A Micrometer Roller Box

Howard Lewis makes a tool for ‘running down’ long thin workpieces

A roller box is usually used on a capstan or turret lathe. Capstan and turret lathes serve the same purpose but differ slightly, both can carry a selection of tools on a turret which is a substitute for the tailstock of the centre lathe.

In both cases, the turret indexes automatically, to bring the next tool into operation, as the turret is racked to and fro.

The capstan lathe is usually smaller and lighter, and better suited to lighter repetitive work, and carries the turret on a saddle which can be fixed at a point along the lathe bed. In addition, the four way toolpost on the cross slide, a rear toolpost is often carried there. (this is often used for a combined chamfer and part off tool).

The turret lathe is a larger machine, intended for heavier work. Here, the turret moves along the lathe bed, under the action of the capstan handle, again indexing a fresh tool into position with each movement.

As an instance of this, a Herbert no 7 Preoptive turret lathe is about twice as large and heavy as a Ward 2D capstan lathe.

Both are intended for semi-automated, high volume, production, with unskilled or semi-skilled operators. The machine will have been prepared by a skilled setter.

They were the forerunners of automatic lathes and cnc machines.

Roller boxes (and the model engineer’s running down tool) are intended to overcome the problem of producing a taper when reducing the diameter of a long workpiece. Here, the outer end tends to deflect under the cutting pressure, leaving the outer end oversize, so that only the inner end, close to the chuck or collet will be at the required diameter.

The model engineer’s running down tool is a light duty version, using a vee shaped steady to prevent the material deflecting under the cutting load. They are all, in effect, a travelling steady with a cutting tool attached.