Many times it is necessary to face off a thin piece in the lathe and it is difficult to hold these straight in the chuck.

This lathe backstop fits in the back of the mandrel and the 1/4" bar is supported by the taper support (centre) which fits in the 2MT mandrel nose. A stop piece such as the two illustrated is fitted onto the end of the bar in such a position to create a back stop for the piece being faced.
The design comes from Model Engineer's Workshop Issue No. 10

Dismantled to Show The Three Piece Construction

The Back Stop consists of three pieces, each made from free cutting mild steel. The centre piece is split and fits inside the main body of the item, which is also split at at the inner end. The end of the centre piece is threaded 40 T.P.I. and the large hand wheel screws on to it.

Thus by tightening the hand wheel, the centre piece is drawn into the main body causing the centre piece to contract, gripping the bar, and causing the main body to expand to grip the inside of the lathe mandrel.

Obviously the centre piece and the main body have matching tapers.

The device works perfectly and makes an otherwise difficult operation relatively simple.