Acoustic Guitar Construction

I've been wanting both an O1 1/2" Violin knife and a shorter 1/2" chisel for some of my work. With a little research on tool steel hardening, I decided to give tool making a shot.

I ordered some basic precision ground O1 tool steel from McMaster, and set up two kilns, and a can of used motor oil for quenching.

I used this document, as well as the Starrett O1 specification on the packaging, as a starting point for my heating schedule:
http://www.buffaloprecision.com/data_sh ... 1TSbpp.pdf

The first kiln I set up to heat to 1500 degrees F as fast as possible - and placed my O1 steel in while cold, and and let it come up to temp with the kiln. This took approximately 45 minutes - I then let the pieces soak at 1475-1500 for about 15-20 minutes.

The second kiln was set to hold at 350 degree F to allow hardening to roughly 62 Rockwell. I started this at the same time as kiln 1 so it would be hot and holding ready for annealing after the oil quench.

After the steel had soaked at 1500, I used a long handled pair of pliers to take the steel directly to a can of used motor oil. PLEASE KEEP A FIRE EXTINGUISHER NEARBY. I did not have any flair-ups, but there is a real potential for an oil fire when quenching 1500 steel. A quick dip and light agitation in the oil bath, and then into the tempering kiln for about 45 minutes.

The whole process was pretty easy once you have your heat sources set up.

This opens up a lot of possibilities for custom tools.

Daniel, I find the idea of making my own tools fascinating and hope to give it a go one day. Here is a link to some more info I think you will find interesting and useful.
http://www.threeplanes.net/toolsteel.html
Thanks for the post.
Jim

Jim - thank you for sharing that link. Of particular interest was the section about cryogenic treatment (something I remember being shrouded in mystery and mojo in my tube amp building days) - very rational/technical explanation for why its valuable in A2 steels, and not necessarily so in O1 (we see this debate on occasion between Lie Nielsen cryo'd A2, and Veritas O1/PMV-11)

I had been wondering if I would gain anything from a liquid nitrogen treatment for my O1, but from that brief explanation I would gain nothing from the effort.

I'm fortunate to have access to an old Vega Brinell Hardness tester - so I can double check my work.

The test is performed by driving a 10mm diameter carbide ball into the surface of your material with exactly 3000 kgf force, and measuring the resulting indentation. This is a destructive test, but the mark is small enough that I won’t mind having it centered on the handle of the chisel. Using a pocket optical comparator with a metric scale you can measure the diameter of the indentation left by the carbide ball - in this case about 2.35mm. Referencing the appropriate chart we see the hardness of 682 Brinell, or 61.7 Rockwell C. Not bad, considering the target was HRC 62.

Very interesting, but without the tools, out of my league.
Thanks
Herman

Herman,

This is just one way of doing it - the same can be accomplished with a propane torch and a mill file.

Way to go Daniel. I have a Paragon 14" oven with that same controller. My knife making has taken a back seat to guitar building the last few years, but I've been wanting to make a couple of small chisels for binding channel, and other detail work. I'm going to have to fire up the oven and get out an annealed file that is just waiting to become a chisel.
Thanks for sharing.

Kevin