11th Oct 2011, 04:43 PM #1
Benchtop drill press won't start.
I have a CarbaTec CH16N/MD and have had a recurring problem.
At seemingly random times it won't start when the 'ON' button is pressed. It just produces a sort of buzzing whirring sound.
I have bought a new switch but that didn't help.
I took it to the local power tool dude - he fixed it but on the first occasion the problem re-emerged after drilling only 3 holes. I took it back and the second time it worked well for a number of months but now today it's doing the same thing.
I cleaned the points - no difference. I taped the wires together bypassing the switch - no difference.
I rang the CarbaTec shop in Auburn and the guy was most sympathetic & suggested it might be the capacitor. (I'm in the bush - NSW Sth Coast)
I can buy one online - $20.00 but I'm wondering can anyone shed any light on this problem as to possible causes & remedial action?
Thanks in advance
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11th Oct 2011, 05:32 PM #2
If it is the capacitor, the motor will hum and poll. If jou grab the chuck and help it turn it should start OK. It does sound like the capacitor, so try that. Remember there will be a bit of gearing down so it may fool you due to power needed, but you should be able to feel the motor chatter as it bounces on the poles. If not, perhaps the capacitor is not the best bet.
11th Oct 2011, 05:41 PM #3
I tried spinning the chuck as I pressed the switch but no joy. I was a bit windy about doing that, so maybe I was too wimpy or my timing was off..
11th Oct 2011, 06:02 PM #4
With the power off.
Take the belt off.
Check by hand that the motor spindle spins freely. If not then you probably have a worn motor bearing.
Turn it on , still with the belt off,
If it starts OK with no load you perhaps have something dragging the the motor down. Check the spindle bearings for tightness or roughness.
A too tight belt could also cause the problem.
Also with the belt off, if the motor does not start, give the pulley a spin , if it starts up then the starting capacitor is probably the culprit.
11th Oct 2011, 06:55 PM #5
I tried the 'turn the chuck' method a bit more courageously and it worked!@!! )
11th Oct 2011, 07:46 PM #6
The 'spin the chuck' working suggests that the issue is with the start winding system. This comprises the start winding, a centrifugal switch and the capacitor previously mentioned.
Whenever the motor slows below about 70% of nominal speed (including stopping), the switch engages, connecting the start winding and capacitor into the motor circuit.
Onced the motor is switched on at the switch, power is applied to the run winding and the start winding simultaneously. The combination of the start winding and capacitor produces a magnetic field with a phase shift relative to that produced by the main run winding and kick starts the motor in the required direction. Once the motor achieves about 70% of rated speed, the start switch disengages, removing the start winding and capacitor from the system until the motor slows again.
A single phase motor like yours will normally not start from stationary without the phase shifted field from the start winding, and will dither and hum. However a flip in either direction would normally start the motor running in that direction, but it will take longer to get to rated speed. In this case, the spin replaces the starting circuit magnetic field.
The problem in your instance will be with the capacitor, the contacts of the centrifugal switch, or the connections linking the whole lot together.
Given the history of repeated failures, I would have someone check the switch mechanicals and contacts, and the wiring before replacing the capacitor. While it is possible to get a couple of short life span capacitors, I think there may be deeply seated problems, and spending a bit more to have the thing fully checked may be more economical than just throwing capacitors at it on a regular basis.
12th Oct 2011, 01:47 PM #7
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