Problems Drilling Nylatron
I use nylatron for various parts from time to time. BTW, in case it is known by different names I am talking about structural nylon filled with molybdenum di-sulfide. This is a dark gray polymer with a linear coefficient of expansion about four times greater than aluminum. It doesn't conduct heat worth a s**t. It is both easy to turn and a female dog to drill. I would like to know what any of you do to make life easier when drilling this material, especially deep holes of several inches. The problem seems to be twofold. First, the stuff melts easily, a usual problem with plastics. I know about the appropriate rake angles for the cutting edge of the bits but that is not enough. It seems that because of the poor heat conduction of nylatron it does not obey the usual rules for expansion with increase in temperature. Since the heat has nowhere to go it seems the hole expands inwards and binds the bit. This results in a runaway effect. The best solution I have so far is expensive. What I have done is to relieve the drill bit on the grinder starting about a quarter inch back from the tip, taking off maybe 20 thou. I then leave a land at original factory size about every 3/4 inch about a 1/4 inch wide just to keep things straight. I would appreciate any advice from you who have more experience with this material, particularly what lubricants work best. So far, I have found alcohol to work better than anything else I have tried, it cools well through evaporation.
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