A few weeks ago, I bought 5 Disston No. 4 saws at an auction. One is a pre-1940 type and is the only one that can really be considered to be a desirable, vintage saw. The other 4 are HK Porter types from the 1950’s or newer. Below are a few pictures that show the general condition of the newer saws. They are generally in poor shape, teeth are missing, there is varnish/epoxy in spots, the plates are wavy and maybe kinked, and the teeth look like someone tried to use them as hacksaws.
Thankfully, the older saw is in probably the best shape of the lot and should be easily salvaged. Because they are basically worthless in their current state, I want to work on these first so that when it comes time to restore the vintage one, I’ve had some time to practice the techniques.
I’ve read a few tutorials (some on this site) about saw restoration, gotten some good advice from fellow LJs, and so I felt confident enough to get started with the first saw. First I removed the handle and then put the saw in the vise and started filing off the teeth. Nothing fancy here. Did the filing freehand with a cheapo bastard-cut file (made in India) that I picked up at the same auction. Once every trace of the teeth was gone, I put the plate on the anvil portion of my 4” metal-working vise and began tapping away with a hammer. The best tutorials and videos I’ve see on this technique recommend a ball peen hammer. My well-used Estwing Framing hammer (20-24 oz., I would guess) was the one on the bench, so that is what I used. I started tapping lightly on and around the kink until I couldn’t see it anymore, and it was barely perceptible to my fingers when I ran them along the edge of the plate. I also tapped a roughly equal amount on the opposite side for good measure. One tutorial talks about doing this to tension/detension the plate. I don’t disagree with the method, it appears to be well-established and proven. But I do disagree with the description of what this does, and why it is necessary. I’ll put those comments below. Anyway, The kink was basically gone and the plate appeared to be straight, so I proceeded to remove the spine. The plate was again put in the vice and the plate was carefully pried up with a large screwdriver, taking care not to re-kink things. The first few inches went a bit slowly, but once I got to the halfway point things went pretty quickly. With the plate and spine separated, they were easier to clean up. Some WD-40 and a 220-grit sanding sponge brought back a bit of shine to the steel. This saw had relatively little varnish/epoxy to remove, so things went smoothly. The disassembled and cleaned saw is pictured below.
Upcoming posts will include the other saws, and will outline filing and setting the new teeth, sharpening, possibly some handle work, and maybe even cutting one of the saws down to a smaller size. Stay tuned.
A Note on Saw “Tensioning”: I don’t agree with the term as used by Bob Smalser on his tutorial here. Hitting the saw with many, many light blows from a ball peen hammer to me is very similar to shot peening. In the case of a curved plate, I propose that there exist imbalanced tensile/compressive stresses on either side of the plate, causing the bow. Hammering, in my view, does not remove any of these stresses, but instead adds areas of localized internal stress that balance the previously existing stresses. The net effect is a cold-working process that results in compressive stresses on the surface of the plate. These may be beneficial because they increase the surface hardness of the steel, while leaving the internal metal ductile. Obviously, ANY internal stresses must be balanced, or distortion will result. Kinks are a different type of defect resulting in local plastic deformation. The only way to remove them is to “bend” the metal back to shape. Because this type of deformation causes excessive work-hardening of the metal in the kink, I would guess it is near impossible to remove all traces of a kink without annealing.
Again, I am not debating the merits of the method…just the explanation of the mechanics behind it. This explanation makes more sense to me and fits my understanding of metallurgy and materials.
-- Dylan C ...Seems like all ever I make is sawdust...