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Inspecting / Replacing your Motor Brushes

The brushes on Nolting machines start off as sticks of carbon, 16mm long and of 3mm square cross-section - the same material as used for pencil leads. Their function is to conduct the electricity from the wires to the rotor of the motor. Carbon is used not just for its conductivity but also because it is softer than the copper it must run on and it is also a lubricant in its own right. It WILL wear down with use, however. When one of the brushes gets to be 8mm long it is time to replace both of them. It is recommended by Nolting to CHECK your brushes after 1500 hours of machine useage. Because one will wear faster than the other you may decide you can do another 1000 hours just by swapping them over. At the very least you will get an appreciation of how fast your brushes are wearing.

To compensate for the wear the brushes are mounted on springs which keep the carbon stick pushed onto the copper rotor. In all but very old motors the brush unit resembles a jack-in-a-box when you get it out and more particularly when you try to get it back in again. On pre-2002 machines there were no side inspection holes drilled in the body of the machine as the motors were still mounted "vertically". In these cases and if your motor has external brushes you will be able to access ONE of the brushes from underneath and the system was designed so that that particular brush is the one that will wear the faster. On pre-2001 machines you may still have a motor with internal brushes. Consider getting a new motor now!!

Most Noltings in NZ will have side inspection ports - holes drilled through the machine body in the vicinity of the rear axle that just happen to be right over where the external brushes are housed on the motor body. These holes are stoppered with a light plastic plug - easily removed to reveal a slot-headed black plastic screw-in cap that retains the jack-in-a-box spring-thing-with-the-carbon-brush-attached. Unscrew this black plastic cap to access the brush assembly. The worse case will be on the left-hand side of the machine so you might like to start there. If this brush is, say, 12mm long you will get good mileage by swapping it with the right-side brush which will be maybe 14mm long. If the left brush is 8mm or less contact  Mike for a new set. At $13 a pair (incl P&P + GST) it is CHEAP INSURANCE.

To get your jack back in the box is a tad tricky. I have developed a technique that makes it a bit easier. Lay a tiny bit of blu-tack in the slot of the cap. This should help it stick to your screwdriver. Alligning the curve at the end of the carbon brush with the long axis of the motor, push the jack back in the box with your finger and then insinuate a very small screwdriver under your fingertip, from the side, to take over the holding-in duties. Now you can position the black-plastic-cap-blu-tacked-to-the-screwdriver over the hole and withdraw your tiny screwdriver. Turn carefully in a clockwise direction until you feel the threads meshing. Do up and replace the cover in the hole.

WHY should you do this? IF you are the lucky sort, when your brushes become too short to make contact with the rotor, your machine will just slow down and eventually stop - usually noticable over a day or so. Replace the brushes and you’re away again. HOWEVER, This Year (2008), we have had several cases of worn brushes SPIKING the controller board which has meant drawn-out and costly repairs. It’s not worth NOT doing this job. Believe me.