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One of the main features of the Doughty Drive's unique design is that it has NO backlash.
The drive now incorporates slew bearings with a 28mm hole through the centre, enabling cables, hoses etc. to pass.
With a reduction ratio of 30 : 1, it gives great holding torque of 20 ft/lbs - 27 Nm.
This ratio gives a very good resolution, 60,000 steps per rev, and 166.666 micro steps per deg., with positional repeatablity of + - 20 arc seconds.
The units have a maximum fast travel of 120 degs per second, or 20 RPM.
They can be mounted vertically or horizontally, and used like an indexing head or rotary table.
With two drives connected together at right angles to each other, they form a B/C axis combination, and a router or spindle can be attached.
The weight is just 3.5Kg. (8lb), B/C drive 9 Kg (20lb)
The Doughty Drive Unit
Chatham carvings, scan copied then routed from 2mtr x 600mm x 300mm log, with 1.5 HP spindle, 1/2" cutter, 1/2" deep, feed at 200" per minute