Straightening a bent sawblade

[TobyC]

I think the hammer does most of the work, along with technique/experience. I would use a flat anvil and go for it. Keep us posted.

Toby

 

[TobyC]

I realize this is an old thread, but I was reading this yesterday and thought you might find it useful in the future. Look on page 421 here, http://www.wkfinetools.com/hUK/Holt...50-TurningAndMechanicalManipulation-Vol.1.pdf he's speaking of bending vs. stretching when using a wood anvil and 'hard' anvil.

Toby

 

[woodbloke]

Toby, I'm sorry, but I don't have any device that takes digital pictures. Some years ago, I made a decision not to spend my hard-earned on things that would likely be supeceded in about a year or two; the camera/phone/computer/i-everything market still seems not to have settled down, so I probably won't bother for a year or two yet. (Computers are bad enough - this one is a mere three years old, and is creaking already.)

That surprises me :shock: I agree about the digital market thingie but I think from a personal perspective, it's a bit of a mind set, if you follow. I buy a camera (for example I use a Nikon D60) which takes perfectly acceptable pics and I know that it's been superseded by a later model which is supposed to be 'better' but as long as my D60 keeps on taking good pics, I'm happy with it...I'll only replace it when it breaks. To progress the discussion a little further, does Mrs CC use an automatic washing machine (which contains a digital processor) or a wash-tub and mangle? What sort of telly do you watch because all the newer flat screen ones contain digital processors?
The camera/phone market situation is a continually ongoing WIP and is never going to 'settle down' so IMO it's probably best to buy something and get the full benefit from the technology, knowing that in 12 months it'll be out of date - Rob

 

[Cheshirechappie]

I realize this is an old thread, but I was reading this yesterday and thought you might find it useful in the future. Look on page 421 here, http://www.wkfinetools.com/hUK/Holt...50-TurningAndMechanicalManipulation-Vol.1.pdf he's speaking of bending vs. stretching when using a wood anvil and 'hard' anvil.

Toby

Thanks for the post, Toby!

By pure coincidence, I came across a note in Holtz II while looking up something concerning The Hill late Howel backsaw thread a few days ago. The section in Holtz I is probably the most useful I've read so far; it certainly clears up some of the confusion sown by other sources of information.

To roughly summarise what it says, if you have a sawblade with slight bulges in it, you need a hard, flat anvil and a heavyish hammer with a slightly rounded face. You hammer the straight bits of blade between the bulges to stretch the metal on those parts - don't hammer the bulge, because the metal is already stretched ('loose' is the term he uses) in these parts, so hammering and stretching it more will make things worse. If you have a blade with an even curve in it, like it's a segment of a cylinder, use a wooden block and a small retangular-faced hammer. Hold the blade concave side down, and hammer in line with what would be the cylinder's length, with the long axis of the hammer's face in this line also. In effect, you're trying to induce a slight bend in the blade opposing the one you're trying to eliminate. Lots of slight bends along the 'cylinder' will bend it straight. The wood block has just enough give to allow the overbend and springback that anyone familiar with sheet-metal bending will be aware of. I think that's what Mark Harrell is doing in the photos above.

He does, however, say that getting good results takes practice - or at any rate, getting good results quickly and consistently takes practice. It should be possible to get acceptable results with patience and frequent checking of progress. One problem is knowing the weight of blow to use - probably best to start light, and when nothing happens, increase weight a bit at a time, checking after each increase in weight, until progress is made.

It's a text well worth reading in full, though. His description is much more extensive than my summary.

 

[bugbear]

Saw texts from my bookmarks:

H W Holly, 1864/1882 @toolemera:
http://www.toolemera.com/bkpdf/hollysaw1864_82BK.pdf

Fred T Hodgson, 1888/1909 @toolemera
http://www.toolemera.com/bkpdf/hodgsonhandsaw1909bk.pdf

Grimshaw on Saws, 1880, hosted at University of California:
http://www.archive.org/details/sawshist ... 00grimrich

BugBear

 

[TobyC]

I go to "Grimshaw on Saws, 1882", and other Robert Grimshaw and Charles Holtzapffel here http://www.wkfinetools.com/mLibrary/mLibrary_index-1.asp, which was already referred to by AndyT.

Toby

 

[JohnPW]

I've got a bent Taylor Brothers saw. The back edge is curved in one direction but the toothed edge is bent one way then another. Is it possible to straighten this saw?

 

[MIGNAL]

Probably. I straightened one yesterday that had two kinks or bends in the blade, one turned left the other turned right. I use a metal anvil and a cheap Chinese hammer that I annealed and then I highly polished the domed face. I guess it's turned it into a planishing hammer. You have to be careful because you can tap away only to find that you have moved the bend to another spot further up or further down the saw plate. I didn't get it perfectly straight but it was a whole lot better than it was. Turned it a usable saw and I doubt that the slight waviness will affect the cut.

 

[Cottonwood]

The man who taught me to file saws showed me an intriguing method to remmove bends and moderate kinks (but not severe dents) He held the saw by the handle with the right hand as normal, and the toe of the saw in the left, then without further ado whaaaanng, bent the 2 hands together in the manner of a ballon artist until he had a perfect loop. I'm thinking oooh if that springs into your face your in trouuble.... :shock: Then he let it go, then repeated onlyy bending in the opposite direction. Amazingly the bends had gone.

 

[Corneel]

Thanks for digging out this old thread. I've got some reading and them some experimenting to do.

 

[TobyC]

Thanks for digging out this old thread. I've got some reading and them some experimenting to do.

Make sure you take pictures! :mrgreen:

Would be a good blog post :idea:

 

[Corneel]

Hmm, well, I read Grimshaw and Holtzappfel, but I am not much wiser now. Boy can these guys write incomprehensible! Some times text not agreeing with drawings. I guess I'll have to continue with the experimenting part of the process. Plenty of buckled sawplates around. (But not any time soon...)