Retention knob breakage

[Crash]

We had a retention knob break today, on a Kitamura 30 taper machine. It tore up some vise jaws, and damaged the taper pretty badly, too. My question is ... Are retention knobs subject to metal fatigue due to repeated stressing (clamping/unclamping)? This machine is about 20 years old, as is the tooling. I have never heard of one failing before this. I'm tempted to replace them all.

Any ideas?


crash

[MILLMANM]

Had 1 Break After A Bad Z Crash About 6 Hrs Later,
Spent 12 Hrs Cleaning Spindle From .011 Tir To .001
Alot Of Blue And Lapping Compond
I Love It When Some One Else Programs It And Walks Away
Brad

[Ken_Shea]

I would be very surprised if this just suddenly failed and broke, if you look at the fracture I would suspect that you will see dark portions which are indications of pending failure.
Something that old and of unknown use would cause me to consider replacing them all. I wipe these with each use and I inspect this area frequently looking for signs of cracking, also apply a light lube frequently.

Ken

[psychomill]

Yes, the studs are subjected to fatigue and wear. 20 yrs is a long time and I know of studs that are older. At this point, I would replace all of your studs. This is cheap insurance relative to the damage and down time it can cause. Whats the life span? Hard to say. Some places replace them every year or two, some at 5 or 10 yrs, some never do until theres severe wear or it breaks.

While you're at it, I'd pull the draw bar and have a look at the clamp fingers and make sure those aren't chewed up or worn either.