180° Hydraulic Copying Attachment
Unlike the dedicated copy millers with hydraulically-powered tables shown on other pages, the unit above was intended as a complete accessory that could be added to, yet not interfere with the function of, a standard machine. The valve, made by the True Trace Corporation of California, featured a very light stylus pressure and was attached to the head in such a way that it could be adjusted relative to the head in all three planes. On the standard installation, whilst the vertical feed was completely automatic, the longitudinal feed had to be reversed by the operator at the end of each pass and the cross feed could only be applied by hand; however, as an option, a Hydraulic "Pick Feed" unit could be supplied that converted the machine to completely automatic operation. Machines fitted with hydraulic copying attachments were recommend to have hard-chrome plated slideways - the porous 0.002" thickness being applied to the back and top of the knee (for vertical and cross movements) and the top of the saddle (for longitudinal travel) as well as to the column-to-knee and cross-slide-to-table gib strips.

Polartrace Unit
This unit was intended for the automatic production of extremely accurate two-dimensional parts made from a master between 5 and 10 times as large as the finished component; the accessory was self-contained and consisted of a base casting that fastened to the ordinary table. Pivoted on the base was a housing that mounted two special Bridgeport-manufactured rotary tables joined by a common electric drive. A follower, held by a weighted arm against a sample mounted on the left-hand table, transmitted the form to a workpiece on the right-hand table; the ratio between the two could be set at either 5 to 1 or 10 to 1 and, of course, any error in the master was accordingly reduced by the same factor; the diagram below shows the principle of operation of the unit,
The control system was built into the front of the unit and allowed both the speed to be varied and inputs from limit stops to reverse the direction of rotation of the tables.

Tandem Rotary Tables. Designed for use in duplicating work - or for making more than one part at once from a single master - the tables were driven by a hydraulic motor.

Combination angle plate and 10-degree sine table.
With 10 inch x 12 inch horizontal, and 6 inch x 12 inch vertical surfaces, the unit was fastened to the milling machine table with two bolts.
Adjustable side supports and hinge bolts were provided for additional rigidity.
By tightening two screws that passed through the base the device was turned into a solid angle plate.