The No. 4 lathe shown on what Rivett described as "Standard Brown and Sharpe Bench Legs."
Mounted on the lathe bed is the beautiful  "Slide Grinding Attachment" shown in detail below. When this device was used at an angle a special compensator guided the drive belt and aligned its run to pass over the spindle pulley in more or less a straight line. The device is partially hidden behind the lathe in the picture above - but clearly illustrated at the bottom of the page.

The "Grinding Attachment", finished with scraped and polished surfaces in the traditional Rivett, was designed to slot into the place normally occupied by the compound slide rest.
Two heads were supplied, one for internal and one for external work. When the head was set at an angle its drive rope was aligned by the special unit illustrated below.
This unit was also made to fit the 8-inch Precision lathe - the early version of the 608.

When the grinding head was set at an angle, the device illustrated compensated for the twist in the belt and applied it to the cutter pulley at the correct angle.