I want to take a lot of metal off a some two blade heads with out messing up the tempered steel.  Any ideas on how to take metal off fast without heating it up too much?

I would use a double cut bastard file.

QuoteOriginally posted by JamesKerr:
I would use a double cut bastard file.

X 2

If you have a pedistal grinder (bench grinder) you can use that to remove the metal quickly. You have to keep the broadhead moving (side to side) and quench it in water after every pass on the grinding wheel. You won't hurt the hardness or temper of the steel unless you let it get hot. Don't let the edge turn color and it won't if you keep it moving and keep it cool by quenching it after every pass. It takes a little practice but it's not too difficult.....Lloyd  

Is the entire head temptered or hardened? I know that some of the replaceable blades can't be sharpened very well. I was told only the edge is hardened on these blades.

What Canadian Idle said. Make sure you keep your passes light and even until you get the hang of it. Single direction pass, dip, single direction pass, dip.  The grinder can save a lot of work, and you just have to finish up with files and stones.

QuoteOriginally posted by Canadian Idle:
If you have a pedistal grinder (bench grinder) you can use that to remove the metal quickly. You have to keep the broadhead moving (side to side) and quench it in water after every pass on the grinding wheel. You won't hurt the hardness or temper of the steel unless you let it get hot. Don't let the edge turn color and it won't if you keep it moving and keep it cool by quenching it after every pass. It takes a little practice but it's not too difficult.....Lloyd    

thats good advice

Thanks guys for the advise.  I had never thought about there being a difference between tempered or hardened.  I will have to check what Zwickey's and Magnus use.