hi guys,
ive got access to a whole lot of 7mm rod that id like to heat treat for speargun spears.my question is does anyone have a good method of heating a long rod evenly ,and more importantly a way ov keeping it straight thru the whole process.i thought about welding the ends of the rod to fixed points so they cant move, but i think they would sag when they get to a heat treating tempurature.your input would be appreciated.
thanks, casey

I would think that only the tips of the spears would need to be hardened and tempered.

because they are so long and skinny they need to spring back to there original straightness.if they get bent they dont shoot straight.

A friend of mine is a swordmaker and his sword heat treat furnace was vertical so he could hang the blades during heating---also inert atmosphere so they didn't scale.

Note that for small stock it may have been coiled at some point and so surprise you with it's memory...

thankyou thomas,sounds like a simple solution. ill try it and report back here.

To be able to be heat treated first you must know if the material is hardenable. The easiest way to know the content of the steel. The field shop way is to take a short section of the bar and heat it to non magnetic and let air cool if that does not harden then do the same with an oil quench,,if needed go to water quench if that does not make it hard your done..If any of the above make it hard you will need to temper. There are bps in here that tell you how to treat known steels. When you heat steels they expand. If you fix each of the ends solid the middle will expand and if it cannot move down its length it will move out from the center line. I think industry uses an induction coil to heat and lets it move downward into a quench bath. may be a bit tough for a home shop but like mentioned above a vertical forge with openings on top and bottom and the quench tank below could let you give it a go. Let us know what you do and how it works.

thanks rich,yes we have got hardenable steel,and the right formula for heattreating it ,its the warpage im concerned about. another thought i had was rolling the rods between two flat plates while tempering them.that might keep them straight but the logistics of that are pretty trickey too.
i guess well have to just give it a go and see.
thanks, casey