Bog's picture in another thread triggered an idea... a toolpost grinder looks a lot like the headstock and motor of the Taig lathe or mill mounted up on the toolpost of a larger lathe. The usual Dremel/Proxon-as-TPG issues of poor runout and poor thrust-bearings won't apply but the bearings are likely only happy to 10K or 15K RPM. Is that in the range of TPGs? Any other issues (beyond dust control)?
Thinking about ersatz toolpost grinders
- Thread starter shred
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Lew_Merrick_PE
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shred said:
As usual, the answer is, "It depends on what you are doing." I am currently using a TPG made from ø.375 shafting (with collars and a left-hand thread screw) that holds a stack of 3 inch cut-off wheels. The motor for it is a 1/15 HP sewing machine motor using a rheostat to vary the secondary coil voltages. I believe I spent somewhere in the $20 range for all the components. My next "rebuild" of it will add a vacuum cleaner support. The "key" is to get "deep groove" bearings for the spindle. I found a set of ABEC 5 bearings at the local scrap yard for dirt cheap. It's wonderful for OD grinding (about 90% of my TPG work).
The advantage of this approach is that I can use a single (1/16 inch thick) cut-off wheel when I need to cut-off something hard. I use a diamond dresser to face off a stack (rarely more than four) of the cut-off wheels before I start the cut. I added a bolt-on dresser tool holder and linear slide as my first modification to the unit.
Shred,
You normally have two speeds on a TPG, one for external, the other for internal. Internal usually runs a lot faster.
I really depends on what you are using to cut with, some mounted stones allows you to get upwards of 50K RPM, whereas a 4" spindle mounted wheel, I wouldn't like to use much above 8 to 10K RPM.
I re motored mine a few years back, and can't remember what the spindle speeds were, but I did make a slight larger curved top dual pulley for the motor to counteract the difference in speed between old and new. The old motor rotated at 16K.
I can tacho my two spindle speeds if that will help.
Or if you are flush, LMS do a nice range of ready made ones.
John
You normally have two speeds on a TPG, one for external, the other for internal. Internal usually runs a lot faster.
I really depends on what you are using to cut with, some mounted stones allows you to get upwards of 50K RPM, whereas a 4" spindle mounted wheel, I wouldn't like to use much above 8 to 10K RPM.
I re motored mine a few years back, and can't remember what the spindle speeds were, but I did make a slight larger curved top dual pulley for the motor to counteract the difference in speed between old and new. The old motor rotated at 16K.
I can tacho my two spindle speeds if that will help.
Or if you are flush, LMS do a nice range of ready made ones.
John
