Dealing with people who dont know fractions

Whoever came up with fractions should be kicked in the balls. Fractions are good for nothing but setting the stage for crappy tolerances.
 
I came across an old home made drill extension that was soft soldered together and a small pin through it. The bottom of most drills have a softened shank to prevent shattering and allows the chuck to hold it better. The standard 12.8mm drill bits out here are less than $20. So if the shank is turned down to 9 to 9.5mm (3/8) and a piece of 1/2 inch 4340 or 4140 bright rod is used, drill out the rod with a 3/8 drill, you could either solder it or glue it with loctite 620 high temp high strength glue and then put in a 3mm or 1/8 cross dowel. You can then ,make the drill as long as you like. Keep in mind that a 3/8 drill is about 1/2 the area of a 12.8 drill. So to reduce the loading on the drill, particular when drilling steel, the pilot drill will want to be 3/8 or larger to reduce the load on the extended drill. Keep in mind that the longer the drill the higher the twisting moment with the cutting forces over the drills length. The above can also be used to extend taps as well, except you can grind a slot in the very bottom of the tap and a pin will align to that slot as you assemble it. The pin will help prevent the initial twisting etc. Again they can be either soft soldered or glued with the 620. Have fun.
Neil
 
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