Mandrel Runout

[Larry Gottlieb]

I received new mandrels that I had ordered and wished to check the runout.

I mounted them in the 1/4" collet chuck and using a dial indicator was dismayed to find the runout in the center of the mandrels was from .005 to over .01 inches.
My old mandrel in the past was about .003.

I routinely hold the mandrel in a center drill driver on a #2 MT.I had been told that the drill driver was a very accurate way to hold mandrels.
I then checked the new mandrels in that drill driver and they all tested from .003 to .005 which I find acceptable.

Now I have to figure what my problem is with my collet chuck.

Larry

 

[randyrls]

Originally posted by Larry Gottlieb

I received new mandrels that I had ordered and wished to check the runout.

I mounted them in the 1/4" collet chuck and using a dial indicator was dismayed to find the runout in the center of the mandrels was from .005 to over .01 inches.
My old mandrel in the past was about .003.

I routinely hold the mandrel in a center drill driver on a #2 MT.I had been told that the drill driver was a very accurate way to hold mandrels.
I then checked the new mandrels in that drill driver and they all tested from .003 to .005 which I find acceptable.

Now I have to figure what my problem is with my collet chuck.

Larry

Larry; 3 slot collet chucks only clamp accurately over a very small range. The reason for this is that if you think about it, the rear of the collet doesn't change size and doesn't clamp on the mandrel all all. If you have the mandrel supported by the tail stock, this will reduce the runout.

The mandrel may be bent too.

Clean out the taper, and the slots in the collet throughly!

hope this helps...

 

[Randy_]

Couple of questions for you, Larry. When you are measuring the runout, is the mandrel supported by a live center or is it running free. Have you measured the runout of the mandrel right close to the face of the collet chuck......say within about a 1/2"?

The runout you have described could be due to the collet, the mandrel, the live center(?) or all three.

 

[Larry Gottlieb]

Randy(s), I support the mandrel with a live center and I measure runout at the center of the mandrel. This is where the two halves of the modified slimlines meet and where excess runout would be detected in the finished pen. I will clean out the collets and recheck.

Thanks,

Larry

 

[Paul in OKC]

You can always 'tap' on the high side and bump it in. Done that more than once. Sometimes I think we are expecting rocket science parts at Walmart prices. All the truest stuff and bells and whistles ain't needed to make a pen. Makes it easier some, sure. To get zero runout always you would have to get some shaft that is centerless ground, and have the center in the end machined instead of done with a center drill. I don't have collet chucks, or turn between centers, or...,or,.....Don't even have Micro mesh, and still manage to make a very nice pen. (Sorry for the rant, but I am having a Monday!!) If I wanted to make pens like I machine stuff on a daily basis in the range of a couple of thousanths, I would have a lot more $$ tied up in equipment than I would get back selling pens! It is possible with a little tinkering on what we have to make excellent stuff.