Surface Grinding A Lapping Plate

[itsme_Bernie]

This thread is part demo, and part request for advice.

Since I got a surface grinder (two now, actually), I've been grinding everything I can get my hands on. Watch out Rover. So I remembered acquiring an old cast iron lapping plate a while back, concerned it was probably out of flat. So I decided to throw it on the surface grinder to bring it back.

Besides knowing not to grind so much away that I lose the grooves for retaining the lapping compound, is there anything that wouldn't be obvious to me about methods to bring this lapping plate back to it's original usefulness, and finish it properly?

For those who want to know, I have ground down almost .005, and look at the pattern that is still not completely true'd up yet!




Bernie

 

[4GSR]

I've never seen a lapping plate that had grooves so close together like yours has. Usually has grooves cut on a diagonal that creates a diamond shape on the surface. The depths are usually around 1/16" deep and spaced about 3/8" apart, depending on the size of the lapping plate.

But anyways, your in the right direction, SG until you get a 100% cleanup.

 

[itsme_Bernie]

I am calling it a lapping plate because I can't imagine what else it could be, the wear pattern with which I discovered it, and because that's what I'M using it for hah hah...
If anyone thinks it is something else, or is a member of a subcategory of lapping plate that would be helpful for me to know, I'm all ears!
So far it has taken me about .010 on each side, slightly different wear patterns, on each side.
Sort of an "L" shape on one side, and perfect circle in the middle on the other. More pics tonight!

 

[chips&more]

I’m with 4sgr, never seen a lapping plate like that before. You would think it would have more surface contact area than grooves for the compound. Like a 95% to 5% ratio or so. That way, the plate would hold up to wear better. I have a lapping plate, the grooves make it kinda look like a checker board. Can’t say that I have used it much. I have several granite surface plates. And have dedicated one of them to stoning. Now that plate gets lots of use. I tape down emery paper to its surface or use the bare granite surface…Good Luck, Dave.

 

[Andre]

Do you plan to cut new grooves into the plate? You could probably dress your wheel to a V by hand the use it to groove the face with light cuts. Looks like by the time you get it flat it'll be smooth.

 

[itsme_Bernie]

Thanks Dave- I have a granite surface as well that I was planning to experiment with emery etc. what is it that you call "stoning"?

 

[itsme_Bernie]

Thanks Andre- and you are correct in that on one side the grooves are barely as deep as they are wide now.
I could use the shaper to deepen the grooves, and then come back to the surface grinder to clean up and smooth the top surface again... Hmmm

 

[itsme_Bernie]

Here are a few more steps, about .0045 (.0015 per pass) ground off between each of the photos