I wanted to find out if others are using a hammer to keep the back of the chisel flat.
I started doing this a couple of years ago and have had to back off a bit as I finally cracked a blade or two. Basically I use a ball peen hammer just behind the bevel of the chisel to push the edge down a bit. Then the back of the chisel sharpens faster.... I'll put a photo up of the chisel, the hammer and the anvil to give a better idea.
Just wanting to share and see if other are doing this, or what folks are doing to keep back of chisel flat.

Hi Mark.

I have never herd of any body doing this. I would imagine that any chisel that has been tempered or one with a laminated and hardened back is not going to like being stretched out in that manner. I flatten the back of my chisels on a rough diamond plate they are expensive but they cut quickly.
Nice anvil.

kfhines

actually, I heard about the technique from a coworker who has some japanese connections. The japanese chisels stretch out quite easily and the older laminated north american framing chisels also stretch out with relatively easy tapping. It's the Barr that's tough to move.
Do you not find that you are doing a lot of lapping just to get the tiny bit behind the edge?

Yes, but not very often unless nick or chip the edge.

Well today I went to try to sharpen the old Witherby Chisels (2"&1.5"). I put a straight edge up against the 2" and over the 5.5 inch length of the blade, it's bowed just over 1/16th of an inch. Thus I am considering this technique. I'm not sure whether to go at it with a ballpene hammer or use my hydraulic press?

I have a Barr slick that has developed s slight 'rounding over' at the very edge of the back. I have thought of trying to tap it out to renew the flatness. I know this is more common with the hollow-ground backs of Japanese chisels because the edge eventually gets sharpened down to the hollow. I'm not sure it makes sense to lap the entire large surface of the back of a slick to eliminate the rounding over at the tip. Maybe I'll contact Barr to get his input. Perhaps I can send it to him to flatten
I also have some antique chisels, among them a Witherby. There is a similar arch (described above) to the backs some of these chisels. My thought is that, rather than straightening/flattening the entire back, I might try to flatten the last inch or two to get a good edge and live with, or possibly use, the curve in the back to suit specific situations. Keep a different chisel for the times when a long, flat back is the right tool. The curved back is often seen in old slicks and can definitely be used to your advantage in certain situations.
Great topic! We're all looking for the fastest, most efficient way to maintain our edge tools.

The more I use this technique, the more I like it. Do remember, however, that I spent a lot of years as a farmer... I have moved down to a lighter ball peen and take about twice as long tapping now. I try to keep the back flat on the anvil as I tap, it's not about bending the chisel tip over, it's about spreading out the steel on the bevel side. A flat back is the only way for me.

Thank you. I'm going to go try it now (with the ball peen). I've got 1.25 inch steel blocks that I use on my press and I think I'll take one and put it on my steady heavy steel welding bench and give it a try.

I think that the warping may be a product of the geometry of the chisel and how the stresses will want to pull it in different directions. Similar stresses that happen in timbers also seem to happen in steel. I have seen a 1/16 of an inch of difference at the base of a blade make the tip want to warp out more than 1/8".... stresses are neat stuff. If you want to make straightening easier, you can heat it up to 400 in the oven and then tap it while it's hot. It will be a little less likely to crack or chip.

When you start heating things, you can open up a whole can of worms.400 is in the tempering range, if you are going to go that far, you could just reforge the end and retemper, seems to be a lot of work to me. I personally have had good luck wiht my DMT stones to flatten out the back.


Dave