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Heat Treatment of punches and chisels


#1

Hello Everyone,

I’ve been researching heat treatment of tools and I want to bounce
this off your collective minds. I’ve read about heat treating tool
steel in Machinery’s Handbook, Corwin’s Chasing & Repousse, C. L-B’s
article here in Ganoksin, some blacksmithing books at the library,
Untracht’s Metal Techniques For Craftsmen and his big book on Jewelry
Techniques, Maryon’s Metalworking, Brephols Goldsmithing book, and
Orchid archives.

My head is full of so much that I’m having trouble
sorting it out. That’s why I need dialogue with you, so I can sort
and make sense of it.

Here is what I’ve come up with.

Step 1. Anneal.
Step 2. Harden.
Step 3. Temper/draw.

I’m using O1 tool steel, 1/4" diameter.

  1. Annealing:

a. The steel is already annealed, so I don’t believe I need to do
that.

b. If I have hot forged the tool should I anneal it to ensure
consistency throughout the piece prior to other operations?

c. If I do have to anneal I must heat it just to the point that it is
non-magnetic, then bury it in some medium so it will cool sloooowly,
around about 1/2 a day or so.

  1. Hardening:

a. Do I need to heat the entire piece then quench, or do I only need
to heat the working edge?

b. Does the striking end need any treatment to better withstand
hammer impact?

  1. Temper/draw: I’ve read of two methods. Is one better than the
    other?

a. One has you quench only the working end for hardening, then
immediately clean the scale off the surface to bright metal, then
watch the heat oxidation colors creep down to your working edge from
residual heat, and then quench the entire tool.

b. The other has the entire tool quenched, then, with scale removed
to bright steel, heat the tool approximately 1 inch from the working
end to watch the oxidation colors creep to the working end then
quench the entire tool.

Thank you all.

Mike DeBurgh, GJG
Henderson, NV


#2

Sounds like you’ve done your homework, Mike. Information overload,
eh?

You’ve got it about right. I wouldn’t worry about annealing, for
this application. If you forged it a lot, you could normalize it to
remove any stresses you created while doing so. That consists of
heating it above non-mag, then setting it aside to air cool. This
brings it back to a normalized state (un-stressed) without taking it
to fully soft. I think for what you’re doing, annealing is probably
overkill.

You want the struck end to be pretty tough (not hard), but not so
soft that it mushrooms. I would personally make the pattern end
about 75 ~ 80% as hard as you could make it, via hardening and
tempering, and the struck end about 40 ~ 45% of same. Not dead soft.
Oh, and do not quench after tempering. Leave it cool naturally. A
nice easy way to temper is to place it in the oven in the kitchen,
run it to about 400 ~ 450 or so, checking the tool color
occasionally, leave it bake for an hour, then shut the oven off and
let the pieces cool with the oven, although that will temper the
whole tool equally, not giving it a differential temper. I suppose if
you were drawing a temper, when it gets to the color you want, you
could quench it, to stop it there. Experiment and have fun!

Just my dos centavos.

Michael
www.radharcknives.com


#3

Hi Mike, Folks…

Here’s a third way to temper and draw…

I have occasionally tinkered with firearms, and the premier source
for gunsmithing tools, supplies etc. is Brownell’s…

www.brownells.com

Their catalog is $5.00 ($10.00 outside US), refunded when you order
something, can order it from their site or call 800-741-0015… If
you know someone into firearms, order an extra one as a present…
Reference and wish book…Shipping free on one catalog…There’s
things jewelers can use in it also…(like O-1 drill rod, e.g.)…

The following info for O-1 tool steel is from their catalog…

As hardened, O-1 is R63-R65 (Rockwell C), which is like extra file
hard…This by taking it to 1500 degrees F, which is cherry to
bright cherry color…

If this is done via kiln or hi-temp oven, then the entire tool
should be draw tempered also…That’s because extra file hard is too
brittle to be a struck end…

If you have a particular Rockwell hardness in mind for your punches,
as long as it’s R54 or harder you can probably use a kitchen oven…
Temps in degrees F…

This for a one hour draw…

As hardened R63-R65 Extra file hard
300 R63-R64
400 R61-R62 File hard
500 R58-R60 Knife hard, Extra Hard
600 R54-R56 Hard
700 R51-R53 Half hard

The verbal hardness designations are kind of subjective, that’s why
knowing the Rockwell C you want is preferable…And again, this for
O-1…Some carbon steels can be spring temper at around 600 degrees
F…

The Brownell catalog has reference the same for W-1, water
hardening…

If you don’t have a quenching oil available, some folks have used
automatic transmission fluid with success…Ventilation is an issue
here…

Hope this helps…

Gary W. Bourbonais
L’Hermite Aromatique
A.J.P. (GIA)


#4

Hi Mike,

I have always made my own chasing and texturing punches. I am sure
ther are many experts out there who will have different methods with
technological terms, but here is a description of my simple process,
as taught to me when an apprentice in a goldsmith’s workshop.

  1. I cut the tool steel rod into the length I require for a punch,
    usually 4 to 6 inches.

  2. To shape the punch I will heat the working end of the punch to a
    red colour and then use a hammer to shape the punch end on a steel
    anvil.

  3. After shaping the working end of the punch I anneal about one
    inch of the working end, heating it to a bright red colour then I let
    it cool naturally on the forge.

  4. Then I will file and shape the punch to suit the purpose it is
    intended for, if it has a smooth surface like a chasing punch, I will
    also polish the working end surface.

  5. Then I heat the working end of the punch to a bright red colour
    and quench in oil or water. This is the hardening process.

  6. Re I polish the working end length with some emery cloth, about
    two inches is enough.

  7. Then I temper the punch, using a small flame I heat the punch
    about one and a half inches away from the working point and watch the
    colours form, while heating the rainbow colours will run up the shaft
    of the punch, as soon as the desired colour reaches the tip I will
    quench in water, the colour will remain visible for you to check and
    if by any chance you over heat you can either repeat the process of
    hardening and tempering or if you under heat and quenched to early
    you can re heat until the desired colour arrives at the tip.

For chasing punches I will quench the punches at a blue colour, for
gravers or skorpers I will quench the tip at a light straw colour.
The punch will last longer if only the working tips are hardened and
tempered. If you harden the whole length of the punch it will be
brittle and may snap in use. I am still using punches that I made 47
years ago with this method, punches made when I was an apprentice.

I make my punches from square and round tool steel rods. The best
are of 3mm. and 6mm. square and diameter. Here in the UK the tool
steels are available from Model Engineer tool suppliers, they are
sold in twelve inch lengths so each length will make two or three
punches.

I hope this all makes sense.
Peace and good health to all.
James Miller FIPG


#5
If you don't have a quenching oil available, some folks have used
automatic transmission fluid with success...Ventilation is an
issue here... 

Do not use ATF this is dangerous both from the flammability issue
and the vapor form it is rather toxic. Corn oil, olive oil, any
cooking oil will work fine.


#6

Thank you everyone for your good Today I’ve finished
making 23 chasing/repousse punches. It is my first time since making
a cold chisel in high school dealing with heat treatment.

I made a list of what I wanted to make first. Liners, repousse,
texture, modeling, running. I used BC" round and square O1 tool
steel. Some I heated red hot and forged, shapes such as rectangular,
diamond, oval, and pear. The rest I ground on a grinding wheel. A lot
of the clean up was done with a cratex wheel mounted opposite the
grinding wheel. I found I could go right to polish after using the
cratex, and with a light touch I was able to refine the shapes very
nicely. Some shapes though were better done with files and sandpaper.
I kept a small bucket of cat litter handy to hold the hot forged
stuff so it would cool more slowly.

While out shopping I bought a gallon bucket of corn oil at Costco
and found empty gallon paint cans at Home Depot. The two made a good
cheap match for quenching. After shaping all the punches to my
satisfaction I secured my torch in a vise and heated approximately
BD" of the working end of each punch, then quickly quenched, moving
it constantly.

After quenching I cleaned them up, removed the oxidation, then
heated each approximately 1" from the working end until I saw straw
color reaching the end, then quenched them. After wiping off the oil,
I think I may have overshot the straw, but I’ll see how they work
out. If I find them a bit soft I can always heat treat them once
more.

Now there is only to use them and see how they work. Again, thank
you everyone for your help.

Mike DeBurgh