Building A Tool Post Grinder

last night i looked up treaded hardened shafts from mcmaster to see if they had something i could use as a main shaft to put on 3/8 hole -grinding wheels onto...they were about 50 bucks an they were not threaded very long...on the way home today it hit me that i have a bunch at home already.....air cylinder shafts ..perfect;-)..and paid for...and a couple days ago i found a 3/8 to 1/4 chuck in one of my drawers for internal bits..

debating to go your route of just pop some holes in a block with flanged bearings and collars to hold everything together
 
I picked up a DC drive for 1 1/2 hp motor for $28 on eBay. I got it hooked up today to test run the grinder.
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It runs good after tweaking the bearing preload. I gotta get the belt guard done . This thing scares the crap outta me at 8000 rpm. Also got to get a small box to mount the drive in. It is getting close to ready to use.
 
TOOLMASTER said:
last night i looked up treaded hardened shafts from mcmaster to see if they had something i could use as a main shaft to put on 3/8 hole -grinding wheels onto...they were about 50 bucks an they were not threaded very long...on the way home today it hit me that i have a bunch at home already.....air cylinder shafts ..perfect;-)..and paid for...and a couple days ago i found a 3/8 to 1/4 chuck in one of my drawers for internal bits..

debating to go your route of just pop some holes in a block with flanged bearings and collars to hold everything together
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I need some small internal grinding wheels , like 5/8" diameter. I ordered some 3/4 Stones on .250 shafts from McMaster Carr. I am currently trying to make a 8" long shaft with a small chuck machined on the end to hold these stones. I'm making it from 1/2" drill rod. Since my grinder spindle is an ER20 chuck with a 1/2" collet , I can put the shaft in the chuck and slide it in or out to any length desired. I am also going to use drill rod to make an arbor to hold my 3" diameter external grinding stones with a .375 " hole. I think I will use 3/4" drill rod for this arbor and turn one end down to 1/2" to fit the chuck and a 3/8" stud turned on the other end to mount the stone. I figure the larger shaft won't flex as easy.
 
Great work,Mark! Does your motor balance well enough to not vibrate?

Back when I had screw on chucks,I never had a problem with running the lathe backwards. Even when I ran it backwards with a threading tool upside down to avoid colliding with shallow lids I was internally threading.

Strange as it may seem,I learned that the best ground finishes were obtained by running the lathe FULL SPEED,backwards.

My Themac manual says to run the grinder 1/2 HOUR before using to get the bearings warmed up to size.

My present tool post grinder is the smallest that Themac made. I got it brand new in the case from a used machinery dealer for a fraction of the retail cost. Haven't used it for a while,so I can't recall the model number. Themac made some of the very best grinders available,in my opinion.

I find it quite sufficient even for my 16" lathe. I had a Dumore "Tom Thumb" back in the 70's. Never could get a decent finish with it. It appeared to be brand new. Then I had a South Bend grinder. It was pretty miserable.
 
Yes George, it runs really smooth . I do need the belt guard done because that belt scares the crap out of me at 8000 rpm. I have to make arbors for the stones next and it will be ready to go.
 
Mark,I finished my post after you read it. Go back,please for more details.

BTW,My grinder uses a VERY THIN factory fabric flat belt. Nearly paper thin. It weighs nothing,and does not add to any out of balance vibration like a heavier vee or round belt can. The pulleys are crowned well.

The South Bend used a small Vee belt,which was not a good idea. The very SLIGHTEST vibration of any kind will print on your grinding,and look like wild grain plywood surface.

The eye can readily see 1/250,000" deep marks,believe it or not.
 
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I thought about the belt and have been thinking about making new flat pulleys and I have a thin flat belt but will have to join the ends somehow. I think the round belt is too heavy and does vibrate some. I haven't tried grinding yet though.
 
Unfortunately,a new belt from Themac is about $40.00,IF I recall right. A belt might be found for less on Ebay,except you've already established your distances between pulleys,etc..
 
mark_f said:
Another thing I don't understand. The operator manuals all say to set the grinder on an angle, between 10 degrees and 45 degrees, then dress the wheel face while set here. If you dress the wheel flat at the angle, what is the point of setting at an angle? Or am I missing something. .
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I just stumbled onto your nice build, Mark. I'm not sure that anyone answered your second question. I have to admit the procedure seems odd to me too but I'm not really 'qualified'. I'm curious, did you come to any conclusion on this issue & what manual referenced this?

This issue has me intrigued because I have some ID wheels that are about .75 diameter & almost as thick. I don't want to expose the entire face of the wheel to the bore. I was wondering if I should dress it with some relief clearance (left sketch). But somewhere in my travels I thought someone mentioned to dress the stone conventionally, but then slightly angle the TPG assembly so it has a leading edge effect (center sketch). This would seem like a much more fragile edge though? But maybe a 'reduced' dressing at the angle would accomplish the desired result (right sketch)? Hopefully my description makes sense. Maybe someone with more grinding experience can comment before I shoot my eye out.

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petertha said:
I just stumbled onto your nice build, Mark. I'm not sure that anyone answered your second question. I have to admit the procedure seems odd to me too but I'm not really 'qualified'. I'm curious, did you come to any conclusion on this issue & what manual referenced this?

This issue has me intrigued because I have some ID wheels that are about .75 diameter & almost as thick. I don't want to expose the entire face of the wheel to the bore. I was wondering if I should dress it with some relief clearance (left sketch). But somewhere in my travels I thought someone mentioned to dress the stone conventionally, but then slightly angle the TPG assembly so it has a leading edge effect (center sketch). This would seem like a much more fragile edge though? But maybe a 'reduced' dressing at the angle would accomplish the desired result (right sketch)? Hopefully my description makes sense. Maybe someone with more grinding experience can comment before I shoot my eye out.
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I believe you are correct with your sketches , as I remember reading in one manual to do just what you drew so as to have a narrow dressed edge doing the grinding. This only requires a slight angle, maybe 10 degrees, as long as there is room in the I.D. On an O.D. There is more room and this is easier. I have little experience doing this type of grinding and what I do have was over thirty years ago. It seems I still have a fair amount of work to do before my grinder is complete , but I hope to be experimenting with it soon. There are so many projects I got going , I move from one to the next as I get parts or materials. I'm usually working on a half dozen projects simultaneously .
 
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