stress risers in air quench steels

G

gshamr

Joined
Jan 18, 2002
Messages
178
I'm about ready to send my first two homemade blades to be heat treated at Texas Knifemakers Supply. They are made from 3/16" A2 from Crucible Metals, and are full tang designs.

I made a deep scratch in the tang of one while trying to deburr the drill holes. I already thinned the tangs out as much as I wanted, and the scratch will be covered by epoxy and micarta.

My question is: Are stress risers a factor in air quench steels like A2? They won't be doing any nitrogen flush, just a gradual cool down. I thought they really only came to play in oil quench, and forged steels.

These knives will be for my own use and not for sale. I'm using a sanding drum on my portable drill to grind the bevels and it's a pain to do.

Thanks.
 
My question is: Are stress risers a factor in air quench steels like A2? They won't be doing any nitrogen flush, just a gradual cool down. I thought they really only came to play in oil quench, and forged steels.
Click to expand...

Stress risers are always a factor, in any steel. Especially in the case of hardening. However they will be more or less of an issue depending on design of the part and heat treatment it receives. With an A2 knife though you should be fine with any standard A2 hardening and tempering operation, even a relatively coarsely finished blade. Hartsfield hardens at a 40 grit, for example. Perhaps a pic would help, but I doubt you made enough of a scratch to be a real issue in your scenario. I think you'll be just fine. Good luck on it.

Oh, if deep scratches are in any part of your knife though, that you later plan on polishing out, you're gonna have all kinds of fun trying to remove it after hardening and tempering. Just FYI. :p

-Jason
 
Thanks Jason.

I thought I would have more leeway with thick A2. Within reason, of course.
 
Scratches, deep and otherwise, are good for any parts that will be covered by a bonding material. You DO want scratches on tang surfaces if a bonding material is used. You also want marks on the inside of scale material. Make them on purpose but only on scale material where profiling the scales will not cut into those areas of scratch, gouge, marks. Of course tangs should not have scratch marks about its visible perimeter.

Roger
 
No problem.

An added note: In my work I tend to grind no coarser than 80 grit and establish an overall 120/180 grit prior to heat treatment and slick up the blunt edge, nice and smooth. Just a minor precaution, but I'm also dealing with differential hardening where edges like to rip apart. You'll still be good, just food for thought.

-Jason
 
Jason,

Are you speaking of tang grind or blade grind at 180 grit? I have to presume its tang grind.

Roger
 
I've got them at 80 grit and thought about scratching the inside of the micarta before the epoxy. Thanks. You saved me from asking that question in the future.
 
You are OK with the scratches in the tang, that should not present to be a problem. When you get the blades back from HT, grind off the discolouration (scale or decarb) from the tang prior to attaching the scales. Make it rough so the epoxy has something to bond to.

A number of folks will hollow grind their tangs somewhat. Most importantly, clean all surfaces to be epoxied well, that is key to a good bond. I use acetone and try to keep my oily hands from touching any of the surfaces. I use latex gloves while applying epoxy. It keeps it off my hands (easy clean up) and prevents any body oils from the cleaned surfaces.

One other bit of advice, request for the heat treater to provide you with what Rockwell C hardness they tested at after heat treat.

C Wilkins
 
Originally posted by rlinger
Jason,

Are you speaking of tang grind or blade grind at 180 grit? I have to presume its tang grind.

Roger
Click to expand...

Roger,
On another note, there are a number of smiths that go no further than a 120 grit finish on their blades prior to heat treat. I personally go to 220 but give it a try sometime...

C Wilkins
 
You must log in or register to reply here.
Back
Top