Tool post grinder design

[DPittman]

I'm trying to get my head around some things about how I would make a tool post grinder for my lathe and need help from those smarter than I.

Should a tpg be able to pivot independent of the compound slide? When they are mounted on a tool post or t bolt they are able to swivel around that (hence the name I guess) but I'm wondering about mounting the grinder stationary to the compound slide itself and just using the swivel of the compound itself.
I can't see a problem with that but I suspect I am missing something that will seem simple once someone explains it to me.

 

[140mower]

Consider it to be the same as your toolpost, you want to be able to "square" up to the work, while still being able to work an angle with the compound.... Or that is how I see it. This comes from a guy with a couple grinders and zero practical experience with them.... So, you know, my input my not carry much value.

 

[Ian Moss]

The way I think about it is that I want the axis of the spindle to be parallel to the work I am grinding whether it be cylindrical or a taper. That at least allows for the most economical dressing of the stone. For a cylinder parallel to the lathe axis, I have a diamond point dresser in a right angle holder that I can chuck in my tailstock and dress the grinding stone parallel to the lathe axis. (covering the bed to keep the grit off of course).

 

[DPittman]

Consider it to be the same as your toolpost, you want to be able to "square" up to the work, while still being able to work an angle with the compound.... Or that is how I see it. This comes from a guy with a couple grinders and zero practical experience with them.... So, you know, my input my not carry much value.

Gotcha. That makes perfect sense. I knew I'd be embarrassed with the obvious simplicity of the answer when it was explained to me.

 

[140mower]

Gotcha. That makes perfect sense. I knew I'd be embarrassed with the obvious simplicity of he answer when it was explained to me.

No reason to be embarrassed, I was only 50% confident in my reply....

 

[RobinHood]

Another advantage of leaving the compound in place is that you can “divide the thou”. Using geometry, you can set the compound at a very shallow angle to the lathe Z-axis and infeed in tenths instead of thousands using the compound dial calibration.

Why is that important? Grinding is typically a finishing process. Rarely do you “hog off” material - that’s what turning tools are for. So controlling the minute amounts of infeed accurately is very advantageous when grinding.

 

[DPittman]

Another advantage of leaving the compound in place is that you can “divide the thou”. Using geometry, you can set the compound at a very shallow angle to the lathe Z-axis and infeed in tenths instead of thousands using the compound dial calibration.

Why is that important? Grinding is typically a finishing process. Rarely do you “hog off” material - that’s what turning tools are for. So controlling the minute amounts of infeed accurately is very advantageous when grinding.

Yes my ever changing plans has always included the compound but I was thinking of eliminating the swivel capabilities on top of the compound.

Here are a couple of pictures of two different compound slides I have to work with. The one is a slide I altered to use in my lathe milling attachment and the other is the current slide on the lathe. I have to make a bearing "holder block" for the er20shaft I have and just thinking of some of the ways I could do it.