View attachment 259597All Around Symbol - indicating that a tolerance applies to surfaces all around the part.
View attachment 259598All Over Specification [Y14.8 - 2009 R2014 (sections 3.14.1 & 3.14.2)] - In addition to a general profile of a surface tolerance there is the option of specifying that the tolerance applies all over on the field of the drawing. It is important to realize that this specification, whether in a general note or on the field of the drawing, applies UNLESS OTHERWISE SPECIFIED.
View attachment 259599All Around This Side of Parting Line [Y14.8 - 2009 R2014 (sections 3.14.1 & 3.14.2)] - To apply a requirement to all features all around one side of a parting line, the graphical symbol for all around this side of parting line is indicated on the leader line.
View attachment 259600All Over This Side of Parting Line [ ASME Y14.8-2009 Section 3.14.2] - To apply a requirement to all features all over one side of a parting line, the graphical symbol for all over this side of parting line is indicated on the leader line.
View attachment 259601Angularity - is the condition of a surface, axis, or centerplane, which is at a specified angle from a datum plane or axis.
View attachment 259602Arc Length - indicating that a dimension is an arc length measured on a curved outline. The symbol is placed above the dimension.
View attachment 259603Basic Dimension - used to describe the exact size, profile, orientation or location of a feature. A basic dimension is always associated with a feature control frame or datum target. (Theoretically exact dimension in ISO)
View attachment 259604Between - to indicate that a profile tolerance applies to several contiguous features, letters may designate where the profile tolerance begins and ends. These letters are referenced using the between symbol (since 1994) or the word between on drawings made to earlier versions of the Standard.
View attachment 259605Concentricity - describes a condition in which two or more features , in any combination, have a common axis.
View attachment 259606Conical Taper - is used to indicate taper for conical tapers. This symbol is always shown with the vertical leg to the left.
View attachment 259607Continuous Feature [ASME Y14.5-2009 Section 2.7.5] - The note CONTINUOUS FEATURE or the continuous feature symbol is used to identify a group of two or more features of size where there is a requirement that they be treated geometrically as a single feature of size. Although the definition only mentions features of size, there is an example of CF being applied to a pair of planar features.
View attachment 259608Controlled Radius - creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. Where a controlled radius is specified, the part contour within the crescent-shaped tolerance zone must be a fair curve without flats or reversals. Additionally, radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit.
View attachment 259609Counterbore/Spotface - is used to indicate a counterbore or a spotface. The symbol precedes the dimension of the counterbore or spotface, with no space.
View attachment 259610Countersink - is used to indicate a countersink. The symbol precedes the dimensions of the countersink with no space.
View attachment 259611Cylindricity - describes a condition of a surface of revolution in which all points of a surface are equidistant from a common axis.
View attachment 259612Datum Feature - is the actual component feature used to establish a datum.
View attachment 259613
Datum Target - is a specified point, line, or area on a part that is used to establish the Datum Reference Plane for manufacturing and inspection operations.
View attachment 259614Depth/Deep - is used to indicate that a dimension applies to the depth of a feature. This symbol precedes the depth value with no space in between.
View attachment 259615Diameter - indicates a circular feature when used on the field of a drawing or indicates that the tolerance is diametrical when used in a feature control frame.
View attachment 259616Dimension Origin - Signifies that the dimension originates from the plane established by the shorter surface and dimensional limits apply to the other surface.
View attachment 259617
Feature Control Frame - is a rectangular box containing the geometric characteristics symbol, and the form, runout or location tolerance. If necessary, datum references and modifiers applicable to the feature or the datums are also contained in the box.
View attachment 259618Flatness - is the condition of a surface having all elements in one plane.
View attachment 259619Free State Variations - is a term used to describe distortion of a part after removal of forces applied during manufacture.
View attachment 259620Least Material Condition (LMC) - implies that condition of a part feature of size wherein it contains the least (minimum) amount of material, examples, largest hole size and smallest shaft size. It is opposite to maximum material condition.
View attachment 259621Independency Symbol [ASME Y14.5-2009 Section 2.7.3] - The Independency symbol is applied to the size dimension in order to invoke the principle of independency to regular features of size and override Rule #1.
View attachment 259622Maximum Material Condition (MMC)- is that condition of a part feature wherein it contains the maximum amount of material within the stated limits of size. That is: minimum hole size and maximum shaft size.
View attachment 259623Movable Datum Targets [ASME Y14.5-2009 Section 4.24.6] - The movable datum target symbol may be used to indicate movement of the datum target datum feature simulator.
View attachment 259624Number of Places - the X is used along with a value to indicate the number of times a dimension or feature is repeated on the drawing.
View attachment 259625Parallelism - is the condition of a surface, line, or axis, which is equidistant at all points from a datum plane or axis.
View attachment 259626Parting Lines [ASME Y14.8-2009 Section 3.14] - are depicted on casting/forging/molded part drawings as a phantom line extending beyond the part in applicable views, with the parting line symbol added.
View attachment 259627Perpendicularity - is the condition of a surface, axis, or line, which is 90 deg. From a datum plane or a datum axis.
View attachment 259628Position Tolerance - defines a zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position.
View attachment 259629Profile of a Line - is the condition permitting a uniform amount of profile variation, ether unilaterally or bilaterally, along a line element of a feature.
View attachment 259630Profile of a Surface - is the condition permitting a uniform amount of profile variation, ether unilaterally or bilaterally, on a surface.
View attachment 259631Projected Tolerance Zone - applies to a hole in which a pin, stud, screw, etc., is to be inserted. It controls the perpendicularity of the hole to the extent of the projection from the hole and as it relates to the mating part clearance. The projected tolerance zone extends above the surface of the part to the functional length of the pin, stud, and screw relative to its assembly with the mating part.
View attachment 259632Radius - creates a zone defined by two arcs (the minimum and maximum radii). The part surface must lie within this zone.
View attachment 259633Reference Dimension - a dimension usually without tolerance, used for information purposes only. It does not govern production or inspection operations. (Auxiliary dimension in ISO)
Regardless Of Feature Size (RFS) - the condition where the tolerance of form, runout or location must be met irrespective of where the feature lies within its size tolerance.
View attachment 259634Roundness - describes the condition on a surface of revolution (cylinder, cone, sphere) where all points of the surface intersected by any plane.
View attachment 259635Runout - is the composite deviation from the desired form of a part surface of revolution through on full rotation (360 deg) of the part on a datum axis.
View attachment 259636Slope - is used to indicate slope for flat tapers. This symbol is always shown with the vertical leg to the left.
View attachment 259637Spherical Diameter - shall precede the tolerance value where the specified tolerance value represents spherical zone. Also, a positional tolerance may be used to control the location of a spherical feature relative to other features of a part. The symbol for spherical diameter precedes the size dimension of the feature and the positional tolerance value, to indicate a spherical tolerance zone.
View attachment 259638Spherical Radius - precedes the value of a dimension or tolerance.
View attachment 259639Spotface [ASME Y14.5-2009 Section 1.8.14] - Counterbore and spotface previously used the same symbol. A spotface now looks like the counterbore symbol with the addition of the letters SF.
View attachment 259640Square - is used to indicate that a single dimension applies to a square shape. The symbol precedes the dimension with no space between.
View attachment 259641Statistical Tolerance - is the assigning of tolerances to related components of an assembly on the basis of sound statistics (such as the assembly tolerance is equal to the square root of the sum of the squares of the individual tolerances). By applying statistical tolerancing, tolerances of individual components may be increased or clearances between mating parts may be reduced. The increased tolerance or improved fit may reduce manufacturing cost or improve the product's performance, but shall only be employed where the appropriate statistical process control will be used. Therefore, consideration should be given to specifying the required Cp and /or Cpk or other process performance indices.
View attachment 259642Straightness - a condition where an element of a surface or an axis is a straight line.
View attachment 259643Symmetry - is a condition in which a feature (or features) is symmetrically disposed about the center plane of a datum feature.
View attachment 259644Tangent Plane - indicating a tangent plane is shown. The symbol is placed in the feature control frame following the stated tolerance.
View attachment 259645Target Point - indicates where the datum target point is dimensionally located on the direct view of the surface.
View attachment 259646Total Runout - s the simultaneous composite control of all elements of a surface at all circular and profile measuring positions as the part is rotated through 360.
View attachment 259647Datum Translation Symbol [ASME Y14.5-2009 Section 3.3.26 ] - This symbol indicates that a datum feature simulator is not fixed at its basic location and shall be free to translate.
View attachment 259648Unilateral and Unequally Disposed Profile Tolerance [ASME Y14.5-2009 Section 8.3.1.2] - To indicate that a profile of a surface tolerance is not symmetrical about the true profile, this symbol is used. The first value in the feature control frame is the total width of the profile tolerance. The value following the symbol is the amount of the tolerance that is in the direction that would allow additional material to be added to the true profile.
Why Do I Need GD&T?
The craftsmen of old could fashion parts in a way that would allow them to slide together and give the impression that the parts fit "perfectly." Today, with the concept of interchangeable parts, credited to Eli Whitney, it is expected that parts will assemble the first time and perform their intended function. Interchangeability does not apply only to mass produced parts. Whenever two parts are expected to fit together and function without rework or adjustment, the parts must be clearly defined. Parts that have been made in other departments, plants, cities or even countries must consistently fit and function even though slight variation from the intended shape and size will exist in every part.
All parts go through a manufacturing process. There is variation in all manufacturing processes. These variations are reflected in the parts. In addition, there must be a way to inspect a part to assure that it was made to the required specifications. As Bob Traver says:
"You can't make what you can't measure because you don't know when you've got it made!"
Most importantly, the part must perform its intended task or function. To accomplish all of this, the part must be clearly and totally defined. In most cases, this definition is accomplished on a detail drawing or within a CAD file.
When used properly, GD&T will get the right questions asked early in the program, simplify the engineering drawing, and directly relate customer requirements to product specifications and process control.
Geometric dimensioning and tolerancing has been evolving for decades, and is now a crucial practice for manufacturers hoping to compete globally.
What geometric dimensioning and tolerancing (GD&T) is depends on one's discipline. To the designer it is a way to describe the design intent of individual parts. To someone in production it is the language of modern print reading. To someone working in metrology it is a guide to the inspection of parts. To management it is a concurrent engineering tool that provides clear communication across the enterprise.
View attachment 259649
GD&T has been developing during the past 80 to 100 years. It really started to be applied during World War II when the military realized the importance of defining parts with a document that had only one meaning to ensure interchangeability and part functionality. For many years companies, countries and the military published their own version of GD&T. This caused much confusion for suppliers trying to produce parts for multiple customers.
Tolerances on component and assembly dimensions are crucial to the success of a medical device.
Today most companies, from those that produce aircraft carriers to those that produce cell phones, satellites or sump pumps, have committed to following either the ASME Y14.5M-1994 standard or the collection of ISO standards on GD&T. The ASME Y14.5 standard has emerged as the preferred standard in the United States and several foreign countries, mainly because of its stability, emphasis on design intent, mathematical definition and translation to several languages.
In addition, there is now the ASME Y14.41-2003 standard, which sets forth the rules to applying the Y14.5 dimensioning and tolerancing concepts to digital data such as solid models. Dimensions and tolerances can now be embedded in the CAD model. Embedding tolerances in the solid (digital) model opens the door to reduced dimension drawings and automated analysis, which can include the expected variation which is bound to occur in production. GD&T enables this change in technology. According to ASME Y14.100 the word drawing now refers to the paper document or digital data.
View attachment 259650Directly Toleranced Dimensions
Dimensions may be directly or indirectly toleranced. Directly toleranced dimensions are those that are not basic. Directly toleranced dimensions may have a tolerance written next to the dimension, be limit dimensions or make use of a general title block tolerance. The drawing in Figure 1 illustrates common tolerancing methods. In addition to the tolerancing shown, tolerances may be unequal bilateral, or applied by using limits and fits tolerance symbols, or by referencing implied tolerances found in standards such as ISO 2768.
Basic Dimensions
Basic dimensions do not have a direct tolerance. The basic dimensions in Figure 1 are 076 and 40. By making these dimensions basic, the general tolerances no longer apply. Their tolerance is indirect. The tolerance is applied to the features on the part, not the dimensions. The basic dimension may be thought of as the goal and the geometric tolerance is the amount the feature may deviate from the goal.
Geometric Tolerances
Where geometric tolerances are used, they are applied to the feature rather than the dimension. The geometric tolerances are found in the feature control frames. In Figure 1 they are 00, 0, 0.1, 0.2 and three 00.3.
Even though there are 0s in some of the feature control frames, it does not mean that production must make perfect parts. The 0 tolerance applies only at one limit of size known as the maximum material condition (MMC) or the least material condition (LMC). Using 0 tolerancing actually provides production with more tolerance because it allows the acceptance of the best parts. This was not possible without GD&T.
Size Dimensions
The size dimensions in Figure 1 are 030, 0100, 050, 012 and 14.1/14.0. The 10 and 30 dimensions use the dimension origin symbol in place of an arrowhead to indicate which surface functions as a "local datum feature" for inspection.
View attachment 259651
Originally only direct tolerancing was used on drawings even though there never was a standard that could provide one clear meaning. Some of the problems with direct tolerancing include:
- Multiple interpretations.
- Tolerancing of points in space that cannot be verified, such as the center of a radius.
- Tolerance accumulation.
- Wedge-shaped tolerance zones where angles are toleranced in degrees.
There are four categories of geometric tolerance characteristics: location, orientation, size (handled with direct tolerancing not shown in chart) and form. There is a hierarchy to these geometric characteristics. Location tolerances also control the orientation of features. Size also controls form.
View attachment 259652
Datum features are labeled using a letter in a box at one end of a line and a triangle at the other. The triangle is associated with the feature that will serve as a datum feature to establish origins of measurement. Figure 2 illustrates a drawing where this approach has been applied. The old general titleblock tolerance has been replaced by a note making the dimensions that do not have a tolerance specified basic and a general profile of a surface tolerance that applies to the entire part unless it is overridden by a tolerance that appears on the field of the drawing. All measurements should be made from the datum reference frame established by datum features A, B and C.
View attachment 259653
GD&T has been evolving for decades and an understanding of it is essential for anyone who reads today's drawings. There is no other standard for defining parts. GD&T is enabling the new technology in CAD, CNC software and automated inspection such as CMMs and 3-D scanners. Becoming educated in GD&T is an essential requirement for those who wish to compete on a global level.
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- Sep 22, 2010
- Messages
- 7,223
View attachment 259658
What is SFM's meaning and how it is used [Surprisingly Simple Guide]
by Bob Warfield | Blog, FeedsSpeeds, Manual, Techniques | 0 comments
View attachment 259662
What is SFM’s meaning? How is SFM used?
You don’t have to be fooling around with machining or CNC long to come across the abbreviation “SFM”. In this article I’ll explain this useful concept.
Let’s get one thing out of the way quickly, SFM is an acronym for “Surface Feet per Minute”. It’s a unit of measurement for a concept in machining called “Surface Speed.”
Now why is that important?
Surface Speed and SFM are used to help determine the best spindle rpm for machining cuts. That sounds pretty useful, right?
Here’s the thing–cutters come in many variants. On a lathe, the work spins and the cutter remains stationary. Typically, there is only one cutting edge. On a milling machine, the cutter spins and the work remains stationary. Not only that, but there are usually multiple cutting edges or flutes on a typical endmill. The goal of surface speed is to provide a single quantity that can help determine the best spindle rpm for every cutter type, no matter whether it’s on a lathe or mill.
Sounds like a tall order, but it’s really pretty simple.
Those cutting edges don’t know whether they’re on a lathe or a mill. They don’t know if there are other cutting edges either. All they know is they are slicing into the workpiece, like dragging a razor over your skin when you shave. Here’s a simple diagram:
View attachment 259663
Surface speed is simply the speed the cutter moves across the workpiece. Pretty easy, right? And now you can see why you might have a unit like SFM: the cutter is moving at that number of feet per minute. The metric measure of surface speed can be either meters or millimeters per minute (or second), but it’s the exact same concept.
What’s the impact of too much surface speed?
Well, the diagram does mention the notion of rubbing two blocks to start a fire. The faster you move the cutting edge through the material it’s cutting, the more heat it generates. Cutting tools are made of materials that are designed to resist heat. Things can get quite hot before trouble starts, and that’s perfectly okay. But, there are limits. If there is too much heat, and temperatures rise too high, the cutting tool can no longer resist. It softens, which causes the edge to dull. When the edge dulls, it creates even more friction and heat. Pretty soon we have a vicious cycle and our tool is ruined.
What about the opposite? Can we have too little surface speed?
This is a logical question to ask. We can have too slow a feedrate and that’s very bad for tools because it causes rubbing, which makes the tool too hot, and we just talked about where that leads. Not good!
But, as it turns out, there is no real penalty for slowing the rpms. In fact, it’s one of the most beneficial things you can do to extend tool life. Slowing things down via rpm will reduce the amount of heat in the cut, which will help the tool to last longer.
How can we use SFM to find spindle rpm?
First thing, is every cutter has a recommended surface speed that is usually based on the material you’ll be cutting. Soft materials like wood or plastic can tolerate relatively high surface speeds. Hard materials require slower surface speeds. The very toughest materials may force you to use very low SFM’s indeed.
To find the recommended surface speed, you’ve got a few choices. If you have a Feeds and Speeds Calculator like our G-Wizard, it will have some default recommendations. Just select a tool and material and you’ve got it:
View attachment 259664
For mild steel and a carbide endmill, G-Wizard suggest 333 SFM…
You can also find tables of SFM’s in places like Machinery’s Handbook or our free online feedrate calculator. Lastly, manufacturers of cutters nearly always published recommended Surface Speeds for their cutters.
Once you’ve got a suggested surface speed, it’s relatively easy to convert it to spindle rpms. The simple machining formula you’ll use is:
Spindle RPM = SFM / circumference
Where the circumference is that of the workpiece on a lathe or the cutter on a mill. Given that simple formula, now you know why small diameter tools such as drill bits have to be spun faster than larger diameter tools. Their circumference is smaller, so the rpm goes up.
There are various reasons to use fancier calculations. For example, if you’re drilling a deep hole, it is often helpful to slow down the rpms a touch. But, for the most part, you’ve just learned everything you need to know about Surface Speed, SFM, and calculating spindle rpms.
Now I know you’re wondering. Given how easy it is, why would you need a fancy feeds and speeds calculator like G-Wizard?
First, not everything is as simple to calculate as spindle rpms. Second, I’ve already mentioned fancier calculations can be beneficial to your tool life. But probably the most important thing is that these variables don’t exist in isolation. Each one impacts the others. For example, your machine is limited to a certain amount of power based on the size of its motor. All sorts of things, including spindle rpm, go into determining how much power is used in a cut.
What should be done if the cut exceeds your spindle’s available power?
We could choose to adjust a lot of different variables. We could throw up our hands and just tell our user that particular scenario is impossible. But, the right answer is to adjust the variables in some optimum order that gets the user as close as possible to their desired result. We just learned we can reduce rpms and all is well–tool life improves!
But, if you have a high speed spindle, perhaps for a CNC Router, you can only make it run so slow. For many machines, slowing down too much also reduces available power. Can you see all the interactions that take place between all these variables?
View attachment 259659
View attachment 259660
View attachment 259661
What is SFM's meaning and how it is used [Surprisingly Simple Guide]
by Bob Warfield | Blog, FeedsSpeeds, Manual, Techniques | 0 comments
View attachment 259662
What is SFM’s meaning? How is SFM used?
You don’t have to be fooling around with machining or CNC long to come across the abbreviation “SFM”. In this article I’ll explain this useful concept.
Let’s get one thing out of the way quickly, SFM is an acronym for “Surface Feet per Minute”. It’s a unit of measurement for a concept in machining called “Surface Speed.”
Now why is that important?
Surface Speed and SFM are used to help determine the best spindle rpm for machining cuts. That sounds pretty useful, right?
Here’s the thing–cutters come in many variants. On a lathe, the work spins and the cutter remains stationary. Typically, there is only one cutting edge. On a milling machine, the cutter spins and the work remains stationary. Not only that, but there are usually multiple cutting edges or flutes on a typical endmill. The goal of surface speed is to provide a single quantity that can help determine the best spindle rpm for every cutter type, no matter whether it’s on a lathe or mill.
Sounds like a tall order, but it’s really pretty simple.
Those cutting edges don’t know whether they’re on a lathe or a mill. They don’t know if there are other cutting edges either. All they know is they are slicing into the workpiece, like dragging a razor over your skin when you shave. Here’s a simple diagram:
View attachment 259663
Surface speed is simply the speed the cutter moves across the workpiece. Pretty easy, right? And now you can see why you might have a unit like SFM: the cutter is moving at that number of feet per minute. The metric measure of surface speed can be either meters or millimeters per minute (or second), but it’s the exact same concept.
What’s the impact of too much surface speed?
Well, the diagram does mention the notion of rubbing two blocks to start a fire. The faster you move the cutting edge through the material it’s cutting, the more heat it generates. Cutting tools are made of materials that are designed to resist heat. Things can get quite hot before trouble starts, and that’s perfectly okay. But, there are limits. If there is too much heat, and temperatures rise too high, the cutting tool can no longer resist. It softens, which causes the edge to dull. When the edge dulls, it creates even more friction and heat. Pretty soon we have a vicious cycle and our tool is ruined.
What about the opposite? Can we have too little surface speed?
This is a logical question to ask. We can have too slow a feedrate and that’s very bad for tools because it causes rubbing, which makes the tool too hot, and we just talked about where that leads. Not good!
But, as it turns out, there is no real penalty for slowing the rpms. In fact, it’s one of the most beneficial things you can do to extend tool life. Slowing things down via rpm will reduce the amount of heat in the cut, which will help the tool to last longer.
How can we use SFM to find spindle rpm?
First thing, is every cutter has a recommended surface speed that is usually based on the material you’ll be cutting. Soft materials like wood or plastic can tolerate relatively high surface speeds. Hard materials require slower surface speeds. The very toughest materials may force you to use very low SFM’s indeed.
To find the recommended surface speed, you’ve got a few choices. If you have a Feeds and Speeds Calculator like our G-Wizard, it will have some default recommendations. Just select a tool and material and you’ve got it:
View attachment 259664
For mild steel and a carbide endmill, G-Wizard suggest 333 SFM…
You can also find tables of SFM’s in places like Machinery’s Handbook or our free online feedrate calculator. Lastly, manufacturers of cutters nearly always published recommended Surface Speeds for their cutters.
Once you’ve got a suggested surface speed, it’s relatively easy to convert it to spindle rpms. The simple machining formula you’ll use is:
Spindle RPM = SFM / circumference
Where the circumference is that of the workpiece on a lathe or the cutter on a mill. Given that simple formula, now you know why small diameter tools such as drill bits have to be spun faster than larger diameter tools. Their circumference is smaller, so the rpm goes up.
There are various reasons to use fancier calculations. For example, if you’re drilling a deep hole, it is often helpful to slow down the rpms a touch. But, for the most part, you’ve just learned everything you need to know about Surface Speed, SFM, and calculating spindle rpms.
Now I know you’re wondering. Given how easy it is, why would you need a fancy feeds and speeds calculator like G-Wizard?
First, not everything is as simple to calculate as spindle rpms. Second, I’ve already mentioned fancier calculations can be beneficial to your tool life. But probably the most important thing is that these variables don’t exist in isolation. Each one impacts the others. For example, your machine is limited to a certain amount of power based on the size of its motor. All sorts of things, including spindle rpm, go into determining how much power is used in a cut.
What should be done if the cut exceeds your spindle’s available power?
We could choose to adjust a lot of different variables. We could throw up our hands and just tell our user that particular scenario is impossible. But, the right answer is to adjust the variables in some optimum order that gets the user as close as possible to their desired result. We just learned we can reduce rpms and all is well–tool life improves!
But, if you have a high speed spindle, perhaps for a CNC Router, you can only make it run so slow. For many machines, slowing down too much also reduces available power. Can you see all the interactions that take place between all these variables?
View attachment 259659
View attachment 259660
View attachment 259661
Last edited:
- Joined
- Sep 22, 2010
- Messages
- 7,223
What is TIR (Total Indicated Runout)
2 Answers
Kyle Chrystal, Mechanical Engineer
Updated May 11, 2013
Like all GD&T (Geometric Dimensioning and Tolerancing) - the meaning is directly tied to both how the part would function and how it would be inspected during or after manufacturing. This topic is actually fairly detailed, but I'll try to stick to the concept - per the question. I'll try to hold off on the dry definition part of the question until after the concept is explained.
Part I - The Concept
Parts that are radially symmetric (like pins) or that will rotate in operation (shafts, hubs, gears etc.) will never be perfectly straight. The axes of these parts will never be perfect lines - they may be bowed, bent, curved etc. If these types of parts have multiple surfaces (like a shaft with multiple diameters, shoulders, tapers...) these surfaces will never be perfectly concentric. So the question is - how straight do the features of these parts need to be? What is the range of acceptable shapes and relative positions and orientations of these features? The answer to these questions depends on the functions of the part in question and total indicated runout gives us a way to specify these requirements.
Let's discuss a few examples. Suppose you are making a tool holder which has a big taper on one end where the holder fits into the spindle of a machine tool. The strength and accuracy of that tool holder depends on the mating tapers in the tool holder and spindle having very good contact over a large conical area. We want to be able to specify that our taper is not only a certain angle - but also that it's very circular in all cross sections and that the profile of the taper very smooth and straight - not wavy. Total indicated runout helps us specify this. How? See Part II.
Image shows two end mills in CAT 40 tool holders. The tapered surfaces on the right hand side must be very precise in shape, size and finish.
Another case would be a shaft on which a gear is mounted. The shaft will spin about the axis between the two centers of the bearings on which it is mounted. However, if the gear is mounted on a surface in the middle of the shaft that is not in line with the bearings then the gear will bind with its mating gear - or it may run loose with too much backlash and a propensity to wear out. We must be able to ensure the mounting surface for the gear is straight and also parallel and also concentric with the bearing surfaces on the same shaft. The center distances between two gears is critical but the only thing controlling where those centers are is the location of the bearings and the straightness of the shaft on which the gear rides.
It's easy to imagine other cases - blades on turbines must run true to be efficient and not collide with housings. Long bores for pistons found in engines or hydraulic cylinders should be straight so that the piston will not get hung up, and the bore size must be consistent throughout the length. Flywheels must have very low eccentricity so that they do not generate dangerously high centripetal forces and explode. etc. etc. It's very clear we need to specify the shape of axially symmetric parts in great detail - no matter if the part is a straight cylinder, a taper or any profile at all.
Part II - Total Indicated Runout Defined
Total indicated runout (which before the days of the double arrow GD&T symbol was specified on drawings by writing "T.I.R.") is measured by setting up a part so that it rotates about a particular axis, then a dial indicator is used to measure a surface of interest as the part is rotated. The difference between the two most extreme measurements of the indicator from anywhere on that surface is the total indicated runout.
It helps to start by thinking of simple 2D runout (which has a single arrow symbol). This is the difference between the two most extreme readings taken on a surface that is rotated once. It's basically the eccentricity of that surface. Now if you perform that simple 2D runout measurement everywhere along the length of a radially symmetric surface and take the two most extreme points you have the total Indicated runout.
Runout doesn't have to be measured parallel to the rotation axis. Here we might be checking the play of a worn out bearing or just making sure this wheel hub is mounted squarely. You could probably check this with just runout at one location and not over the whole face - but I still think the image is useful.
Part III - More GD&T
So as the earlier image above indicates - the tolerance you put on a drawing for total indicated runout is the radial width between two theoretically perfect surfaces that are exactly coaxial with the rotation axis you have chosen as a datum for the surface being measured. The two most extreme points read by the indicator must be no further apart than that tolerance value. This is important because these surfaces enclose what is called the tolerance zone and the shape of the part itself determines the shape of that zone. For example, straight shafts would have two concentric cylinders as a tolerance zone and a taper would have two cones enclosing a tolerance zone... For a part to be compliant with the given tolerance requirement, every point on the measured surface must lie within the tolerance zone.
How all of this relates to and contrasts with lots of other GD&T concepts - circularity, concentricity, straightness, profile tolerance, true position etc. is complex but suffice it to say it all depends on how you need the part to function and consequently how you want the extremes of part shape to come out. A part could be perfectly circular in every cross section but have terrible total runout if it's axis is not straight. So diameter dimensions and even 2D runout or circularity tolerances are often not enough to control a critical part.
2 Answers
Kyle Chrystal, Mechanical Engineer
Updated May 11, 2013
Like all GD&T (Geometric Dimensioning and Tolerancing) - the meaning is directly tied to both how the part would function and how it would be inspected during or after manufacturing. This topic is actually fairly detailed, but I'll try to stick to the concept - per the question. I'll try to hold off on the dry definition part of the question until after the concept is explained.
Part I - The Concept
Parts that are radially symmetric (like pins) or that will rotate in operation (shafts, hubs, gears etc.) will never be perfectly straight. The axes of these parts will never be perfect lines - they may be bowed, bent, curved etc. If these types of parts have multiple surfaces (like a shaft with multiple diameters, shoulders, tapers...) these surfaces will never be perfectly concentric. So the question is - how straight do the features of these parts need to be? What is the range of acceptable shapes and relative positions and orientations of these features? The answer to these questions depends on the functions of the part in question and total indicated runout gives us a way to specify these requirements.
Let's discuss a few examples. Suppose you are making a tool holder which has a big taper on one end where the holder fits into the spindle of a machine tool. The strength and accuracy of that tool holder depends on the mating tapers in the tool holder and spindle having very good contact over a large conical area. We want to be able to specify that our taper is not only a certain angle - but also that it's very circular in all cross sections and that the profile of the taper very smooth and straight - not wavy. Total indicated runout helps us specify this. How? See Part II.
Image shows two end mills in CAT 40 tool holders. The tapered surfaces on the right hand side must be very precise in shape, size and finish.
Another case would be a shaft on which a gear is mounted. The shaft will spin about the axis between the two centers of the bearings on which it is mounted. However, if the gear is mounted on a surface in the middle of the shaft that is not in line with the bearings then the gear will bind with its mating gear - or it may run loose with too much backlash and a propensity to wear out. We must be able to ensure the mounting surface for the gear is straight and also parallel and also concentric with the bearing surfaces on the same shaft. The center distances between two gears is critical but the only thing controlling where those centers are is the location of the bearings and the straightness of the shaft on which the gear rides.
It's easy to imagine other cases - blades on turbines must run true to be efficient and not collide with housings. Long bores for pistons found in engines or hydraulic cylinders should be straight so that the piston will not get hung up, and the bore size must be consistent throughout the length. Flywheels must have very low eccentricity so that they do not generate dangerously high centripetal forces and explode. etc. etc. It's very clear we need to specify the shape of axially symmetric parts in great detail - no matter if the part is a straight cylinder, a taper or any profile at all.
Part II - Total Indicated Runout Defined
Total indicated runout (which before the days of the double arrow GD&T symbol was specified on drawings by writing "T.I.R.") is measured by setting up a part so that it rotates about a particular axis, then a dial indicator is used to measure a surface of interest as the part is rotated. The difference between the two most extreme measurements of the indicator from anywhere on that surface is the total indicated runout.
It helps to start by thinking of simple 2D runout (which has a single arrow symbol). This is the difference between the two most extreme readings taken on a surface that is rotated once. It's basically the eccentricity of that surface. Now if you perform that simple 2D runout measurement everywhere along the length of a radially symmetric surface and take the two most extreme points you have the total Indicated runout.
Runout doesn't have to be measured parallel to the rotation axis. Here we might be checking the play of a worn out bearing or just making sure this wheel hub is mounted squarely. You could probably check this with just runout at one location and not over the whole face - but I still think the image is useful.
Part III - More GD&T
So as the earlier image above indicates - the tolerance you put on a drawing for total indicated runout is the radial width between two theoretically perfect surfaces that are exactly coaxial with the rotation axis you have chosen as a datum for the surface being measured. The two most extreme points read by the indicator must be no further apart than that tolerance value. This is important because these surfaces enclose what is called the tolerance zone and the shape of the part itself determines the shape of that zone. For example, straight shafts would have two concentric cylinders as a tolerance zone and a taper would have two cones enclosing a tolerance zone... For a part to be compliant with the given tolerance requirement, every point on the measured surface must lie within the tolerance zone.
How all of this relates to and contrasts with lots of other GD&T concepts - circularity, concentricity, straightness, profile tolerance, true position etc. is complex but suffice it to say it all depends on how you need the part to function and consequently how you want the extremes of part shape to come out. A part could be perfectly circular in every cross section but have terrible total runout if it's axis is not straight. So diameter dimensions and even 2D runout or circularity tolerances are often not enough to control a critical part.
- Joined
- Sep 27, 2014
- Messages
- 3,123
This was more like a good sticky start,
https://www.hobby-machinist.com/threads/common-machine-shop-abbreviations.67225/
https://www.hobby-machinist.com/threads/common-machine-shop-abbreviations.67225/
Last edited:
- Joined
- Sep 27, 2014
- Messages
- 3,123
Here’s a few may not need them all, but a lot easier to copy
ATC - Automatic Tool Changer
BP - Blueprint
BUE - Built Up Edge
CAD - Computer Aided Design
CAM - Computer Aided Manufacturing
CBN - Cubic Boron Nitride
CCW - Counter Clockwise
Chfr. - Chamfer
CMM - Coordinate Measuring Machine
CNC - Computerized Numerical Control
CRES - Corrosion Resistant
CW - Clockwise
DOC - Depth of cut
DP - Diametrical Pitch
DPM - Degrees per Minute
DTI - Dial Test Indicator
DWG - Drawing
GPM - Gallons per Minute
HMC - Horizontal Machining Center
HP - Horsepower
HSM - High Speed Machining
HSS - High Speed Steel
HSSCO - High Speed Steel Cobalt
IPM - Inch per minute
IPR - Inch per revolution
kW- Kilowatts
mm- Millimeters
MT - Morse Taper
NC - Numerical Control
NPT - National Pipe Thread
OBI - Open Back Inclined (press)
PCD - Poly Crystaline Diamond
PD - Pitch Diameter
PSI - Pounds per Square Inch
PVD - Physical vapor deposition
QC - Quality Control or Quick Change
Ra - Roughness Average
RFQ - Request for Quote
RG - Returned Goods
RMS - Root Mean Squared
RPM Revolutions per minute
SFM - Surface feet per minute
SMM - Surface meters per minute
SS - Stainless Steel
TiAlN - Titanium Aluminum Nitride
TiC - Titanium Carbide
TiCN - Titanium Carbonitride
TiN - Titanium Nitride
TNR - Tool Nose Radius
TPI - Threads per Inch
VMC - Vertical Machining center
ATC - Automatic Tool Changer
BP - Blueprint
BUE - Built Up Edge
CAD - Computer Aided Design
CAM - Computer Aided Manufacturing
CBN - Cubic Boron Nitride
CCW - Counter Clockwise
Chfr. - Chamfer
CMM - Coordinate Measuring Machine
CNC - Computerized Numerical Control
CRES - Corrosion Resistant
CW - Clockwise
DOC - Depth of cut
DP - Diametrical Pitch
DPM - Degrees per Minute
DTI - Dial Test Indicator
DWG - Drawing
GPM - Gallons per Minute
HMC - Horizontal Machining Center
HP - Horsepower
HSM - High Speed Machining
HSS - High Speed Steel
HSSCO - High Speed Steel Cobalt
IPM - Inch per minute
IPR - Inch per revolution
kW- Kilowatts
mm- Millimeters
MT - Morse Taper
NC - Numerical Control
NPT - National Pipe Thread
OBI - Open Back Inclined (press)
PCD - Poly Crystaline Diamond
PD - Pitch Diameter
PSI - Pounds per Square Inch
PVD - Physical vapor deposition
QC - Quality Control or Quick Change
Ra - Roughness Average
RFQ - Request for Quote
RG - Returned Goods
RMS - Root Mean Squared
RPM Revolutions per minute
SFM - Surface feet per minute
SMM - Surface meters per minute
SS - Stainless Steel
TiAlN - Titanium Aluminum Nitride
TiC - Titanium Carbide
TiCN - Titanium Carbonitride
TiN - Titanium Nitride
TNR - Tool Nose Radius
TPI - Threads per Inch
VMC - Vertical Machining center
Last edited by a moderator:
- Joined
- Jun 26, 2014
- Messages
- 619
Should be:
kW- Kilowatts
mm - Millimeters
in SI units capitals are generally only used if it is a unit named after a person, Watt, Volt, Hertz, etc or large multipliers Gig, Tera, etc