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Down and dirty on fine surface finishes with a tool post grinder

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Mutt

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Just looking for some opinions

1.145" diameter, 3" long, steel shafting, 52Rc, grind to 1.125"
Themac J3 Tool post grinder installed , 2" AO 220 grit wheel for rough grinding, 800 rpm lathe spindle speed ( is this spindle speed proper?)
Grinder only came with 2 of the 4 pulleys (#1 & 4 used with very small diameter wheels or reversed and used with 2-3" wheels)

Optimum carriage speed for roughing? This 220 wheel easily takes off .004 in a single pass, no heat even without coolant
Optimum carriage speed for finishing?
Optimum grit / material for high surface finish?
600 diamond or 1200 diamond ?
 

BROCKWOOD

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I'd like to see pics of your set up!
 

BROCKWOOD

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Thanks Mutt. Just mounts right up to a proper compound! You can still get parts, like wheels for your grinder from TheMac. McConnell sold the company a couple of years back & last I heard they're still going.

I have 2 TheMacs: a J2A1 & a J4. My benchtop lathe compound is the centerpost type. I have adapted a QCTP to it though. Might make an adaptor or go ahead & spring for the right Monarch. Either way, I am looking forward to putting these grinders to work!

I have to ask, though, how do you go about cleaning your ways without fear? I'd have to cover them up, since I don't know how to prevent abnormal wear.

J2A1 with Rosewood case:
THEBOX 017.jpg

J4:
01.jpg

Or perhaps you could make the wheels. Whatever specs &/or info you need I'll gladly provide. When I went to order parts, I referenced material the old man had forgotten about (before he retired). Great design!
 

Mutt

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I don't move the carriage until I finished the grinding. Then just clean everything up with a shop vac and paper towels.
If this was a Monarch 10EE .. I would be concerned about it, but it's just a 20 year old Grizzly. I am looking for a nice Clausing 14-40.
 

benmychree

John York
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The grinding wheel is way too fine, the spindle speed way too fast, and one NEVER uses diamond wheels on carbon steel, it is destructive to the wheels.
 

Mutt

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Ok, so all is wrong, what is correct?
Why would a 36 grit stone produce a finer finish than a 220 grit stone?
What are diamond stones used on?
 

benmychree

John York
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Fine stones are not much used in cylindrical grinding (and I have done a lot of it) actually 36 grit is about right, 60 grit would be considered as medium and perhaps 120 is a fine grit; when properly dressed, coarse stones cut with a fine finish and grind cool. I'd think about 200 RPM would be about right for the spindle. Generally cylindrical grinding is done with a fast travel and shallow depth of cut. Grinding wheel speed makes a big difference in the behavior of the wheel, too fast and the wheel glazes over and "sings", like the grade is too hard, slowing down makes it act softer and cut effectively. The art of grinding is somewhat a "seat of the pants" thing. Diamond wheels are for grinding carbide and ceramics.
 

Mutt

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OK. I am pretty confident of the speed of the grinder, as it's on the speed that is recommended by the manufacturer for a 2"-3" wheel. So the next time I have it out, I will try the lathe spindle speed of 200 and get a 60 grit stone. So what speed would be good for the carriage?
 
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