D1-4 chuck mount fit?

I really hope you get this worked out. Unfortunately problems with the fit of the chucks to the D1-4 spindles is a common problem on chinese lathes and its one of the things about them that scares the hell out of me.
If its new and you bought it from someone with a real service department (Jet or Grizzley) its time to give them a call. If its used or from a vendor without real service support, use google.com to search the web on this topic for others that have had the problem and how they solved it, I've seen plenty of discussion on it.
Good luck-
Paul T.

There should be no gap between the spindle face and the back of the chuck, and at the same time, zero clearance between the chuck and spindle tapers. Unless there's something preventing the chucks seating, I'd be suspicious that the spindle nose is out of spec.
Try removing the studs from the China 3-jaw and Bison chucks and see if they'll seat then--perhaps there's something in the locking mechanism that the studs are hanging up on.
Ned Simmons

While the studs are off, try wiping on some prussian blue on the spindle nose to see where the contact points are. If the chuck does seat on the flat and you have play on the taper then either the chuck mount is oversized or the spindle nose is undersized. specs for the spindle are at http://sh> >

I've adjusted the studs in and out, and compared how far they protrude on each chuck, those that touch the shoulder and those that don't. They all lock down nicely at 1.256". When I try to shorten them, to pull the chuck back closer, the cams didd't pull the studs in. See my reply the Paul T.

Thanks!
See my reply to Paul T.
One thing that now concerns me is, for the face plate and chuck that touch the shoulder, is the spindle taper actually holding these concentric, or is there clearance between the internal and external tapers. I think I'll pull the studs and see if there is eccentric play.

Thanks Paul!
I Googled a lot of good(?) information from RCM. Especially from a posting by David Lindquist. He was able to paraphrase ANSI standards on these mounts. And, he also enlightened me on the problem of spindles manufactured to one extreme of the limits and a chuck adaptors manufactured at the other extreme.
The lathe is a new JET 13x40 Gear head. I've contacted WMH, but have gotten a satisfactory answer back yet. David's ANSI info will help me in dealing with them and my vendor.

The way I see it is that when mounted, the chuck backplate MUST be in hard metal to metal contact with the spindle plate because this controls the the longitudinal angular location of the chuck - a tenth here can result in thou's of error at the end of a long workpiece.
The very short taper section on a camlock chuckmount is for radial location only. It serves the same function as the parallel register part of a screw mounted chucks used on smaller lathes. When mounted with the chuck in hard metal to metal contact with the spindle plate register, the male to female taper radial clearance should be close to zero - ideally zero to the lightest of light push fits. It is ESSENTIAL that the taper fit does not prevent metal to metal backplate contact.The ill effects of a very small residual taper to taper radial clearance are very much less severe than the results of failing to achieve zero clearance at the backplate.
The short taper is a much better radial location system than a parallel register because of the relative ease of corrective machining to overcome errors or wear. The rather intimidating 7deg 7min 30 sec taper angle is simply a taper of 1 in 8 and, because the taper is so short, the angle is not particularly critical (quite unlike the usual long morse tapers where even the tiniest deviation produces unacceptable errors).
A good corrective machining strategy is to first setup a toolpost grinder for a 1 in 8 taper on the top slide and take a very light skim off the nose taper. Unscrew the camlock bars from a known good (or your tightest fitting) backplate. Press the bare backplate hard against the spindle nose and measure the total radial clearance by back and forth radial pressure, monitored by a tenths clock measuring the backplate rim movement. Because of the radial scaling effect of the 1 in 8 taper this radial clearance is simply removed by grinding off eight times the radial error from the backplate locating surface of the spindle mount. Check the fit as you proceed and stop when a very light tap is needed to release the backplate.
Jim

WOW!
I was just hoping for a "plug-n-play" lathe, but it looks like I have a lot more work to do with the vendor, manufacrurer, and in my shop.
I'll keep you all posted on the (hopefully happy?) outcome.
Thank to everyone for all the input.

I purchased a HF 12 x 36 lathe 2 years ago, several months after a friend also purchased the same model lathe. I had previously purchased a 6" 3 jaw chuck with a plain back. My friend subsequently purchased a plain back Bison 6" 3 jaw chuck. All of these chucks displayed to some degree the problem you are having. I also read almost all of the posts on RCM I could find about D1-4 or similar chucks and their mounting.
After trying the same techniques that you tried including very carefully tightening the camlocks while using the tailstock to press on the chuck, I could achieve .003" TIR. But, I could not repeat this without going through the same routine. I even exchanged the original chuck with another from a lathe at the store where I purchased the lathe. Pretty much the same results. BTW, I also had a measurable gap between the chuck mount and the spindle as you observed.
SO, I mounted one of the 3 jaw chucks on the lathe and chucked a piece of 3/4" drill rod about 8" long and then chucked the second chuck on the piece of DR so that the chucks were facing each other. Then I took a piece of 220 silcon carbide paper and turned the chuck by hand while sanding on the taper of the second chuck (I hope this is clear). The camlock pins make this somewhat awkward. I dismounted the chucks and tried the fit of the one I had just sanded. I measured the gap to see what progress I was making, then I remounted the chuck and took off a little more. IT DOEDN'T take much off the taper to get a good fit. May 3 or 4 iterations and you should see a difference. I then tried this same technique on the other chucks. ALL of the chucks now fit with less than .003" TIR consistently. One of them will mount to .001" TIR. I re-check mine every so often and they still mount the same.
You can return the chuck to Jet (Grizzly, HF, Enco....etc) and you may get one that mounts better or you may get one that does worse. I have read of some owners sending a chuck back 4 times with the same results.
I would not alter the taper of the spindle.
My 4 jaw chuck and faceplate mount without a problem.