• Overview
  • Strengths
  • Technical Details

Planetary Scaif Benches for Single Crystal Diamond

Coborn’s Planetary Scaif benches are generally used to polish facets on single crystal diamond tools. They may also be used in gem diamond polishing. The bench combines the high speed rotation of a scaif plate with a relatively slow, smooth, horizontal planetary motion. The planetary motion speed is variable between 0-50 cycles/minute.

This motion gives a number of advantages over a standard scaif:

  • The plate does not become tracked as polishing takes place over an annular band. The scaif surface remains smooth and flat.
  • The motion results in a constantly changing angle of attack: this gives a ‘self-zooting’ action producing line free facets without manual work.
  • In many situations the tang can be set on the machine and the diamond or tool left to polish
  • ‘Knarted’ stones become easier to polish as the angle of attack constantly changes.

All planetary benches are fitted with a 2.2kW, adjustable height spindle. The working height of the plate surface can thus be re-established after the plate has been remachined. PS benches can be supplied with either a fixed (type A) or adjustable (type B) planetary stroke. An inverter drive can be fitted as an optional extra.


  • A diamond or tool in a tang can be placed on the plate and left to polish without manual movement.
  • The plate does not become “tracked” since it moves under the diamond.
  • The polishing angle of attack constantly changes so that difficult ‘knarted’ stones are more easily polished.
  • A ‘self-zooting’ action operates producing line free facets.
  • An optional inverter can be fitted to control the speed of spindle from 1,500-4,000 rpm.
  • Planetary stroke on B Type benches mechanically adjustable from 4 – 32mm by 24 steps.
  • Standard bench 920mm wide x 610mm deep. Welded steel construction.
  • Bench top made from 23mm steel plate for stability, covered in plastic laminate to reduce wear on tangs.
  • Top can be drilled and tapped as required for fixtures.

Technical Details

Characteristic PS2 A-S PS2 B-S
- Machine type Fixed stroke Adjustable stroke
- Dimensions (w x d x h) 934mm x 630mm
x 914 ± 50mm
934mm x 630mm
x 914mm ± 50mm
- Total machine weight 290kg approx 300kg approx
- Bench construction Welded steel frame Welded steel frame
- Bench top 23mm steel plate, plastic laminated coated 23mm steel plate, plastic laminated coated
Planetary Motion
- Stroke amplitude adjustment facility Not applicable - fixed stroke Yes - adjustable
- Planetary motion adjustment method Not applicable - fixed stroke Mechanical adjustment - 24 steps
- Planetary motion range Fixed - to customer request in range 4 - 32mm 4 - 32mm
- Planetary motion speed Adjustable 0 - 50 cycles/min Adjustable 0 - 50 cycles/min
- Planetary motion direction (viewed from above) Clockwise Clockwise
- Spindle type Coborn precision spindle Coborn precision spindle
- Spindle power 2.2kW (2.9 H.P.) 2.2kW (2.9 H.P.)
- Height adjustable Yes Yes
- Height adjustment range 19mm 19mm
- Speed range (without inverter fitted) 2,850rpm at 50Hz 2,850rpm at 50Hz
Electrical requirements 3 phase 3 phase

1. Spindle speed control inverter drive - speed control range Available 1,500 - 4,200 rpm
2. Bi-directional spindle rotation Available
3. Expanding nose Allows plate to be removed easily and centred
4. Expanding nose spanner To fit above expanding nose
5. Cast iron scaife plates Available - ask for details
6. Impregnated plates Available - ask for details
7. PB1 - Portable balancing unit Allows plate to be dynamically balanced on the machine
Coborn PS Series Planetary Scaif Bench for Single Crystal Diamond polishing. Single Crystal tool making & gem diamond manufacturing.