Thread: Bowl explosion

Wow,
Glad no serious injuries happened, personally I would have been charging my pants definitely.

The pieces really must have been moving to break the cast iron clamp.

Cheers Matt.

Artful

Good to hear you are still in one piece (unlike the bowl).

Did the Blackwood have any of the heart in it? If it did, that would be the cause of it breaking up. Hardwood logs should have the heart removed from any boards or turnings. It may look solid when first cut, but it will break up eventually. On a lathe it can be very serious. Our son during his early adventures with a wood lathe was turning an Ironbark bowl and did not appreciate he should avoid the heart. It let go on the lathe, nearly took out his heart and went through the side of his shed!.

Regards
Paul

No Bushmiller, there was no heart.

Thanks for posting AB. Its a reminder that even an experienced turner working with solid wood can have this sort of thing happen.

Originally Posted by Simplicity

Wow,
Glad no serious injuries happened, personally I would have been charging my pants definitely.

The pieces really must have been moving to break the cast iron clamp.

Cheers Matt.

Matt, I agree about your concern about the seriousness of the incident Bodger posted, but as not being from Australia, I have to ask whether Charging is another term for Loading or the real 4 letter word beginning in S? It's a term I gonna be using when a situation arises like Bodger's. It's just plain funny and makes it publicly acceptable. ......... Jerry (in Tucson)

Some pieces I tend to stand a bit out of the line of fire shall we say. just in case!

I can't recollect seeing a "bowl explosion" with such complete destruction as this example.

Then to smash a cast iron clamp across the room??? (looks like a good quality Record too??) That requires some serious energy from the shrapnel, mass by velocity sort of physics.

460 mm is a decent sized bowl so it is not difficult to reach a staggering rim velocity as lathe rpm increases.

Time to reassess how you turn methinks.

Using a Dale Nish proposed rough rule of thumb bowl speed formula that, RPM x diameter (in inches) = 6,000 to 9,000 suggests that upper rpm should not exceed 500 rpm for a sound blank.

The old road safety message - Speed Kills - applies in wood turning too.

We're you using old fashioned positive rake scrapers doing your final scraping? If so, it's very easy to get a catch and get that result. Since I changed to negative rake scrapers I have felt much, much safer doing inside bowls.
Rgds,
Crocy.

A couple of replies.
Nutsandstubs. Did not have to change my underpants I am glad to say but I did say "FUDGE" out loud or something similar. Then had to sit down for a minute to try and process what had just happened.

Mobyturns, I did have the bowl spinning way more than 500 rpm. Generally I like to have the work going as fast as it can go before vibrations kick in. It is a large heavy lathe and is very capable for larger jobs. Luckily at the time I was standing on the opposite side of the lathe where the edge of the bowl facing me was rotating from bottom to top and most of the shrapnel went the other way. Did thank the lucky stars that nothing hit me in the head or eyes even though I did have safety goggles on.

Old Croc, It was a regular type scraper and there was no catch. You would be able to see the tell tale signs of a catch on the fragments. I have lost the odd bowl from catches in the past and would have been happy to own up to it if it was one. Personally negative rake scrapers do not float my boat. I remember some older patternmakers using that type back in the day but never saw the real need to use them. Maybe I am a bit set in my ways.

Originally Posted by Nubsnstubs

Matt, I agree about your concern about the seriousness of the incident Bodger posted, but as not being from Australia, I have to ask whether Charging is another term for Loading or the real 4 letter word beginning in S? It's a term I gonna be using when a situation arises like Bodger's. It's just plain funny and makes it publicly acceptable. ......... Jerry (in Tucson)

Jerry,

My apologies it was just a typo mistake.(Bloody auto correct).

It should have been “Changing”

Cheers Matt.

Originally Posted by Simplicity

My apologies it was just a typo mistake.(Bloody auto correct).

It should have been “Changing”

Maybe so, but I suspect "charged my pants" is going to work it's way into my vocabularly at least.

Originally Posted by Skew ChiDAMN!!

Maybe so, but I suspect "charged my pants" is going to work it's way into my vocabularly at least.

More genteel than saying "I just $hit my dacks."

Originally Posted by Mobyturns

I can't recollect seeing a "bowl explosion" with such complete destruction as this example.

Then to smash a cast iron clamp across the room??? (looks like a good quality Record too??) That requires some serious energy from the shrapnel, mass by velocity sort of physics.

460 mm is a decent sized bowl so it is not difficult to reach a staggering rim velocity as lathe rpm increases.

Time to reassess how you turn methinks.

Using a Dale Nish proposed rough rule of thumb bowl speed formula that, RPM x diameter (in inches) = 6,000 to 9,000 suggests that upper rpm should not exceed 500 rpm for a sound blank.

The old road safety message - Speed Kills - applies in wood turning too.

A good face shield is required. Not the sh%t sold by bunnings and others that is more token than good. My shield is about 2mm thick lexan. And I wear a half face respirator. So, if something crashes into my head the energy will be mostly absorbed by the forehead head band and respirator.

Originally Posted by artful bodger

I did have the bowl spinning way more than 500 rpm. Generally I like to have the work going as fast as it can go before vibrations kick in. It is a large heavy lathe and is very capable for larger jobs.

Don't want to sound like I'm lecturing you, but it has nothing to do with a large heavy lathe. It has all to do with centrifugal force and the defects in the wood (which are extremely unpredictable). You got lucky, this time. You should be thinking the opposite and have such large platters going as slow as possible, but still allow for a good cut and or sand. Sanding is another issue in that so many think you should crank up the speed. When in fact, if you think about how sand paper works, you should slow the rpms down. And if your project lets go, your fingers are right there when it does... Not a pretty sight.