picks made from hacksaw blades?, why do they break?

[Hotroddal]

I have recently made a few rakes from brand new hacksaw blades, the picks have turned out great and work great for picking maybee 2 different locks then they snap off inside the lock, why would they keep doing this, Am I making the picks wrong or what? This is what I do to make the picks- make a stencil of the pick on the hacksaw blade and then proceep to grind out the pick on a bench grinder, and then finish it up with a hand file, the pick really never gets really hot, I try not to grind off to much at once either, what is the problem?

[MacGyver101]

Hmm. Your description of how you are making the picks sounds fine; would it be possible to post "before" and "after" pictures of your picks?

[raimundo]

have you looked at how candy bars are made like metal ingots, with a narrow thin place just so you can break them, when you put the pressure on the bar, its supposed to concentrate all give on the thin area, which cannot bend much because its got no length to spread the stress along.
(don't tell me how it worked on the candy bar you had, just listen to the theory as I tell you how its supposed to work)

If your picks have a narrow weak point, that point will break, if the entire shaft is made as narrow as that point, the stress will distribute more evenly along the lenght.

If you are heating the picks, this can harden them and make them brittle. if you are grinding the metal and it becomes blue, then gets dipped in cold water, that is hardening, you can do some and get away with it, but if the metal ever loses its blue color and becomes gray, you have definatley gone too far and have either annealed metal with no strength or you have hardened metal that is brittle and will break easily.

[Jaakko]

If the pick gets so warm that you can't touch the grinded area with your fingers without getting burned, then you are grinding too much without dipping in water. My advice: Grind a second, dip a second, repeat until ready.

Other thing is, how much tension you use when picking? You only need to use very light tension, at maximum the amount that would be needed to turn a key.

[ATM tech]

I agree with Jaako you are not realizing how hot they can get which makes them brittle unless you temper them correctly it will be futile.

I suggest reading up on metal working and tempering different types of metals.


google would probably be your best bet.

Also make sure your cuts are distibuted with stress in mind. You need to distribute the stress on the pick end and down evenly to the handle.

hope this helps.

[Pocket Weasel]

Good points about tempering, but one tip I have is to select your hacksaw blades carefully. They are not all created equally!

I bought a bunch of (fairly) cheap ones a while ago, but they're as brittle as dry twigs. They're absolutely useless for picks. They're probably useless as hacksaw blades too!

Now I'm using more expensive brands such as Sandvik, and in particular I'm using blades designed for cutting soft metals. These are not as hard as some other blades, but the extra flexibility seems to reduce breakages. At least, I've had no problems yet.

Hope this helps

[Siegel]

Another thing is check for flaws in the material of your pick (aka the hacksaw blade) Because as you A level physics will tell you any flaw in a material will increase the stress on the pick by a hundred or even thousand time making it a lot easier to break.
A good point on the tempering and if it gets even warm there is a good chance it is too high. Between every cut dip it water and if you are like me you may want to re temper some parts by heating it with a lighter and then squirting with 3 in 1 oil.
Finally the problem may lie in your picking technique if the pick is used to apply tension like i do with some small keyways i increase pressure on just on point on the pick and have had a couple of my picks become very fatigued which with prior knowledge can be remedied. I am proud to say I have never broken a pick (at least what i can remember )
Hope this helps you problem
No-one/Siegel