Material question

[Brad]

I have some material that is driving me nuts.
I thought it was 1144 for but it doesn't machine that nicely. What bugs me most is that the chips are very small and act as if they are magnetic. They stick to the stock in the lathe and the HSS tools. Drives me nuts.

Is this inherent to the material or is there something I can do to stop this?

 

[KeithB]

Can you tell us more about the size/condition/provenance of the material? Is it a part made for something else that you are re-purposing? I've run into some grades of nodular iron that do something like that, small chips with enough residual magnetism to be really annoying. On new stock I think it comes from induction heating, the induced magnetic field and the susceptibility of the material to being magnetized playing a part.

If it's really bad about the only way I know to cure it is to (a) run it through a degaussing/demagnetizing field, or (b) anneal it, heat it above 1450F, hold it at that temp until a magnet won't stick to it, and cool it off slowly. This will not only soften it and make it easier to work with but also destroy any residual magnetism.

 

[Brad]

It is 9/16" rod I bought online. It was, I thought, 1144. I may have gotten it confused with some 4140 annealed I bought. It had not been heat treated by me. It was sold as new, in from the foundry condition.

I haven't found anything else that makes these small chips that seem magnetized.

 

[KeithB]

It could be you ended up with some 4140 pre-hardened, especially if it were induction hardened. Strong stuff but a little hard on the tooling.

 

[Brad]

That would make sense. The HSS cuts but it leave a rough finish.

 

[fiver]

4140 is a common steel for slides and such, it's pretty hard but not so hard it doesn't machine work pretty easily.

it sounds like your not really cutting it, but chipping it away.
a hardened 4140 would be hard enough to act like that.

 

[freebullet]

Brad,
There are metal shops near us you might could get the stuff local. The one I go to most is over in cb. Reasonable price wide selection of metals. I've bought specific types from a joint downtown too. Mine is mostly for cut/weld projects but, I'd bet a decent local source could be found.

 

[Pistolero]

If you want to soften it, heat up to red heat and cover with dry sand to let it cool
slowly. This should eliminate magnetism, too, if it is magnetized, which it sounds like
it is...fits with induction hardening, big circulating currents induced in the part to heat it.

I regularly machine 4140 round stock and have not had much problems, it seems to
do pretty well for me, but I am sure it is normalized state, not hardened.