Marking knife dilemma

Re: Marking knife dilemma

Bill Houghton, Sebastopol, CA

>How about trying it and seeing how it works?

Re: Marking knife dilemma

Skip in Falls Church

>Hi Bill,

Well, I thought about that and it may be a first (possibly final) step. However, it seemed that the steel was a bit on the soft side as it was easily worked with a file. I worked the back and the bevel down to 220 grit using SS and then thought that if I *did* need to harden it I might not want the tip of the knife sharp. (Although it was a little late then.) It was at that point I thought it might be a good idea to see what everyone here had to say.

Skip

Re: Marking knife dilemma

ThomD

>I'm assuming the blade will be OK?

If you need to harden the spike tip, and it isn't made out of HSS (which seems unlikely) then it needs to be heated until it isn't magnetic/cherry red. When magnets no longer stick, give it 20 more seconds in your torch, and then imediately immerse the hot bit in a good sized can of Olive Oil or congelled fat. Move it around so that the oil won't catch fire. You need to keep the red bit long enough in the oil so that when you take it out it isn't hot enough to flash any oil vapour. This is a small tool, but with larger tools it can get everything so hot the oil flashes, so have a plan and a lid for the oil. Don't heat anything but the tip section you want to immerse, and hold all that in the quenchant.

After the hissing has subsided, and everything is cool. Try cutting the point with a file, the file should skate, and while some oxide should come off, the file shouldn't be able to cut the steel. If you get this far, polish the hardened tip till it is white again, then you can either heat the shank back from the hardened bit with a torch until the colour creeping down the tool turns the hardened bit a faint straw colour, or you can throw the whole thing in the oven at 400-425 for an hour. Hard to know what temp will be required since it is mystery steel. This whole process takes a lot longer to write about than do.

Like BBQing, there are any number of ways to napalm yourself, or blow yourself up. Be careful with the oil, think what would happen if you pierced a plastic can, the oil flashed, and flaming oil went everywhere.

It is for you to judge whether this process is within your comfort zone.

Re: Marking knife dilemma

ernie miller

>if you think it will be to short why not cut the blade in 1/2 then stick each part it the oppisite ends of the handle, if you don't have a torch use cole and a hair drier for a blower to make the fire hot enough.

Re: Marking knife dilemma

dave j

>That is how I would do it too. It is difficult to predict what the final outcome will be without knowing the steel but it is probably either a high carbon steel or high speed steel. Most "tool steels" will at least get hard by the method you mention even if the end properties (toughness, etc) are not optimized.

Skip, A File or a Grinder

Tom Colligan, Peoria

>Skip, did you not do most of the shaping on a grinding wheel? Or, did you simply use a file? Thx., Tom.

Re: Marking knife dilemma

Skip in Falls Church

>Hi Ernie,

I figure I'll give it a try the way it is and see how it works. If it doesn't work as well as it could I'll give that a try.

Thanks,

Skip

Re: Marking knife dilemma

Skip in Falls Church

>Thanks Thom,

I'm not sure if the blade will be okay - but I guess I'll try hardening the awl point and then see how the blade does. If it doesn't work at the 25 degree bevel I have now, I'll boost it to 30 and see how that works before going any farther.

Thanks for the safety tips too - I'm very safety conscious, really!

Skip

Thanks Dave!

Skip in Falls Church

>

Re: Skip, A File or a Grinder

Skip in Falls Church

>Hi Tom,

I did a lot on my hand cranked grinder, a bit with a file and the rest on 40/60/100/220 grit sandpaper.

Skip

Re: Marking knife dilemma

ThomD

>By the way, you should probably dull back your scribe so that it is about 1/16" across, before heat treating it. Otherwise the end tends to burn which may mean a little more work. This is what one does with edges, leave about 1/32+ of square edge to protect the metal, and minimize the grinding. If you don't on edges, you tent to find the corners get overdone.

Re: Marking knife dilemma

Bob Fawcett

>Skip,

I made one of a spade bit just like yours. I use it regularly. It has held its edge pretty well. Could be my bit is different steel than yours, but I would think it should work as is.

I did not do anything to harden mine. I did all the shaping on a grinder. Since it was hand held, it was easy to make sure I didn't overheat on the grinder.

Re: Marking knife dilemma

Skip in Falls Church

>Thanks Bob,

That's encouraging! :) I don't remember the "parentage" of the blade at all, it might be a Black and Decker bought several years ago. It was marked "Japan" - something that it no longer says. I'm dithering over whether to harden the awl point or not, it doesn't sound too hard to do. I've stifled any smithing tendencies up to this point and I'm not sure I need to start sliding down a third slope. :)

I guess I'll just sharpen the blade and see how it holds up.

Skip