blades too brittle

[thunderforge777]

a couple of blades i forged from files keep snapping easy. the tips will break off. i can put it in a vice and put very little pressure on it and it snaps off. i hardened them using oil quench and tempered them in a kitchen oven at 400 deg for an hour. i may have forged them too thin, they were between 2-3mm thick. is it the steel type of the file that is the problem or did i not temper it correctly?

[Steve Sells]

you didnt state what steel you used, but if they are too brittle to use then  you didnt temper them at a high enough temp. read the heat treat articles in the referance section of the knife making classes for details.

[jmccustomknives]

What did the brake look like?  Could you see a grain (almost sand paper like) or did it look silky?  If you could see a grain you overheated the steel causing grain growth which weakens the steel.  If you've done it properly then the steel will be silky.  Did you polish a section before putting it in temper?  It should be a light straw for a small blade, dark straw for a larger blade.  You might also look into doing a soft back draw for added strength.  I'm sure there's a sticky somewhere here for that.

[thunderforge777]

What did the brake look like?  Could you see a grain (almost sand paper like) or did it look silky?  If you could see a grain you overheated the steel causing grain growth which weakens the steel.  If you've done it properly then the steel will be silky.  Did you polish a section before putting it in temper?  It should be a light straw for a small blade, dark straw for a larger blade.  You might also look into doing a soft back draw for added strength.  I'm sure there's a sticky somewhere here for that.

the break looks grainy. what do you mean by overheated the steel?

[thunderforge777]

you didnt state what steel you used, but if they are too brittle to use then  you didnt temper them at a high enough temp. read the heat treat articles in the referance section of the knife making classes for details.

i think it is w2. they are old nicholson files

[jmccustomknives]

You'll find this in the stickies.  When steel is heated past the point where a magnet stops sticking crystals start growing.  These weaken the structure making failure more likely.  Use a magnet to determine the proper temp when quenching.  Most literature say "cherry" or "sunrise", those colors must look different to me as the magnet sticks past what I would refer to those.  Heat the steel evenly taking it out and testing, when the magnet stops sticking quench it quickly.  It takes practice, be prepaired to ruin some steel.  A lot can be learned from breaking your blades, the steel never lies.  :blink:

[ThomasPowers]

In traditional blacksmithing "cherry red" refers to *PIE* *CHERRIES* which are sort of an red/orange colour when ripe and *NOT* bing cherries which are a dark red/black colour.

Bing cherries are what most people are familiar with these days but are a fairly recent cultivar compared to the history of blacksmithing!

When heat treating an un-known alloy you have to TEST it until you get the right temperature for tempering, seeing how a file bites is usually considered a better way than breaking them...So start at 400 degF and if too hard/brittle go to 425 degF test and repeat until you get the properties you want.

Don't forget to normalize 3 times to deal with grain refinement *before* hardening!