|Twelve inch 3 jaw|
|Plate ready for pilot|
|Backing plate attached|
This page features a 12 3/4" scroll plate chuck of Chinese origin. It came to me with a D1-6 back on it which was of no particular value since I don't have a D1-6 mount lathe, however, upon dismantling the chuck, I determined that it had a sturdy backplate that would allow me to drill additional hole for mounting purposes. I could not use the bolt holes left by removal of the cam locking studs because they conflict with the necessary hub that would thread on the Sidney spindle. For mounting I welded a 10" diameter plate to a hub treaded for the Sidney Lathe spindle, turned a pilot on the face to utilize the D1 mount pilot, and then bolted the plate to the back of the chuck with 3ea. 1/2 inch bolts which were tapped into the back place. I considered using 6 but decided that 3 would be sufficient.
The chuck itself is a robust model with very large jaws. It is all metric with metric bolts throughout. I assume the oddball diameter corresponds to some metric size. The jaws are a little over 5" long, with 3" bolt spacing which is similar to my 18" Cushman, though I haven't checked to see if the jaws are interchangeable. The centerhole of the chuck is 4" and bottom jaws are quite long. With the chuck fully closed the bottom jaws only miss a couple outside threads on the scroll plate. One of the photos to the left shows this. Conversely, the chuck will open until the jaws stick out beyond the body about 1" before they begin to leave the scroll plate. This makes for an opening of around 6" without reversing the jaws and with full gripping strength. This is important because the way you mess up a scroll chuck big time is to open or close it so it is partly off the scroll plate and then overstress it distorting some of the scroll threads. Then when you normally position the jaws, they will be partly on distorted threads and partly on normal threads leading to the 'tight spots' as you attempt to adjust the chuck. That is not a good thing. These chucks are cast iron and are quite inexpensive. My take is favorable, however.