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Dumore tool post grinder for SB heavy 10

pghlost

Plastic
Joined
Nov 16, 2017
What I am I missing in the second sentence?


From Dumore instructions:




External grinding is done with the work rotating in the same direction as the grinding wheel, while internal grinding is done with the work rotating in the opposite direction. In both cases, the result is the contact faces of the work and wheel moving in opposite directions, thus maximizing cutting action.

pghlost
 
Makes sense to me. The usual arrangement is the grinder spindle is pointing left and rotating CCW when viewed from the end. A big external wheel will be traveling down at the contact point, so the lathe needs to be running backwards so the work is moving opposite. With the same setup and a small internal wheel, cutting on the close side of an ID, the lathe runs forward. In the first case you're cutting on the far side of the wheel. In the second case you're cutting on the near side of the wheel. Thus the need to reverse the lathe spindle.
 
What I am I missing in the second sentence?


From Dumore instructions:




External grinding is done with the work rotating in the same direction as the grinding wheel, while internal grinding is done with the work rotating in the opposite direction. In both cases, the result is the contact faces of the work and wheel moving in opposite directions, thus maximizing cutting action.

pghlost

What you are missing is probably the import of the FIRST sentence.

Try this:

- lathe is rotating the work counterclockwise. Surface of the OD that the wheel will contact is moving downward, taking the toolpost as fixed reference point.

- grinder is rotating its wheel counterclockwise as well. Surface of the side of the wheel that will contact the work is moving upward, taking that same toolpost as fixed reference point.

Extrapolate respective surfaces and which side of the wheel is in-contact to an ID bore.

CAVEAT: Grinders can be back-mounted. ID's can be ground on the back up-curve. Both players are reversible.

That's why Dumore stated the GOAL of maintaining opposite directions, regardless.

There is a bit more to it, given that the grinder's wheel is nearly always far faster moving than the work.

Rotating such that gravity's UPSIDE surfaces are converging rather than departing would increase the possibility of debris being pinched and wedged before gravity and centrifugal force could fling it out of harm's way.

If grokking that is still "not convenient", to use the Chinese excuse?

Peddle the Dumore!!!

:)
 
I know how to use it, and been grinding pieces in opposite direction.
It was in my senior moment that I decided to look at the directions
after all these years, and that line baffled me (easy these days).

O.K. what I typing?

pghlost
 
I know how to use it, and been grinding pieces in opposite direction.
It was in my senior moment that I decided to look at the directions
after all these years, and that line baffled me (easy these days).

O.K. what I typing?

pghlost

Kinda scary to read manufacturer's instructions. The seniour moment was in forgetting why we just don't do that!

:)
 
It was in my senior moment that I decided to look at the directions
after all these years, and that line baffled me (easy these days).pghlost
It's kinda like after riding motorcycles for decades, I looked at a motorcycle operators manual and it said...To turn, lean the motor-cycle and press on the handgrip in the direction of the turn. That confused me to the point I had to go sit on my bike and see. That's something I picked up when I was five years old and learned to ride a bicycle, but never thought about. Reading it in print, for some reason, gave me a brain cramp.
 
I don't think it matters a hill of beans.. the 300 or few hundred lathe speed doesn't make much difference to the perhaps
3400 or so speed of the OD wheel or the perhaps 25,000 rpm of an ID wheel.More to do with the way the sparks travel and how rigid the set up might be to grinding forces going one way or the other..
But do agree with go with directions and the way wheel hub threads go on, or not spin off.

One might say climb grinding and plane grinding, that can make a difference..holding the part tight to the driving forces perhaps a lathe dog..
going the way the wheel hub nut tightens..
Grinding into or away from a material that might fracture like a carbide sharp edge.
Grinding into something very hard so the lead edge takes up all the slack or deflection in a machine or set-up, so may have a roll bevel into the lead grind so choosing the best place for that in an interrupted grind...

qt:[External grinding is done with the work rotating in the same direction as the grinding wheel,] that would be conventional grinding not climb grinding

Guess one might think what direction might lose the wheel nut, what direction might loosen the part or even the chuck..where do you want the sparks to go.
 








 
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