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Buddy, can you spare a spindle?

A broken spindle will halt production, so be prepared with a backup and a plan for service and repair

They’re a big investment, and when they go down production can screech to a halt. Any shop using CNC routers needs to have a plan in place to handle repair, service and backups for its spindles.

Heat is the biggest enemy. It takes time for a spindle to heat up, and the lube to flow. While that’s often part of the controller software program, in some low-end machines it’s not an automated task. The woodworker needs to go through the process and cutting corners here can seriously reduce the working life of a spindle. Heat is a factor during processing, too. The first step in liquid cooled spindles is to get the coolant mixture right, and in air-cooled ones make sure the fins don’t clog. Don’t use compressed air on routers or spindles as it will just force debris inside the housing and screw up the bearings.

Watch your chip load. It can exceed recommendations if the bit (tool) is dull, too large, plunging too quickly or moving too fast. You can hear the stress and see, or sometimes even smell, burning. Rough surfaces can be caused by skipping, where the bit moves erratically in stops and starts because it’s being pushed too hard. A tool out of balance can also cause spindle deterioration. Perhaps the easiest way to monitor stress is to watch the Amps, and an electrician can add an inexpensive gauge to any machine to help the operator avoid redlining.

Make sure your variable frequency drive (VFD) is in tune with your spindle. This device changes the frequency and voltage of the electric supply to meet the needs of the motor under load, and also ramps the current up or down when starting or stopping. It’s a good idea to ask the spindle manufacturer or supplier about VFD requirements before running the router.

Is your spindle sized for the work that you’re asking it to do? Does it spin fast enough, and have enough horsepower and torque? Some low-end manufacturers list the power draw rather than the output when rating their spindles, so ask a few questions as you may not be comparing apples to apples. The relationship between torque and speed is critical for shops that are going to be using larger tools to profile hardwoods or machine thick materials such as 3/4” MDF. It’s not so critical if you’re performing tasks such as surface engraving, or machining foam for signage.

The first line of defense with spindles is having a spare on hand. It should be stored in a climate-controlled environment, especially in parts of the country that go through periods of high humidity or are subject to salty sea air or wild temperature variances. Don’t forget to allow a dormant spindle to warm up properly before use.

The second line of defense is networking. Find out from the factory or online user groups who else close by has a machine that’s using the same spindles. Several manufacturers of CNC routers maintain user group databases and also host forums. The more connections you have, the easier it will be to deal with an emergency – such as a Friday morning burnout on a job that needs to be delivered on Monday, or a holiday when the factory technician isn’t available. Borrowing or renting a spindle for a week from somebody local can save days, even if the repair shop provides loaners. And the shop that bails you out now knows that they can ask you to reciprocate later.

One more way to prepare for a rainy day is to spend the money to buy a high-quality spare, and perhaps even upgrade the factory spindle if it’s a cheap import. This is one piece of machinery where we absolutely get what we pay for. One thought is to buy a high-quality used spare from a reputable repair shop, who will probably even offer some kind of warranty. Be aware that rebuilding a more expensive spindle will be, well, more expensive. But it shouldn’t need to happen as often.

What’s involved?

Repairing a spindle can include any one or several options from a huge menu of possibilities. It depends on what failed and what needs to be addressed such as burnout, or an erratic arbor. The first step in a reputable repair shop will be taking a series of photos so there’s a record of the spindle’s condition when it arrives. Next, it will be disassembled, cleaned and then go through a rigorous parts inspection, which is often captured on video. A good technician won’t assume that the obvious damage is the only damage. Once the inspection is complete, the repair shop will contact the woodshop and explain what needs to be fixed and what it will cost. The best shops will also posit some opinions at this time on why the spindle ended up on their workbench and suggest ways that the woodshop can either extend the repair interval in future, change some practices to avoid potentially catastrophic damage.

The woodshop now faces three choices: have the spindle repaired, buy a new one, or buy a reconditioned one. This is almost always a simple matter of arithmetic – which choice delivers the earliest date upon which the shop stops paying for the spindle, and the spindle starts paying the shop. Warranties are a very important part of the equation, too. A complete rebuild on a high-quality spindle will cost a lot more than a cheap replacement, and if the warranty is short then the woodshop may end up paying for a second repair. The industry standard seems to be on the neighborhood of six months or 1,000 hours.

Most repairs involve replacing components such as bearings or seals, and some of these parts have improved over the years so the rebuilt spindle may actually be in better shape than it was when new.

Where to go

One of the more well-known repair facilities is Precision Drive Systems (PDS, online at, which is a global provider with facilities in the U.S., Canada, Brazil, and Germany. The company repairs and retrofits all brands, makes and models of electric spindles, and offers the options of 24-hour emergency service or three-day turnaround to minimize downtime. When PDS accepts a spindle for repair, the rotating assemblies are tested and rebalanced, and the bearing pre-load spacers are reground. Each spindle is worked on in a clean room, where it is performance checked to OEM specifications. The spindle’s tool retention system (the arbor, collet lock nut or power actuated drawbar) is tested for correct operation, secure tool retention, run-out and dynamic balance. After repair, the spindle undergoes a thoroughly documented inspection where it is precision balanced to ensure optimum life and performance. Then it is cycled through a computer monitored break-in/ramp-up cycle to make sure the lubrication is dispersed properly, and the spindle is running at the optimum temperature. The spindle’s wiring, connectors and cover plates are reassembled, and then the sensors are adjusted.

Quebec-based MEC Precision (, which also has offices in Niagara Falls, specializes in the repair of electric high-speed motors, spindles, servo motors and AC/DC motors. The climate-controlled facility is completely self-contained, and an avoidance of outsourcing contributes to quick turnaround. MEC can do complete in-house rewinds if needed and does precision machining and grinding of parts according to manufacturers’ specifications. The shop is equipped with conventional lathes, plus CNC lathes, milling machines and surface and cylindrical grinders. There’s also advanced equipment to perform dynamic balancing of parts such as motor rotors, shafts, fans, pumps, impellers and pulleys.

Finding a reputable shop is relatively easy – most CNC router manufacturers offer some repair, or they can recommend a facility that works on the spindles they supply. And don’t be discouraged if your spindle’s brand isn’t a household name. For example, Precision Spindle & Accessories ( in Otterville, Ontario lists a jaw-dropping list of 723 brands that it repairs, and then notes that even if your spindle isn’t on the list, they can still repair it.

That same capacity is evident at Ekstrom Carlson ( in Rockford, Ill., which offers an astonishing list of almost 1,400 different spindles, live tools and aggregate head brands that it has repaired to date. The company is also an original equipment spindle and motor manufacturer, and it has built a clean room where technicians work on more than 600 spindles each year, following ISO 9001 process controls.

Advanced Spindle Technology (AST, online at is headquartered in Winston-Salem, N.C., and is another premier provider of machine tool spindle repair service. Bob Hodge of AST notes that “the spindle is the heart and soul of any machine tool”, and that in some cases he returns a spindle to his customer that is better than new because its performance is now matched to the specific parameters of the woodshop’s machine. AST repairs virtually any make and model of spindle.

Atlanta Precision Spindles ( works on repairs for customers throughout the U.S., Canada and Mexico. The company says it will repair spindles to exceed the original factory specifications, and do so in “one of the finest state-of-the-art spindle repair facilities in the U.S. today. We offer a Certified Class 10,000 Cleanroom to insure the highest precision technology available.”

The repair team at Northland Tool & Electronics ( in Weare, N.H. notes that delaying spindle service can cause added damage and more costly repairs. Woodshops that keep using a spindle even after noticing a decline in performance are opening up the possibility of deforming the ball bearings and damaging the outer race. The best way to stay ahead of spindle issues, according to Northland’s experts, is by “adopting a predictive maintenance program, which allows machine operators to monitor their equipment over time with vibration analysis to predict failures before they happen.” 

This article was originally published in the January 2021 issue.

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