grind cutting edge before or after hardening?
So seeing everyone's work here has inspired me to try my hand at making a few blades. I have roughed out two blanks this week from some A2 I had around the shop n they are now ready to bevel. I am going for a chisel grind for simplicity and want to do a 15 degree primary bevel to take out weight and then come back with a 30 degree cutting edge. My question is should I grind both bevel and edge before hardening, or should o only grind the primary 15 degree bevel, leave about 30 thousandths of thickness n harden it, n then come back n put the final 30 degree edge on it after hardening?
Take down to a dimes thickness. You want some thickness to keep the metal from cracking or bending while heat treat.
Posted Via AR15.Com Mobile
Do most of the work prior to heat treat. It can be a b**ch to try to smooth out grind lines and divots after it is hard. Get it as close as possible and clean it all up.
This is funny cause it seems there's alot of ways. I make them sorta sharp and then hit the edge a couple times, as evenly as I can across the belt. The edge is about as thick as a credit card when I get heat treat done.
To make it sharp and evenly remove the edge will show you any fucked up spots to. I tend to get the base of the blade thinner the the belly fatter when I grind.
I would say that you need to work with the equipment you have. If you have a nice belt sander go ahead and leave the nickel or dimes width before heat treat to avoid any problems. If you're working it with an angle grinder, file and a wet stone you might want to take the grind down further before heat treat to save yourself some serious time.
Before I invested heavier in my equipment in my "garage days" I would go down to a nickels width before heat treat and just slug it out with the piece I was working on. Well, before I got smarter..
I always grind my primary bevels down to about 20 thou before heat treat. The only blades I've had warp during heat treat were high carbon steel and were ground down to almost zero. If you leave the edge between 20-30 thou you should be fine.
leave 020-030 on the edge, if its sharp it can crack, even A2. Finish all you can while the steel is soft its alot easier to work than when its hardened. 58-59Rc is nice. I do a cryo temper after the first temper then temper again.
Took the edge down to a dime thickness today, going to sand and buff it all out and then send it for heat treat. I am going for around a 59rc hardness i think. Any suggestions? Photos to follow.
I tend to leave mine just a tiny bit thicker than normal. It takes a shit ton less time to finish grind off a little more material than it does to straighten a blade that warped because it was ground too thin.