I hit an auction a couple of weeks ago and scored a Jacobs Rubberflex collet chuck and complete set of collets. It had a strange mount, which turned out to be something adapted to an A1-6 mount. Once the oddball mount was removed, it became apparent that it would be simple to make a backplate to adapt it to my 2-1/4"-8 spindle.
At the NAMES show, Richard Triemstra came up with a semi finished backplate with enough thickness to accomodate the A1-6 taper and I set to work. The rough backplate was 8" diameter & I needed a bit over 6" OD so a lot ended up in the chip pan.
Ultimately, I prevailed and ended up with this;
I had been wanting a Jacobs Rubberflex setup for quite a while, but could not justify the cost. This only set me back $25.00 plus the backplate.