Backsaw with copper back 3, the saw plate

When I attended the ATC class at Dictum five years ago, Chris Schwarz told me that it was possible to make a backsaw using the steel from a plaster scraper, if a person just wanted to try making his own saw, and do it in a cheap way.

I found a shop in the port where we are at now, that has cheap tools. So I walked there the other day and bought myself two 10" scrapers at around 10$ a piece. 

Normally I dislike destroying usable tools, but I decided that this destruction would serve a higher purpose.

I didn't want to accidentally bend the steel plate, so I decided not to bash the handle with a hammer to loosen it. 

After a bit of experimentation, I decided that the easiest way to remove the future saw plate from the scraper was to first split the upper part of the scraper where the two halves met. I think the two handle parts were cast separately and pressed together later. There was a clear joint that was easily split using  hobby knife.
With the plate mounted in the vice, I used a heat gun to soften the plastic on both sides.
As soon as the plastic softened, I pulled the two halves from each other. That made the upper part of the plate accessible.
A bit more heating and I cut through all the plastic that was in the holes of the plate.

I didn't time myself, but I think the process of removing the plate could be done in 10 minutes, if you don't try to experiment with other removal methods first.

The plate itself is 0.5 mm thick (0.02"), and on the plastic handle it said "Made in Sweden", so I guess that the steel is also Swedish. There is a very slight cupping along the length of the steel suggesting that it came from a roll. But it is easily within the capabilities of the back to keep it straight.

I used a tool bit from the lathe to scribe a line on the plate, so I could cut off the holes in the top. A small file or a permanent marker could have done the same. A pair of metal shears easily cut the thin plate.

The dovetail saw I have at home has got 20 TPI, but I didn't think I could manage to file that fine a set on my first attempt. So I settled for something a bit easier: 18 TPI.

I printed out a diagram, but it was 7% too small, so instead I wanted to use a trick advocated by Pedder from Two Lawyers Toolworks. The trick is that if you are going to make very fine teeth, you can use the blade from a hacksaw with the same toothing as a guide.

After about a third of the saw plate, I decided that it didn't work very well for me. Probably due to a crappy work station. I couldn't stand in a decent way with the file, and the whole idea of a narrow saw vice was somewhat destroyed by the way I had fixed the plate.
I took a quick decision and removed the hacksaw blade - and made the rest of the teeth freehand.
In hindsight I should probably have read up on how successful people file a set of teeth, but I never bothered.
My approach was to file every other tooth, and then reverse the plate and file the remaining teeth. It doesn't look too pretty, but the saw works which is the main thing. I'm sure the correct tools will help quite a bit, but it can be done without them as well.
My file was a triangular needle file, without a handle, so I ended up wrapping some tape on it to protect my palm a bit.
At first I just made an indication of where each tooth should go, then followed up with a second stroke to form it.

Raw material for a backsaw.

Splitting the handle.

Heat and a hobby knife gets the plate out.

This is what it looks like.

Nice looking Swedish spring steel (presumably). 

Start of filing the teeth.

These were filed freehand.

Half the teeth done. The other half started.