Inexpensive diamond laps.

[Rorschach]

Thought I would share this info for anyone looking for cheap solution for grinding carbide tools.
I just got myself a set of 6" diamond laps from ebay, it was £11.99 for a set of 3 (240, 600, 3000), other sets are available with different grits. You can buy them from china for a few pounds less but I was happy to pay a little extra and got them within 3 days.

The plates are 6" in diameter, about 1mm thick and have a 1/2" arbour hole in the middle all of mine were very flat or rather flat enough and fitting them to an arbour will pull them flat anyway. I made a simple arbour for them that fits in my lathe collet chuck so they run perfectly true and I can adjust the speed or run them in reverse depending on the tool geometry. The arbour hole in the plates was a nice snug fit on a 1/2" bench grinder shaft if you want to go down that route, I plan to use them at a very slow speed maybe with a little water bath to keep the tools cool and stop carbide dust going everywhere.

The diamond coating feels well adhered and very consistent, grinding marks on my test piece were very consistent and smooth. For the money I am incredibly happy.

Happy to link if allowed but if you search ebay for diamond lapping disc or plate you should find them, between £9-12 for a set of 3 plates.
Finally I have a faster and more accurate way to sharpen my carbide tools, doing it by hand on a diamond hone was getting rather dull!

 

[Bodgers]

The question will be how long they last. My faithful two sided diamond plate was only £25, but after only a year of light use on a few chisels and my block plane its basically finished on the 400 side...


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[Rorschach]

Well they don't strip immediately I can say that, I carried out a quite heavy grinding session this morning and they all held up well. The 240 of course lost it's rough feel right away as any coarse diamond hone does but it still cut fast. The 600 and 3000 seem unaffected. Put a razor sharp edge on my turning tool.

I have added a picture of the setup I was using. The water bath is a must in my opinion, there was a thick layer of carbide sludge by the time I was done, I don't fancy that being airborne in the shop or around the lathe ways. I turned the discs at 77rpm, might go a little faster next time but 200rpm was too fast and started spraying water everywhere. No dust got into the air though and as I was grinding I could watch it flowing off the disc into the water.

Oh and of course even if they don't last a super long time, they were only £4 each, that's the cost of some angle grinder discs that only last a few minutes, if I get a few hours worth of grinding out of each disc I will consider it money well spent.