Hard spots in 11L14?
Just a dig in the dark - but was the cutter tip below center ?
Or above - and not on the center line ?
Martin
Wes wrote:
I just had something weird happen.
I was boring a .475 deep .624 dia hole in some 11L14 on my lathe.
Work was held in a 4 jaw chuck, boring tool was a boring bar for my Bridgeport's offset
boring head, one of those brazed carbide bars.
I noticed I'd start taking a cut and after a certain distance in, I'd start hearing
chatter. I removed the tool, double checked it was set it on centerline, and even gave
the cutting edge a light honing to touch it up. Didn't help any. I also looked for tool
rub as in insufficent relief.
Anyway, as I worked away, it became apparent my finishing cuts where not tracking the
amount of infeed. I was using a telescoping gage and mic to measure.
Getting near where I thought I should be at the right diameter, I tried the hex bushing
that I planned to press into the hole and it went in about 1/8". Now that is weird. Why
only that far?
On each pass, I had stopped the lathe, and retracted the carriage w/o backing off the
cross feed. That little scratch that can result isn't an issue since I'm pressing
something in.
I decided to dismount the work and use the bushing to check the back side and that was at
least 0.006" oversize.
The ways do not have detectable wear. This isn't a whooped lathe.
So what the heck happened? 11L14 generally cuts like butter and I've used a lot of the
stuff.
I've turned a shorter piece from the same round w/o issues using the same setup and I made
the same piece I was making tonight earlier.
For those that remember my recent post about screwing up a barrel plate by tapping the
wrong sized holes, this was the replacement.
Wes
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