Recommend me a stone for flattening old chisels

[Lasse Hilbrandt]

Im trying to restore a full set of socket bergs from 1/8" og 2" They all need som work and at the moment im working on flattening the back of the 2" Berg.

Im using adhesive sandpaper on a marple slab which is flat enough, but even though I use 80 grit paper the flattening is really really really slow and I wear down the paper too fast IMO.

I was thinking of trying ceramic stone that won´t dish too easy but it need to be really coarse.

Is it really possible to have a stone that wont dish and being really coarse at the same time ?

I have a Norton 220 waterstone, but it is soft as a piece of soap and useless.

[Doug Hepler]

Lasse

I gave up flattening with sandpaper, although I like it in finer grits for honing.

Consider diamond plates. I use a DMT extra coarse, followed by a DMT coarse. That's approximately 220 grit (60 micron) followed by P320 (45 micron). The extra coarse stone is really aggressive at first and makes some deep scratches but it wears in after a while and then is very durable. You probably know this already but (a) you need to flatten only the area directly behind the edge, say 1/2" to an inch. (b) be very careful not to allow a back bevel on your chisels.

Doug

[lowell holmes]

I use a diamond hone,
https://www.sharpeningsupplies.com/D...RoCoNIQAvD_BwE

It will make short work of it.

[Malcolm Schweizer]

+1 for Diamond plates. I use DMT diasharp. Beware that coarse is REALLY coarse. Get the medium to fine. It works fast and leaves less finish work to do.

[Mark Hennebury]

I use a 1/4" die grinder with a 2" cut-off disk to lightly hollow out the middle, check by occasional lapping on a fine stone. Just stay away from the edges and tip of the chisel. You don't need to remove all of the grinding marks, there is no reason to have the entire back flat and polished, just as long as the outside edges are flat, the Japanese seem to manage quite well with hollow back chisels. I will touch them up on occasion with the die grinder. It's a 100 times faster and easier then lapping all of the back for absolutely no practical benefit at all.

[Lasse Hilbrandt]

Thank you guys. I just ordered the DMT 10" diasharp. I opted for the coarse and hope it smoothes out.

[lowell holmes]

You won't regret it and it will last forever.

[Tom Bender]

In any case you will need the diamond plate to flatten your water stones, once you give up on sandpaper

[Brandon Speaks]

I have a bunch of diamond stones and love them, but if I need to really remove some metal its 80 girt on granite. It is so much faster than the roughest DMT stone. You might go through some paper but it is cheap compared to time. Some windex will revive paper that is pretty caked up, you still go through it fast, but it takes 1/10 of the time of the roughest DMT. I do still love the diamond stones, just dont see them helping with your specific issue.

[Eric Rathhaus]

Another option is foregoing the paper and buying the abrasives loose and grinding directly on granite or your surface. Here's one provider - you can buy 40 grit silicon carbide material: https://www.willbell.com/ATMSupplies/ATM_Supplies.htm

[Tom M King]

If you use loose grit, you might as well use diamonds. I flattened a steel plate on a surface grinder, and use that. I think the steel plate is something like 1/2" x 6" x 18", but don't remember exactly. There are many listings on the auction site for loose diamonds. I forget what grit I bought, but think it was either 60 or 80. It does a really fast job, and hasn't come close to slowing down. I just spray 3.36, or WD40 on it, and leave it sitting until next time.

They go from that to a 300 King, which is a lot different than all the other King stones, but I mostly only use 01. I don't think that stone is much good for fancier metals.

edited to add: I used to use silicon carbide grit, on glass, but found out that I owned a surface grinder, and have a bunch of scrap steel. That sort of mess doesn't go in the woodworking shop though.

[steven c newman]

sanding center.jpg
Do you see that 6" disc on the side? That is what I use to flatten the backs of both chisels and plane iron,,,
flat back.jpg
Does not take very long, either. That shiny "bar" across this iron? Is from the shop light overhead.

Grit on the disc? Have no idea,,,,disc is pretty well worn down....

[Robert Hazelwood]

Your comment on sandpaper is odd to me. If you use 80 grit paper you need to change it often, like every few minutes, so a roll of PSA paper is the most convenient. I have bought all kinds of coarse stones and such trying to do these jobs quickly, and was disappointed with the speed of X-coarse DMT plates. Actually my conclusion was that all coarse stones suck in some way for flattening, either they are too slow or do not stay flat. Fresh out of the box, a new DMT stone might be ok, but it quickly becomes too worn to be efficient for a heavy job.

They are worth having for maintaining other stones, though, and for oddball sharpening jobs that might damage something like a waterstone.

[Jake Rothermel]

I might be one of the few who doesn't care for diamond stones, like, at all. I love the IDEA of them, to be sure; but in practice I've never had one that worked as fast or as well as I felt it should have. Diamond stones, in general, just have never felt right to me. The feedback is entirely different and it's never jived with me. I'm sure they work and the issue is with me & my technique and/or expectations; certainly plenty of craftspersons use and swear by them (and THEY seem to do wonderful work *and* get good results from diamond stones...).

When I left behind abrasive paper, the only grits I kept for sharpening purposes were the lower ones (i.e. 100, etc.) for serious lapping. Yes, I go through a lot of sheets on a really intense lapping job (which, thankfully, is not very often these days), but that's preferable knowing the my substrate is not dishing, uneven, or otherwise not flat. The feeback feels better to me, too; which I never would have thought to be as important as it apparently really is to me.

You might try a coarse Norton Crystolon stone for flattening and/or lapping. They're supposed to be roughly 120 "grit". I've got a medium (180-ish) and it eats metal in a way that's efficient and feels right to me - more like my other arkansas stones. It also stays flatter longer than the few low-grit waterstones I've tried (which I confess, hasn't been many...).

Your mileage, of course, may vary.

-Jake

[Lasse Hilbrandt]

jeeee now im wondering if I pulled the tricker on that DMT to fast..... well time will tell