Shawn, almost every knifemaker has made one or two just because. I have made and sold probably around a hundred and still make them on a regular basis. Very handy tool, especially for folks with hand problems like arthritus, missing digits, etc. because they require a different style of ergonomic grip.
An ulu in the hands of a skilled hunter, butcher, chef, etc. is something to watch. Lot of sharp edge, good penetrating points (2), and excellent pressure points for skinning, slicing and chopping.
I think one of the reasons northern indigenous people used them so much is the ease of making them and they can be used even while wearing heavy gloves. Keep in mind "ulu" is the Inuit name and most common, but this style of blade has been around in almost every culture since man became aware he needed to cut things.
Still wondering what your question is. Be glad to help if I can.
I made one from a circular saw blade. I use it all the time. Keeps me from dulling my other knives on sweet potatoes and chicken wings. I've about learned how to joint a wing without cutting the bones though.
Well in theory and early development of the metal "ulu" (via the Inuit direction), Art's approach is not that far off. Also it would work ok in a pinch if you are a survivalist. Many of the recovered early Inuit made metal ulus were made from wrecked ship parts that included cast iron, wrought iron, and other types of thin metal that they could coarsely shape and sharpen and get a handle on. Not a lot of metal lying around in the tundra.
Many you see today are made from circular saw blades - makes sense, thin reasonably good metal, already curved shape, already heattreated to hold a fair edge for cutting, worn ones are readily accessible, etc. And, if frugal and thoughtful enough material for 3 - 4 blades. So I'd say go for it.
Being a knifemaker, I'm a little more driven to get as optimum a performance as I can from any cutlery metals I use so I do a lot of testing both physical and thermally on any unknown or "mystery" steel I re-purpose. That's just me. A lot of my ulus, head knives and round knives are indeed made from reclaimed steels, but I have years of experience with testing. For example below are made from a used edger blade. Forging makes it easy to get two from such blades.
If you do make one (or more) from an old sawblade, just be careful not to over heat during grinding. A cutoff wheel on a side grinder will quickly remove the teeth and cut to shape with limited heating, if you don't linger in the cuts. Grinding the cutting bevel(s) is where you can mess up real fast. Keep a bucket of water to dunk in and grind barehanded (feel the heat - dunk) and don't try to do it all in one pass.
Good luck with your project and above all have fun - WEAR SAFETY GLASSES while cutting and grinding!
Different mfgrs used diff steels back then as they do now. For the most part they are usually decent steel for your intent. Be aware that not all handsaw blades are hardened and tempered the same from cutting edge to spine. If you are not able to re-heattreat you might run into differentially hardened material - harder at the teeth and somewhat softer main body and spine. With a little skill you can flex a blade and tell if it is differentially heattreated by the way it reacts as it is bent.
If you do have the means and the skills to do your own heattreat, you will find using quench plates the most effective way to complete hardening with out warpage - and would recommend a tempering heat of 400 to 425 deg. F. for at least an hour soak.
I just finished up a batch of paring and kitchen utility knives for a friend that are made from an old Ontario Brand handsaw. With the quench blocks they came out quite well. I suspect the saw blade was 15n20, by the way it responded to testing. I got the best results with a "15n20" recipe.
Odd because I had never heard of ulu knives until my wife gave me one for my birthday and I love it. As someone previously stated they are great for those of us who have arthritic fingers. I use the one she gave me which if fairly small to chop vegetables etc