Cutting heat treated knife

D

Destroyer 666

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Nov 9, 2013
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I have a carbon steel Mora Companion that I want to shorten the blade into a sort of utility/wharncliff style. I have access to a metal cutting bandsaw and angle grinders at work. What's the best way to do this without heating up the knife and ruining the heat treat?
 
Destroyer 666 said:
I have a carbon steel Mora Companion that I want to shorten the blade into a sort of utility/wharncliff style. I have access to a metal cutting bandsaw and angle grinders at work. What's the best way to do this without heating up the knife and ruining the heat treat?
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I'd use a cutoff disk in an angle grinder, make a couple quick passes then dunk it in water repeating till I get through.
 
Of the two options you list, probably the angle grinder will work best. I don't think a band saw will work good on a thin heat treated blade. I can see it catching and jerking the knife out of you hand or clamp. The angle grinder would work better, if you can put an abrasive cutoff blade on it. You will need to grind just a little and then dunk in water, and then repeat till done. You don't want to let it start getting hot. Ideally you would have a dedicated cutoff saw with a continuous supply of coolant being sprayed onto the blade while you cut. Short of the frequent dunkings is you best option.

O.B.
 
Thin blades cut quickly, with a Mora you could even go down to a Dremel with a fiberglass reinforced cutoff wheel. I clamp the blade to a piece of wood on a table and use a spray bottle of water to keep it cool. If you can't touch the metal with a bare hand, the thin cutting edge might be getting hot enough to mess with the temper. After you mark your line in Sharpie, wrap the area next to the cut with a couple of layers of tape. When I am making light passes to keep the heat down, it is easy to get a skip that leaves marks on the blade that aren't going to come out easy if at all.
 
I agree with the grinder approach the others have already described. A metal saw might have trouble with high hardness steel.

If I want to reshape a hardened blade I grind very briefly and dip it in water frequently to it to keep it cool enough to touch. Never let it start to change colors. If you see it start to turn gold you are grinding too fast and are severely damaging the heat treat, if it turns blue you have ruined it.

I did this recently to reshape a blade for someone who broke the tip off a cheap Kershaw. I ground the spine down and formed a clip point and it seems to have held up fine as far as hardness goes.
 
Such a task can be handled by files. It takes time but this time can be used at thinking twice at what you do and avoid mistakes. The good use of a file solves many cutlery problems. And you won't ruin the heat treatment.

Dan.
 
Mr.Wizard said:
dantzk8 dantzk8 I think Mora heat treats a bit too hard for that, unless you mean diamond files?
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Yes, i would pick a thin rounded diamond file to cut the blade stock thought i've modified yet some GEC 1095 blade with a good quality classic file. It takes time.

Dan.
 
Thanks to everyone here! I clamped it in a bench vise and had someone hit it with a squirt bottle while I made the cut. No color change at all and got a clean cut.
4UyVzOu
 
Glad you had some success!
For anyone that runs across this thread in future I'd say the best practice is to use as thin an abrasive wheel as possible to minimise the actual cutting process and in turn heat. if you can use a dremel, use a dremel. Secondly I saw a great tip recently on how to make your own 10 second automatic water coolant machine. It's as simple as filling a big palstic bottle with water, poking a hole with a thumb tack then screwing or unscrewing the lid to control flow.
Shown at 1.49 in this video here
At the end of the day though, this is all just best practice. If you understand the fundamentals of what to avoid and try your best, you'll likely do a very passable job.
 
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