There are a few secrets to this backing plate that are explained in the following diagram and description.
The bolts and washers in the hub of the spindle adapter are not drawn up tight. The 'washers' are actually Belville Washers that are really springs. (They look like a football under the bolthead in the drawing ) Their claim to fame is that they can develop great pressure in a compact package. You have no doubt seen them before, they look like this when used in a pair (). They are useful to provide constant and heavy spring pressure on projects like this backing plate. In this case, the Belville Washers allow adjustment of the backing plate without loosening and then having to retighten the bolts.
The holes in the hub need to be about 1/8" oversize to allow for the adjustment.
Be certain you pay particular attention to the use of self-locking nuts and use a locking fluid on the studs. Don't skimp on this design or you may have a backing plate leave your lathe at somewhere around Mach 2 or greater. If it makes several laps around your shop at eyeball level, it will make a believer out of you!
This is a low-speed device!
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