Subject: Of knives and files...

From: Jim McCarty <[email-masked]>
Date: Tue, 16 Jul 1996 10:14:53 -0500

To add to the discussion on old knives as files, I dug through my back 
issues of the BAM newsletter and found an excellent article on teh 
subject. Thought I would share a little with you all:

Since the beginning of this decade Nicholson files have been 1095 (the 
10 stands for plain carbon steel while the 95 is the percentage of 
carbon = 95 percent carbon).Even with this much carbon the files need 
to be harder. So files are usually casehardened. In the old days this 
was done with the following recipe:

"Take ox hooves, and put them into an oven to dry, that they might be 
powdered fine; mingle well one part of this with as much common salt, 
beaten glass and chimney soot, and beat together and lay them up for 
your use in a wooden vessel hanging in the smoke; for the salt will 
melt with any moisture of the place or air. The powder being prepared, 
make your iron into a file, then cut it chequerewise and crossways 
with a sharp edge tool. having made the iron tender and soft, then 
make an iron chest fit to lay up your files in and put them into it 
strewing on the powder of course, that they may be covered all over; 
then put on the cover and lute well the chinks with clay and straw 
that the smoke of the powder may not breathe out; and then lay a heap 
of burning coals oall over it that it might be red hot about an hour; 
when you think the powder to be burnt and consumed, take th echest out 
from the coals with iron pinchers anbd plunge the files into very cold 
water and so they become extremely hard. This is the usual temper for 
files; for we fear not if the files should be wrested by cold waters."
(This is from the 13th Book of Natural Magick, 1589, GB Della Porta)

Back to files: this 400 year old case hardening is basically the same 
process used until recent times. INstead of ox hooves modern files 
were made with potassium ferrocyanide and boiled in salt water.

While the article says the current 1095 files are OK, it recommends 
getting some made before 1980 for the best edge holding steel. These 
files will be 1.2 to 1.4 percent carbon steel, which is higher carbon 
than can be found anywhere else. (Rasps are 1035 steel case hardened 
to save the tips.)

Ther are a couple of ways to identify pre-1980 files. Look for files 
marked Black Diamond on both sides, which dates them to 1975 or older. 
Later files were marked Black Diamond on one side and Nicholson on the 
other.

Also, look at the tangs -- on old files they were  hot rolled to save 
steel. Modern ones were sheared out.

The high carbon in these steels makes them much trickier to wrk than 
say 1070 spring steel. If you overheat and coarsen the grain it won't 
take a good edge. The article recommends forging at a lower 
temperature than you usually would. Invest in a couple of Tempilstiks, 
which are crayons tha tmelt at a specific temperature. In this case 
you want to work at 1550-1600 deg. F. After working the blade heat to 
1300-1400 for a while, then buryit in wood ashes or lime to anneal. 
Most steels would be annealed at a higher temperature. Use this lower 
heat to keep the fine grain structure.

Now grind off all the scale or it will crack in heat treatment. To 
harden heat to 1440 or 1450 deg F for about 4-5 minutes and quench in 
brine. Again, invest in a Tempilstik becuase it's too hard to judge 
this temerpature. Do not overheat.

The quench is important. If you want to be traditinoal use the urine 
of a 3-day old goat fed only ferns for 3 days. Otherwise, use salt 
brine made in this way: Mix 13 ounces of common salt to a gallon of 
fresh water. This makes a 9 percent salt brine. Keep your brine cool 
or at room temperature.

Don't quench file steel in oil. It won't harden well at all.

How you dunk it in the wquench is equally imprtant. If you belly flop 
it in it is guarenteed to warp. and may crack too. Instead plunge it 
straight into the brine. Move the knife in a figure 8 pattern while it 
sizles Remove while still warm and temper as soon as possible.

Temper at least at 450 deg F or better, 500 deg.F Try tempering at 
500, then see it is too hard. If it is temper again at 600. You can 
use an oven for this if you get all the grease and oil off and have a 
sympathetic spouse.

If the blade is crooked temper first before trying to straighten. Then 
heat to 300-400 and straighten while hot. Do not heat to blue and try 
to straighten. For some reason knives tempered to this range become 
brittle.

Rasps are another animal. They are case hardened but under this layer 
are fairly soft. Raspos are worthless for edge hilding tools but great 
for throwing knives, which don't need a great edge but must be tough 
so they don't break. Temper these at 700 degrees.

If anyone wants the complete article, which originally came from the 
California Blacksmith, send me a stamped, self addressed envelope and 
I will make a copy. Hoep this helps out -- my address follows:
Jim McCarty
5821 Helias Dr.
Jefferson City, MO 65101

-- 
Jim McCarty
Father Helias Forge
Taos, MO
Editor Rural Missouri Magazine
Newsletter editor, Blacksmiths Association of Missouri

³Foolish consistencies are the hobgoblins of little minds³