On Tue, 06 Mar 2012 17:48:20 -0500, Wes wrote:

The other day, I needed to turn a shaft to 25mm diameter for a machine
at work. Not a big deal I thought. I only need a 7" shaft, I'm turning
12L14, this should be easy.

The first problem I ran into is that the normal CMNG tool holder I use
would not clear the live center (this is a big lathe). So I looked
around, I found a tool holder of the trigonal type. It had a ceramic
insert in it but I knew where we had a machine running a carbide
trigonal insert and installed one of those.

Well, I never got a decent finish, it was so bad you could ridges across
the item I turned. I tried a different carbide insert and it wasn't any
better.

It got to the point that I used a bit of sand paper, pressing the shaft
through a bearing to burnish it to get a shaft I could use.

I tried playing with the feed, speed and tweeking the tool height.
Nothing made a difference.

I should have just turned a longer shaft using the CMNG tool holder that
always worked and parted off the excess.

Anyway, what was the likely issue? It did look like the trigon tool
holder had a bit more inclination but I didn't measure it.

Thanks,

Wes


If you are using the live center be sure its actually *on* center.

John