• Announcements

    • Alan Longmire

      IMPORTANT Registration rules   02/12/2017

      Use your real name or you will NOT get in.  No aliases or nicknames, no numerals in your name. Do not use the words knives, blades, swords, forge, smith (unless that is your name of course) etc. We are all bladesmiths and knifemakers here.  If you feel you need an exception or are having difficulty registering, send a personal email to the forum registrar here.  
Sign in to follow this  
Followers 0
Bill Kirkley

A2 Heat Treat Questions

19 posts in this topic

I got a box of A2 at an auction. It included a 3/4X1 1/4 inch flat bar. I used it to make a tang filing jig I have seen on the net. 

I used 3/8 inch W1 drill rod for the pins. Now I need to heat treat the blocks.  

I found a recipe that called for stress relieving, preheat, and hardening. 

Do you keep the part in the same foil for each cycle?

After hardening do you take it out of the foil to cool in "still air"?

Should I set it on a brick or metal to cool?

They describe putting wood in the foil.  Would wrapping the part in paper do the same thing?

Is there a need to heat treat the pins?

Is there something I am overlooking?

Thanks!

 

IMG_2926.JPG

Share this post


Link to post
Share on other sites

I think you can leave it in the foil until hardening, and yes, paper is as good as wood.  Since it was annealed to start with and you didn't forge it I doubt you really need the stress relief step.  Since it's thick I'd put it between a couple of heavy steel plates to "quench."  Finally, you don't really need to harden the pins.  Note that I have only used A2 a couple of times for lathe tools, and I didn't use foil. It worked just fine. They were 1/4" x 1" flats, and I just let them air cool holding the non-hardened end in tongs.

I really need to make one of those myself!

Share this post


Link to post
Share on other sites

Thanks Alan! It will be interested to see if the drill rod still has a good fit after the heat treat. I've never done something like this.  

Do you take it out of the foil to "quench"?

I saw on YouTube where someone blasted the part with compressed air to "quench".  Is that advisable or would it be too rapid a cool down?

Edited by Bill Kirkley

Share this post


Link to post
Share on other sites

In case you haven't seen this thread: question-about-a2

Also, here is the TTT (sorry about the image quality, if needed I can redo it better):

A2_TTT.JPG

Share this post


Link to post
Share on other sites

Thanks Jerrod.  Below is the information I found for A2.  It looks like tempering at 950 degrees gives the best toughness and good hardness. 

But what would be best for resisting the file, toughness or hardness?

 

IMG_2918.PNG

Share this post


Link to post
Share on other sites

Hardness is what you are looking for in a file guide.  Toughness is what is going to keep it from snapping like glass.  Hardness resists abrasion.  I would think you want it a bit harder than 56 HRC.  I would think that 60 would be better, but I am not familiar enough with A2 to say how brittle that would be.  A super hard file guide does no good if it snaps in half.  

Share this post


Link to post
Share on other sites

I agree, most files are around 59-60 HRC.  The holes ought to be okay. Air hardening steels were developed to hold dimension after hardening more precisely than oil- or water- hardening steels.  Ideally you should take it out of the foil.  Dunno about compressed air, that may be too fast a "quench."

Share this post


Link to post
Share on other sites

Thanks guys. According to the chart I have tempering at 300 degrees gives a hardness of 62 and 400 degrees a hardness of 60. 

Do you think it would matter if it were a little brittle?   There should be no impact. The only problem might be if I dropped it. I believe files are pretty brittle yet functional. 

My foil is supposed to arrive tomorrow so I will heat treat it Saturday. 

Thanks again for your help. 

Share this post


Link to post
Share on other sites

It isn't just impact that you have to worry about.  Flex is what I would worry about the most.  If you over tighten the clamping on the ends and flex the brittle bars, they'll crack/break (possibly shooting a wedge of A2 straight out).  

Share this post


Link to post
Share on other sites

Good point!  I guess I'll temper it at 400 which in theory will be a hardness of 60. 

Share this post


Link to post
Share on other sites

If you're able to machine.
One of the things you can do is machine inlets to take carbide inserts.
That way you can temper back below file hardness and the carbide inserts are what contact the file.
You can also use it on the belt sande.

 

Share this post


Link to post
Share on other sites

J J, that's an interesting idea!  If I did that I don't think there would be a need to heat treat. Taking it a step further they could be made out of mild steel. 

I guess I would machine a slot so the carbide blanks would sit a little proud and epoxy them in place.  Does that sound right. 

Share this post


Link to post
Share on other sites

I don't know anything about carbide blanks. A 1/8x3/8x6 inch blank from usacarbide.com is about $11.00. The same size on mscdirect.com is about $57.00.  Any idea why the discrepancy?

Share this post


Link to post
Share on other sites

J J, I have used carbide inserts on my lath and had one break from misuse.  I think they may be brittle. If that's the case would they possibly crack if the steel flexed from tightening as Jerrod pointed out?

Share this post


Link to post
Share on other sites

Carbide is very brittle.  Though, if it is glued on really well, that may not be a problem.  Who cares if it cracks?  The base metal (mild steel) that it is glued to won't, and thus everything stays together.  Just a thought.  Maybe I'm wrong and everyone doing this should care.  

Share this post


Link to post
Share on other sites

The carbide idea is interesting but I am going to heat treat for the experience. I may try J J's idea later. 

Share this post


Link to post
Share on other sites

I actually made my file guide by brazing carbide onto mild steel plates. I have very easy access to both, and felt better about brazing than using epoxy

Share this post


Link to post
Share on other sites

Dan, I've never done brazing.  I'll have to give it a try. I'd love to see your guide. Will you post a picture?

Edited by Bill Kirkley

Share this post


Link to post
Share on other sites

Well guys I don't know!  Unfortunately I did not test the jig with a file after it cooled down. After one 80 minute cycle at 400 a file did not skate across the edge with moderate pressure.  With light pressure I guess it did. It definitely bit into an annealed bar more than the one I heat treated  

My anvil is advertised as a hardness of about 54.  I tried the file on an edge and it didn't skate any more than on the "hardened" filing jig. So again I have no idea if the jig is hardened much.

Each half of the jig was wrapped in paper then foil. They were placed in a room temperature Paragon fernace and heated to 1400 degrees at full ramping. They were held there for 30 minutes then heated to 1775 and held for 30 minutes.  It took about 45 minutes to cool to the point I could grasp the pieces for a couple of seconds.  At that point they were tempered once. 

The file does skate on the flat surface. But it does that on mild steel as well!   So maybe it will work as is.  

I am going to do another one.  Maybe the file will skate if I try it before tempering. 

The pins fit just as well as before the heat treat.  The bolts also fit, but one was a bit snug.

 

IMG_2946.JPG

IMG_2945.JPG

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0