d1-6 4 jaw backplate fitting problem

Lathe is a VIctor 1660, chuck is a 12" plainback Cushman with 4 through holes for 1/2" bolts from the front to mount to the backplate.
The issue is that the 4 through holes in the chuck are the exact same diameter bolt hole circle as the pins on the d1-6 chuck. THe problem with this is that is that two of the bolt holes will be interfering with the camlock pin. I'm not going to drill new through holes in the chuck for fear of weakening it.

So far Ive come up with a few options,
1. Use only two bolts. Problem with this is weakness of the mount.

2. Use only 4 camlock pins, I like this better, but again am worried about weakness or not pulling the backplate snuggly onto the spindle.

3. drill six holes from the back of the backplate into the chuck in between the camlock pins using 3/8" bolts and tapping the back of the chuck. Again I'm worried about the strength of smaller bolts, but there would be two more.

4. cut half the threaded shank off two of the camlock studs and cut back the through bolts some. I feel I could get 4.5 threads on each into the backplate. I cant see a serious downside to this.

5. Grizzly sells a "thick" backplate for mounting an adjust tru type chuck on, I could use the full length of the camlock stud and possibly full length of the through bolt, but this would cause the chuck to hang out about .5 inches further from the spindle.

Any suggestions are appreciated, and any other ideas as well

I would go with the Griz. Regards, Clark

akajun said:

2. Use only 4 camlock pins, I like this better, but again am worried about weakness or not pulling the backplate snuggly onto the spindle.

Click to expand...

Hello Akajun
That would be 1 more pin than I'm using on my setup. My Monarch lathe has a D1-6 spindle using only 3 camlock pins. My 10" Set-Tru 3 jaw, 10" 4 jaw & 16" faceplate all came with 6 pins. I now have 9 spare D1-6 camlock pins.

Ever consider shifting the chuck BC enough of an angle to NOT interfere with pin holes?

I'll use Autocad's standard of 0 degrees is at the 3 o'clock position

So let pin holes be at 0, 60, 120, 180, 240 and 300

Put chuck holes at 15, 105, 195 and 285

This will put hole centers no closer than .685" measured on the chord

You will have to pay attention to not drill into lock screw holes for pins if they happen to be in the way

johnoder said:

Ever consider shifting the chuck BC enough of an angle to NOT interfere with pin holes?

I'll use Autocad's standard of 0 degrees is at the 3 o'clock position

So let pin holes be at 0, 60, 120, 180, 240 and 300

Put chuck holes at 15, 105, 195 and 285

This will put hole centers no closer than .685" measured on the chord

You will have to pay attention to not drill into lock screw holes for pins if they happen to be in the way

Click to expand...

I had thought about it but was concerned about the holes being so close weakening the backplate.