head and face protection part 2 with pictures.

[Richard Demler]

Pictures of the bowl that went airborn on me yesterday.

[brian zawatsky]

Wow man that wood looks awful sponge-y. Maybe it's just how it appears in the pics, but that looks to me like it's overshot spalted and gone right to soft & punky.

[Richard Demler]

actually very solid..But the grain is wavy and apparently separates easy..Not soft or punky..

[robert baccus]

The first pic looks cracked all theway and dangerous. Those are cracks right?

[Richard Demler]

Robert,it is cracked all the way..this is after it flew apart..Just put together for the pics.All pics are after..

[Geoff Whaling]

Pretty much the scenario I described in the other post, add spalted wood into the mix as well. Only experience will tell you how far you can push punky / spalted / wormy / holey wood. Untill you gain the experience it is a wise move to keep lathe rpm down.

That looks to be approx 12" dia?

Dale Nish had a suggested speed formula for bowls and platters -

bowl dia (in inches) x lathe rpm > 6000 & < 9000 (i.e. between 6000 & 9000)

even less for punky woods etc. So a sound 12" dia bowl blank should be turned at around 500 to 750 rpm according to Dale's formula. http://www.docgreenwoodturner.com/lathespeed.html
Many chuck manufacturers publish suggested turning rpm's in their manuals.

Just re-read your first post - you say 20" - suggested speed should have been 300 - 450 rpm. You were doing two to three times that recommendation.

[David Delo]

Richard,

I would suggest you take a look at one of Stuart Batty's videos on how to make a recess. This is a good explanation of what to and what not to do when making a recess.
https://vimeo.com/68649135

[David Delo]

There's also a good discussion of recesses here on the creek with an older thread.

http://www.sawmillcreek.org/showthre...essed-Dovetail

[Richard Demler]

Geoff,I gave the starting size of 20in in the original post..The size of the bowl when it broke was 14 1/2 inches..The recess is 3in in diameter and half the depth of the jaws on my hurricane chuck.The very outside of the wood had some soft wood on it and it was removed right away when I started turning it..I will read the lnks you gave on the recess,but what does it look like is wrong with the way I have done it..Thanks again for all the replies and suggestions.I will read and remember them all.

[Geoff Whaling]

Richard, I'm a conservative turner, so I have a pretty good think about what I put on the lathe, how I am going to proceed and what processes will offer the highest probability of success while keeping me safe


That said I think the only things you could improve on are not placing to much faith in the structural integrity of spalted wood, reduce lathe rpm, consider using a face plate vs a chuck, consider stabilizing the blank with Cactus Juice or similar, make a recess that is more suited to and conforms to your chuck jaw profile, and monitor turning progress more often by stopping the lathe and having a very good inspection of the blank and chuck recess for signs of failure.

Personally I would favor a glue waste block and face plate for heavily spalted or punky blanks.

The structural integrity of spalted wood is already compromised from within as the fungus decays the wood. When you have a requirement to keep tightening the chuck it is probably becasue of two factors, the wood is soft so is compressing or the recess is failing due to the wood splitting, neither is a good sign. Continuing on at relatively high rpm without constant inspection and / or modification of the mounting method etc is simply inviting disaster.

You also mentioned that you had to find a suitable rpm that the blank was in balance. Manipulating speed to find a harmonic balance for blanks is fine within limits and often there is two or more speeds that will achieve that result, choose the lower speed if at all practicable. Speed kills, as the old road safety messages stated. Stuart Batty's comments mentioned are well worth heeding.

I'm not trying to be sensational or alarmist however around the time Lynne Yammaguchi was injurred there were four deaths attributed to lathes, three on wood lathes & involved severe head injuries. The potential for severe injury is there. Your comments re the damage caused by the flying blank add much credibility to the amount of energy that a large piece of a blank comming of the lathe possess. It can do very real and lasting harm.

I sincerely hope this helps for future work.

[Jim Underwood]

My experience with Ripply Oak is that the grain isn't very... um.... "cohesive", for lack of a better word. The ripply grain stuff just doesn't hold together well, even if it isn't spalted.

What I see in your pictures is a pretty far into the degenerative process as well- you can tell that by all the tearout on otherwise clean cuts. So, I think you're quite lucky this thing didn't put you in the hospital. I'm so thankful it didn't too. I hate to see this kind of thing happen to folks enjoying their hobby. It quickly becomes anything but...

[Reed Gray]

Well, no, that is not a solid piece of wood. Looking at picture #3, you can see deep end grain tear out which is a symptom of rot. If you consider that finger sized piece that broke off in the middle, and the way it broke off across the grain rather than following the grain straight through, that is another symptom of rotten wood. Most of the time I will not even put a piece like that on my lathe. Even if I could have turned it to finish, the extra work involved in getting it presentable to sell just isn't worth the effort unless you are wanting a challenge... A tenon might have saved this piece, but still, a high risk piece of wood at any speed.

robo hippy

[Richard Demler]

Well,I learned a lot reading all your replies..I will be learning more about spalted and punky woods..My idea of solid was'nt the best example..I appreciate and respect all of your experience and I will try to learn from it all..Thank you again,hopefully I won't be posting any more experiences like this.. Have a great weekend!!! and thanks!!!!!!!!!!

[Dane Riley]

It seems to me that recess chucking is always a balancing act. Too tight and the wood will split (unless the chuck or your arm breaks first). Too loose and it comes off without splitting. Tough to know how much to tighten.