Have you missed me? Sorry for leaving you hanging for so long, but work was a bit manic leading up to Christmas. Now where was I? Oh yeah, I was just about to sharpen the last of my crosscut backsaws, a 12” carcase saw made by W. Tyzack, Sons & Turner.
I restored this saw in part 1 of this blog series. It had a number of issues and honestly, it still has a few of them.
1) The plate was heavily pitted in places.
2) The plate had a wave in it.
3) The spine was bent.
4) It was missing a split-nut.
5) The screws were bent and very little of the thread remains.
6) The spine doesn’t fit the handle very well.
The above problems mean that this will never be a pretty saw, but I didn’t have the heart to just throw it in the bin. As part of restoring this saw, I straightened out the wave in the plate, or so I thought. However, when I came to sharpen it today, I noticed that the wave had returned. Bummer! On closer examination, I found that the spine was also slightly bent. As I’ve said before, there’s no point in sharpening a saw with a wave or a bent back, you have to fix those problems first, starting with straightening the spine.
When I straightened the back of my S&J Carcase saw in part 4, I used the following method where I sighted along the underside of the back and placed my finger on the convex side where it was bent the most. I marked that point with a bit of masking tape so I knew where to direct my mallet blow.
This time I placed my combination square on the convex side of the plate and rocked the straight edge until the gap was equal at either end. I could then see that the fulcrum point was so many inches from one end and that’s where I needed to hit it. If the spine is stamped with the maker’s name, you can sometimes use the lettering to remember where the fulcrum point is. (E.g. Hit the ‘T’ of the word Tyzack.) Then I placed the back on the blocks and hit it with my deadblow mallet. You need to sneak up on the right amount of force and check it frequently with the straight edge until it no longer rocks. One point worth mentioning is that steel backs take a lot more force than brass backs.
Once the spine was straight, I sighted along the toothline. Although much improved, it still wasn’t straight enough. Usually you can hold the saw as shown below and rap the toe end of the back on your bench to straighten out a wave.
I managed to improve it a bit, but I couldn’t get it perfect using this method. This gave me the opportunity to try something new and that was to remove the spine and refit it. The act of refitting a plate in a spine has the effect of re-tensioning the plate. These days many makers use slotted backs on their saws where the slot is machined to the thickness of the plate. Some makers even glue or pin the plate in the spine. However a folded back is different. In order for the two sides of the spine to grip the plate the spine has to be sprung. This means that when you remove the plate from the spine, the sides close up.
I think there are pros and cons for both types of backs, but for me a folded back is preferable, as it allows you to adjust the tension and also to easily replace the plate should it get irreversibly damaged.
Anyhow, I gripped the plate in the vise and used a block of hardwood and a mallet to knock off the spine. It was a BITCH to get off let me tell you, but I got there in the end.
After cleaning the plate and spine, it was time for re-fitting. I used the method kindly documented in the following four videos by Tools For Working Wood. Notice how the saw maker positions the plate and spine to get it started and how he then turns the whole assembly over and bashes the teeth (yes the teeth) with a softwood bat shaped a bit like a little cricket bat. In the last video he adjusts the position of the plate relative to the spine so that the assembly will fit into the handle correctly and the holes in the plate will line up with the holes in the handle. Enjoy.
I watched these videos a few times before I plucked up the courage to try it for myself. I’m pleased to report that it was far easier than I thought it was going to be and the plate went straight back into the spine first time. Adjusting it was a bit more tricky than it appears in the videos because the Gramercy saw in the demonstration has a nice notch in the plate that comes to rest on the metal block in his vise. Old saw plates didn’t have that feature (at least none of mine do), so I had to keep tapping and offering it up to the handle to know when the alignment was correct.
The good news was that the wave had now gone and the back was still straight. HOORAH! Now I could do what I set out to do when I got up this morning and that was to sharpen the damn thing. Don’t you just love these little distractions?
After filing off all the old teeth, I retoothed it by hand to 12TPI and sharpened it with 15 degrees of rake and 25 degrees of fleam. This will be great for making crosscuts in softwood. So here she is folks. She isn’t pretty, but she cuts beautifully.
You know when I had almost finished sharpening her I had to smile, because although I haven’t sharpened a saw since I last posted here (145 days ago), I hadn’t forgotten either the process, the technique or the feel. And that my friends, is exactly the place I hoped I’d get to when I started this journey last year.
Well that was the last of my backsaws. In my next and final post (ok it might be two), I will try to sum up what I think I’ve learnt about restoring and sharpening saws. I have formed some surprising and somewhat controversial conclusions about tooth geometry, which I’ll also share with you.
-- Andy -- Old Chinese proverb say: "If you think something can't be done, don't interrupt man who is doing it."