1075/1085 Steel, What Hardness would you recommend for a utility knife and why

[hathegkla]

I'm wanting to get in some heat treating practice with a used ht oven my father is giving to me by making a few simple utility knives for friends. they'll probably be tanto style, 1/8" thick x 1" wide x 12" long and a heavier one I'll forge at 3/16" thick x 1 1/4" wide x 12-14" long (or whatever I can fit into my ht oven when I get it), the bar stock is 1/14 wide so when its forged it'll probably be around 1 1/2" wide.

they are going to be very simple, flat or slightly convex ground with paracord wrapped around the tang for a handle. the idea here is a very durable knife that can be abused a little and not chip. they don't need to be razor sharp, a utility edge is all that's necessary but I want them as hard as would be practical for this use.

so what I'm asking is what hardness would you recommend that I temper them to and why. what do you prefer for a utility blade?

 

[cotdt]

There are different utilities so it depends. Temper it to 400F if you want it to be able to bend to the elastic limit, 340F if you want it to cut for long periods of time. Personally I like 63-64 rc for cutting.

 

[richard j]

i only use 1075 in the knives i make. i only heat treat the edge which i take up to 63-65rc. i do not temper the blade since i'm only heat treating the edge (about a 1/2" wide portioin of the edge)

 

[hathegkla]

There are different utilities so it depends. Temper it to 400F if you want it to be able to bend to the elastic limit, 340F if you want it to cut for long periods of time. Personally I like 63-64 rc for cutting.

these knives will be given to people likley to abuse the knives so I guess I'll try 400F. they'll be cutting things but nobody's using these to slice fugu. I'd also bet somebody tries to throw one of these into a hunk of wood. I don't mind sacrificing the longevity of the edge a little for some durability.

i only use 1075 in the knives i make. i only heat treat the edge which i take up to 63-65rc. i do not temper the blade since i'm only heat treating the edge (about a 1/2" wide portioin of the edge)

how do you heat the edge? do you just use a torch to heat the edge and let the residual heat from the spine temper the edge or do you insulate the rest of the knife somehow (holding it under water etc?).

I'm thinking of picking up some clay eventually but I feel like I should try a few without it first. at this point I've just forge hardened/tempered but soon I'll be using an oven.

 

[richard j]

i use a cutting torch with the oxygen turned down to where its almost off. the flame is not much longer than 5"-6". the tip is held a few inches away and you have to watch out for any yellow sparks which will indicate you are getting way too hot. an occasional (a few here and there) yellow spark isnt bad but you dont want a steady ammount of them.

you need to move the flame along the length of the blade being careful not to overheat the tip but you want the blade to be the same bright orange the full length. never hold the flame in one spot, always keep it moving. sometimes you have to move fast if its a long blade (over 6").

dont hold the flame directly on the edge but up from the edge. if the tip is thin, dont get close to the tip but stay back and up from it. leave the edge the thickness of a dime or a hair thicker to prevent cracks. i quench the whole blade in canola oil. i have been using this method for 18 years with good results.

 

[hathegkla]

nice thanks, I might give that a try someday when I get my torch back. sounds like it would be hard for large blades though.