This guide is the specification checklist buyers and maintenance engineers should complete before requesting a quote. For selection theory (torque, service factor, self-locking physics), see our companion article How to Select a Worm Gearbox.
1. Centre Distance (CD)
Centre distance is the distance in millimetres between worm axis and wheel axis. On Anand Gears cast iron worms it is written as the size number (for example 72CD, 100CD). CD sets torque capacity and physical envelope more than almost any other field on the RFQ.
- Measure CD on the existing unit if you are replacing one (housing face-to-face method or drawing).
- Cast iron range on our standard line: roughly 50–305CD.
- Aluminium NMRV / ALM uses series sizes (025–150 class) rather than “CD” branding — still record the body size.
2. Ratio
Ratio = input speed ÷ output speed. Standard single-stage worm ratios run about 5:1 to 100:1. Double-reduction specials go much higher (into the hundreds or ~1000:1 class depending on stages).
- If you know motor RPM and required output RPM, we calculate ratio.
- If only the old nameplate exists, photograph it (see nameplate decoding).
- Need the load to hold when power is off? Prefer higher ratios for reliable self-locking.
3. Mounting Orientation (use Anand Gears names)
Orientation changes oil level, plug positions, and sometimes the shaft which is “high”. Use these house terms on the RFQ:
- Under Driven — worm below the wheel (common standard).
- Over Driven — worm above the wheel.
- Top-Bottom — vertical stack arrangements used on multi-output or special process drives.
- Vertical up / vertical down — output or input vertical for agitators and lifts.
- Adaptable / NU — body family; Adaptable for flexible mounting and cover sets; NU for the classic industrial worm pattern.
4. Shaft Ends (always in mm)
List for input and output:
- Diameter(s) and step lengths (mm)
- Overall length (mm)
- Keyway width × depth × length (mm)
- Solid vs hollow (and hollow bore diameter)
- Which side is drive / free / double output
5. Motor Interface
IEC frame (e.g. 80, 90, 100), B5/B14 flange, solid shaft coupling, or servo square flange with PCD and pilot in mm. Aluminium packaging boxes often need non-catalogue servo flanges.
6. Duty and Environment
Continuous vs intermittent, starts per hour, ambient temperature, dust or washdown, outdoor exposure, and whether cooling is required (genset and extruder duties often need forced oil cooling).
Copy-Paste RFQ Template
Application: CD / body size: Ratio (or motor RPM / output RPM): Orientation: Under Driven / Over Driven / Top-Bottom / Vertical up / down Input shaft: solid/hollow — Ø __ mm × __ mm long — keyway __ Output shaft: solid/hollow/double — Ø __ mm × __ mm long — keyway __ Motor: kW __ ; frame __ ; flange __ Duty: continuous / intermittent ; ambient __ °C Photo or sketch attached: yes/no
Related reading
How to Select a Worm Gearbox · Hollow vs Solid Shafts · Aluminium vs Cast Iron · Custom & Special Gearboxes · Contact