Hard lesson learned

[pfduffy]

Last Thursday, while turning an 18 in dia x 2in thick platter of cherry that was ten years in the drying barn, it blew apart on me, causing a significant injury to my left upper arm. The cause? - -a catch, you say? NOT! I was not even touching the wood when it flew apart! Post accident analysis shows a hidden and deep bark inclusion that I put under stress by mounting the blank on a 4 jaw chuck in the expansion mode. The inclusion runs all the way to the rim from just off the center and it shows a complete separation with no scars for tools, etc. The expansion pressure caught up to me and the wood at the same moment. That the natural crack was not visible certainly is regrettable because, with my experience, I would have known better than to use the expansion mode.
Just a word to the wise; keep the expansion mode for something tiny, and solid!!

 

[Frank Kobilsek]

Phil

I wish you a speedy recovery.

Created a similar hazard for myself a couple years ago but my sin was high RPMs on big plate. It missed me but destroyed a 4' light fixture.

Frank

 

[Charlie Knighton]

injury

heal fast, thanks for the heads up

 

[john lucas]

Scary. I often use expansion mode for platters. I never use it for bowls. I've got to turn 2 platters here shortly. One is wood that might be suspect. I'll have to look at it very closely and might consider using the vacuum chuck now.

 

[Paul Engle]

Or screw to a face plate, waste block then platter. take it almost to finish then cut in mortise or tennon.leave the waste block on , make tennon then turn on tennon till you get to waste block then take it off, should be able to see if defect there , the waste plate will at least keep the center portion together in the event of hidden fault.

 

[MichaelMouse]

Just a word to the wise; keep the expansion mode for something tiny, and solid!!

Nope, just understand how to use it and it's not a problem. You could have as easily crushed a flawed tenon.

Which leads to the key in chucking. Snug, not tight, and sized to spread the load so that it is not going to pull anything apart until it crushes the material at 90 degrees to the crack.

Fifteen by seven holds in an eighth inch deep 2" mortise just fine. Use it all the time.

 

[Bill Pottorf]

Unfortunately, I think you would take a large risk with that 18" blank regardless of how it was mounted. If the hidden bark inclusion was that large and the blank that weak, centrifugal force will cause a disaster as did happen. I myself have turned some large blanks this way, knowing that the inclusion is inside the blank by close examination prior to mounting. Fortunately, I have not had that happen - YET - but am cognizant of the fact that it just might fly apart on the lathe. I have not used the expansion dovetail tenon method on any of these large blanks however. Phil, your accident will cause me to reconsider some of the things that I do as well. I hope that you heal fast and return to turning. Good luck and thanks for pointing this out for all of us and particularly myself.

 

[Gretch Flo]

Arm position??

Last Thursday, while turning an 18 in dia x 2in thick platter of cherry that was ten years in the drying barn, it blew apart on me, causing a significant injury to my left upper arm. The cause? That the natural crack was not visible certainly is regrettable because, with my experience, I would have known better than to use the expansion mode.
Just a word to the wise; keep the expansion mode for something tiny, and solid!!

I have a max of 16 inches so don't work with the big stuff. But I usually have an expansion mode. I have had wood fly apart. Usually north/south and I am east. Where was you arm when this happened???? Sorry to hear about your problem, Gretch

 

[dkulze]

Not just size. I took a hit in the face mask while simply roughing out the outside of a blank of hard maple. Was about 8" diameter with a tiny bit of inclusion showing. what didn't show was the inclusion that ran all the way through the entire piece and ended about 1/4 short of the whole outer surface in an eirie parrallel line to the curved cut I was making. Knocked off my face mask, cut my forehead with the retainer strap, and left me stunned for about 15 minutes.

Can't always see it coming so wear your face mask and be careful.

Dietrich

P.S. (I didn't mention that I was in a hurry and had it running faster than it needed to be cause it looked fine)