I recently obtained some old rasps and tried to forge weld one to an
old leaf spring.
I didn't fully anneal the rasp and after ~20 blows I had a major break
Besides cracking/breaking of metal thats too hard during forging, would
having the metal at dead soft actually -help- get a good forge weld?
I know its not nessassary but.... anything to help get a cleaner and
quicker weld is always a good thing.
When you heat the steel to welding temperature it will be dead soft.
The important thing to remember is that high carbon (tool steel) is
very fussy when it comes to welding. It burns at a lower temperature.
You will need to be very careful when you get to the critical temps for
welding. I would suggest that you make sure that your fire is very
clean and that you flux thoroughly. Also, make sure to wire brush the 2
pieces VERY CLEAN prior to fluxing.
Sounds like the rasp is getting too hot.
When the metal cracks does the metal look granular or is it a shear?
If it's granular then it's too hot, if it's a shear then you're working
the metal cold.
You're very adventurous, welding high carbon with high carbon, I tip my
hat to you for "balls".
P.S. Paul's advise is very good btw
John Fly wrote:
I'll have to check that out, but I believe it was shear. I might have
let the piece get too cold on my first heat.. so that could have
started a crack, I know that it piece was good the second heat(when it
opened up) because my first 3-4 hammer blows felt very good and the
metal moved quite nice. Its just when I hit a paticular spot it just
kind of "opened up on me".. oh well..
As for keeping the metal clean.. I think that was my last real visit to
a coal forge.. i'm planning on working up a propane forge so no more
time lost tending the coals and pulling out metal covered in
I suspected that at working temp the metal was dead soft but I'm no
metallurgist and turn to the community to make sure I'm not missing
Heck for most guys this is hobby-talk and hobbyist would almost pay
someone to listen to our crazy hobby-talk. ;)
My girlfriend gives me special rates depending on whether its about
guns or knives or dogs or old pickups. Anybody else got that good
of a deal? :)
Alvin in AZ
Did you grind all the teeth off the rasp before you started? It might have
cracked because a tooth got folded over and acted as a fulcrum. I've tried some
file material before; it has a tendency to be finickey during weld. I've had it
crumble, and crack. I think it's a temperature thing, narrow working range.
Keep after it, you can get good results if you're careful. There's no such
thing as too much flux. One thing, it's gorgeous after the HT, so it's worth
just a couple of silly thoughts for you.
Were they good quality rasps? as some files/rasps are case hardened and
this might cause a problem, can't think why though.
Also i remember hearing that some files/rasps are cast - cast steel I'd
suspect - anyone think this could be the problem? if it were cast and
case hardened, well that could be a nightmare.....
The only issue I have with the teeth is that they can cause a cold
shut, or possibly lots of them, and harbour lots of crap inside the
weld, Maybetry taking them off first and see if this helps.
finished on the first weld and you have stressed it. The cracks have
opened up when you started working it again. Work your carbon steels
in a narrower range of temps, - the higher the carbon, the smaller the
range you have to work them in -, soon as it starts to cool don't be
tempted to keep hitting it as you would with mild steel, get it back in
Also, don't forget to flip the work on the anvil, as the side in
contact will cool quicker than the other side, and stress quicker.
John Fly wrote:
And I have a couple of those too. :)
I've spark tested about 100 files and about 20 hoof rasps, stuff
from all over the world.
Only one appeared to have a high carbon case on it and that was an
old Nicholson hoof rasp and the inside was just like all the rest
tho'... looks like 1080 or cold chisel or railroad rail.
The files seem to be "1.22% straight high carbon steel" with nothing
at all added to it to protect it from you and your forge fire or me
and my heat treating fire even. ;) I've got a few around here that
when broken look like cast iron from the excess carbon oozing out
into the grain boundries from me over heating them in the effort to
simply normalize them.
About one out of five of the files are higher carbon than the 1.22%C
steel like 1.4%C. Those were the "good cuttin" ones. :)
Don't know what good that will do you guys, but for sure it's going
to be tricky to work with. :/ If you can master it you will be way
ahead of me, I wasn't even able to correct those files I messed up.
A knife made from those files (and some 1095 I over heated too)
can't be sharpened. No kidding, it's like trying to sharpen a
brick. The edge crumbles away and never feels sharp, not "rough
edged" like it'd been sharpened with a file... just dull, like the
corner of a brick.
It's easy for me to work around their finiky nature tho, I simply
don't normalize -anything- anymore. :)
Instead I do what might be called a "lazy man's anneal" or what I
call "draw the temper all the way" by getting files and circular
sawblade steel and other stuff like that, up there between 1000F
and 1300F and call that good enough.
Alvin in AZ
I find file steel really nice to work with, the occasional one is a
total steaming pile, but other wise good for forge welding. I did find
that trying to forge weld a piece of spring to a piece of file steel
didn't work for me, although I was thinking of putting in a mild steel
divider between the spring and file steel.
P.S. If it wasn't for silly thoughts I wouldn't have any thoughts at