One is a Draper 09788 (as per the link above) and the other is a “Perform” (bought from Axminster a while back).
Both have pretty stable legs, but are let down by the rear jaw of the table top, which wobbles.
The Draper was particularly bad, as can be seen from the Goniometer readings at the two extremes:
As can be seen above there was almost 4 degrees of wobble.
I took the offending jaw off to expose a nut and screw:
The nut is on the end of a bolt which has a tapped hole at right angles, taking one of the threaded rods which move the jaw back and forth when the handles are turned.
The screw seems to be intended for fine tuning of jaw loose/tight-ness or to limit wobble.
I tightened the nut up until it became too difficult to wind the handles on the front of the bench, then slackened it off a quarter turn.
I also tightened the screw up until it affected the movement of the jaws, then slackened it a as little as possible before the jaws moved freely again.
Having reattached the rear jaw the amount of wobble is dramatically reduced:
As can be seen the play is now less than 1.5 degrees – a 2.3 degree improvement.
It’s not perfect (and the jaws could perhaps do with being a little more free moving) but it’s a lot better than before.
The jaws still rack slightly when tightened (the inner face of the jaw ends up rising slightly and the rear of the jaw falls slightly, meaning the table top I built for it still ends up wobbling slightly when I place the bench radial drill on it, but again it’s a lot better.