Brittle Metal

[dan_c]

I recently attempted to make my first homemade tension wrench. When I was finished it was way too brittle at the bend and broke witht he lightest pressure. I'm not sure what I did wrong I tryed to follow what I saw from guides on this site. I first grinded a Jr. Hacksaw blade to the proper size. Then I heated it with a propane torch until it turned bright red. I used plyers to put a 90 degree bend in it and dipped it in water as quickly as possible. Is there some step I'm leaving out?

[freakshow]

Personally, I would advise *NOT* using hacksaw blades to make tension wrenches. They are far to easy to break. I use a simple street cleaner bristle, bent at about 1.5 cm, at 90 degrees. Mines still rusty, and it hasn't broken yet. Of course, try to polish your tools, makes them look nicer . Of course, Hacksaw blades work great for the picks themselves.

[sawtenor]

I use the same tension wrench made out from a hacksaw blade since many months now. You may want to make a 90° twist in the lenght of your tension wrench where you hold it (I dunno if i'm very clear...) so the tension used while picking will not be all distributed where you've made your first curve. I'm not sure about what I said (just a theory) so if others could post what they think about...

[digital_blue]

I used plyers to put a 90 degree bend in it and dipped it in water as quickly as possible. Is there some step I'm leaving out?

Yes. Once you've effected the bent and quenched, you need to re-heat to a light straw colour and air cool. Let me explain....

When you heat the metal it will pass through several colours. There's more to it than this, but this'll clear things up a bit I hope.

Heat to blue, metal ends up soft... probably too soft.
Heat to cherry red, metal ends up very stiff, but very brittle.

Heat to light straw (sorta yellowish), probably best of both worlds. Just rigid enough not to bend easily on you, but not so brittle that it breaks on you.

Also, the air cooling will prevent the brittleness.

This is the process I've used and it seems to work well. There is actually a whole heap of information available both on lp101, and on the web in general on heat treating metal. Search for "heat treating" or "metalurgy".

Hope this helps.

db

[Minion]

I believe he meant
'metallurgy'

[digital_blue]

No, I meant "metalurgy", but I probably should have meant "metallurgy". But just for kicks, search for both, 'cause I can't be the only poor speller.

db

[Shrub]

Just to add some weight, Db is exactally right, you hardened the metal but didnt take out the stresses afterwards