Advanced Precision Machining

CNC Milling and Machining - Take Care of Your Spindles

[February 16, 2015] As most of the country looks forward to the arrival of spring, the news out of the precision machining industry, and APM's CNC machine shop, continues to look robust. All leading economic indicators and growth factors point to another great year as demand for milling and machining services is forecasted to further increase. In order to maintain a competitive advantage however, CNC machining facilities must still rely on a variety of best management practices to take advantage of the improving economy and boost their bottom line. Without sacrificing quality, service and safety, cost cutting in a machine shop environment is always at the top of the list for owners and managers.

High speed machining equipment is likely the biggest capital investment a shop makes, and its proper care and maintenance is critical to reducing costly downtime, repair bills, and replacement while maintaining throughput and efficiency. Spindles are the lifeblood of CNC milling and CNC turning machines, and no one wants to see production negatively impacted due to poor maintenance practices. Upkeep is a critical component in keeping costs down while running an efficient and money making CNC machine center. Here are a few of our favorite tips to cut down on the number of repairs:


A critical care function you can perform. Maintain lubricants at the OEM recommended levels, keep clean (check for discoloration), and replace according to the suggested maintenance schedule. Daily inspection of oil levels in all operating tanks including; gear boxes, spindle chillers, hydraulic units and central tanks must be adhered to, in addition to ensuring that all spindle bearings are properly lubricated.

Cooling System

Before powering on any CNC machine, make sure that coolant levels are correct and that strainers are clear of any debris. If so equipped, chiller systems are designed to warn you of a spindle problem; therefore it is critical to ensure that they are running properly. In addition, be certain that your coolant is aimed correctly and not splashing directly on top of the spindle. This can result in damage.

Vibration Levels

If you notice increased vibration or unusual noise, the spindle bearings have become worn out and need replacing (use OEM technicians and/or parts). Keep an eye out, and an ear out, for any triggered alarms on your milling and machining equipment.

Spindle Spring Force

The pull force of the spindle spring is critical to proper CNC machining; it secures the tool holder in the spindle. If this force becomes too weak, excess vibration, runout, and damage to the spindle and machined parts could result. Check the spring force regularly using a "draw bar pull force test". It is also good practice to perform routine runout tests using an OEM recommended spindle test bar.

Avoid Accumulating Chips

When running any CNC milling machine, avoid any accumulation of chips near the end of the spindle. These have a tendency to work their way inside the bearings, limiting their lifetime, resulting in potential damage to the spindle.

To sum up, if you're not producing accurate and quality machined parts, if you notice a rise in operating temperatures, vibration levels or unusual noise, then you have spindle problems. With proper care and regular maintenance, including investment in quality spindles to begin with, you can significantly reduce costly downtime, errors, and repairs. Take care of your most significant investment, and it will take care of your CNC machining operations.

APM is dedicated to manufacturing the highest quality precision parts while providing the best customer service experience in the machine shop business. For additional information or to request a quote, please visit or call 303-776-1910.

About the Author

Gerry Dillon is a co-founder, current owner and certified CNC machinist at Advanced Precision Machining (APM), a full-service machine shop located in Longmont, Colorado. Before making his home in the United States in 2000, Gerry was born and raised on the emerald isle of Ireland and took an interest in milling and machining from an early age, ranking #1 in the Irish National Apprenticeship Program. In 2005, he partnered with his friend and colleague, Kirk Tuesburg, currently APM’s machine shop manager, together launching what’s grown into a leading Colorado machine shop. Gerry brings over 30 years of machining experience to the shop floor, and is certified in all aspects of geometric dimensioning and tolerancing. 



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