Straightenning a saw advice needed.

[adrspach]

Hi guys. I am in process of hand restoring old Spear and Jackson Alexandria hand saw. My issue is that after I have sanded and honed off most of the rust and pitting the saw is still not straight. There is a significant bend to one side. Not a kink just continual bend.
Any advice how to sort it out.
Many thanks.

 

[Cheshirechappie]

The first thing to try is just flexing the blade opposite way to the bend. You may have to flex it right back on itself - a 180 degree bend - and see if that corrects things. Sometimes, this works cold, sometimes not; depends on the exact grade of steel the blade is made of.

If that doesn't work, try pouring plenty of boiling water over the blade - get it good and hot - and flex it again. You might need two or three goes - the blade loses the heat quite quickly. You'll need a decent pair of thick leather gloves (or similar hand protection) for this.

Another method (probably the professional one!) is a bit more involved. Using the polished cross-pein of a smallish Warrington pattern hammer (about 8 to 12oz), and holding the blade firmly hollow side down to a piece of fairly solid hardwood, strike a line of blows from toothline to back, so that the hammer pein makes a line across the saw blade. Repeat at about two-inch intervals along the saw. Start with very light blows, check the effect, and increase the weight of blow if necessary. Check progress frequently. If necessary, strike more lines a bit closer together. Thicker sawblades will need heavier blows, with lines of blows closer together.

The first method is probably the best; the second ideally needs a bit of practice on a scrap saw first, just to build up the confidence, and the feel for it.

The final (pragmatic) option is just to buy another saw with a straight blade!

 

[swagman]

http://www.woodworkforums.com/showthread.php?t=191688

 

[adrspach]

Thank you guys for pointing me out towards possible solutions.

 

[matthewwh]

This may sound wierd, but if you turn the saw over and bash a lump of scrap wood with it, the blade will reseat itself and the spine will re-tension it. Andy King did a feature on it in one of the mags under the delightful sub heading 'tap and unwarp it'.

Aim for about the same action, confidence and force that a butcher would use when cutting a chop with a cleaver. If you don't get anywhere after a couple of goes you may need to resort to heat or hammers, but it's worth trying the roadside fix first.

 

[swagman]

Hi Matthew. Are you referring to a backsaw. My impression is the originator is talking about a handsaw. (non spined).

Stewie;

 

[matthewwh]

Thanks Stewie,

My apologies, I stand corrected.

In that case, if it's just a user you could do worse than google up Bob Smallser's advice on 'straightening bent handsaw blades' complete with guidance on where to hit etc.

If it's precious, you might consider enlisting the skills of a trained sawsmith.

 

[AndyT]

This page from Paul Hasluck's "Woodworking" might help. It shows how to hammer a bent backsaw and also something like Matthew's tip for backsaws. This is just for interest and may show why Matthew mentioned giving the job to someone who knows how to do it... :wink: