View Full Version : Hardened O1-Maximum sustainable temperature without loosing temper?

01-08-2007, 12:04 AM
I have a metal stamp with raised letters made out of hardened O1 tool steel. I use it to stamp very hard exotic woods. It is not imprinting far enough into the wood (using an arbor press) at least not without dangerous force. I would like to heat the stamp a bit as I'm sure any heat will contribute to softening the wood to allow a deeper imprint.

I would like to take the stamp to within say thirty degrees of the maximum temperature it could sustain without risking a loss of hardening. Would anyone know what would be a fairly safe starting point?

01-08-2007, 01:49 AM
I'd say you're safe to around the 300* range. Which I'm sure will burn the wood. I've never heard of wood getting "soft" with heat. You might try using a steam jet or steam iron to soften the area of the wood to imprint. (Just don't let the wife catch ya messing with her tools.) :D

If your tool has been hardened and tempered, you could also use a hammer for more imprint force. Or, a make-shift fly press, shop press, hydraulic jack, large C-clamp ...

J Tiers
01-08-2007, 08:40 AM
Wood gets "soft" with heat, to some degree.

I would think, as you seem to, that any effect of heating will be at temperatures far below the "softening temperature" and probably below the temperature at which ANY significant change in hardness occurs.

However, I am skeptical for a different reason. The WOOD needs to be hot, not the punch. So if the wood will only be heated by the punch, it may have much less than the desired effect.

Probably if you pre-heated the wood, possibly with a hot metal block laid on it prior to your stamping, it might work quite a bit better than heating the punches hot enough to scorch or burn the wood.

A.K. Boomer
01-08-2007, 10:50 AM
The first thing I thought about was changing the wood also, maybe a steam iron would do the trick, maybe just a simple pre-soak with water and no heat would be needed, i would experiment but if you were even close before you should really be able to bring it around with changing the wood, perhaps a real controlled heating of the stamp and wetting of the wood surface would give a slight burn effect and this would be a welcomed look?

01-08-2007, 12:31 PM
Thanks for the replies so far. I must admit to having much more experience with exotic woods than with maintaining tempers. I have tried some of the ideas mentioned, and each has limitations. Due to the small size of characters (9pt.) heating the wood results in the whole region indenting rather than nice crisp letters like one would be seeking. What you end up with when you heat the wood instead is a gulley with a barely legible imprint.

The strength of wood drops adequately with heat and at lower thresholds than one might imagine. A hot (not scorching) stamp will imprint better, and it only needs to be say 10-15% better than I am getting now going cold.

I have successfully imprinted with hot stamps in the past with heated inexpensive magnesium stamps, but of course they wear out fast. It seems the local heating of only the characters leaves the surrounding material cold and thus at greater strength to support the imprint.

Hammering might work but it is out of the question due to the special needs of the end product.

I just want to add enough heat to the stamp to soften the wood locally, and without jeopardizing the hardened O1 stamp.

CCWKen, I assume you mean Fahrenheit?

01-08-2007, 03:27 PM
300F is safe enough. Depending on the punch it might draw the temper a bit but not enough to matter. It won't scorch the wood, remember Fahrenheit 451, the ignition temperature of book paper?

01-08-2007, 03:31 PM
I'd think you just might get better results by freezing the wood first.
Might be worth a try anyway.

01-08-2007, 03:51 PM
This made me curious so I tried it. I used a letter "M" from a set of 3/16 stamps on a scrap of nicely finished rosewood. With everything at room temp it stamped the rosewood pretty well using an arbor press. Wasn't very deep though because of spring back. I tried freezing the wood with freeze spray which takes it down to -70 or so. That made no apparent difference.

I then heated the stamp with a lighter to the ouch-damn-that's-hot temperature and tried that. It definitely makes a deeper imprint. But, there seems to be a drawback. The open legs of the letter M made a much deeper imprint than the crowded top of the letter regardless of how I placed the stamp.

This was only slightly noticable with no heat but very apparent with heat. Could just be the rosewood? YMMV.

01-08-2007, 03:55 PM
Thanks, I'll try 275 to start. I can't freeze (again due to certain constraints), but I could try cooling the spot first with an ice pack. that is an interesting idea.

01-08-2007, 04:01 PM
Lone characters are fairly simple to imprint, but as one adds letters (say 14) in a single row, it gets more difficult to get it straight, even, and sufficiently deep. The freeze spray in conjunction with heat might make the top of your m more clear. I would be curious to know how that turns out.

01-08-2007, 04:02 PM
I had slightly better results by pressing and holding for a while. I guess it gives more time for the heat to form the fibers, like a curling iron.

A.K. Boomer
01-08-2007, 06:25 PM
Keep in mind that with the letter M some of the m is going with or against and some is going diagonal, this could make a slight diff.

Maybe you get one of those hand held temp. guns and a torch ehh?

01-08-2007, 06:39 PM
Depending on the amount of marking you anticipate doing, you might want to consider either getting a heated branding iron marker, or a dedicated set of stamps that you can heat enough to brand the mark into the wood. A cheap Chicom set can be had for less than $20.00.

The action of marking wood and metal are different, and I doubt that you will be able get enough penetration with common metal marking stamps to make an impression acceptable to you. Once the stamp is pressed beyond the depth of the stock the letter is on, a square mark with an indistinct mark will be the result. If you cannot get it with the arbor press, unless the stamp is hot enough to burn the impression in there will be little to gain, as the wood fibers will rebound.

When hand stamping, assuming you are right handed, stamping from right to left will aid in getting better alignment of the characters, as it permits you to see the previous character.

01-09-2007, 01:53 AM
Back in my factory days, "we" burned the "codes" (date/ lot#/etc) on parts during the production run. It was the operators (not maintance) job to set this up prior to start up. Letters/numbers were heated electrically, and stamped by machine after the part was "spun, folded, and mutilated".
There was no "compensation" for the different shapes of the characters and "burn marks" weren't considered a "blemish". All that was important was that the codes were readable.