Cnc-ing a blade

[Airmanearl]

Hey all, this is my first post so if this is simple info please don't go too hard on me

About a year ago I made a knife out of an old high chromium (or cobalt? cant remember which) saw blade by milling it. The blade turned out decent for a first knife. The saw blade was already heat treated, meaning i simply had to mill and cut out a shape and a bevel without heating the material too much. Recently I got into 3D modeling and 3D printing. Through this I was able to print a plastic knife blade I designed and after tweaking it I've come up with a decent design that I'd like to have cnc'd. The only problem is I don't know how to go about the heat treating process. Would it be viable to heat treat and temper the stock before milling it to reduce finishing time? or should I mill the stock and then heat treat it and deal with the possible warping afterwards? The knife/handle are one piece and there are some complicated angles that i would like kept as close to the 3D model as possible, which is why I'm asking.

Thank you for your elaborate knowledge on the subject

Tl;DR: Heat treat the stock then cnc it or cnc the stock then heat treat the blade?

 

[JG Custom Metal Works]

I'd cnc the stock, grind the majority of the bevels, and then heat treat the blade. Grind/cnc the the majority of the bevels to .040-.050in at the edge and then heat treat. You won't get a ton of warpage if you leave the edge around .050in. Grind real slow after heat because if you go higher than the tempering temp you will lose the heat treatment effect.

I'm not sure how much CNC'ing heats up metal but I'm real paranoid about ruining the heat treat.

 

[Nathan the Machinist]

Milling under flood coolant with sharp cutters won't damage the HT. However a hard blade is usually around HRC60 and you won't be hard milling that very quickly, so this approach will be very slow.

I mill soft then heat treat and use steel that air quenches such as A2 or D2 to minimize warp. You can send to Peter's HT for them to harden, they have a lot of experience keeping things straight.

Edit to add: long thin things like blades are frequently warped a little after machining due to uneven stresses. This can be minimized by using sharp cutters for finish passes which will reduce machining induced stress. Some of these stresses come out during ht and turn straight, sometimes they don't. If you send it to some place like Peter's they can tweak it for you.