$20 cast iron lap for 1µ diamond

[bill tindall]

WD40 on cast iron with diamond powder or paste works fine. 100 micron diamond does not embed well in my experience. Those are big rocks. I have had better success with the coarser grits on acrylic plastic and water lube. Cast iron plates will last a long time with the more modest sizes of diamond, for example 15 micron.

I used dry powder for a while but found it inconvenient.

[Noah Wagener]

Thanks.

They have been sold out of those kanaban at Tools for Working Wood for awhile so i went the old plane sole route.

The diamonds did not really imbed but somehow they did stick into my chisels. I can not upload the pics but they look like diamond hones.

Is mdf or hardwood a bad idea to try? I see people use real fine pastes on those substrates for stropping. What type of thing should i look for as an acrylic plastic plate?

every old chisel and plane iron i get is recessed right by the edge to an eighth back and humped to match the old dished stones.

Steve, you mentioned above that glass is not a good reference plate. Almost every book i read recommends it as a lapping plate. How is it assumed flat and why do you disagree? I got a 3/8 thick piece from my neighbor to flatten this plane sole lapping plate but it was visibly out of flat. It was a furniture part so i assumed it is tempered. Does tempering potentially spoil the flatness? I was told all glass is float so i do not know what else to look for in terms of glass type as a spotting plate.

[Steve Voigt]

Thanks.

Steve, you mentioned above that glass is not a good reference plate. Almost every book i read recommends it as a lapping plate. How is it assumed flat and why do you disagree? I got a 3/8 thick piece from my neighbor to flatten this plane sole lapping plate but it was visibly out of flat. It was a furniture part so i assumed it is tempered. Does tempering potentially spoil the flatness? I was told all glass is float so i do not know what else to look for in terms of glass type as a spotting plate.

Er, I'm not finding where I said that. Maybe another Steve.
But anyway, if you want a reference plate, something you can rely on as the highest standard for flatness in your shop, then glass is not it, unless you get lucky. Get a granite surface plate, or maybe an old piece of cast iron from a machine, if you've got a way to check it for flatness.
On the other hand, if you want a lapping plate that you are going use to flatten old planes irons and chisels on, glass should work fine. Just check with a straight edge and make sure it's not bowed.
Now, that's if you're using the glass as a surface to stick sanding rolls or belts to. You don't want to use SiC or diamonds on glass to flatten tool steel, because the glass is harder than the steel. SiC on glass works great for flattening oilstones, because the stones are harder. For tool steel, you need something softer. Like cast iron.
You asked about mdf or wood as a substrate. Too soft. But plexiglass (acrylic sheet) is a good alternative. Your local glass shop should have some, won't cost too much.

[Greg Portland]

Don't use the surface plate as a lapping surface but to reveal the high spots on the anvil face for scraping as demonstrated in this very old training film. Make a scraper from an old file and buy a tube of prussian blue oil paint, Dykem or equivalent.

Scraping—Why and How, by Ron Gerlach, short article with photographs

The Art of Hand Scraping, by Robert R. Wade

Scraping a wooden block plane, a video. Same idea but on wood instead of iron.

The ultimate manual of scraping: Machine Tool Reconditioning and Applications of Hand Scraping Try libraries

I found this video to be helpful: https://www.youtube.com/watch?v=nOJrhrne80s

[Noah Wagener]

I think you were commenting on the video of the guy scraping a wooden plane and said he did not have a proper reference plate. Just about every book i have read suggests using a piece of "float" glass with spray adhesive to lap the planes themselves, not the irons. I was just curious how glass is presumed to be flat. The piece i got you could see was out of flat without a straight edge. I thought i could use it to check my planes but i'll just stick to winding sticks and straight edges. I gave up on metal soled planes.

I tried SiC before and was euphoric for about five seconds and then it completely lost its cutting action. I may have to retry it as i see it is only 10 dollars a pound. I think these diamonds i got are too big but i can not afford to experiment with smaller ones.

I do not know how people got things done before these modern abrasives. Well, i do not know how people get things done with them either. I spent 3 hours hollow grinding a chisel back and lapping it with a 1k stone. My grinder is foot powered and i thought i could use the side of the stone but the sides of those Norton 3 x wheels polish. Very odd for 80 grit stone.