Live tools only or Y-Axis?

[grweldon]

I'm trying to decide if I can get by with a lathe that has only live tooling and a C-axis or whether I actually need a full Y-axis.

We frequently cut keyways on shafts and the tolerance required is usually + or - .001 from nominal size. Can this be done reliably and with good results using only a C-axis with live tooling? It seems to me that the sides of the keyway would not be parallel, causing the top of the keyway to be loose and the bottom of the keyway to be tight.

With a Y-axis, this would not be a cause for concern and an endmill that is smaller than the size of the keyway could be used for precise size adjustments.

I have never used or purchased a lathe with live tools and I'm looking for some opinions from people who do this all the time who can speak to the results. Anybody do this on a regular basis?

Thanks...

[lapoltba]

I dont know what machine you are planning on getting but i can speak from my experience using a Mazak With the mazatrol programming software. It only had a C axis and live tooling.

I did retrofit and repair work for papermills and medical device manufacturers and also frequently cut keyways from 3/16 up to 3/4 on this machine. I just used the sharpest endmill i had (usually a whisperkut) and took between .01 and .04 depth of cut with a conservative plunge rate. The keyways came out great but the were not "precision". You could get +/- .001 but it wasnt always predictable. I always just used CRS square stock and made my keys to fit by honing them to the correct dimensions.

So i guess your answer is, If you can afford the live y-axis then get it. If your keyways can be worked around a thou or two then dont bother you can deffinately do without it. There are some times that it can come in handy but for the most part, a job shop wont need it. Besides your probably only gettings +/- 4" of travel right?

[ALLtra Mach]

I must totally disagree.

If your cutting keyways, you cannot control the size, and maintain a square wall without a Y-axis.
Yes you could "work over" the key way, and for repairing machinery that may be OK. But if your doing work that needs to maintain accuracy, you can't get it.
If you have a key in a 1" shaft with .001 "wiggle", how far will a 6" gear move at the tooth?

BTW, you didn't mention what Lathe your looking at?

Another thing the Y axis will give you is flat bottom side pockets,which is what a key way is, can't do that with C-Axis.

I'd say it would depend on how accurate and flexible you need to be.

If you have ever used a Y axis lathe, you'll never want anything else!