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Louisiana Metalsmiths’ Association, It’s staff, directors, officers and members specifically
Disclaim any Responsibility or Liability for damages or injuries as a result of any construction, design, use or application of information contained in any of the following articles. The use of any information is solely at the USERS OWN RISK

Ed,
This subject has come up before on theforge. I had the following copy of a handout from a Brunner&Lay rep on a disk so here it is. Be warned that sharpening these points may make you open for a lawsuit if
someone is hurt when a point you sharpened breaks. Even if you have insurance you could go broke defending yourself as apparently has happened before. (thanks Bob Bergman and Dave Mudge)
You are on your own Ed.  Bob Schade
________________________________


Instructions for Sharpening and Rehardening Brunner & Lay Moil Points

Brunner & Lay Moil Points are hardened all over and in order to maintain
this hardness throughout the life of the tool we suggest the following procedure:

To reshape the point, it should be heated to a bright red, preferably not to exceed 1700° F. The heat should be very short, not to exceed 1", and only sufficient to do the necessary pointing. After forging, the tool should be allowed to cool in air. If quenching oil is available it would be well to quench the point immediately after repointing and then proceed to harden. For hardening, heat the point a very short distance back from the cutting edge to a cherry red or about 1450° F. and quench in brine about one inch back, leaving a certain amount of heat in the steel just above the quenching line. This heat is usually
sufficient to draw the temper in the point back to a blue color and as soon as this takes place, the entire point should be quenched in water.

The proper tempering heat is 450° F. To observe the temper color the point should be polished with an abrasive or by rubbing on a sanded board. This should be done immediately on removal from the
brine quench. When drawing the temper by color, it must be carefully watched and the entire point quenched in water immediately the color is observed.

The average blacksmith is inclined to give the steel too much heat, both for forging and hardening. It is always advisable to heat the steel slowly and harden with as low a heat as possible to obtain
the required hardness. Also note that the heat must be confined as closely as possible to the point to avoid drawing the temper out of the remainder of the tool.

If the tool appears to be soft on the cutting edge, it indicates hardening at too low a temperature or too high a drawing temperature. Brittleness or chipping is due to hardening at too high a
temperature or insufficient drawing of the temper.

Keep the point sharp, because a dull tool is hard on the steel, the hammer and the operator. Sharpen them properly and your tools will pay dividends on performance.
__________________________________________________________

>I had the opportunity to re-work jackhammer bits with an experienced smith from a local paper mill one day.  I was impressed with his technical skills, and he worked many bits over the years but Iím still not confident that he was tempering the bits correctly.

He simply heated the end of bits to red (after forging) and quenched the last 1 1/2 inches or so in oil, then  rubbed it with emery cloth and watched the color until the tip was purple-blue.  Then he dunked the whole thing in oil, while the bit was still red about 2 inches back.  Seems to be inviting brittle failure.  I have always understood the objective with tools like these was to provide softer steel to back-up the hard tip.

It seems to me that you should allow the bit to slowly cool all the way down after forging, then heat a limited amount of the tip to hardening temperature, quench, then re-heat back from the tip but NOT to the hardening temperature, and then quench the whole thing when the tip is blue.

Maybe a better way to do it his way would be to allow the tip to cool, heat the tip to red, then submerge the tip in oil just the right distance so that the heat left in the bit back from the tip was just enough to make the tip get blue but not enough to re-harden the heated area (back from the tip) when the entire bit was finally quenched.  Although, this method would not get the tip down to a very low temperature in the hardening stage.  Some smiths are adamant that this is important.

I have been asked to re-work 3/4 in. and 5/8 in. air-hammer bits and I am especially concerned about embrittlement of the bit.  I would guess that the large diameter bits that  me and that old smith worked could be more forgiving (tougher to shatter).  Not to mention that these smaller bits can be placed in a hammer and held near the face!  Another concern I have is the possibility that the bits were made from some wild Swiss steel or something that wonít behave as Iíd expect.

Is anyone out there willing to share some knowledge and experience on this?     Ed

Ed:
    For the last three years I have been working in a shop were we do 100 to 200 bits a week on average. The large bits (points, chisels, and asphalt cutters) are forged under the power hammer, tips ground while
yellow/orange, and approx. 3/4" of the tips quenched in water for about three seconds. The tip which is gray is watched until the residual heat in the shank turns the tip to purple, the tool is then plunged into the
water for approx. a sec. to stop the tempering and put aside to cool. The smaller bits are heated, forged by hand, edges ground while hot and put aside to cool. Later that day or the next the cutting edge of the
toll is then heated to a cherry red and the tool put in the oil bucket (used crank case oil). Tools have been done this way here for the last 20 years, and the only breakage we get is when the operators use the
bits as pry bars while hammering, and they break up around the collars. I don't know if this is the technical way to harden and temper these tools but it works for us.     John C.