In article ,
Nick Mueller wrote:

Joseph Gwinn wrote:

I'm not sure that this could be the mechanism, because even the larger
bar is well centered between the two rails of the way. Â*Nor can I
imagine the person that allowed the dovetails to become so loose
concerning themselves with something like the hold-down plate.

Two vectors of cutting force during parting off:
1.) pointing vertical downwards from the tip of the blade
2.) pointing horizontal outwards (along the blade) from the in-feed force

If you add the two vectors and the resulting vector is not pointing between
the two rails, the rear will lift. To prevent that, there is a 3rd guide
(rear, downside).

Right. I'm saying that given the small diameter stock (compared to the
spacing between way rails), it could be hard to arrange this. But I'll
look.

Joe Gwinn