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Avoiding explosive breakups on the lathe.....

Odie

Odie

Panning for Montana gold, with Betsy, the mule!
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In 43 years of turning bowls on a lathe, I've only had two in memory that have broken up. Both times there was a telltale sound that warned me that something was wrong, and I thankfully shut down before there were flying missiles! Now admittedly I don't usually turn rotten suspect pieces of wood, but those pieces that I do turn sometimes have some indication that there is possible danger......and I usually avoid the obviously problematic chunks of wood.

(This does not include the newbie experiences I've had when wood broke up on the lathe because of mishandling of tools. What I'm addressing here is wood that breaks up because of flaws in the wood itself.)

Now I have a question for the more experienced turners here who have had a breakup while turning. Do you remember hearing a telltale change in the sound that tells you something drastic was about to happen?

=o=
 
I remember hearing a small ‘tick’ an instant before a small bowl blew up on the Fourth of July, 2020 (appropriate 😊). I heard the tick right about the time I realized it had gotten thin enough that the shear scraping I went back in with just to clean up the curve was a bad idea, although taking just a whisper shaving it created enough pressure to force it out of round - **BANG**

The pieces of that bowl sit on top of a cabinet a few feet away from my lathe as a reminder…

On edit: this wasn’t due to a flaw in the wood, just a flaw in the woodturner 🤣
 
Yes, have heard it a couple of times. Sometimes the wood goes out of round for a brief second, then the rapid disassembly occurs. I think in these cases it was the imbalance that created a difference in pitch. Not sure I could have reacted in time as it only lasted less than a second.
 
Only two episodes I can recall. One fairly early on when I failed to recognize the depth of a bark inclusion and what would happen as I turned the blank smaller. Turns out a fist sized hole in the sheetrock was what would happen. Don't recall hearing anything, but that was probably before I recognized what sounds meant. Second time was fruitwood, invisible cracks when the blank was mounted that opened up as the bowl got thin. Not nearly as exciting, just flopped in half. Also can't recall a sound, but I was hearing the sound of thinness prior, I'm pretty sure.

I do know that when I'm teaching students at the high school shop, I can unconsciously hear form 20 feet away when they're doing something wrong and going to get in trouble, and respond to it before anything bad happens.
 
I've learned from reading posts here if I hear any odd noise stop and investigate and it usually is a crack in wood that needs dealt with. I had screws come loose on one jaw of the chuck and cause vibration. Only had one bowl break into pieces, I have a woodcut coring machine and when I was pulling the blade out of the cut the back side of the coring plate that holds the blades contacted the wing of a thin natural edge bowl and made it blow up. I didn't get hit with anything. It was thin and broke pretty easily.
 
Funny you should ask this question Odie. Just a couple of hours ago I had a piece come apart, into 3 pieces, with the smaller of the three hitting me right between the eyes. Luckily I had my face shield between it and my face. This particular piece was kind of the opposite of the wood you usually turn. It was very suspect from the gitgo but was also some very beautiful wood so I want to make it work. And no, I didn't hear the tell tale tick. It's now sitting on the work bench all glued back together with rubber bands all around it so I can give it another go tomorrow. The late John Jordan said life is too short to turn crappy wood. That's usually true. You can't anticipate what a piece of wood will do all the time. That's why wearing a face shield is such an important practice. But to answer your question, in my memory the worst breakups I've experienced have had no warning.
 
The last few I blew up had no indication that there was an issue. I can usually hear it and stop and then address it before continuing. I had a piece of Kapok that had a void in the wood that you could not see. Made no sound until I exposed it then BANG! Was working on a cedar platter and all was going great. It had a little dimple in the center that I wanted to get out...as soon as I put my tool back onto the center BANG! No warning sounds 😕
 
By extension, this leads us to locations of power switches, or secondary kill switches. Consider the pathway of your hand and arm, and your body, when going for a power switch as your ear is picking up a funny sound from that spinning lump of wood.

I've always practiced having the motor controls at the tailstock end of the machine. I do what I can to stay to the right side of the spinning wood. If the lathe design does not allow for control relocation away from the headstock, work an accessory kill switch at the tailstock end somewhere, and routinely practice using it to kill the motor.
 
My worst blow up was mostly operator error. No warning sound except the lathe speed which is visual.

I had a piece of fairly dry wood about 12-14” diameter with a known defect that I soaked with CA and put aside the day before.
Next day put it on the lathe the lathe hesitated a bit when I increased the speed so I turned the speed up
In an instant it going way to fast I hit the stop button - realized I had left it on the high speed belt.
Well it held together for a bit and I was standing back out of the line of fire while it was slowing down for a fraction of a second
but then a piece broke off, ricocheted off the tool rest, hit my face shield and bounced into my chest hard enough to knock the wind out and leave a bruise. The face shield had a plastic overlay that was sliced with no damage to the shield itself.

I’d played enough sports to know I would be okay while I was struggling to get the lungs working again. It’s just a few seconds but it seems like hours. And not being able to breathe is no fun.

One bad- didn’t check the belts
Three goods - had the remote switch handy, hit the big red stop button quickly, had my respirator helmet and face shield on.

Got in another 6 hours of turning before hitting the shower and finding the hand size bruise.
 
The cherry burl I was working on made no noise. It just burst apart. The 12 inch diameter birch log started making noises before it broke. The rest were my own stupidity with the tools.
 
Over my 25 years of turning I have only been hit in the face shield by bark. One notable turning was a very dry piece (don't recall the species) that I was about 3/4 of the way through it when (all I remember) I heard this very very loud BANG and I was looking at an empty chuck and hearing pieces bounding around the shop, no warning, no bodily harm just wonderment as to what happened. I gathered all the pieces (7 I believe) and have no idea why it came apart. All the pieces went away from me, nothing came back. Very strange.
 
At what lathe speed do you turn most bowls, etc.? To frame that question a bit more, let's assume a 10" bowl. I aim for 1,000 RPM give or take 50 RPM. The RPM will be a factor in how spectacular the failure is, or at least how far the pieces fly.
 
Ron Solfest said:
I remember hearing a small ‘tick’ an instant before a small bowl blew up on the Fourth of July, 2020
Click to expand...
Although it's been quite a few years since I had a breakup, describing it as a "tick,tick,tick" is probably the best way to describe the sound I heard.
Kent Reisdorph said:
At what lathe speed do you turn most bowls, etc.? To frame that question a bit more, let's assume a 10" bowl. I aim for 1,000 RPM give or take 50 RPM. The RPM will be a factor in how spectacular the failure is, or at least how far the pieces fly.
Click to expand...
I generally shoot for 800rpm, but the deciding factor is searching for the best vibration free rpm. I'd say the great majority of bowls I turn are between 6-800rpm for a 10" bowl.

Extreme out of balance can be much less rpm, and I can't remember the last time I turned a bowl over about 850rpm.

When you have sharp well-shaped tools with great presentation, the rpm requirements are much lower.

It's newbies who have to speed it up to make less-than-sharp tools cut. (I know that from my own experience as a newbie!)

=o=
 
The tick-tick I’ve heard a couple times was with a very thin piece just before the explosion. Other pieces have exploded with no warning—hit a knot, had too much tool on wood, operator errors.
 
Well, my biggest explosion came while I was turning what I thought was a good solid piece of madrone. Part stuck in the wall, and the other part bounced off of my Baldor grinder. I did a video about it titled some thing like "Standing Out of the Line of Fire". That has kept me from any injuries and I practice it always! I have torn a few pieces off of the lathe, mostly from trying to hog too much off in one pass. In all those situations, it was with a big scraper. I have heard ticking noises, and mostly they warn me about cracks that I didn't see at the onset.

robo hippy
 
Have had 2 spalted arbutus bowls fly apart into many pieces. Always stand off the right so no operator damage. Last one was using the EasyWood hooked tool and could hear clicking as the tool was pulled towards the rim. Think this was because of vibration so next purchase is going to be the Oneway Bowl Steady Rest to hopefully stop unwanted vibration at the rim.
 
I turn a lot of what some might call crappy wood. But I enjoy the challenge and most time the results are good to spectacular. Speed here like on the roads can be a killer, some pieces are turned low speed 4-500 rpm and in doing so I have had virtually no explosive results. But then I dont turn for a living, nor do I production turn and most if not all are statement pieces so time taken is not a criteria. But as Odie mentioned you have to stay alert and watch out for complacency.
In the first days of turning I did manage a very spectacular break up at speed. Turning a decent sized piece of dry Norfolk Pine 300mm+ dia thin, as I wanted some translucence, thin at around 2-3mm during sanding I stepped away briefly to get something and for the life of me cant remember what, anyway at this point it disintegrated dramatically leaving the tenon only, never found all the bits. Later looking at the bits I found its probably 2mm maximum, no one was hurt but the heart got a good work out if only briefly 🙂
 
Bill Blasic said:
Over my 25 years of turning I have only been hit in the face shield by bark. One notable turning was a very dry piece (don't recall the species) that I was about 3/4 of the way through it when (all I remember) I heard this very very loud BANG and I was looking at an empty chuck and hearing pieces bounding around the shop, no warning, no bodily harm just wonderment as to what happened. I gathered all the pieces (7 I believe) and have no idea why it came apart. All the pieces went away from me, nothing came back. Very strange.
Click to expand...
serendipity gotta love it 🙂
 
Dean Center said:
I do know that when I'm teaching students at the high school shop, I can unconsciously hear form 20 feet away when they're doing something wrong and going to get in trouble, and respond to it before anything bad happens.
Click to expand...
Absolutely. If I hear something odd when I'm teaching, I immediately head that direction.
 
Good question Odie …. I’m going to assume you’re really only talking about blanks that seem solid at the start and turn into something more dangerous as it is shaped.

I exclusively turn the crappiest, worm eaten, punky, cracked, shaken, void filled abominations that might not even qualify as “wood” anymore in some cases. Most of the folks here wouldn’t even find what I turn to be worth burning.

That said, I’ve become a relative expert at keeping pieces together that otherwise might come apart if I sneezed on them. These pieces give utterly constant warnings and speak to me in very loud tones
“You don’t want to do that…”
“You need to stop now and take a look…”
“You need to sharpen now…”
“Are you sure that tenon/recess is solid enough to do what you want to do…?”
“You should probably slow down the rpm’s…”
“I’m about to blow apart…. Move away now…. Boom…”

I would guess I’ve blown up well over 500 blanks in the last 15 years. Almost all of them happened in the first 5 years as I was figuring out how to do what I wanted to accomplish. And I’d guess I might only lose 1-5 per year at this point.

I’ve used all manners of straps, wraps, tapes, glues, screws, dowels, hardeners, epoxies and lots of other things to get my stuff turned. There was one very large bowl blank I turned while wearing my full motorcycle leathers and helmet because I was sure it would injure me…. It didn’t.

For me, precaution is the name of the game. And if I’m in doubt, gear up, sharpen up, strap up, keep out of the way and make small cuts. Nibble away at crappy wood…. That’s the best advice I can give for people in terms of avoiding blow ups.
 

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@John Ames, what are you using for protection from the neck up? Wow!

Your message prompted me to look at options I've always wondered about. Both of these would still need added small debris eye protection implemented, but both should provide pretty good large debris impact protection. And I'm a bit surprised by the pretty affordable prices on lots of these options.

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It looks like some baseball catcher's mask styles would allow for safety glasses to be worn.
 
I know this has been referenced in the past, but it's worth revisiting this discussion by Lynn Yamaguchi following an unscheduled disassembly that caused her a serious head injury. Safety Matters

I have had a couple of explosions due to material flaws and poor technique. They don't necessarily announce themselves but I am sure I have avoided some others due to hearing incipient problems. I urge folks not to overwhelm the sound of turning or other machine processes with music or other aural entertainment. I used to work with a friend who used earbuds under his ear pro and it was just about impossible to get his attention without being directly in his line of sight.
 
Kevin Jenness said:
I know this has been referenced in the past, but it's worth revisiting this discussion by Lynn Yamaguchi following an unscheduled disassembly that caused her a serious head injury. Safety Matters
Click to expand...
Riot helmet with 3.8mm faceshield, from Streicher's Police Supply-
www.streichers.com

Premier Crown 906 Series Riot Helmet - Riot Gear - Streichers

HELMET: RIOT DUTY W/VISOR & SHIELD, BLACK
www.streichers.com www.streichers.com

Re-reading this message thread and thinking back over my own experiences, when the lump of wood has come apart, whether it was a innocent pen blank on a mandrel or a bowl undergoing rough turning, it really does not matter what the cause of the failure was, only the result of the failure mattered. And to that end, did I get hurt? Should I have taken greater measures to protect myself? Is that $10 hardware store faceshield enough? (No!) After reading about Lynne Yamaguchi's life-altering accident (and a similar account from the AAW Journal 20-some years ago of another pro turner) there is no reason at all why each of us shouldn't be upping our game to safety. No reason at all. And if you think you can give a legitimate reason, it ain't a reason. It's an excuse. And excuses are never valid, they just give merit-less explanation for bad judgement.
 
If it’s really sketchy, my motorcycle helmet is what I use. The best other helmet I’ve ever seen for turning was the headgear used by Olympic Fencers.

The masks are made of a very tightly woven steel that allows you to see out and keeps the pointy ends of swords out.

And they are lighter than you think.
 
I just spent a few minutes looking at fencing helmets. The wire mesh would be great for small, lightweight shards coming at you (at least as good as a hardware store shield), but I don't see the fencing helmet having overall structure meant to resist a half pound, a pound, or more weight traveling at 40-60mph. Fencing athletes aren't protecting themselves from woodturning's equivalent of hockey pucks, baseballs, and bats. Even a motorcycle helmet visor is barely thicker (if at all) plastic than a hardware store faceshield.

Ideally, the hockey goalie helmet or catcher mask, covered in the thick polycarbonate mask of the riot helmet, would probably be ideal, especially if it also protects the neck.
 
Steve Tiedman said:
I just spent a few minutes looking at fencing helmets. The wire mesh would be great for small, lightweight shards coming at you (at least as good as a hardware store shield), but I don't see the fencing helmet having overall structure meant to resist a half pound, a pound, or more weight traveling at 40-60mph. Fencing athletes aren't protecting themselves from woodturning's equivalent of hockey pucks, baseballs, and bats. Even a motorcycle helmet visor is barely thicker (if at all) plastic than a hardware store faceshield.

Ideally, the hockey goalie helmet or catcher mask, covered in the thick polycarbonate mask of the riot helmet, would probably be ideal, especially if it also protects the neck.
Click to expand...
40-60 mph is pretty high. There's an old rule of thumb suggesting that blank diameter x rpm should be < 6000-9000 and if my arithmetic is correct 9000 correlates to about 27 mph. I have watched some Stuart batty videos where he is turning bowls with a rim speed of 40mph or so. That's fine for him with a select "flawless" blank, but it seems like pushing the envelope for a mere mortal like me. Good tool control and a slow feed rate can give good results at lower rpms with a larger margin of safety. Your mileage may vary.
 
I'm corrected, I didn't apply the formula 9000rpm/diameter. Hence being off by a factor of 10.

Gregory

Edit: which makes me want to ask when is this formula applicable? I've heard that when turning smaller spindle work to run it wide open if it's trued up, that obviously breaks this formula.
 
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It's just a guideline. You can use your own experience and do the calculations of how big a mass at what velocity you are willing to have impact your head. Small diameter spindles are probably less likely to break apart and will have less kinetic energy than a large diameter bowl blank at the same rim speed. You can adjust your risk assessment based on circumstances.

I have been laid up for the past three months following a toe amputation resulting from a heavy bowl blank dropping from the lathe ways at 0 rpm. If that piece had gone into orbit at turning speed and hit my head...
 
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Not to downplay the concern to employ best practices (stand to side, don’t spin too fast, wear a face mask, PAY ATTENTION, etc) but I also think normal turnings by us mere mortals shouldn’t cause us to search out excessive body armor.

By the time we’re spinning a 10-12in bowl up to 1000rpm we’ve removed the vast majority of the weight. If it were to fly apart at 30mph, the piece that bounces into our face mask will weigh a fraction of a pound and lost a bit of its speed.

On the other hand, if someone’s ramping a 20lb out of round blank up to 1000rpm I’d want to have a solid wall between me and them 🙂

Make your own decisions, don’t be embarrassed or afraid to be conservative but also don’t be too fearful *provided you employ standard good practices. My two cents…
 
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