# Understanding Grinding



## glenbjackson (Nov 2, 2016)

grinding I don't see how grinding, correct me if i'm wrong, is the last word in surface finish. my question is if grinders use wheels that are consumables how can this process be consistent for any length of work. Even a thin gear, after one pass on a tooth the wheel will be a smaller diameter, so on the next tooth to be grinded, it will be taller after it's grinding pass then the previous tooth and so on. and yes I realize these are very small amounts but still a difference. Am I missing something? do the machine taper depending on the wheel material or just step up slightly on every pass?


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## intjonmiller (Nov 2, 2016)

You understand correctly, but assuming you're doing it right (correct wheel selection for the material being ground, appropriate feed rate, etc.) you're overestimating the rate of wear. I am not a grinding expert beyond having done enough to know that it can definitely be done wrong, resulting in exactly what you're picturing (among other problems). Sometimes on large parts it requires multiple paases, dressing the wheel between, to accurately remove as much material as you can in a single pass on a smaller workpiece. 

The Suburban Tool YouTube channel has several excellent videos on the subject, covering theory and best practices. And they'll happily sell you some very shiny mag chucks and other grinding accessories.


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## kingmt01 (Nov 2, 2016)

You first answer pretty well sums it up. Everything wares. Even your carbide tooling. If it's in spec tho it doesn't matter. If your goal is .0001"+/-.00001 & your to wares .000005" you'll probably hit your goal. If not you measure reset & take another pass.


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## Christian Poulsen (Nov 2, 2016)

...wheel selection on all grinding ops and machines (Surface (and Blanchard), Universal (ID/OD), C/L is a major key to this question (with, of course, the machine itself)...Examples: A CNC Universal grinder can be programmed for wheel wear during a production run of X amount of parts (ops)...There are "rock" wheels, say form dressed (angle, corner radius on both sides of the wheel) that with proper feed (and coolant (or not!) etc) can grind 5  .050 deep "slots" in a 4" X 4"  hardened tool steel work pc on a surface grinder in X, then turn 90 to Y and grind 5 more (a "checkerboard") and loose only about .005 total at the end (then yoose' "go backwords" once (after redressing for your angles and corner radiususseses) and finish depth and contours will be within .0002...a manual Universal grinder, with a good resin bonded diamond wheel (say 220 grit) can plunge grind (with again, proper feed and coolant) .o50 off the end ("step") of about 5 solid carbide rods 3/8" in diameter (6% cobalt, (about as hard carbide as you can get') , and "loose" (or "wide" groove the end of your wheel) only about .oo1 to .oo2....Cheers!


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## glenbjackson (Nov 2, 2016)

ok thanks guys for y'alls replys... makes much sense


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## Christian Poulsen (Nov 2, 2016)

Since and while I see your reply glenbjackson I thinks I will add: I'm trying to think during 35 yrs, of a part of any material, on any type of Machine Tool grinder with any type of wheel where/when I took more than .001 a "pass"...

...oops, I do remember OD grinding a bunch of a type of rubber coating wheels about 1 ft long x 8" OD formed around a 1"center shaft...on an old Brown and Sharpe Universal with the most aggresive, porous "rock" wheel I ever saw and I would take 1  .o50  pass to straighten and "round" out the OD and it would only take off about .010 as I let it dwell back and fourth (on X) and that wheel left the perfect, rough surface on that rubber the customer was looking for to coat with whatever they were using and coating whatever they were coating (weird for a guy that is all steel and carbide LOL)


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## glenbjackson (Nov 3, 2016)

I need to see one of the grinding wheels and maybe machine, they sound precise and slow. I'm gonna check out those youtube videos intjonmiller recommended. I'm thinking more of wheels that have rounded edges, relatively un-flat flats and wears horribly. I was a shipfitter and I'm stuck on the image of grinding wheel, the wear, finish and abuse associated with a hand grinder. but comparing a human to feedrate/depth, I should've guessed the machines would wear out a wheel more efficient.


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## JimDawson (Nov 3, 2016)

The wear on a grinding wheel on a surface grinder is not like grinding on any hand machine.  The leading edge wears away leaving the rest of the wheel intact.

In the picture below I have already taken about o.o30 off of that plate in 0.010 increments since I dressed the wheel.  The wheel is 2 inches wide and as you can see, only the first 1/4 inch of the wheel is worn, the rest of the wheel is as dressed.  That means that the plate will be cleaned up by the untouched portion of the wheel.  This is the final pass at 0.005 inch.  I turned the coolant off for this picture.




And another view from the front with the coolant on


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## glenbjackson (Nov 3, 2016)

lol all those sparks for just 0.005 wow. that's another reason I thought more was being taken off with grinders because of some many sparks. thanks for pics
I can also see the disc's diameter is larger, so a longer grinder surface.


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## Joe in Oz (Nov 3, 2016)

There are almost as many sparks at 0.0005" - and yes, it is surprising.


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## Christian Poulsen (Nov 3, 2016)

Nice pics (Although in my grinding world (which was 90% hardened D2 or S7 tool steel and the various grades of carbide), .oo1 was a perty' heavy cut (on a small Doall or B&S to a "big" Kent), .0002 and then dwell (Universals and Blanchards) or "back over" or through (when surface grinding and C/L) with zero feed was my normal finish depth of cut...as for seeing some Machine Tool Grinders" glenb; Here's some googled picture links:

https://www.google.com/search?q=sur...X&ved=0ahUKEwj3gaSb8ozQAhXjyVQKHYCqBSwQsAQIGg

https://www.google.com/search?q=Uni...X&ved=0ahUKEwjd-9ai9IzQAhWorFQKHb1mCR4QsAQIGg

https://www.google.com/search?q=cen...X&ved=0ahUKEwjPr5bC9IzQAhXLgVQKHW59AWgQsAQIIQ

https://www.google.com/search?q=bla...X&ved=0ahUKEwivprKP9YzQAhXLi1QKHTNQCIQQsAQIGg


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## Christian Poulsen (Nov 3, 2016)

Add: My "lead in" dress on "rock" wheels and diamond wheels (angle?) for just flat surface grinding and straight Universal grinding was usually about .003  with the "big" (+.003 or so) diameter of the wheel at the front (surface grinders) or to the left towards the headstock (facing the machine) (Universal grinders).....therefor I only fed down (or in) on the proper side thereby preserving the lead in and "sharp" front edge of the wheels (when called for)....Cheers!


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## Christian Poulsen (Nov 3, 2016)

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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## Christian Poulsen (Nov 3, 2016)

Here's a google link to pictures of old and newer model  Moore continuous path Jig Grinders (X, Y, Z and some like I ran with an integrated C turn table)...IMO: The end all, Holy Grail of Machine tools (I get light headed when I see a fully equiped  one! LOL) 

https://www.google.com/search?q=Moo...source=univ&sa=X&ved=0ahUKEwimtYPWhY3QAhWqqlQ


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## bfd (Nov 7, 2016)

just to set the record straight lapping gives a far superior surface finish to grinding. yes the wheels wear. that's why grinding is such a slow process(among other things) but grinding is lots better than milling. bill


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## glenbjackson (Nov 7, 2016)

making sense! I see me getting one for the lathe too.


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## Randall Marx (Nov 8, 2016)

Or MAKE one for the lathe toolpost. There have been several made and posted by members on this site. Might be good to check them out.


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## Christian Poulsen (Nov 8, 2016)

Yes, Dumore toolpost grinders are the most numerous around or make one for a good project....but best is to rig up a vacume while grinding or at least cover as much as you can during grinding and good cleanup after... as the fine grinding dust can wreak havoc with your lathe surfaces (the grinding "dust" from wheel wear and the stock being ground acts as kind of a dirty lapping compound, especially on the ways when its trapped under the carriage (etc)


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## Christian Poulsen (Nov 8, 2016)

....and yes Bill I see where you're coming from...I have a small lapping plate I have charged (smeared) "blue" diamond paste on here at home ....on the job we had a couple with blue and "pink only" charged on them for "mirror" finish/polish (2rms or less)...
However, say and depending on yada yada; A 900 to 1200 grit diamond wheel and some fine (some "blue" wheels  we had come to mind) "rock" wheels don't leave too bad of a finish (I have gotten down to 8rms  with these wheels on carbide and toolsteel (for various Armor  tooling (up to about 12" x 12" flat punches and ejectors) that the prints called out 8rms or better and we got them down to 6 right off of Surface grinders...the trick  (to pass surface inspection (avoiding scratches) was to knock off any loose "pebbles" (LOL) with just fine sandpaper or scotchbrite from the spinning wheel after dressing the "rock" wheels and make sure the coolant filter was keeping out "loose rocks" in the coolant to the head plus we would rig up secondary fine screen right at the coolent spraying onto the wheel/part
Add: When cylindrical grinding with any fine wheel I still always left around .0002 polish stock on all ODs and ID's...


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## glenbjackson (Nov 8, 2016)

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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## Christian Poulsen (Nov 8, 2016)

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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## glenbjackson (Nov 9, 2016)

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!!


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## Ronster Irons (Nov 9, 2016)

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?


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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## Christian Poulsen (Nov 9, 2016)

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.


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.


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## intjonmiller (Nov 9, 2016)

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)


Look! Someone who uses even more parentheses than me!!


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## glenbjackson (Nov 9, 2016)

yeah Ronster Irons

 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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## Christian Poulsen (Nov 9, 2016)

....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)...


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## branway (Nov 10, 2016)

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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## branway (Nov 10, 2016)

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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## glenbjackson (Nov 10, 2016)

I know this is the right thread but heads up if you're looking for a grinder, two in SC:
http://bid.yellowtagauctions.com/cgi-bin/mnlist.cgi?yellowtag21/category/ALL


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## Christian Poulsen (Nov 10, 2016)

If I was there I'd be bidding a few of those next reqd. bids!

FYI glenb that Sunnen hone is pretty much a staple in most Toolroom/Machine shops.
(Once in around the middle of my 35 yrs. I was "disenchanted" with some of my Mgt. group and I almost went after a regional Sunnen rep. job that I had an "in" to possibly get)
But I "rode" it out ("Mgt can come and go but the trade is for life")


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## spike7638 (Mar 19, 2022)

It's 8 years later, and I came to ask the same question, and these answers are terrific. The main "aha" moment was in realizing that the grinding wheel gets moved in the _axial_ direction a tiny bit each time which in retrospect seems like the only reasonable way to do things, but it's not at all what I was imagining!


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