Quote Originally Posted by Elizabeth Greene View Post
Howdy. I'm going to be making an awl and chisel for my multi-tool, and I need some steel advice. Both tools will be less than 1.75 inches/50 mm long with a maximum width of < 1/2 inch/13mm.

Would I be completely off the mark if I used HSS Tool steel for these applications? I'm sure it would be fine for the chisel, but I'm less confident for the torsion loads on the awl. I can get a "HSS Steel Square Flat Bar Strip High Speed Steel 2 3 4 5mm x 200mm Lathe Tools" from eBay for super cheap, but I don't know what I don't know. If a kryptonite alloy steel from McMaster would be better, I'm willing to pay more.

If it changes your answer, I'll have to anneal these to drill the pivot hole and the new heat treatment will be done under less than ideal (Torch, oil, oven for tempering) conditions.
The answer depends on what you mean by "Multitool". Here in NZ it is an electric powered saw that cuts by vibrating a saw blade. See e.g. https://www.bunnings.co.nz/aeg-300w-multi-tool_p0088692. The Leatherman derivative of the Swiss Army Knife is also called "Multitool".
The distinction is that a vibrating tool gets so hot at the cutting edge that nothing short of HSS can give reasonable edge life, and even that is way below my expectations for a useful tool. If you mean a hand tool a la Leatherman, heating the cutting edge is no issue, and any steel having 0.6% or more carbon is good enough after ordinary hardening. HSS retains its 60 HRC hardness to 550 Celsius or so, plain carbon steel is down to 40 HRC already at about 300 Celsius.
I have made myself a chisel for wood cutting out of 8x12mm HSS with a wooden handle, and it has not failed me, hammer blows or not. Is it any better than chisels made out of carbon steel? Of course not, edge holding is first of all determined by the steel's hardness, and secondly by the angle to which the cutting edge is ground (25 degrees or more for cutting timber). Toughness in the form of Charpy tests or equivalent is irrelevant for such small tool sizes. My steel-cutting scraper is also HSS, 25x2mm glued into a wooden handle.
But if you decide to use HSS, don't attempt to heat treat it yourself. That is for experts only, and they need to use rather sophisticated, electrically controlled ovens with salt or lead baths to ensure uniform and repeatable heat treatment conditions. If you need to machine HSS, buy yourself a carbide endmill advertised for 65 HRC. In thinner gauges, they are available from Aliexpress for under 10 US$ - they cut hardened HSS like the proverbial butter.