Perfection-precision

ronboult said:

I wonder how many actually know the difference between accuracy and precision.

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THANK YOU. As I was reading this thread, I got more and more annoyed with the incorrect useage of the terms.

FOLKS, Here it is:
Precision is the ability to repeat a task the same way time after time. It has nothing to do with the dimension being correct or not. One can be extremely precise but have a pile of IDENTICAL useless parts that will not fit.

Accuracy is a measure of how well one achieves the target or in our case hitting the desired dimensions.

So..... A question for the group. If you are making a single part, is there precision involved or just accuracy?

Perfection. Hmmm. In my mind it depends on the criteria. Is 100% acceptable production a perfect situation?
In order to do that, are tolerance bands needed? Usually.
Once tolerance bands are properly set, Quality becomes digital. The part is either good or not. No grey area of interpretation. Unfortunately, few manufactured items are engineered to that detail.

Incase anyone is interested this is straight from Dictionary.com. They use each word as definition of the other.

precision
Synonyms

• Examples

• Word Origin

See more synonyms on Thesaurus.com
noun
1.
the state or quality of being precise.
2.
accuracy; exactness:
to arrive at an estimate with precision.
3.
mechanical or scientific exactness:
a lens ground with precision.
4.
punctiliousness; strictness:
precision in one's business dealings.
5.
Mathematics. the degree to which the correctness of a quantity is expressed.
Compare accuracy (def 3).
6.
Chemistry, Physics. the extent to which a given set of measurements of the same sample agree with their mean.
Compare accuracy (def 2).
adjective
7.
of, relating to, or characterized by precision:
precision swimming; precision instruments for aircraft.

accuracy
Examples

• Word Origin

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noun, plural accuracies.
1.
the condition or quality of being true, correct, or exact; freedom from error or defect; precision or exactness; correctness.
2.
Chemistry, Physics. the extent to which a given measurement agrees with the standard value for that measurement.
Compare precision (def 6).
3.
Mathematics. the degree of correctness of a quantity, expression, etc.
Compare precision (def 5).

I think what RZBill is referring to is Repeatability.

And then there is these.

perfection
Examples

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noun
1.
the state or quality of being or becoming perfect.
2.
the highest degree of proficiency, skill, or excellence, as in some art.
3.
a perfect embodiment or example of something.
4.
a quality, trait, or feature of the highest degree of excellence.
5.
the highest or most nearly perfect degree of a quality or trait.
6.
the act or fact of perfecting.

excellence
Synonyms

• Examples

• Word Origin

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noun
1.
the fact or state of excelling; superiority; eminence:
his excellence in mathematics.
2.
an excellent quality or feature:
Use of herbs is one of the excellences of French cuisine.
3.
(usually initial capital letter) excellency (def

I have a product that requires either Accuracy, or Precision, I've yet to figure it out. One piece of a mechanism comes extruded in gear form, about 5/16 diameter, metal (not sure just what metal. I mount it in a collet in my Ames turret lathe, Center drill and drill it to .118 or so and bore it to .125, fitting it to a .125 piece of drill rod, then cut it off about 1/2" long. It fits on a shaft turned from 5/16 drill rod. I chuck the drill rod in an ER40 collet, center drill it with a no. 0 center drill, put a center in it and turn it to .127 or so. Then I file it until the gear goes on with a light press fit. The two get pinned together later. This puts the gear concentrically on the shaft so that it meshes with a 3" diameter gear without run-out which would be noticeable if present.

The fit is precise, but I'm not sure how accurate it is. I've never measured the shaft, just fit the gear to it. If I don't do it this way the two gears have tight spots as they turn together.

Well I don't know about all you guys, but EVERYTHING I do is precise, accurate, and exulant.

CHuck the grumpy old guy

Me too

Precase, accurite, and exulant that's the way I like it un hun un hun

Ok so I'm in the same boat. 60 and just starting out with this hobby. Don't think I have done anything yet that is straight, repeatable, or close to accurate, but I'm sure smiling when I get a chance to make a few chips on the lathe. All of the posts here on this thread are inspiring and another reason I am happy I came upon this group. I know I have a lot to learn and limited time play in the shop, all of your advice combined with different ways of accomplishing a task is priceless. What I am struggling with is how to afford all the things I now want and keep the wife from having me locked up for financial insanity


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Don't know how repeatable I get things, as so Far all I have made is one off, But did get a from scratch steam engine, that ran on air, and a Steam engine kit running on air, to work. I have been working on tools etc for a used lathe, and hope to make a few small cannons to play with. Maybe a few more steam engines etc. But may have to get something bigger than a Sherline Mill Did get an old 10x24 lath but that have to get it to cut better first. But I have fun

Hi Randy,
Both of the definitions you kindly posted refer to the chemistry or physics definitions. They are the same as is used for engineering which was what I was trying to express in different words.

John TV said:

Ok so I'm in the same boat. 60 and just starting out with this hobby. Don't think I have done anything yet that is straight, repeatable, or close to accurate, but I'm sure smiling when I get a chance to make a few chips on the lathe. All of the posts here on this thread are inspiring and another reason I am happy I came upon this group. I know I have a lot to learn and limited time play in the shop, all of your advice combined with different ways of accomplishing a task is priceless. What I am struggling with is how to afford all the things I now want and keep the wife from having me locked up for financial insanity


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I tell mine that tools and hobbies are cheaper than medication and it seems to be working.