Thread: Flattening really bellied chisels

When the backs are round like that it is going to take forever to hand lap them down to flat.
You need help.
In the past I have used both a belt sander mounted upside down on the bench, and a linisher. Both of these won't get the back flat and you will still have to go through the flattening process as you do now, however it gives you a good walk up start and saves hours of tedium.
You have to be careful not to rock the chisel sideways as you do this or it doesn't get you very far.

PS I am assuming in this, that the round is across the back of the blade and not down its length

How flat does it need to be?

The greatest depth you're likely to cut into?

I assume that the bow is lengthways on the shaft and is convex when seen from the bottom?

Originally Posted by snafuspyramid

Finally, I can't see any good reason not to establish the bevel on the other side instead (except that it would take bloody forever).

Any ideas?

That sounds like a good plan. It might be a shorter "forever" option that flattening!

A pic would kind of help!

Well, it must have been bent to get it into that shape, probably levering something?

How hard is the steel? If not brittle you could wack it back into flat. If it was mine, and worth the trouble (which I doubt), I would anneal the steel with heat, flatten it with a hammer, then re-temper the blade.

Regards from Perth

Derek

I once tried as follows on a used & abused chisel with the same problem:
using an angle grinder in a vice, with a disc like this

and VERY CAREFULLY sliding the back toward the center.

I noticed a tendency to round the side angles, but the diamond stone fixed that later.

Ok, don't wear gloves, pay extreme attention, this is not a toy, don't try this at home.

Grab a ball pein hammer, lay the chisel belly up and give it a really smart whack in the guts.

I haven't done this on a chisel before, but at 38mm your getting close to wide enough that it may deform across the width. With a narrower chisel I imagine it would tend to want to deform length ways.

... try everything else first perhaps

I'm still trying, using the Sigma #120 and #400.

It's taken me many, many hours and I'm still a long way off, with many more to do.

Unless I can figure out some mechanized way of doing this bulk material removal (I was thinking maybe using the side of a white wheel on a hand-cranked grinder) I think I should consider saving up for a diamond stone.

What's the longest time you've had to spend on a really banged-up chisel using a course diamond plate? Can I expect a significant increase in speed over course ceramic stones?

Alternatively, might large grit diamond paste on hardwood do the trick, assuming it were planed flat enough?

I would have flagged it away long before then. Some things just aren't worth the effort really.

Just buy some new ones?

I would prefer to use a means of some sort of grinder that would take off metal very quickly. Then once you have it sort of flat continue on with the rest of what needs to be done.

It's not just this one I'm working on - otherwise I would just chuck it and find another.

It turns out that an 8" DMT Diasharp is only $65. I'd also like something to flatten my waterstones other than SiC on glass, assuming that the extra-course wouldn't do any harm to my 6000 grit King.

Anyone have any thoughts on the side of the wheel on hand grinder? I know some people do the same with a Tormek. It would be a terrible idea on a high-speed grinder, of course. Assuming I can dress the surface...

EDIT: My mistake, the extra-course 8" whetstone I had in mind is $79 from Carbatec.

Do you have a pedestal drill? Or an old hand drill mountable on a bench with VS?

Originally Posted by rsser

Do you have a pedestal drill? Or an old hand drill mountable on a bench with VS?

Cryptic.

I have a Makita powered drill and an old-school, cast iron drill stand?

Cut a 150mm diameter disc of sealed 3/4 MDF or melamine, mount in drill press via a home-made bolt arbour, apply some PSA SiC discs, run at c. 100 rpm. (See thread on 'flattening backs' in Sharpening for more).

Better than the side of a Tormek wheel as once glazed the wheel is difficult to clean.

If you've got more to do and the money, search for Worksharp 3000 discs ... they come in #80 and #120 in Norton 3X (seeded gel AlOx) (but only in mixed grit packs) that outperform the SiC. In Aus they work out at around $5-$6 a disc. For normal lapping of say a 1" chisel a disc will last for several.

Snafu

Short of chucking the chisel away, I suggest you get yourself a Dremel and a couple of grinding disks
working carefully grind out the belly -- much of the belly can be tapped out with a hammer, but you need an anvil