The Rockwell Delta 11" underdrive lathe was  much more heavily built than the 10" model and available with either a threaded spindle (21/4" x 8tpi), or the much superior L-00 tapered key fitting at no extra cost. Two bed lengths were produced giving a capacity of either 25" or 37" between centres.
The same type of variable-speed drive as the 10" was fitted, but only to an underdrive cabinet stand, which was supplied as standard equipment. Above the variable-speed drive pulleys was an intermediate countershaft from which a double V belt drove the 13/8" bore headstock spindle at speeds between 45 and 1550 rpm. A single lever on the front of the headstock controlled the engagement of backgear and also acted as a spindle lock; this mechanism, designed to be foolproof, offered an interlock to prevent engagement of gears when the spindle was rotating.
The leadscrew thread was used only for cutting threads, the power sliding and surfacing feeds being taken from a slot running its full length; this slot was unique in have a "T" section, designed to prevent the edge of the sliding key from raising a burr along its edge.
Besides the normal range of centre-lathe accessories, a complete set of production extras: - bed-mounted capstan units, cut-off slides and quick-release collets holders, etc. was also available - as was the option of a flame-hardened bed.

Standard bed length 11" x 36" Delta Lathe. The handwheel protruding beyond the tailstock-end of the bed is the collet draw bar tube in its storage position.

The thread on the leadscrew was used only for cutting threads, the power sliding and surfacing feeds being taken from a slot running its full length; this was unique in have a "T" section, designed to prevent the edge of the sliding key from raising a burr along its edge.

Cut-away view of the Delta 11" headstock showing the massive double tapered roller bearing and heavy-duty 21/2" diameter spindle. The headstock is illustrated turned through 90 degrees, in its operating position the backgear engagement and spindle locking handle on the "top" was situated on the headstock's front face - and shown in close-up below.

The "Drive Selector" was unique in that the choice of open or backgear drive, and a locked or a free spindle could be obtained from just one lever without the need to reset or remove pins or other devices.
The mechanism was also interlocked against attempts to operate it whilst the spindle was rotating.