Ever straightened the sawplate of a backsaw?

[jmk89]

I have a nice 14" Spear & Jackson backsaw which I have jointed, shaped, sharpened and set but which doesn't cut very well! I have looked more closely at the sawplate when that happened and I can now see some very slight wandering of the sawplate - the back is straight (according to my Academy Saws straingt edge), but the plate veers back and forth a bit (less than 0.5 mm either way but I haven't measured it) about 20 mm above the tooth line.

I've never tried straightening the sawplate of a backsaw before. Does anyone have any experiences that they could pass on to me? BTW I have read Bob Smalser's article on the WK Fine Tools site.

Thanks in advance

[RayG]

Hi jmk89,

but the plate veers back and forth a bit (less than 0.5 mm either way but I haven't measured it)

That sounds like the blade needs to be re-tensioned....

You need to hold one end of the saw and gently tap down the spine.

Clamp the blade firmly at the toe in a vise with some blocks of wood for protection and give a couple of taps on the top of the spine at the toe end.

That will pull the plate back into tension on the tooth line.

Regards
Ray

[jmk89]

Hi jmk89,




That sounds like the blade needs to be re-tensioned....

You need to hold one end of the saw and gently tap down the spine.

Clamp the blade firmly at the toe in a vise with some blocks of wood for protection and give a couple of taps on the top of the spine at the toe end.

That will pull the plate back into tension on the tooth line.

Regards
Ray

thanks Ray

I'll try that tonight and see if the blade straightens out with a couple of taps

[RayG]

Hi Jeremy,

Of course I should have added, that you can tap down the back down at the handle end, (rather than the toe end) just so long as you don't whack the handle in the process.

You are just pushing the blade up into the spine at one end only. So that the saw plate is under compression at the spine (along the length of the blade) and under tension at the tooth line.

Regards
Ray

[jmk89]

Ray
I tried tapping down the spine and it helped to get rid of most of the 'wave'. The saw now cuts without binding. Thanks.
Btw what if the back is already all the way down on the sawplate?

[Heavansabove]

Jeremy,

Saw plate rarely (ever?) went right into the back, you can see from the marks on the plate when removed from the back where it started off. Tapping each end of the back up and down will eventually (usually) get to the "sweet spot". There have been some useful discussions on Sawmill Creek, go to
Neanderthal Haven

and type "straighten saws" into the search box - and a number of threads will be listed.

The Traditional Tools Group is having a saw sharpening workshop on 20 February which will help you. The details are:
The Traditional Tools Group (Inc.) -- Coming Events

Cheers
Peter

[RayG]

Hi Jeremy, Peter,

Pleased to hear it worked, any chance of a picture, I'm collecting pictures of S&J backsaws..

Straightening saw blades can be a tricky business, especially if they are kinked.

My only attempt at Bob Smalser's anvil and hammer method for removing kinks resulted in a weird propeller shaped object with teeth down one edge...

Regards
Ray

[jmk89]

Hi Ray

Here's a couple of pictures of the S&J saw.
Attachment 160892

Attachment 160893
Two of the saw nuts had been replaced by a previous owner with zinc-plated cuphead bolts, so that's why there are two Wenzloff screws. The dark line along the teeth is marking blue - I will remove with meths soon. I haven't finished with the handle yet - some more smoothing required, and then a couple of coats of Ubeaut hard shellac.

BTW on another forum, Mike Wenzloff provided the following information:

++++++++++++++++++++++++
If it is a bow/bend without a kink, you can simply bend it gently the opposite direction. Usually you will need to over bend further to the opposite side than it is presently.

I usually grasp the toe and the handle and simply arc the blade to the opposite side. But I as often run the side of the saw blade across one knee, bending the blade, sliding the blade from one end to the other.

On localized bends such as at the toe, you need to be a tad more gentle, but the same principles apply.

Go slow, sight down the blade frequently. To properly sight the blade, have the saw in front of you, teeth away from your body. Hang the saw by placing just a finger or two through the handle. Do not grasp the handle. Look down the tooth line. If you actually hold the handle it is difficult to judge whether you are allowing the saw to hang without the influence of twisting the handle from truly vertical.

Most saws with a bend can be brought back straight in less than a minute or two.

A lot of saws take on a cast such as this from simply being leaned against a wall, handle on the floor. Even at a pretty upright lean, a saw will eventually take on a cast (a bow).
++++++++++++++++++++++++

Now, for what I take as a "hump" along the blade can be simply a more localized bend, in which case the procedure above works fine. If it is due to stretched metal, there is hammering involved. One way to tell the difference between a localized "hump" versus stretched metal is whether this hump goes from the toothline up to the top edge of the hand saw. If it is only at the toothline, then hammering is needed. If it extends up to the top edge, then you can normally bend it back into place.

For the back saw, if it has a kink instead of a bow, the best bet is to simply replace the blade. However, if it isn't kinked metal, one can usually adjust the back (make the back at the toe higher on the saw plate) to straighten out. In these cases, what normally happens is that somehow the toe of the back is forced down onto the plate. Because a back saw blade is held in tension inside the back and at the handle, the back when forced downward forces tension on the toothline and a bow of varying degrees is created.

To drive a back upwards at the toe without removing the handle, I use a piece of wood about 1" square, half again as long as the distance from the toothline to the back. So if there is a usable depth of 3", I use a length of 5" to 6" of 1" x 1" stock. I use a pretty hard wood such as Jatoba, but even Cherry or Oak will work fine. I cut a slot in the middle of the piece of stock a bit longer than the usable depth.

My face vise has a liner against the apron of the bench top to allow this, but if yours does not, simply cut a couple boards to give the needed clearance. The saw is placed in the face vise so as to hold most of the saw plate firmly. The stock of 1" x 1" is slide up onto the saw plate at the toe of the saw so the kerf cut into it straddles the plate. With a good squeeze to hold the stock firmly against the saw plate, use a hammer to tap hard enough to drive the back upwards. Once it moves a little, release the pressure on the vise and retighten. This allows the saw plate to regain some straightness with each adjustment.

Take care, Mike

[RayG]

HI Jeremy,

Thanks for the pictures, I've being compiling a gallery of sorts, of S&J backsaws. Mainly focussed on the way the handle shape changed over time.

Comparative Dating by Style - Saw Discussion Forums


And, thanks for posting the link to Mike Wenzloff's notes. Very handy to have that archived.

Regards
Ray