Lathe Setup

[FilthyPierre]

As a follow on from my post about brush problems, I have some questions about setting up a comm lathe.

The lathe I bought is made by Eagle, it has a carbide cutting tool, adjustable bearing armature supports, an on/off switch but no motor. It has a second drive shaft to eliminate vibration, so the motor doesn't drive the armature directly. All for $288 Oz, about $144 USD in the current economic climate.

So, questions:
1) Where should the tip of the cutting tool be in relation to the commutator being cut ? If I look from the end of the armature shaft, should the tip of the tool be at 90 degrees to the shaft or slightly above or below ?

2) Which way should the armature rotate ? If the tip of the tool is to the right of the comm should it rotate clockwise or anti-clockwise, or in other words, "down" onto the bit or "up" from below.

3) Is cutting fluid just some sort of light machine oil or is there a magic ingredient ? Can I just use sewing machine oil ?

Sorry if these are confusing, it's difficult to describe the way it looks when it's sitting on your bench.

Any tips on cutting would be appreciated too.
Thanks.

[Railman]

Filthy Piere, I don't have an Eagle lathe but it should all be the same. On a lathe that is driven by an o-ring from the bottom: The bit should be sharp side down with the point facing toward the windings. Set the cutting face .002" above the arm centerline (probably set up that way from factory).The arm rotation should push up on the bit, forcing the arm down in the ways as it cuts. I've used the following lubes WD40, & kerosine. Ive heard that mineral spirits works but sounds too thin to me. Sewing machine oil might be a little thick, but would probably be ok. A common practice is to to take a Majic Marker (felt tip pen) & cover com while it's spinning. This has 2 purposes: one is to lubricate, the other is to see when you are done. (just take all the black off). Be sure to shim the ends of the arm to keep windings etc from hiting anything. Use a pinion gear to keep the armature from any end play, but do not bind up, it should spin free. Adjust the cut stop so cut stops before com tabs. Use 4 cell pack (5v) to power a stock drive motor for proper speed. Use either a snapped off Xacto blade, or a piece of lexan from body cutouts to clean out the com slots. Take very light cuts starting from outside & work toward comm tabs. May take 2 pases for a light cut, or up to 5 for severe dammage. clen out slots again with Xacto blade. & then use a ball point pen to relieve the edges of the comm slot so as to prevent a brush from catching on a slot. Be carefull to hold pen @ proper angle on this step so as not to skip over face of com. Clean up with motor spray when done. Practice on old arm 1st.

Another thing that I like to do is to make a sleave to slide over the arm to reduce vibrations of the o-ring drive to the irregular arm surface(not round or continuous). I use a plastic medicine bottle or anything that is close to the same diameter to the arm, slot it & slide over the arm. Then take black vinyl tape & put about 3 tight wraps around sleave. This way You don't have to wory about where the spaces in the laminations. Did I miss anything Guy's?
Good luck.

[This message has been edited by Railman (edited 04-08-2001).]

[FilthyPierre]

Thanks Railman, that sounds pretty comprehensive, you've answered all my questions. I must have guessed right, I've set the tool up the way you suggest, with the sharp side down and the point facing towards the windings. I used one included shim to raise the tool slightly above the arm centreline (it wasn't installed as it came out of the box). The instructions were in Chinese only so I was in the dark!
Good idea about the sleeve. Once I've gotten a motor (tomorrow if I can get away from work at lunchtime) I'll give it a whirl (so to speak). Only problem is that I don't have any old arms to practice on.....