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cold hammer finishing blades?


Kristopher Skelton
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  • 3 weeks later...

I went and tried this two ways on two different blades both 1095. First I did it room temp after normalizing then I did it from a red heat and worked until I decided to stop. My hammer is about 4 oz (or so) and I used a lot of fast taps.

 

The effect was about the same for the room temp and red heat. The deeper indentations were not there and cleanup was easier. I'd say the scale removal was more dramatic with the room temp blade as it went chipping and flying; the hot blade scale just sort of popped off without much fanfare

Kristopher Skelton, M.A.

"There was never a good knife made from bad steel"

A quiet person will perish ~ Basotho Proverb

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  • 8 months later...

Cold working tool steel! I wrote a little on this issue in another thread (about how to do marking on blades)In the last ten years I've been learning the arts of coining and coinmaking. This necessarily involves steel dies and the techniques of die sinking. It turns out that in die work there is a very well-understood technique called "hobbing" in which a tool of some shape, called a "hub" or "matrix" is pressed into another piece of ANNEALED tool steel. Having come from a blademaking tradition I was totally shocked at the amount of cold work that is routinely administered to coining dies... the US mint makes tens of thousands of dies every year... all of them are cold-hobbed in D-2 tool steel! I have been playing with this technique... in W-1 and A-2 steels... learning the limits... and I feel confident in saying that it is perfectly safe to administer 10 to 15% cold work to water-hardening tool steel that has been thoroughly annealed. You can anneal again and take it further if you wish.

 

I have not tried it on blades... but I hope to do so. Now 10 to 15% is really quite a lot of cold work! So the planishing that I hear you speak of should be well below that. Annealing is the key though... and must be done fully, preferably by slow cooling in a furnace.

 

I'm hoping to do some further tests and (hopefully) even create some blades completely press-finished with no grinding at all on them... except the edge of course.

 

Be well!

 

Tom Maringer

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Hey Daryl!

 

Long time indeed! Yes, still doing metal work... or back doing metal work after taking a break depending on how you want to look at it.

 

Making the hubs!! Yes that is the trick! Dies can of course be cut directly, either by hand engraving, acid etching, rotary engraving, or the use of small punches. But dies are always in reverse, and some kinds of designs are notoriously difficult to do in reverse... like human faces. For many such shapes it's easier to make the design in the positive and hob it into the die. Techniques can include use of lathe, mill, pantograph, gravers, punches, files, and any combination of the above. I have gotten used to working under a 20x stereo microscope for that sort of task. I also work with a master engraver named Gerg Franck-Weiby and we collaborate on many projects.

 

I have also been seeking (and sometimesfinding) antique vintage steel die-hubs that were made and used in the many small die-sinking shops that used to be in almost every town across the USA. The rise of computer controlled machining has put most of them out of business and this precious library of image tooling is in danger of being lost. Hubs can be used in any combination to make a die. Overlapping hubs is a very powerful technique for creating scenes with depth.

 

One of the techniques of hobbing that was not obvious at first was that you usually cannot hob into a flat surface... the die-blank is turned into a shallow cone shape and the hub pressed into the top of the cone. When I first heard this described I could scarcely believe it... but after doing a number of experiments... it works! The cone apparently provides sufficient backing metal to support the metal flow into the design. The angle of the cone is critical. I have not figured out how to calculate the right angle, but it doesn't take very many mistakes to figure out what works. The process is described in some detail in the book I reviewed in the LIBRARY forum on this site.

 

How the coning can be applied to a blade is not yet clear to me.... it would more likely be a ground or forged extra-thick ridge than a cone. Some experiments at small scale should prove illustrative!

 

 

Be well!

 

Tom

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