Drilling 440c

[Hitandhope]

Help please. I'm a bit of a novice, been making knives for a few years from broken car springs, lawnmower blades etc with decent results.
So I bought some 440c to make a useable kitchen knife for my wife but I'm lost with the heat treatment, I'm trying to anneal it to drill holes for rivets, 40 minutes on yellow heat made no difference cobalt drill bit still fails to bite. Is 440c tricky like this? I have a normal propane forge, my ir thermometer does read past 600c.
Tempted to cop out and put dummy rivets in but advice welcome.

 

[Stuart Davenport Knives]

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Just some advice.....

440C comes annealed. You shouldn't have to anneal it just to drill some holes. Sounds like the steel might be work hardening due to dull drill bits, wrong speed, something wrong with the drilling process. 40 minutes at a "yellow heat" is just going to make things worse. Plus, you really can't heat treat 440C in a propane forge without a very tight temperature control system. And your IR thermometer is not going to be accurate to judge heat treat temps.

With your setup, I don't think there is much you can do with a stainless steel like 440C. After the 40 minute hold at "yellow heat" the knife is now hardended to some extent, and will require an annealing process to soften it and set it up for the hardening stage. Not really a thing you can do with your equipment.

I would start over with a new knife, but this time make sure your drill bits are sharp, at the right cutting speed, using the right pressure, and with cutting fluid. You should have no problem drilling annealed steel with good drilling practice. If you don't want to start over, you can always use a caribde tipped masonry bit. Go high speed, no cutting fluid, just let the carbide tipped bit go to town. It is sort of the opposite of normal drilling with cobalt bits. The hole will be slightly oversized, but you can drill through hardnened steel with those carbide tipped masonry bits.

However, the microstructure of the knife is going to severely compromised after that 40 minute hold at a yellow heat, and 440C requires a long soak at a precise temp to harden correctly, and is just about impossible to do in a forge without thermocouples regulating air/propane flow. And also the knife needs to be protected from the atmosphere inside the forge (or electric heat treat oven). Normally this is done with stainless steel heat treating foil.

 

[DevinT]

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