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Listen up: Machines talk


I don’t know what you guys are trying to run on your molders but based on the condition of some of the spindles in for repair, I think it might just be concrete. Broken shafts, seized bearings, “welded” tooling all can be prevented, and it starts with listening for signs.

Let’s start with molder spindle basics. These bearings just don’t fail in one instant. They have been failing for some time. You’re just not paying attention. Most bearing sets in today’s spindles are rated for 6,000 to 7,000 hours of run time. Now there are a lot of variables here since material, chip load and balance all have an impact on bearing life. Obviously the lighter the work load and the better the tool balance, the longer the bearing life. During every tool change the operator sh erator must break the plate loose before making a radial adjustment, so it can float with the spindle. But the operator often forgets or disregards this basic instruction. Think of a paperclip that you bend back and forth until it breaks. That’s what is happening with every revolution of a tightened spindle. The shaft will eventually break in the same place every time - right at the shoulder of the spindle housing.

If you see this on upper spindles, have a qualified professional check the alignment of the complete spindle/outboard bearing assembly. If you have multiple machines that are alike, make sure every OBB plate is in its original position and never swap them around.

HSK molder spindles can fail for a number of reasons. They are an excellent tool holding interface used in almost all of the most critical of material removal machines, but they don’t like dirt and dust, especially around the cone area. Make sure the cone-clean feature is working and if you are not using a spindle on a particular set-up, put in the cover plug.

Drawbar spring tension holds the tool in and it must be adjusted to specifications for safety and cut quality. This is a job for trained professionals, though drawbar gauges and testing kits are available for end users comfortable with making the adjustments. Your springs will last longer if you don’t leave tooling in the spindle for an extended period of time.

The HSK clamp group – a segmented assembly inside the end of the spindle - has a very specific adjustment. If any of the segments are missing, cracked or severely worn, have the spindle in for service immediately as the tool cone may not be held securely in the taper.

A bad panel saw arbor is often overlooked. Signs for this include bad cut quality, tear out and unusual vibration. The arbor post, both flanges and pins can and do wear. Don’t always blame the blade.

Have a close look at the pins as these take the most abuse. Replace them if they are worn or out of round. Check the flange surfaces for nicks. These units can be rebuilt at about 25 percent of the cost for a new one but find a rebuilder that has surface grinding and balancing capabilities.

I’m a proponent of vibration monitoring, which involves placing wired or wireless sensors on critical machine components such as router spindles, molder spindles and saw arbors. They record bearing frequencies and temperature in real time and relay the data back to a central monitoring service. Should a monitored component report any abnormality, the service notifies the user by text message or email. This can save your company thousands of dollars per year in unnecessary repair costs. Sensors can also monitor other rotating equipment such as compressors, blower motors and vacuum pumps.

Photo of Bob Barone

Bob Barone

In the end, the amount of money you spend on repair is directly relative to the amount of time you spend on prevention. Your machines are trying to talk to you. Take a good listen. 

Bob Barone is a 35-year veteran of the woodworking industry and Vice President of Precision Drive Systems. Send questions to

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