At a leading British lock manufacturer, production of plugs, pins, keys and thumb-turns has been transferred from five single-spindle cam automatics to three Traub TNL 12 sliding-head lathes.

At a leading British lock manufacturer, production of plugs, pins, keys and thumb-turns has been transferred from five single-spindle cam automatics to three Traub TNL 12 sliding-head lathes. The ability of the lathes to turn-mill components in one hit has also resulted in the removal of 30 milling, drilling and tapping machines formerly used to perform secondary operations on parts turned on the cam auto's. Space has been freed on the shop floor and five fewer operators are needed on each of two shifts, resulting in a significant labour cost reduction.

A before-and-after comparison of brass plug production gives an indication of the savings being made.

The previous process was to turn a blank from 14mm diameter brass bar on a cam auto; drill six pinholes on a rotary transfer machine; mill a boss on the reverse using a special-purpose machine; drill two holes at the same end on a single-spindle drill; and then tap holes on an adjacent, identical machine.

Between each of the five stages, the components were transferred manually to a degreasing station.

This was necessary as there was always a lot of work-in-progress and parts would frequently be held in bins for three or four days, with the potential to leak cutting oil onto the shop floor.

Economical batch size before setting up all the machines to produce a new component was typically 10,000-off.

On any of the Traub TNL 12 lathes, all of which are equipped with a sub spindle, the plugs are machined completely in one visit to the machine in a 28s cycle.

This is achieved as a result of a generous allocation of tooling, both driven and static, in two turrets and in two gang tool posts for front and reverse end-working respectively.

Batch size is down to around 1,000-off, reducing significantly the money tied up in inventory, bearing in mind that each plug costs UK 28 pence to manufacture.

Another benefit is better component accuracy by eliminating tolerance build-up caused by repeated re-clampings.

Tolerances of +/-0.01mm on diameters and +/-0.02mm for other features are easily held.

The manufacturer advised that Traub sliders were selected for the project as comparative trials on four machines from different suppliers showed the TNL 12 to be capable of cycle times that were on average 10% faster than the next best lathe.