Brand new Lathe Spindle Adapter to fit 5/8" plain Shopsmith spindle to 3/4" x 16 TPI threaded chucks and other lathe accessories.. This spindle adapter is bored 5/8" for the plain Shopsmith spindle and has a locking set screw. The other end is threaded 3/4- 16 (3/4" diameter x 16 threads per inch) for lathe chucks and accessories. Drilling Buffing Polishing Shaping on a Shop-smith Wood working lathe Safety Note: It is very important that you securely fasten the spindle adapter to your lathe spindle, and any of your 1-8 threaded accessories to the spindle adapter. Failure to properly secure these components can result in injury.