Chuck runout

Pete Wass

Pete Wass

Well-known member
I bought a Central Machinery Micro Mini lathe last winter. I finally got around to checking the spindle/chuck for runout yesterday. It appears to be runing out around.007". What is the best way to take the runout out of the chuck? I have bored them out in the past but was wondering about grinding it out. .007 is a lot ot grind wih a tool post grinder, isn't it? Thanks, Pete
 
Pete,

If the chuck is bolted to a mounting plate, the plate may be the problem. First, remove the chuck from the spindle and make sure the mating surfaces are clean and free of burrs. Then pull the chuck off of the plate, and check to make sure the chuck counterbore fits tight over the boss in the center of the mount. If it does, take a facing cut off of the plate and remount the chuck. BTW, be sure to mark the position of the plate to the spindle, so that you can get it back on the machine the exactly the same if you pull it off to use a 4-jaw chuck or collet or whatever.

If the chuck doesn't fit the plate well, or if it attaches directly to the spindle, call the company and see if they wil replace the offending pieces.

-Dave-:)
 
Pete

You said "checking the spindle/chuck".
Are you referring to the actual chuck body running out, or something running out in the chuck after you chuck it up.
Do what Dave said. But keep in mind, some of these cheap little pieces won't ever run very true, ever. That is why some chucks cost more than that entire machine..........jackie
 
I checked it out

jackie schmidt said:
You said "checking the spindle/chuck".
Are you referring to the actual chuck body running out, or something running out in the chuck after you chuck it up.
Do what Dave said. But keep in mind, some of these cheap little pieces won't ever run very true, ever. That is why some chucks cost more than that entire machine..........jackie
Click to expand...

The chuck is threaded on to the spindle. it locks up acainst the face on the spindle. I indicated the face of the spindle and it was zero in terms of runout. I lightly stoned the face of the chuck that buts up against the spindle and then screwed it back on. It is still running out .007", meaning I chuck up a ground pin and indicate off that.

I first used a long ground pin and the last time I used one about an inch long; same results. If I bore the inside of the jaws do you think I can make it come in to running close to zero? I have done this before to straighten out the bore of chucks. I use to have a mentor who was in the Machine tool rebuilding business to go to but sadly he is no longer with us.

This is a cheap little machine and I basically bought it to do very small round projects and case work. I would like it to be as accurate as I can get it to be. I don't expect precision. I have a Heavy 10" SB at my house that is in a divorce settlement if I need it but it is 40 minutes away.
 
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hi pete
if your tailstock is in line with your head stock you can
chuck up a mandrell known to be true then undo the chuck from the
head stock then place it between centers and true the back of the chuck
this will get you very close. but your tailstock must be true to the
spindle bore .:D

regards tasy_ted
 
Pete Wass said:
I first used a long ground pin and the last time I used one about an inch long; same results.
Click to expand...
Click to expand...

If you are getting the same reading at different distances from the face of the chuck, that tells be that the chuck and the spindle are parallel, but not coaxial. If this is the case, facing the back of the chuck won't fix it. Grinding the jaws should.

If you wanted, you could eliminate or minimize the problem with a piece (or two) of shim stock, provided the readings are the same at different points over the length of your ground pin. If the highest reading is in the same clock position as a jaw, just shim between the jaw and the work. The correct shim thickness is half the TIR. You may have to shim two jaws if the high point is somewhere between them.

-Dave-:)
 
The biggest problem is

This little machine, while looking modern and haveing modern electronics which run the motor, is CRUDE. There is no power feed and the lead screw in the apron is coarse and has lots of backlash in it. It has an O.D. threaded quil in the tailstock and came without a Chuck or live center. I ordered one of each of those but they were a special order to China and I haven't seen them arive after 3 months now.

The hook that got me to buy this little jewel was the weight, 35LBS. I live in a tiny space and being able to do simple turning on the kitchen countertop was appealing. I expected a bit more quality and they cut corners in one of the most criticle points of the machine, the leadscrew! Figures, don't it. I could live with that if I could just get the hole in the chuck parallel to the ways.

I just want to get it to within .001 or so. I was wondering if I moved the jaws around in the chuck if that might correct the problem, wadda ya think about that? Thanks
 
I would take a cut across the face plate from the center and remount the chuck and take a reading again. The standard way to mount a chuck is to do the same after the lathe is leveled.

Just cause it's small, does not mean the same does not apply to this lathe just like the big boys.:D
 
Go to Little Machine Shop.com. they have a free download of Mini Lathe Users Guide [35 pages] Explains how to do this with a Dremel tool .
I did it this way and reduced TIR to .0003.

Chuck
 
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