Preventing hammer head scale

[Frank Turley]

I am in the middle of offering a 6 day toolsmithing class. One student is a Santa Fe talented silversmith, Liz Wallace, and she had a texturing hammer head with tiny squares indented in contiguous, concentric circles on the round face. Some of the indentations were worn away, so we made a tool to complete the texturing on the normalized face. When finished, we wanted to protect the face from scale when hardening the W1 face to a cherry red. Too much scale would wreck the sharpness of the work. The student had an answer that she used in her work. She mixed technical grade boric acid acquired from the silversmith supply store with denatured alcohol and applied about 3 coats to the hammer face letting each layer dry completely.  Finally, for extra insurance, she put on a thicker coating, allowing it to dry. I decided to water quench rather than use oil, because the thermal shock would cause the throwing of the coating off of the face, or so we hoped. I heated the face at the edge of a coal fire and quenched vertically while agitating. Perfection! The face came out clean and showing bare metal, so we could temper right away while looking for temper color, a dark straw. We tempered with a 3/4" square bar with a turned eye for a snug fit over the hammer head. The head was protruding above the vise jaws and we applied the tempering tool at a welding heat. We achieved the dark straw by heat conduction, and then quickly poured water on the work to hold the temper.

 

The moral. Listen to your students. You might learn something.

[HWooldridge]

That's a great tip - especially for the knifemakers - thanks for taking the time to share.

[mitch4ging]

Neat tip! Thanks for sharing Frank.

[Crazy Ivan]

Sounds like a useful little trick! What was the ratio of Boric acid to Denatured alcohol? 

-Crazy Ivan

[Frank Turley]

Liz did the coating at her home, but she gave me the little jar of the mixture, about 1/3 cup liquid. It had about 1/4 inch of boric acid powder that settled in the bottom. I think she stirred it up and painted it on the object.

[basher]

 you guys state side are lucky enough to have anti scaling compound freely available and ready mixed.

 look up ATP anti scaling compound, its clay based and easy to brush on cold . I use it on all my  blades after they have been ground.

 very easy and much recommended.

[BIGGUNDOCTOR]

At work I use silver solder flux for keeping parts clean, works great.

[Frosty]

I've used borax to prevent scaling with good results. I agree though, listening to your students can be very educational.

 

Thanks Frank.

 

Frosty The Lucky.

[ThomasPowers]

Some of the old tricks used to keep file teeth from scaling during heat treat should also work