Drill Chcuk Runout

I noticed that there seemed to be a fair amount of wobble in my drill bits, and I decided to see if I could identify what was causing the problem. To start with, I decided to measure the runout. On both my 3/8" drill chuck and my 1/4" drill chuck, I was getting somewhere between 0.007" and 0.010" of runout on the shank of the drill bit right next to the chuck. Some really cheapo chucks that I had were only giving about 0.003" of runout. I thought something was fishy.

3/8" Drill Chuck

Unfortunately, I forgot to take "before" pictures of the chuck. Here's an after picture and you can still see the trough that's left (highlighted by the arrows). The metal that was in the trough was ploughed up and caused the chuck to tilt slightly to one side. Bigger...

1/4" Drill Chuck

The identical looking scar on the 1/4" drill chuck. I removed the high spot on both chucks using a diamond hone. Bigger...

#1 Morse Taper (Headstock)

I had two #1 Morse taper adapters for the drill chucks and both had similar looking troughs on them as well. Bigger...

#0 Morse Taper (Tailstock)

Here we have the source of the problem. A gouge, and some rust in the tailstock adapter. I wasn't expecting this on my new equipment. Now I know better to look at ALL mating surfaces. Bigger...

Face #1 Morse Taper Adapter

To remove the gouge in #1 Morse taper adapter, I just mounted it in the lathe headstock and took a couple of very light facing passes. Bigger...

#1 Morse Taper after Facing

Here's a closeup of one of the #1 Morse Taper adapters after facing. Bigger...

Facing the #0 Morse Taper Adapter

I disassembled the tailstock, so that I could use the ram to mount the #0 Morse Tapter Adapter in the lathe and clean up the mating surface. I used paper to protect the surface of the ram, and used an indicator with the 4 jaw chuck to get things running true. Bigger...

Things run MUCH better now. I can get the drills running between 0.0003 (3 tenths) and 0.001 depending on how the drill chuck is seated, and how good the drill bits are. I found that the stamps used to label the drills (on the drill shank) sometimes cause material to be pushed up outside the diameter of the drill bit, and removing this helps as well.

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Copyright 2006 by Dave Hylands