As chosen by you, the next back saw is a 12” carcass saw also by Spear & Jackson with the leap frog trade mark.
I bought this saw, not because I really needed another 12” carcass saw, but because it features an extra heavy brass back. I wanted to see and feel how this feature influences the cutting action of a backsaw.
The blade is filed 10 TPI crosscut and canted by 1/8”. That means that the distance from the toothline to the underside of the brass back is less at the toe than it is at the heel (handle end). At the toe it measures 2 7/16” and at the heel it measures 2 9/16”. I don’t know whether this is the result of bad jointing, the plate slipping in the brass back, or if the saw was originally supplied with a canted plate. Personally though, I quite like canted backsaws. It means that if you saw with the brass back horizontal, the teeth at the heel end (closest to you) will reach full depth before the teeth on the far side of the cut that you can’t see. When the teeth at the heel reach full depth, you simply lift the handle slightly and make a couple more strokes to bring the back of the cut to full depth. I’ll be returning to the subject of canted saw plates in a later episode in this series, so I’ll leave it there for now.
The plate shows signs of light pitting over the entire surface and a few localized spots of heavier pitting.
The handle on this saw shows many signs of abuse. Dents and scratches abound, as do the obligatory paint splashes.
I have to say that the shape of this handle doesn’t exactly inspire me. It doesn’t feature the bump on the back of the grip that I’ve come to appreciate and the horns are far too thick to my eyes. The bit I hate most though is the bottom part of the handle that joins the grip to the cheeks. No longer the graceful sweeping curves of the lamb’s tongues we saw on the Tyzack handles, but rather a hurriedly mass-produced spindle-sanded mish mash of flats and thicknesses, that don’t look good from any angle. There’s nothing elegant about it I’m sad to say.
Having rubbished this handle however, I have to admit that it is not uncomfortable to actually hold and I do like the saw bolts. Unlike the old split nuts that are prone to breaking and never look as good when you reinstall them as they did before you took them off, these bolts are much more durable and easy to use. Each bolt features four lugs that grip the wood and prevent the bolt from spinning when you tighten it.
So I took the saw apart, cleaned the plate and then started sanding it. I should mention that when I sand a backsaw plate, I put it on a granite cutting board that I bought for £10 from the supermarket with the brass back hanging off the edge. Using this method, the saw plate is resting on a flat surface and I can apply as much pressure as I like with my sanding block as I progress up through the grits. On this saw, I started with P80 grit and after about fifty strokes, I noticed that I was getting a 3” long by 2” wide shiny spot in the middle of the plate, just under the brass back.
Now one thing I always do before I start sanding is sight along the toothline from one end to see if it is straight. There is no point in sanding a wavy toothline as you will just make the plate thinner in some places than others. If the saw plate is wavy, you have to fix that before you start sanding. The toothline on this saw was the straightest of all the backsaws I’ve done to date. However, this saw taught me a valuable lesson. It isn’t enough to sight along the toothline, you also have to sight along the underside of the brass back. On this saw, although the toothline was straight, the brass back was bent in the middle. I wasn’t expecting that and I must admit I scratched my head for a couple of days trying to think of a way to fix it.
Now you might ask “Why is it so important?” Well I like my backsaws to have the least amount of set possible. On a dovetail saw, I try to get away with no set at all. On a carcass saw, I would want a maximum of .003” either side. That will create a kerf of .006”, so if the back is bent more than that, not only will the saw not cut straight, but it will bind in the kerf.
So this is what I came up with. First I had to determine exactly how much it was bent and at what point along the back it was bent the most. I tried sighting along the saw and putting my finger where I thought it was bent the most, but after doing this three times, I got a different point each time. As you can see in the following photo, what I did was to lay the saw concave side down on the granite worktop in my kitchen. (The two sheets of paper under the saw are only there to make the saw stand out in the photos.) I propped the saw plate up with four hotel card keys so it was lying horizontally. I took a sheet of paper and measured it’s thickness to be .005” with my micrometer. I then used the paper like a feeler gauge. Sliding it under the brass back, I moved it to the left as far as I could and marked that spot with the inside edge of a piece of blue tape. Then I moved the paper to the right and marked it again. I then measured the distance between the two inside edges of the tape and marked the center point with a felt tip pen. That gave me the point where the back deviated the most from straight. I measured the gap at that point to be .010”; too much to ignore.
To fix it without marking the brass or bending it too much the other way, I put the granite plate I use to sand saw plates on my workbench and supported the saw on three MDF blocks cut from the same sheet. I then used another MDF block as a gauge. Initially I could slide the block under the back and it didn’t touch it. Using a deadblow mallet, I gently hit the back on my center mark. I gradually increased the amount of pressure with each strike and kept sliding the gauge block underneath the back. When the block just slid under the back and there was no up and down movement, I knew it was straight.
When I sighted along the underside of the brass back, it was perfectly straight. However, now the toothline had a wave in it. That didn’t scare me though. I held the brass back with the teeth uppermost and rapped the toe end on one of the MDF blocks.
A few whacks later, the toothline was straight again. After testing that the holes in the handle still lined up with the holes in the plate, I got back to sanding it.
So here’s the finished saw. There are still a few dents and marks on the handle, but you can only sand so much. I did rasp and file some of that thickness out of the horns though to make them look a bit more in proportion.
Thanks for watching.
-- Andy -- Old Chinese proverb say: "If you think something can't be done, don't interrrupt man who is doing it."