Drill chuck for a mill

[trlvn]

Do the ends of your arbor still have center drills like what they may have used to set it up originally when grinding? It would be interesting if you could support it on 2 centers & rotate if the ground tapered surfaces are egged. Of course there could be other distortions that might be giving you runout but I would expect their grinding would be the very last step they would do after hardening etc. & presumably stay that way.

I have a similar dud, shiny potato syndrome. I also have an older gen USA Jacobs = bang smack on (but was more $$ at the time). Some of the Eastern Europe stuff can be quite good, but the price is up there too.

I think the homemade one has centre holes but the purchased arbors did not.

Craig

 

[trlvn]

The good news: the Accusize arbor (0222-0774) has imperceptible runout. Seriously, the DTI needle barely moves as I rotate the spindle!

The bad news: the threads for the drawbar are annoying tight and since the arbor is hardened, I can't do much about it. Any other arbor that I've tried, the drawbar threads in easily with just fingers until the very end where I use a wrench to cinch it up. I tried to run in a 7/16-20 tap but it is too tight to turn after about 3/8 to 1/2 inch or so.

After cleaning, I was able to get the drawbar to turn in all the way. It only takes light pressure with the wrench but is still too tight to turn with just my fingers. Maybe it will loosen up over time.

The bottom line is that the really low runout is more important to me than the annoyance with the drawbar threads. I'm keeping this one.

Next step, I decided to soak the Rohm 1/2" chuck in Metal Rescue as it has a couple of sticky spots at the limits of the jaw travel. I tried using brake cleaner to flush it and a fair bit of rust came out without the sticky spots getting getter. Hopefully a couple of hours in Metal Rescue will eliminate any rusty spots.

Next comes the moment of truth for the chuck. Will drill rod run true or wobble like the stick-on Hulu dancer on a dashboard?!?

Craig

 

[Brent H]

Great news on the run out - the threads should “wear in” I would expect and the draw bar seats the taper so if the fit is great the draw bar is not too big a deal

I just ordered an NMTB 30 to JT3 so we will see how that works

 

[PeterT]

I've had tight thread syndrome too. It could be distortion from HT but it also could be grunge from HT. I've run a plug tap through the threads with cutting oil & it cleaned out some crap so threading was net improved. Careful if the tap appears to be tightening up & avoid hitting bottom, you don't want to break it. It's all these QC 'little things' that explain the price difference of imports. But glad you got the runout issue licked.

 

[trlvn]

I mounted the Rohm 1/2" chuck and did a quick test. No fairy-tale ending: 6 to 7 thous of runout. Not bad for chuck that is at least 25 years old--it is marked "West Germany". I'd like to do another couple of tests--re-chuck the drill rod a couple of times and re-install the arbor in the R8 taper at least one more time. See if the measurements are repeatable or not.

I do think I'll try to find a decent small keyless chuck. Probably a 3/8"; 1/4" seems too small. Hopefully I can get one with better runout for drilling small holes.

Thanks everyone for the comments, suggestions and advice. Even just being able to air my thoughts 'out loud' helps me to think through things like this.

Craig