View Full Version : I buggered a drill chuck...

02-23-2008, 10:06 AM
The chuck slipped on my R-8 mill. I was working a 3/4" drill pretty hard and the chuck spun off the taper. OK... put it in the press and press it back on. Thing has baaad run out. Take it off and apart...look for something fishy... nothing. Press it back on.. TIR is horrid. Take it apart again... reassemble a half turn different than last ime. TIR is still horrid.
So what do you think happened?
The soft china arbor or something soft inside the chuck body... got buggered when it slipped?
I can't really see it bending. A JT6 mount on an R-8.(.002 run out on that now) (probably always was)
It was a POS chuck anyway so I'm not too broken hearted. Just wondering what got screwed.

A.K. Boomer
02-23-2008, 10:21 AM
My guess would be a hard to see Caca-burr inside the chuck.

Lew Hartswick
02-23-2008, 10:41 AM
Russ, Lesson 1: when at all possible (especially with large drill bits)
use a collet to hold tool.
I have been trying to get people to use a collet any time they use a
S&D drill bit. I even use them when I have the right size collet for
smaller ones.

Paul Alciatore
02-23-2008, 10:52 AM
Are you sure the run out was good before the accident? Some drill chucks are off by 0.010" or more when new. The Jacobs Multi-Craft is a "good" example of this. Really bad run out when new off the shelf.

You may not have an easily seen problem. When you spin a chuck like that, metal is moved around both on the chuck and on the adapter. They may even exchange metal. If you want to fix it, you may have to rebore the chuck and buy a new adapter. Most chucks have enough metal to rebore them a bit larger.

02-23-2008, 11:03 AM
002 aint that bad for a drill chuck.

Alistair Hosie
02-23-2008, 11:16 AM
exactly Macona why his lordship works within the nearest half inch.:DAlistair

02-23-2008, 09:32 PM
You might try checking the run out from the start so to say. R8 installed and runout on the JT6. Add the chuck check again? Maybe help in pointing you in the proper direction. I know I can not get there from here. Jay:D

02-23-2008, 11:20 PM
Set up the R-8 between centers in your lathe and check for rou out. Gary P. Hansen

02-23-2008, 11:45 PM
.010 runout? Heck far, most of my cheap drill bits have more than that. :rolleyes:

02-24-2008, 01:09 AM
Ya.. the run out was "usable". Like I said.. it was a POS right from the getgo but now it's horrible. About 1/4" run out at the end of a 3" piece of drill rod.
I'll recheck the R-8 in the lathe. Never thought of that.
I was looking at the chuck a half hour ago. The problem may be that the adapter is bottoming out and not getting tight. That could be cuz the metal got shifted or spun out as was mentioned.

02-24-2008, 03:34 AM
I use end mill holders when using S&D bits.
Accurate, cheap,one piece rigidity plus they gain you some distance spindle to table.

02-24-2008, 04:38 PM
I hate S+D drill bits. Thet are hard on chucks, they eat their own shanks and are not very rigid. But they are cheaper than an equivalent MT bit.

02-24-2008, 04:44 PM
I use S&D bits to remove a bunch of metal quickly. Not elegant, but effective. With the keyless chuck any tendancy to rotate tightens the chuck on the shank so that part is almost self correcting. The Morse taper is only a #2 so I have to be sure to keep it clean and seat it with a soft hammer.