M321 – Routing spindle

The M321 is an upgraded version of the industry proven M320 PCB light routing spindle, with a maximum speed of 125,000rpm. Controlled depth routing and pocketing is possible through the front thrust bearing design and liquid cooled body and bearings. A powerful AC motor is utilized with a shaft tacho for optimizing feedrates to increase productivity. This reliable and rugged air bearing spindle also incorporates interchangeable collets, dust ingress protection and an optional radial load limit sensor.

Specifications of M321 spindle

Speed range10,000rpm - 125,000rpm
Motor power (max)750 Watts at 1400 Hz
Automatic tooling systemPnuematic, with interchangeable collets
Collet sizes1/8”, 3, 4 and 6mm shank dia.
Bearing air supply pressure5.6 kg/cm*2
Bearing air consumption85 nl/min
Coolant flowrate1.5 l/min (water) or 3 l/min (oil)
Heat dissipation to coolant (max)640 Watts
Axial failure load (push)200 N
Collet torque (max)4 Nm with 6mm bore collet
2 Nm with 1/8” bore collet
Dynamic runout at tool7 microns
Motor type3 phase, 2 pole AC
Speed sensor (tacho) - optionalTTL signal
Weight (approx)4 Kg


Have a question about the Air Bearing Spindles product range? Here we answer a selection of frequently asked questions.

If your question doesn’t appear, please get in touch with one of our experts.

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The Westwind product line spare parts are manufactured to the same high quality and tolerances as our spindles (Westwind product line is ISO 9001:2015 registered). Our manufactured collets are specifically designed to operate at the high rotational speeds and dynamic run-out accuracy demanded by our customers. Alternative components cannot only reduce the life of the spindle, but may also affect product quality and output. Experience has shown that by fitting only genuine Westwind replacement parts, the high productivity, consistent accuracy, and outstanding operating characteristics can be maintained.

It is likely that contamination over a period of time has prevented the shaft from floating freely. We strongly recommend the unit be returned to your local Westwind product service centre for investigation.

Please refer to your machine manufacturer’s recommendations.  Currently 6.35mm is the maximum we recommend for most Westwind PCB Spindles.

This should be carried out at intervals recommended by the machine manufacturer. You are strongly advised to refer to the appropriate Westwind collet maintenance booklet (available free on request), and to use the Westwind collet maintenance kit available through your machine supplier. However, as a general rule we would recommend a maximum of 5,000 hours between removal/cleaning/re-setting, although some end users maintain their collets every 100 hours.

Westwind recommend the use of distilled water with the addition of chemical agents to prevent algae or bacterial growth. Each spindle needs an uninterrupted flow at between 16-20ºC. Many spindles used in production are fitted with temperature sensors that shut the machine down before damage is done.

By clean air we mean the supply should be filtered to better than 0.01 microns and 99.99% free from oil and water as a liquid or vapour with a PDP (Pressure Dew Point) @ 7°C. Westwind are able to supply suitable filter units. Please note that in all cases we strongly recommend that the compressor system is backed up by a reservoir tank to maintain a steady pressure and to minimise the effects of an air failure.

Westwind spindles, when correctly installed and supplied with clean adequately filtered air, give many years’ service with the minimum of attention. Routine maintenance is limited to changing the air filter elements so that the air supply remains uncontaminated. Guidelines can be found online for spindle and collet maintenance.