A word of caution: By coincidence (?) I happen to have a 'needs work' headstock in my shop right now with a bunch of rotational free play between the upper drive and quill spindle. I presume that's due to a worn or cracked spline adapter (#57, aka Drive and Ring). Do bear in mind that on newer headstocks that spline adapter is plastic! Very tough plastic, but plastic. And by newer, I mean since the '60s. The torque you apply to the quill spindle using any of these lock methods is applied to this plastic part, and so needs to be reasonable.
- David
method to lock the spindle
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