how coarse a stone do I really need?

[dan sherman]

I have seen people recommend everything from 220 grit to 1000 grit, for flattening the back of a plane/chisel, or re-establishing the bevel.


So how low do you go, and why?

[Augusto Orosco]

I have seen people recommend everything from 220 grit to 1000 grit, for flattening the back of a plane/chisel, or re-establishing the bevel.


So how low do you go, and why?

I guess it really depends on what you are trying to flatten. I once made the mistake of trying to 'flatten' the back of the blade that came with my new Lee-Valley BU Jack with a 220 grit water stone. The back ended up looking less polished than when I started (and yes, I was also re-flattening the 220 stone frequently... those suckers get out of flat pretty quickly). I took me a while to get it back to where it was with my 1000 stone. Only when I got to the 4000-8000 grit I noticed some improvement. Newbie mistake

I am sure the case would have been different had I been working with a rusted old blade from a flea market.

[Sean Hughto]

If you need to restore a nicked or chipped blade ( or worse yet, a broken one - never pry with a chisel, for instance ;-)) and don't own a grinder, a 220 stone is nice to have as the thousand will take for-freakin-ever.

[Mark Roderick]

If you're trying to flatten the back of something or re-create a bevel, don't use a waterstone. You'll go crazy trying to keep the stone flat. Instead, glue some sandpaper to a sheet of glass and have to it. Yes, the sandpaper can get "dull" after a while, but that's easy to fix. The key is that it will stay flat forever.

[Doug Shepard]

It all depends on how nasty it is. I've gone as low as 60 grit paper on some real ugly stuff. I always attempt to flatten or redo the bevel with the finest grit I can that will get the job done. But if you check after a minute or so and you're only making contact in a couple of spots, it's going to be a long slow job unless you start getting more agressive. 180 grit sanding screen works pretty well on some of the nastier jobs as it cuts a little faster than sandpaper.

[Wilbur Pan]

I like using waterstones. I really really really really like using waterstones.

But if I need to do some major work, like reestablishing the bevel, or grinding out a nick, I'll use Norton 3X 80 grit attached with some spray adhesive on a granite plate. Not so much for the coarseness of the grit, but for the flatness of the surface. I have yet to find a <1000 grit waterstone that will stay flat for very long.

[dan sherman]

so it sounds like for rough work, it's scary sharp or grinder, because solid diamonds stones aren't flat enough?

[Wilbur Pan]

People have reported issues with the flatness of diamond stones. For me, it's that they start cutting aggressively when new, but after a short while the cutting speed slows down quite a bit.

One other option for rough grinding is to use a cast iron plate with carborundum powder, which is pretty fast, but that's not a real popular option.

[Sean Hughto]

I wouldn't agree with that. These, for example, would work fine:

[Jim Koepke]

My vote is for using sand paper on a flat surface. At this grit, the stone will be more costly than the paper.

My choice is Pressure Sensitive Adhesive backed paper on a 4-1/2 inch wide roll.

Supergrit.com has been a good source for me.

jim

[Mark Roderick]

You got it exactly right.

[Mike Brady]

Sean, you show a photo of two new DMT stones. I have those stones as well as the DMT Dia-Sharp continuous stone in X-Coarse grit. Technically, you are correct that any of those stones in the coarser grits will easily, when new, establish a new primary bevel on a plane blade. After one or two honings of, say, a Lie-Nielsen low-angle jack plane iron, you might come to a different conclusion. The cutting ability of diamond stones degrades very rapidly. I would estimate that to put a new bevel on on the above blade (not a micro bevel) would take at an hour of constant lapping on a extra coarse diamond stone that is not brand new. Granted, from that point, it is then easy to put a tiny microbevel on and get back to work. I would agree with the other poster that 80 grit 3X Norton paper is much more up to the task.

[Sean Hughto]

Here's my experience: If I need to change a bevel or remove any serious amounts of metal, I use my grinder(s) (yeah, I have more than one because I was still learning the "buy the best once" lesson), so, no, I'm not routinely using my Duosharp to take 10 degrees of steel off a 2" wide blade. I do have a coarse/extra coarse Duo sharp, however, and use it routinely to start to flatten backs and when rehabbing vintage chisels and the like. This is my second one, because after about 3 years of use, my first had indeed lost some aggressiveness. In short, the Duosharp:

- would not be my first choice to remove serious amounts of steel
- it would however work and be a lot faster than a 1000 grit stone/plate as suggested in the original post
- does wear out like most other abrasives of any sort
- but does not wear out at anywhere near the rate you suggest

YMMV

[george wilson]

Sean,our millwork shop used your same stones,and they were not particularly flat. I had to choose a steel backed diamond stone from several to find a flat one. It's a little tricky to tell which stones are the flattest,because the steel rule sits on top of the diamonds,showing light under the straight edge all across the stone.

[Sean Hughto]

I tend to use Norton Water stones for most chisel and plane iron sharpening (1000, 4000, 8000) - and regularly flatten those. I have only the coarse/extra coarse Duo sharp for prelimianry shaping and back flattening. I've never even checked its flatness in any way, though unless it was grossly out of flat, I think it would still do okay on the coarse work I ask of it to get the steel ready for the finer stones. I've never used the DMT metal plate stones. I assumed I wouldn't like the fact that their abrassive can't be refreshed by flattening/ exposing the next layer of bound grit as with oil and waterstones. Good to know that they aren't flat either!