Skimming an armature

[TurboNutter]

Hi

I've got the Eagle Racing comm lathe with their 55T slave motor and the standard cutting tool. I am intending on getting a diamond tip, but for now I'm focusing on buying other things.

The problem is that when I cut a comm, it doesnt come up as shiny as I expected. Should I be using a light oil on it, if so, which type?

Also, how many cells should I be using to run the lathe?

Cheers

[damo]

4 cells/3 cells depends what the manufacturer recomend, and i know eagle do a comm cutting fluid..couldnt say what is in it tho...

[Doomanic]

Eagle recommend a 6 cell pack for their slave motor.

I wouldn't expect to see a mirror finish from a carbide tool.
Copper is self lubricating so shouldn't need any cutting fluid.

[damo]

in the eagle lathe i have used of a friends of mine in the instructions it reccomends you use the "cutting fluid" they provide with the lathe/carbide tip combo....mind you they do sell it so it could be self promotion i spose....it does give a better finish tho...

[PDW]

Chris, with a carbide tool you won't get a mirror finish (sorry Doomanic, seems to be an echo in this thread!!) because carbide cuts at a lower speed than diamond. It has to do with shear forces on the metal during cutting. However, some cutting oil will help, and I suggest you get the one they recommend.

The objective is to get a round commutator, not a shiny one. Don't worry about the finish. When using the carbide tool, take care to look for burrs in the slots. Carbide is more likely to give them, and they need removing with a scalpel blade. Carbide is cool, don't go buy a diamond if you cut less than a dozen comms a week.

Make sure you run exactly the recommended number of cells on the recommended motor when using carbide. HTH. :)

[burgie]

chris - if you want a shiny comm, run your comm stick (the oblong end!) across it whilst it's still on the lather, spinning.

I run my eagle lathe off my indi dyno, at a slow speed, and get a very shiny comm, without the aid of oil etc.

[Steve Cann]

Echoing PDW you do not need a shiny comm, just a nice parallel cut. In fact the slightly less smooth finish of carbide tools will help bed in new brushes.

For lubricant apply a coat of ink to the comm from a felt tip marker pen, nothing fancy is required, this will also help you in seeing that you have made a complete cut accross the entire surface.

[Dave Treacy]

I'm with Steve, get yourself one of these boardmarkers they use on whiteboards (Nobo) and coat the com in it. Then when you cut you can see how well the cut has worked andit provides lubricant.

[DA_cookie_monstA]

And also gives of a lovely pungent smell... lol but it works