Shop safety - got nailed with a broken bowl today

[David Brimm]

Just posting this as a safety reminder not to get complacent at our lathes.

I got off easy this afternoon when I had a white oak bowl come apart on me unexpectedly. It was actually my wifes bowl and she'd just finished sanding it and needed to wax it (carnauba/bees mix) but she's a little skittish about being up close to things on the lathe while they're spinning too fast so she stopped and asked if I'd wax it for her. No problem dear.

It didn't have any cracks or other visible damage/weakness and had been turned and sanded at a variety of high speeds for most of the morning but I always move out of the line of fire when bringing the speed up on these things. Today I didn't do that when I started and didn't think of it until about halfway thru bringing the speed up at which point I started to move my body to the side. I didn't quite make it before the bowl came apart and took a solid hit to the face.

Unfortunately I didn't have my face shield on since it's too hard to see fine detail thru while applying finish. Fortunately I always wear plastic safety glasses, even under a shield (when I'm wearing it) and those almost certainly saved my eye. The glasses took the brunt of the impact (it broke them in multiple places) right over the center of my eye. I suspect the bruising will be impressive over the next couple days and is a nice solid oval in the exact shape of my glasses. Then some abrasion from where some of the bowl deflected down and scraped across my face. Also a moderate amount of bleeding in my sinus on that side that stopped before long. No concussion thankfully.

Very lucky and very glad that it was me instead of my wife.

The bowl was white oak (air dried 5 years), 3" by 12" (ballpark) and was about 1/2" thick in most places so nice and heavy. Photo taken a few minutes after the fact.

[Jay Mullins]

You are a lucky man, you coul have been very seriously injured.

Jay Mullins

[Steve Arnold]

Sorry about your mishap, but you may have saved a few of us in the process. All too often I only wear my safety glasses and forego the face shield. I may have to rethink that after reading your post.

Thanks.

[Brian Kent]

Wow. What a hit!
Can you help us with a couple of details? Is that mounted on a tenon or in a recess? How fast was it spinning when it broke?

Thank you.

[David Brimm]

Wow. What a hit!
Can you help us with a couple of details? Is that mounted on a tenon or in a recess? How fast was it spinning when it broke?

Thank you.

It was mounted by a dovetail recess on my SuperNova2. Not sure the exact speed but somewhere in the 1800-2000 range I suspect. I was bringing the speed up to put a little wax on it and hadn't touched it yet.

[Matt Schrum]

....Not sure the exact speed but somewhere in the 1800-2000 range I suspect. I was bringing the speed up to put a little wax on it and hadn't touched it yet.

Full disclosure-- I don't use wax finishes and have not made myself all that familiar with their application. That being said, for turning, I've always followed the Bowl Diameter (in inches) X RPMs should be in the 6000-9000 range. That is, for a 12" bowl, I'd probably be in the 500 to 750 RPM range. For finishing, I generally don't stray from this range either.

Am I ultraconservative and off base or do any others have similar rules of thumb I should be aware of?

[Leo Van Der Loo]

Spinning a 12” bowl at near 2000RPM with splits in it, (seen or unseen, they were there) is asking for trouble, you are just lucky you did not end up in the ER or worse.

Quote :{ I find myself slowly getting more and more comfortable doing things that might not be completely safe} and that is another indication of unsafe behaviour, I would advice to change that for your own self interest.

There are several splits in that bowl, more than the lines indicate, though a little harder to see in a picture of Oak wood, but easier when held and swivelled in the light.

splits in Oak bowl.jpg

[Robert Henrickson]

Full disclosure-- I don't use wax finishes and have not made myself all that familiar with their application. That being said, for turning, I've always followed the Bowl Diameter (in inches) X RPMs should be in the 6000-9000 range. That is, for a 12" bowl, I'd probably be in the 500 to 750 RPM range. For finishing, I generally don't stray from this range either.
Am I ultraconservative and off base or do any others have similar rules of thumb I should be aware of?

I use speeds similar to what you do. I've turned several hundred bowls up to 16". For bowls, I don't think I've ever used anything other than the low range speed setup (1200 rpm max), even for smaller ones, and never to that maximum. 10-12" bowls would probably be 600-700 max. And sanding much slower. I do most finishing off the lathe.

2000 rpm means that a point on the rim of a 12" bowl travels over 6000 feet per minute, or 100 feet per *second* -- over a mile per minute. That's highway speed -- 60+ mph.

An extensive discussion of turning speed and guidelines (uses the Diam x RPM = 6000-9000), complete with chart/graph:

http://www.docgreenwoodturner.com/lathespeed.html

[John Keeton]

David, I am glad you are OK. I do notice there are a couple of cracks - one in each of the two larger sections and it may be that the separation occurred in other existing cracks. Also, the bottom/floor appears to be considerably thinner than the side walls and spinning a piece like that puts considerable stress on the floor of the piece, particularly if there is any difference in the density of the wood - and there almost always is some.

[Glenn C Roberts]

Is it an end grain bowl? And is there a recess?

[Lamar Wright]

Glad you are ok David. Very lucky indeed.

[Steve Mathews]

David - First and foremost, I'm glad you're OK and thanks for the safety reminder.

While finishing my last bowl project I noticed that a lot of heat can be generated during the buffing process. Does this have any effect on the structure of the wood possibly contributing to the fibers breaking apart? I was using the Beall system so the bowl itself wasn't turning but wondered at the time about what effect the heat might have on the wood.

[William C Rogers]

David, glad you are ok. I had one come apart on me. I was wearing a face shield and it didn't cause any injuries. Mine was due to too high speed and I did see a small crack that I super glued. I now think about that every time I have a piece on the lathe knowing it can happen.

[David Brimm]

Is it an end grain bowl? And is there a recess?

Not end grain unless I misunderstand your meaning and yes there was a recessed dovetail for the chuck.

[David Brimm]

David, I am glad you are OK. I do notice there are a couple of cracks - one in each of the two larger sections and it may be that the separation occurred in other existing cracks. Also, the bottom/floor appears to be considerably thinner than the side walls and spinning a piece like that puts considerable stress on the floor of the piece, particularly if there is any difference in the density of the wood - and there almost always is some.

Thanks John. Yeah I noticed those cracks when I gathered the pieces afterwards.. they weren't there as far as the wife or I could see prior to it coming apart. Now the whole piece of wood is coming apart in strips like that so I suspect the entire piece was weak but looked good at the time. I also didn't realize until after the fact how (comparably) thin the wife had gotten the floor, it's more like 1/4" to 3/8" thickness. Both of us made poor decisions that led up to the accident.