Planishing hammer/hammer for straightening saw blades

[Adrian Ponik]

Over the last year or so I've managed to get a small collection of hand saws (only 5, I said it was small...), and all of them have been decidedly on the cheaper end. I've gotten decently good at cleaning up the plate and refinishing the totes, but 3 of the saws have slight curves and one has a little kink in it. I've read Bob Smalser's and several other articles on straightening a saw plate and I think I'd like to give it a go.

Everything I've read talks about the hammers having a slightly convex face. I understand this, but I'm struggling to figure out how to find or make such a hammer. It seems like a hefty hammer would be beneficial (ie just let the weight of the hammer do the work) but finding one with a curved face as thus far eluded me. Any suggestions? What about a steel hammer vs brass? If I were to try to make one, how much of a curve should be given to the face and how would you go about doing it? Thanks

[Shawn Pixley]

I'll offer two responses neither directly relevant to saws. For blacksmithing, I take various hammers and dress them with grinders, files and then polishing medium. These then will not transfer marks to hot steel. After which, these are never used on cold steel.

My wife has a large number of hammers. Some of these are plainishing for copper / silver. She buys hammers and dresses them out herself.

My advice, buy a hammer from Harbor Freight and take a file to it to round the head to the needed profile. These aren't rare or expensive hammers, so you are unlikely to ruin it. I polish to 220 grit.

I have never sharpened or worked on a saw so I my advice is pretty naive. I might go for a broad faced, double headed small sledge. To avoid leaving marks, you'll want to dress and polish the anvil or surface you are pounding against.

[Ryan Mooney]

I've straightened a handful of saw old plates, not very many so clearly no expert and take this for what that's worth..

I used a fairly small ball-peen hammer (maybe 3oz or less - haven't weighed it, its an old one I got at a yard sale and cleaned up and put a new handle on) and used the very slightly rounded side (not the ball side). It doesn't really need a lot of curve, just a smidge seems to work. A lot of light small blows are less likely to over do the fix or cause other problems than a few heavy blows. You want to just tap tap tap along the line you want to re-curve and doing 3-5 (or more 6, 8, 10 in some cases depending on how the curve of the wave goes) overlapping lines is pretty much required to get it back to straight.

For the slight curves (and start there - kinks are a lot harder) it take surprisingly small amounts of hammer work to move the plate quite a bit. The first couple I over did it and had to come back from the other side. Since then I've taken a lighter hand and its been easier to hit the mark.

For the anvil, while I wish I had a nicer one, the lee valley small anvil (http://www.leevalley.com/US/wood/page.aspx?p=69331&cat=1,43456,43465) works pretty well (although I wish the horn was polished, its basically useless as it is except for some very rough forming) - before I had that I have a decent vise with an anvil on the back but I don't really like to bang on it to much because .. well decent vise :D It works a bit better if you fill it with something (concrete or better epoxy and some sort of metal fill). Its not a "real" anvil (i.e. don't expect to do any significant forging on it) but for stuff like this its a pretty good deal - especially during free shipping :D

[John Vernier]

I agree that you should shape hammer faces to suit your own needs. Very few new hammers are sold with decently shaped faces - I see a lot of sharp edges, crudely bevelled rather than rounded over. I've reground plenty of hammers and I find I can form a gentle crown with a few passes against a stationary belt sander - use a lot of wrist action to keep the face rolling and rotating. check your progress a lot, the more you grind the tighter the curve tends to get. Make sure there is no sawdust around to ignite with your sparks, but you should be able to get the shape you want quickly enough to avoid heating the hammer head much at all. Then polish with wet-dry sandpaper in the palm of your hand, or buff the face if you have a buffing wheel available.

[Bill Rhodus]

All sawmills have a saw shop outfitted with a variety of saw hammers for flattening saws. I've never see. A round head in one of these shops; they are all square or rectangular shaped. May be an old saw filer that will sell his hammers; post on craigslist.

[george wilson]

I think you should first try pouring boiling hot water over the bent area of the saw,then bending it in the opposite direction to straighten it out. This method worked for us (Jon and I) in the toolmaker's shop. The boiling water temp is way far below the tempering temperature of the spring steel in the saw blade-about 500 degrees cooler at the least.

I think it will prove very easy to ruin a saw if you are not experienced in what you're doing. Try the hot water first. It can at least do no harm. We at first bought spring steel that came in a coil,and the blades would not get straight until we figured out an easy way to deal with the problem.'

This recommendation is not for sharp kinks,just for gentle curves. And,if you are talking about back saws,I straightened many,many by clamping the front edge of the blade in a vise,and tapping the nose of the back in the direction of the handle. This jerks the blade straight. If the blade still has a mild curve in it,adjust a crescent wrench to fit over the back. Gently twist the back in a corkscrew fashion JUST A LITTLE. Observe the tooth line of the saw(sight down the teeth). You will soon get the tooth line straight. Do not try CURVING the back until the tooth line is straight. A curved back is unsightly,and un necessary. A slight twisting of the back will not even be noticeable. We made dozens of saws of all sizes and straightened them with the described method.

[Dale Coons]

Thanks for this thread, I've got a related question--If one does need to tap, on which side do you do it? The side the blade curves toward or the side it curves away from?

[Noah Wagener]

Thanks for this thread, I've got a related question--If one does need to tap, on which side do you do it? The side the blade curves toward or the side it curves away from?


both. http://www.wkfinetools.com/contrib/bSmalser/strSawBlade/strSawBlade1.asp