Is hollow weaker than solid?

For the same outer diameter, a hollow shaft has less torsional section modulus. We size the outer diameter and wall so allowable stress still meets the torque — do not assume the solid diameter can be copied blindly as a hollow OD.

Can clutch gearboxes use hollow input?

Yes. Hollow clutch input is a standing special pattern for compact motor interfaces on clutch worm units.

Do you build hollow both ends on aluminium boxes?

Yes on request. Aluminium servo specials often use hollow input; hollow output or both ends are confirmed per project.

Buyer Guide July 17, 2026 • 7 min read

Hollow vs Solid Shaft Gearboxes — Which Should You Specify?

Solid shafts are simple. Hollow shafts save space and enable through-bores. Here is how to choose — including hollow both ends specials.

Shaft form is one of the first decisions after centre distance and ratio. It decides how the gearbox couples to the motor and to the machine — and whether you need a coupling at all.

Solid shafts

A solid input or output is the default industrial arrangement. Advantages:

Simple couplings and keys
Easy sealing with standard oil seals
Straightforward strength calculation for a given diameter (mm)

Use solid shafts when the motor sits beside the gearbox on a base plate and the driven machine accepts a keyed solid pin.

Hollow input

Hollow input lets a motor shaft or intermediate shaft pass into the worm, or allows a compact flange motor stack. Common on NU industrial worms and on aluminium servo boxes for packaging. Specify hollow bore diameter and fit (push-fit gauge notes often appear on special drawings).

Hollow output

Hollow output mounts onto a machine shaft (shaft-mounted reducer concept) or accepts a customer shaft through the wheel. Useful on conveyors and roll drives where the machine shaft is continuous.

Hollow both ends

Anand Gears regularly builds hollow input and hollow output on the same NU or special body. That combination supports through-drive layouts and compact dual interfaces — seen on specials and double-reduction packages. If you need this, state both bores in millimetres on the RFQ.

Double solid output

Not hollow, but related: double output extends a solid shaft both sides of the wheel to drive two loads in phase. Common on mixers and dual conveyors.

Decision table

Need	Prefer
Simple base-mounted motor + coupling	Solid input + solid output
Compact servo / IEC flange stack	Hollow input (often aluminium)
Mount on existing machine shaft	Hollow output
Through-shaft both sides	Hollow both ends
Drive two loads in phase	Double solid output

What to put on the RFQ

For every hollow bore: diameter, depth or through length, keyway or spline, and seal arrangement. For solid: diameter, length past the seal, keyway width × depth × length — all in mm.

Talk to Anand Gears

Send CD, ratio, mounting, shaft ends, duty, and a photo of your existing unit (or a sketch). We manufacture cast iron worm, NMRV aluminium, KL bevel, Adaptable, NU, and custom specials from our shop in Bhayander East, Thane.

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