Drill chuck runout

[tool-man]

I finally got a new magnetic base for my dial indicator and made some runout measurements. My lathe headstock as well as a MT2 shaft inserted into it measure less than .001 runout. So far so good.

But the two used drill chucks I have measure .007 and .009 runout measured on a drill bit and a piece of drill rod just outside the jaw tips. That seems excessive.

Is it time for a new chuck? What runout should I expect on a new chuck?

 

[Larry in Harrow]

Hi Andy,
I had this same problem.:frown: A machinist buddy examined the equipment and told me that my Jacob's chuck was a thread mount on the MT adaptor and that was probably not the best. He advised me to toss it and get a taper mounted chuck. Too late, I had already switched to mostly MT shank bits that totally got rid of any chuck runout.

 

[mredburn]

It may be the chuck itself. When i went to buy a chuck for my lathe I found that among other things the chucks themselves are built at different levels of quality. They make cheap chucks to use on the tools found in the big stores that will hold onto a drill bit most of the time. They make chucks that have .004 run out tolerances. They retail for about a 100.00 Check out the Jacobs web site and you will find which models of chucks have the tolerances and capacities your looking for. I found a Jacobs 33b chuck that goes from 1/16 to 1/2 with .004 runout on ebay for 10 dollars.

www.jacobschuck.com

mike

 

[KenV]

The tolerance and precision of drill chucks is quite variable -- you pay for precision, and used (sometimes abused) gear and cheap gear tends to the less precise -

Desirable for a 3 jaw drill chuck is about 0.005 or less. Twice that is not uncommon. (You can get very precise chucks but you pay for the precision)

On the otherhand, the precision of the alignment of the head stock and tailstock on a wood lathe is generally off by more than that. (Wood lathes are not contolled to the same tolerances that metal lathes commonly use).

Most scroll chucks do well to be inside the tolerances you cite for the drill chucks.

Machnists are taught ways to approach the work that minimizes the bad effects of lack of precision, and pay a lot of attention how things are mounted and used.

So -- depends on what you are going to do -- keep your work close to the jaws, and do not make assumptions of precision (not a good thing to do on a wood lathes in any case). Probably will work for most things, but I suggest you use the drill chucks with that run out in the tail stock to hold drill bits (and keep the tailstock loose so the bit tends to self center). Expect some oval on your holes and keep on turning.

 

[johnnycnc]

Andy, I would expect .002, maybe .004 at most, from a decent drill chuck
on your wood lathe. I think I would get a new one if it was me.