I also thought the steel on a hardpoint would not be suitable but I have seen it done by some on the Australian forum.
How to Make Handsaws - Australian Wood Review
Shim steel is another source.
DIY Frame Saw Blade from Carbon Steel Shim - YouTube
Regards
John
I will fess up as the author of the article John pointed to. Yes, the steel they use for hardpoints is hardened & tempered to pretty typical saw hardness. If you think about it, it has to be much the same as any saw blade to work as a saw - I don't think it takes much imagination to predict what would happen to a piece of dead-soft 0.020" steel the first time it jammed a little! I've re-purposed many a hardpont blade successfully & only one, very cheap example seemed a wee bit on the soft side as judged by filing it, but it was within the range of other saws I've sharpened & performed quite satisfactorily.
The impulse hardening of the teeth extends no more than a mm above the gullets, so all you need is to take your trusty angle-grinder and a 1mm cutoff wheel and cut off the discoloured part (best done against a guide if you want straight lines). If you cut quickly, there is very little local heat, but I like to clamp the plate to a piece of 5 or 6mm steel to act as the guide and also a heat-sink. At the most, you will get a few dags of metal that heated & cooled so quickly they hardened, so run (an old) file along the cut edge a few times 'til it cuts evenly & you have a nice, clean edge.
Tempered 1095 shim stock makes excellent blades. If anything, it's slightly on the hard side for filing, but I've struck a few old saws that were a good deal harder again, so it's not outside the pale. And btw, I've not found very hard plate translates into the sharpness lasting noticeably longer, so it's not worth chasing up on that account.
If you haven't cut teeth from scratch before, it's tedious & a saw that size will eat up at least one file. A saw-sharpener shouldn't charge much more than the cost of the file to tooth it, & you'll have nice, even teeth to start with.....
You can get away with a fair bit of pitting on a saw blade, but badly pitted blades are an eyesore, and when you get to pitted areas, teeth often break off as you try to set them, which is even more of an eyesore. I can't imagine great-great grand-dad minding in the least if you replace the blade & make the saw serviceable again.....
Cheers,
Ian