Friday, May 20, 2016

Part #3 - Drawbar Addition

I have in the past tried some milling on a drill press. Usually by using the side of a drill bit (crude to say the least) and I was never aware of the danger in doing that. Since then I have read many posts that strongly state how dangerous this is. The Morse taper in the spindle and Jacob taper in the chuck will come loose if side pressure is applied. I didn't even know these tapers were present and so I have reached my first hurdle. How do I keep the chuck in the spindle? Like a milling machine does, with a draw bar. That required drilling a hole through the center of the spindle. I had no idea how that is done but after some research the answer was a gun drill. My press has an MT3 taper and mills with that taper use a 3/8"-16 draw bar. I didn't feel that the diameter of my spindle shaft would be happy removing that much material so I went with 1/4". My rough calculation says I would still have over 90% of the shaft strength left which like plenty of margin. After some web research, e-mails and phone calls I found a shop that would drill it for the shop minimum of $75. I considered this the riskiest part of this whole project because if the spindle was damaged the press would become scrap. He said he could keep the hole within a few thousandths of center so I went for it.

The spindle ready to be drilled

Still plenty of shaft left

Hole in the top of the belt guard.

Close up showing the drawbar end and 12 belleville washers.

The ER32 collet, drawbar and threaded adapter.
The hole came out within the 0.010" of center. So with the spindle drilled, add a hole drilled in the top of the belt guard, a long piece of 1/4"-20 grade 8 thread all ($5), a cool 1/4" to 3/8" adapter (e-bay $2 for 2) and an ER32 collet holder ($60) and I could now safely apply side force to the spindle without fear of spinning parts flying around the shop.

1 comment:

  1. Not sure if you are still around but this is great. I found it because I would love to do this so I could mount a large Chuck and safely "lathe" a piece of 1.5 inch round Al bar. But, I would need a lathe to drill the hole in the spindle! If I had a lathe, would not need the mod. Catch 22! Could do as you did with the machine shop though. Well done!