3 Jaw Chuck Issues

[old mart]

I forgot to ask, is the chuck 6" or 160mm diameter? Is there any makers name on it?

[brian Rupnow]

The chuck measures 160 mm outside diameter. After a bit of Googling, I decided that I would grease it, so I greased the gear side and the scroll side with heavy duty grease. With a 1" diameter hardened and ground shaft clamped in the full length of the chuck jaws, I can slide a 0.0015" shim about 0.100" in from the face of the jaws. However, the jaws have about a 0.060" chamfer on the inside end of the jaws, so that test for "bell mouth" is rather inconclusive. The jaws are marked with two parallel lines looking kike a capital H with no cross bar, and a round smaller circle where the cross bar would normally go. This "logo" is inset in a round circle about 5/8" diameter on the face of the chuck.

[old mart]

I could get a 160mm Chinese made chuck in the UK for about £100 or less. I actually have two, both bought privately for quite a bit less in unused condition. They are not the same as the jaws differ in size, one being the standard Chinese and the other a copy of Bison dimensions. The rear mount screws are in a similar position to yours, but I cannot measure the pcd as the museum is closed during lockdown.

[J Tiers]

If the chuck is bell-mouthed enough to matter, you will normally see a trapezoidal wear on the jaw faces. However, that may not be the case with yours, or it may be hard to see. Best to do the regular check and see.

Also, see if the jaws are at all loose, they should normally be snug on their slides. Otherwise they may tip a bit, with the exact same result.

From your results, it seems as if those may not be your problem. Which leaves a mystery.

[old mart]

I have found the K11 Chinese 160mm chuck fitting dimensions.

PCD of the screws 142mm

Register size 130mm

[The Metal Butcher]

The chuck measures 160 mm outside diameter. After a bit of Googling, I decided that I would grease it, so I greased the gear side and the scroll side with heavy duty grease. With a 1" diameter hardened and ground shaft clamped in the full length of the chuck jaws, I can slide a 0.0015" shim about 0.100" in from the face of the jaws. However, the jaws have about a 0.060" chamfer on the inside end of the jaws, so that test for "bell mouth" is rather inconclusive. The jaws are marked with two parallel lines looking kike a capital H with no cross bar, and a round smaller circle where the cross bar would normally go. This "logo" is inset in a round circle about 5/8" diameter on the face of the chuck.

That's not terrible. It could certainly be a little better, but I doubt that will cause much issues.

[mattthemuppet]

like a mullet, grease at the back (pinion side) and oil at the front (scroll side). Grease in the scroll will trap swarf and grit, whereas oil is less likely to do so. Just stand to one side or put a bag over the chuck when you spin it up for the first time or you'll get a line of oil up your shirt.

[dian]

The chuck measures 160 mm outside diameter. After a bit of Googling, I decided that I would grease it, so I greased the gear side and the scroll side with heavy duty grease. With a 1" diameter hardened and ground shaft clamped in the full length of the chuck jaws, I can slide a 0.0015" shim about 0.100" in from the face of the jaws. However, the jaws have about a 0.060" chamfer on the inside end of the jaws, so that test for "bell mouth" is rather inconclusive. The jaws are marked with two parallel lines looking kike a capital H with no cross bar, and a round smaller circle where the cross bar would normally go. This "logo" is inset in a round circle about 5/8" diameter on the face of the chuck.

in the last thread about runout i described a procedure to see if chuck is bellmouthed, if you care to look it up.

[Sparky_NY]

It appears you got the lathe back from repairs at Concord. What turned out to be the problem with it? You said "electrical" in a earlier post.

Glad to hear the spindle runout is far better than you originally measured. This begs the question, did you re-measure the runout at the chuck again using the more suitable indicator? If so, what did you use for a test bar?

I am guessing that the chuck teardown at this point is just for routine maintenance, not due to a remaining runout problem, pending clarifications.

[brian Rupnow]

A wire had came loose on the foreword/reverse switch. Power was intermittent. Fix was cheap.

[reggie_obe]

A wire had came loose on the foreword/reverse switch. Power was intermittent. Fix was cheap.

I hope they checked and re-tightened each and every electrical connection.
What did they find when testing the spindle run-out?

[brian Rupnow]

They checked the spindle runout and said it was within "acceptable limits". I checked it when I got the lathe home, and measured 3 different places on the spindle with lathe removed the runout was less than 0.001".

[old mart]

Looks like you are good to go, things have turned out well and your chuck is clean and sparkling, get turning.

[brian Rupnow]

I am still chasing chuck runout. I have carefully checked the spindle with the chuck removed, and on both the faces and diameters and inside diameter available to be checked, there is extremely little runout, less than .001". Any of the diameters or faces that mate with the chuck show little or no runout. The spindle bearings have been tightened to specs given in the lathe manual. If I chuck a piece of ground and polished 1" round-stock in the lathe, I am still measuring 0.003" runout on the material. One thing I have noticed. When I bought the lathe new, the chuck would slide off the spindle nose with no problem when the chuck was unbolted from the spindle. Now it doesn't. I have to run the chuck jaws out enough that I can whack them with a soft faced hammer on the back side to get the chuck freed up enough to remove. This tells me that something has changed. Now I will do a very close inspection of the inside diameter of the back recess in the chuck which the spindle nose fits into, to see if there is any swarf embedded in that surface.

[Cuttings]

On my lathe the fit between the chuck and the spindle is not that great so when I put the chuck on I snug up the mounting bolts then put a new end mill in the chuck backwards to check the runout.
I few taps with a dead blow hammer brings it as close as it can get, then I tighten up the bolts.