Understanding Grinding

Oh yeah (correct) glenb...just one basic example of a set of ops without getting too complicated here for a simple tool steel OD Job but close tolerence (+/-.0002) with a 4rms finish could be: Lathe; Turn od leaving .005 stock... Heat treat (lets say to rc50-55)... Grinder: Grind OD (a typical ground 16 rms or so finish) leaving, lets say .0006 or 7 stock...Lathe: Spin and use 600-800, then 1000-1200 grit paper just a bit leaving .0003 or so then polish (with as above pastes or compounds) to hit the dim. at the top to the middle of the tolerance (remebering along the way steel grows with heat, shrinks with cold, when considering tolerences in "tenths")

Or yeah, if knowing your lathe; Just turn OD to whatever you can hit and leave whatever you need for to "sand" and a finish to want you want to hit at what dim. you're after
(You can hit "tenth" dimensions with finish right on a "toolroom" lathe but considering yada yada its not practical and too risky (to go undersize) unless, well, more yada yada (LOL)

May I suggest, along with reading and watching around here, there, everywhere and ifn' you have no machine shop job with training now, grab one of the basic all around Machining text books such as the old "Machine Shop Operations and Set Up" (or whatever is around these days here, there, wherever (LOL)...
.....I always suggest no CNC....yet ("Don't put the carriage before the horse")
 
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trust me, im reading. im mostly read older books, I want the older techniques vs new. I see more thinking/math in those older techniques. ill get to the newer stuff later. I have started turning but had to stop, I only have a storage and it's FULL. No room to work. my last project, a flywheel, is still in the chuck rusting away.
i have interest in g and m code, there are jobs there, but im not in a rush.

btw thank you all for y'all input so far!!
 
glenbjackson said:
So safe to say no matter how rigid a lathe you have you cant get .0001 with a toolbit? It'll just rub and not cut?
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What your doing that 0.0001 is going to matter is beyond me. Keep in mind thermal expansion. When grinding for surface finish coolant flooding is a must. Dry grinding will cause the part to heat and expand so you may start at 0.0001 and end with 0.0005 concave in the center, more or less depending on part size. Also any grinding on a lathe requires major clean up, i hate doing it cause I end up disassembling and completely cleaning my lathe afterward, so I find myself stock piling projects for grinding all at once. I also continuously clean my lathe during grinding operations and cover everything in leather. If you are only aiming for a minute amount taken off look up Clickspring on Youtube. He has a video about making emery sticks. You can easily remove 0.0001 by hand with a little attention to detail and they are not nearly as messy as grinding. You will still want to wipe everything down afterward and cover your ways. But unlike a tool post grinder you carriage is not moving during the operation so grinding dust is not getting under it. The other complication is moving a grinder attached to a lathe 0.00005 to achieve a 0.0001 tolerance, it can be done but what a headache. Good luck.
 
Ronster Irons said:
What your doing that 0.0001 is going to matter is beyond me. Keep in mind thermal expansion. When grinding for surface finish coolant flooding is a must. Dry grinding will cause the part to heat and expand so you may start at 0.0001 and end with 0.0005 concave in the center, more or less depending on part size. Also any grinding on a lathe requires major clean up, i hate doing it cause I end up disassembling and completely cleaning my lathe afterward, so I find myself stock piling projects for grinding all at once. I also continuously clean my lathe during grinding operations and cover everything in leather. If you are only aiming for a minute amount taken off look up Clickspring on Youtube. He has a video about making emery sticks. You can easily remove 0.0001 by hand with a little attention to detail and they are not nearly as messy as grinding. You will still want to wipe everything down afterward and cover your ways. But unlike a tool post grinder you carriage is not moving during the operation so grinding dust is not getting under it. The other complication is moving a grinder attached to a lathe 0.00005 to achieve a 0.0001 tolerance, it can be done but what a headache. Good luck.
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Yeah Ronster if you see glenb's original post and follow (read) the following posts you will see he is just really, really starting out (Only knew about hand snag grinders and wheels on a ship and we somehow got to and were talking about "tenths" while telling/showing him about all the Machine Tool Grinders.
 
Christian Poulsen said:
Another note! (Blab) (LOL): For the home shop, finding a used midsize Universal grinder (ID/OD) will be probably the hardest and most expensive Machine Tool on a list to find (even used EDM's will be cheaper)...I once cut a purchase order for a new midsize "manual" Kellenberger (over $100,000.00 !!) and the Co. turned it down and went for a $60,000 Tshudin...Seeing these pictures I see and reminds me of the 3 small Myfords (British) we had plus a Big B&S and a huge Landis...all these Grinders I'm listing were built like "battleships" (brute castings), were (are) 50 + yrs old, and still grinding day in/day out holding "half tenths" (.00005)...But the most accurate, most expensive ($180,000 used) Machine Tool I ever ran or had anything to do with was a grinder (A Moore Continuous Path CNC (GE Control) Jig grinder (The Moore bros. (Herman), way back before even I was born (LOL), invented the"tenth" (.0001) as applied to an actual machine and results)
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Look! Someone who uses even more parentheses than me!! :)
 
yeah Ronster Ironsclear.gif im sure I wont be going to the tenth anytime soon, was just wondering. but I have talked to a guy who used to be a nuclear machinist, and he stated that they have such tolerances. never got to ask how they got there though.

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....speaking of .0001 and while cruising around this site I was thinking (Hey! I heard that!) of the heading of these machining sub subjects being "A Beginners Forum", me thinks' it's right to clear up a pc. of U.S. shop slang (at least it is around my area here) that may be confusing to some beginners. Although saying a tenth to one that is brand new might think is a tenth of an inch (and would be correct? LOL)...when we say a "tenth" we mean .0001 (a tenth of a thousandth of an inch)... and a "half tenth" (LOL) is .00005
I would add an old Toolmakers anecdote to my friend and the best Mechanical Engineer/Tool Designer I ever knew personally (Wilson Ford, a Native American) but I guess it wouldn't be nice? (Although he wouldn't be or wasn't mad at all (I think)...
 
just my 2 cents worth as just about every thing has been covered already, in addition, to grinding shafts,crankshafts,hardened measuring gauges being finished to international standards ,grinders are also used for ground threades [an example air compressor head studs aprox 1.6250 dia thread tolerance was only +0.00001"to -0.001 ,these studs the thread had to be ground after stud toughened by heat treatment] this same grinder was also used to grind hand and machine taps [all dia and pitches] and coud also do the relief of the thead form in same operation ,
all down to wheel selection, wheel speed [this on the thread grinder was extremely important you could vary the wheel speed by over 1000rpm to suit type of material and hardness ], as well as the coolant fed onto wheel and job,this machine the coolant was a straight oil [special type, cannot remember exactly ,but the coolant oil had to be fed through its own refrigeration plant]
type of accuracy for grinding threading taps it could do all thee taps [taper ,intermediate ,and finish and be accurate in the correct form selected[magnified 150 times] for taps as small as 1/8 dia all way up to 4 1/2"dia [this size you did not need to magnify much if at all to check the form]

we also used to grind forms on special tipped tools that had to pass nata standards before they could be used inhouse [the finished form tool was measured in all aspects as well as being magnified 30 times to check the 3 thou radius was a true 3 thou radius that truly blended in.
to sum in nutshell any form of grinding from using angle grinder,offhand grinder, through to specific industrial and beyond
the criteria is the same being
- wheel selection for type of material and the hardness of the same also what final finish is required

-surface speed of wheel
-coolant if required and of correct type coolant can be a jet of air all way through different mixes to straight oil eg almag oil
or nothing at all
and then the variables ,accuracy/precision of grinder and,operator, dressing of wheels also is extremely importatant,ie size and shape of dressing diamonds. dressing stones etc

ONE IMPORTANT NOTE
,ALWAYSplease use appropiate safety equipment, eye protection,guards at all times ,especially with items such as 1/64"thick unreinforsed 6 inch dia cut off toolroom wheels [picking wheel slivers out timber walls reminds you that not only could you be blinded from sparks in eyes ,broken wheel fragments could also kill] this machine even had its guard in place at time.
 
just my 2 cents worth as just about every thing has been covered already, in addition, to grinding shafts,crankshafts,hardened measuring gauges being finished to international standards ,grinders are also used for ground threades [an example air compressor head studs aprox 1.6250 dia thread tolerance was only +0.00001"to -0.001 ,these studs the thread had to be ground after stud toughened by heat treatment] this same grinder was also used to grind hand and machine taps [all dia and pitches] and coud also do the relief of the thead form in same operation ,
all down to wheel selection, wheel speed [this on the thread grinder was extremely important you could vary the wheel speed by over 1000rpm to suit type of material and hardness ], as well as the coolant fed onto wheel and job,this machine the coolant was a straight oil [special type, cannot remember exactly ,but the coolant oil had to be fed through its own refrigeration plant]
type of accuracy for grinding threading taps it could do all thee taps [taper ,intermediate ,and finish and be accurate in the correct form selected[magnified 150 times] for taps as small as 1/8 dia all way up to 4 1/2"dia [this size you did not need to magnify much if at all to check the form]

we also used to grind forms on special tipped tools that had to pass nata standards before they could be used inhouse [the finished form tool was measured in all aspects as well as being magnified 30 times to check the 3 thou radius was a true 3 thou radius that truly blended in.
to sum in nutshell any form of grinding from using angle grinder,offhand grinder, through to specific industrial and beyond
the criteria is the same being
- wheel selection for type of material and the hardness of the same also what final finish is required

-surface speed of wheel
-coolant if required and of correct type coolant can be a jet of air all way through different mixes to straight oil eg almag oil
or nothing at all
and then the variables ,accuracy/precision of grinder and,operator, dressing of wheels also is extremely importatant,ie size and shape of dressing diamonds. dressing stones etc

ONE IMPORTANT NOTE
,ALWAYSplease use appropiate safety equipment, eye protection,guards at all times ,especially with items such as 1/64"thick unreinforsed 6 inch dia cut off toolroom wheels [picking wheel slivers out timber walls reminds you that not only could you be blinded from sparks in eyes ,broken wheel fragments could also kill] this machine even had its guard in place at time.
 
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