Steve Lane - Modified design of David Mueller Offset Chuck - March 2015

David Mueller Offset Chuck Modifications

By: Stephen Lane, Chesapeake Woodturners

I built the offset chuck as described by David Mueller in the February 2015 issue of The American Woodturner (Vol. 30, No.1, pp 35-40). I made several modifications/improvements to the design which I believe make the assembly more robust and user friendly.

First, I replaced the small wood screws and washers that hold the offset disk in place during operation with ¼ - 20 machine screws and insert nuts. Tee nuts or helicoils would work equally well. These fasteners are loosened and re-tightened every time adjustments are made to either the offset disk or the rotation disk. I felt that more robust hardware than the small wood screws screwed into plywood was needed. This change required that I move the screws about ¼” outboard of the offset disk and use larger (1 inch) washers. I used the same fasteners for the rotation disk as well. (Photo 1)

Second, I noticed that, by rotating the offset disk to the zero position, the screw holding the rotation disk was dead center of the fixture. Thus, this screw could be accessed by drilling a hole all the way through the offset chuck body and the glue block tenon. I used a faceplate instead of the reference design glue block, but the idea is the same. (Photo 2)

The designer (David Mueller) realized this as well, after publication. He mentions and demonstrates this change in his video referenced at the end of the article on Vimeo (click). He showed that the screw could be accessed without dis-assembly of the chuck. But, and this is crucial, he still required that the entire assembly be removed from the lathe to access the screw.

What I realized was that the screw could be reached without removing the chuck from the lathe if one used a long-handled Phillips head screwdriver, one that is long enough to reach all the way through the hollow headstock drive shaft of the lathe. On my Delta, the shaft length is about 10 inches. I didn’t have a screwdriver this long so I made one with a bit, 12-inch extension and homemade handle. (Photo 3) The extension is available at Harbor Freight (PN 67975) for about $5.

So, with these modifications, all of the screws needed to change the offset and/or rotation can be reached with no dis-assembly at all. The more robust hardware will assure long and reliable use of this device. Soon, I hope to be able to show off some of the interesting and decorative pieces this offset chuck allows.

Showing enlarged hardware, insert nuts

With offset dialed to zero, Phillips head screw can be accessed through hole in mounting plate.

Homemade long-shank Phillips head screwdriver.