Excessive comm lathe noise

Radio Control Car Action, Apr 2003 by Casarez, Ruben

I've been having trouble using the lathe I bought a couple months ago; when I get everything set up and begin cutting the comm, the comm makes a loud grinding noise. I use a carbide bit, and it sounds as though it's chipping away at the comm. Do I need a diamond bit, or can the problem be fixed? [email]

Ruben Casarez

You don't have to buy an expensive diamond bit; your problem can easily be fixed. First, check to make sure that the cutting portion of the bit is lower than the rest of it when it's clamped into the lathe. Next, install a comm and line it up so that the bit cuts directly in the middle (or slightly above the middle) of the comm's diameter. Before you move the bit closer for cutting, drip a couple of drops of cutting oil on the comm. Plug in your power supply, and set it at 4 volts, or, if you're using a 4-cell battery, make sure that it's fully charged. As your bit gets closer to the comm, turn the adjusting knob very slowly until the bit contacts the comm just slightly. Now you can use the cross-slide to complete the cut. Don't try to cut too much all at once; it's better to make a few small cuts than to make one large cut that can damage the comm. For an in-depth look at comm-cutting, check out our newly published book, "Radio Control Power Tuning," available at bookstores now.