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Old 12-13-2004, 03:19 PM   #1
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Default Cutting a Comm w/ Full-Sized Lathe

Do any of you use a full-sized lathe to cut commutators? I've got access to several lathes at work and was about to buy a comm lathe when I considered that I should easily be able to chuck up the shaft and just buy a good diamond bit.
Any tips or pointers? What feeds/speeds would I use?
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Old 12-13-2004, 03:21 PM   #2
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Its hard to bring that big lathe to the track. I did the same thing but got one anyway so I had one when I needed it.
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Old 12-13-2004, 03:31 PM   #3
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Yeah, I guess that'd be somewhat of a challenge. And a little bit of a nuisance to the others in the pits! But man, you'd be the envy of everyone at the track!

Anyway, I'll probably end up ponying up for a portable comm lathe down the line, but it just moved itself way down the priority list. If I've got a handful of motors that are trued and ready to go when I hit the track, I should be good to go.

I'm sure someone is doing it - I'd like to get some feedback. I might bring in some old armatures tomorrow and practice with some of the mild steel bits they've got here.
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Old 12-13-2004, 03:37 PM   #4
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It's not a good Idea to cut the comm in a full size lathe only because the armature is not supported at both ends like on a comm lathe. You could risk bending the shaft if the tool bit catches on you.

I would just invest in a comm lathe.
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Old 12-13-2004, 04:46 PM   #5
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Quote:
Originally posted by D_Ames
It's not a good Idea to cut the comm in a full size lathe only because the armature is not supported at both ends like on a comm lathe. You could risk bending the shaft if the tool bit catches on you.

I would just invest in a comm lathe.
Hmmm, yeah that would not be good. I might be able to find a tailstock that would work, though.
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Old 12-13-2004, 05:02 PM   #6
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Many years ago, before comm lathes were commom, I used to do it at work. The real problem is the speed needed to get a good finish on copper. If you crank it up high enough, it will work. Not too many lathes are happy at that speed though.
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Old 12-13-2004, 06:08 PM   #7
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SammyXP...

I've used a lathe from work numerous times for my r/c arms and for slot car arms... I used collets instead of the 3 jaws, and put a drill chuck in the tailstock with a bushing for support. I bought a synthetic diamond from McMaster-carr for about $55.00. Run the lathe about 300 to 400 rpm with a feed of .002" to .003" per rev. (good starting point). I also used tap magic for cutting fluid.

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Old 12-13-2004, 06:11 PM   #8
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Listen to Wayne he knows what he's talking about!
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Old 12-14-2004, 01:58 AM   #9
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Umm, you can get collets that will support both ends of the arm.....Reedy arms last I heard were cut on a full size lathe....I have one that can do it, but I just think it takes too long and in the end, it really doesn't seem to cut any better....


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Old 12-14-2004, 07:11 AM   #10
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Thanks Wayne, you're the man!

That's exactly what I was looking for. I brought an old endbell, trying to figure out a way to mount it to the tailstock and I hadn't even considered using a drill chuck to just hold a bushing.
I've got a few old armatures with me today that I'll practice on before cutting any good comms.
Using a collet instead of the jaws is an excellent idea, as well.
Thanks for all the tips!
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Old 12-14-2004, 02:11 PM   #11
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using a full size lathe for cutting a com, unless you've spent some time on a lathe would not be wise, never seen a machine that did'nt need the tailstock dialed in to the headstock,time spent would be better to invest in dedicated com lathe, even so they still need setup at first. do some more research first, go talk to a real local machinist, find an old guy. just my 2cents
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Old 12-14-2004, 04:00 PM   #12
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No problem Sammy..
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