My Christmas Woodturning accident/the dangers of woodturning

[alex carey]

Today I consider Santa to be real and I think he gave me an early Christmas present.

I was in my garage finishing a 13" by 4.5" and about 3/4" thick eucalyptus bowl. I had finished all of the cutting and I was just finishing the bowl with some sanding. I turned it up to 2100 rpm which is higher than I normally go but there was some bad tear out I was trying to get rid of. BIG MISTAKE. One moment everything was normal the next there was a loud bang and I was keeled over. I ran into my house as fast as I could screaming in pain for help. I thought I was on the verge of death. My mom quickly called an ambulance while my dad tried to help me with my breathing. Meanwhile I felt like I got hit by a car in the chest. The ambulance got there in about 3 minutes which I was quite pleased about. I was still in tons of pain but was able to sit still enough for them to hook me up to an EKG and start testing all my vitals.

My chest was swollen and there was a cut over my sternum but it didn't look too bad. The test showed that I now had an irregular heart beat. They called it a right bundle branch blockage (if anyone knows what that mean, I sure don't). They took me to the hospital to give me a few tests to make sure my heart was ok. After about 4 hours a few X-rays and a CT they cleared me to go.

I can't use my left arm in certain positions, breathing is once again painful because the morphine wore off and even sitting up is painful, yet I am thankful. If that block of wood had hit my face I don't think I would be writing this right now. I think everything would have turned out very differently.

When I got home and was out of pain from the morphine :) I went to the garage and looked at the damage. It turns out the bowl didn't explode, the bottom of the bowl broke where it was being held on by the chuck.

Here are a few pictures of everything.

1- these are the paramedics who will soon be receiving a few turnings after I am healed up and turning again.
2- The bowl after I had broken it with my chest.
3- You can see where the bottom of the pieces broke off.
4- A few things in my garage got messed up. This is or was my broom.
5- The metal bar on my garage is normally tensioned quite a bit but I guess the bowl must have hit it right after.

The bowl also destroyed one my work lights and put a small hole in the garage door. My dad found pieces of it in the neighbors bushes. I still haven't found all of it

I knew how dangerous wood turning is but I never experienced it first hand until today.

Does anyone have any safety tips I should be following so this never happens again? I am going to buy a heavier duty Face shield. I am thinking of getting something that will protect my body a bit more. I think I should be using a bigger chuck or just stick to a face plate. Lastly the RPM was too high. Anything else I need to consider?

I have had several bowl come of the lathe before but NONE have ever come towards me. They always go the opposite way it is turning. Why did it hit me?

Sorry for the depressing news, I hope everyone is having a great holiday.

Alex

[Ted Shrader]

Alex -

Wow! What an experience. Glad you are OK (basically).

Heal up quick and get back out there. Not with any drugs still in your system, though. And keep the RPMs down on the bigger stuff.

Regards,
Ted

[Kurt Bird]

Alex,
So glad to hear that you made it through this OK. Hope the rest of your Christmas is better!

A couple of safety suggestions. It looks as if you were turning this piece with the chuck in expansion mode. You have to realize that if there are any internal stresses in a piece of wood this size, there is a good chance that the expansion mode will only add to those stresses. Add to that the weight as well. I suggest you convert to using large tenons for pieces of this size where the compression mode isn't working against you.

You already mentioned the speed. For a 13" bowl, 2100 sounds like it is extremely fast. There are numbers available out there that show how fast the outside rim is moving at various rpm's. If you plug in the numbers on this bowl, you'll probably be astounded at the speed.

Again, very glad you're OK - and hope you mend quickly!:)
Merry Christmas
Kurt

[Wilbur Pan]

Does anyone have any safety tips I should be following so this never happens again? I am going to buy a heavier duty Face shield. I am thinking of getting something that will protect my body a bit more. I think I should be using a bigger chuck or just stick to a face plate. Lastly the RPM was too high. Anything else I need to consider?

I have had several bowl come of the lathe before but NONE have ever come towards me. They always go the opposite way it is turning. Why did it hit me?


I'm really glad you are okay. You were pretty lucky.

As far as safety tips:

1. I use a leather turning apron (http://www.woodcraft.com/product.aspx?ProductID=835598&FamilyID=20066) that Woodcraft sells. It's saved me from taking a piece of wood in the chest once.

2. There's a concept in woodturning called the "line of fire". Basically, draw a line perpendicular to the ways of your lathe across the piece you are turning. If something should come off your piece, it has the potential to go anywhere along that line: up, down, back, and yes, straight forward. Try to position yourself so that you are out of the line of fire as much as possible.

If this isn't sinking in, imagine covering your piece with a lot of paint and then turning on your lathe before the paint dries. The paint will go in all directions. If your previously orbited bowls went away from you, all that means is that you've been lucky up to now.

3. 2100 RPM for a 13" diameter piece is pretty fast. The outer rim of your bowl was traveling at 80 MPH, which is how fast it would have been going when it came off and hit you.

A good rule of thumb for lathe speeds is by using this formula:

d = Diameter of piece in inches
RPM= Revolutions per minute
6,000-9,000 – numbers used to determine lowest speed or highest speed

d x RPM = 6,000 to 9,000, or your RPM should be between 6000/d to 9000/d.

In your case, the diameter was 13", so 6000/13 = 461, and 9000/d = 692. So many people would say that you shouldn't have been above 700 RPM for this piece.

There's a lot more information on this in this article (http://www.woodturnerscatalog.com/woodturners/Images/safe_lathe_speeds.pdf) on the Craft Supplies USA website.

Have a great holiday, and be safe.

[Ted Calver]

Some good advice here, Alex. Glad you survived to turn again!!

[Andrew Nemeth]

Alex,

Thank you for sharing your story with us. A opportunity to learn and reflect about shop safety is your gift to all of us.

Hope you are feeling better soon and get to enjoy the holidays a bit.

[Jim Kountz]

Whoa Merry Christmas right!!?? Glad to hear you're going to be ok, that scared the heck out of me just reading the post!! Take it easy enjoy the holidays and get back to turning soon!!

[Cyril Griesbach]

Wow, Alex. I'm also glad you're OK. Kurt and Wilbur said it best...especially the information about using a tenon to chuck up your bowls.

Cyril

[Gary Herrmann]

Glad the EMTs cleared you. Wow irregular heartbeat. That's scarier than a broken nose or anything else I've read. As was already suggested - try moving to tenons. I don't like using chucks in expansion mode for fear of something like this. Merry Christmas.

[Steve Schlumpf]

Alex - I am glad it wasn't worse and hope you will be fully healed real soon!

Lots of very good advice so far and you are already aware of the speed issue. Also, I normally turn the speed down when I start to sand so the sandpaper can do it's job without overheating. May take a little longer but works for me. Also agree on the suggestion of using a tenon. The majority of times that I have lost a bowl was due to use of a recess and having that area fail - just like in your photos!

Hope you heal quickly! Merry Christmas!

[Doug Thompson]

Alex, thankfully you are OK and I'm glad you took the time to write this story for all to learn. As you learned speed (rpm) was the problem, I know people who believe roughing a bowl at 2,000 rpm is safe but they never had this happen... yet. A turning can come off a lathe in any 360 degree direction but only 90 degrees of that will be a direct hit, so there is a 75% chance of not being hit. A face shield will only absorb an impact but won't take a major hit like this... there are limits even with safety glasses.

I do know of one professional who was knocked out from a accident like this so it can happen to anyone.

Enjoy the day then get back to the lathe tonight or tomorrow at a slower speed.

[charlie knighton]

thanks for sharing your experience, glad you are recovering, thanks for the suggestions of other turners, something to think about and help plan a turning

[Russ Sears]

First of all: thank you. I appreciate when people swallow their pride and share accident stories; it makes me pause and think a little more.
Second: do I understand correctly that the bowl flew off and broke when it hit your chest? If so...:eek:
It's really too bad this happened, not only for all of the obvious reasons but it looks like you were finishing a very nice looking bowl.

[Jeff Wright]

I guess it's a sign of my still being a rookie wood turner, but I DO use the cage that came with my Powermatic 3520, in addition to a face shield. While it does make for some awkward turning, I am making an effort at developing good habits in the beginning. Thanks for sharing your mishap.

[Gordon Seto]

Glad that it didn't get worse and thanks for sharing.
Other than the obvious too fast factor, I think the recess was too deep.
It didn't crack at the recess. That means your piece didn't come off the chuck because of wood failure.
From the black marks left from the jaws, it seems to me that the face of the jaw didn't have contact with the bottom of the recess. The wedging action against the face is very important for the stability. A chuck is only as secure as how good you cut the recess or tenon. A clean corner of the two faces to roughly matching your jaws is vital and never too long or deep to bottom out. Merely brute force crushing the wood would not help.
Sanding at 80 MPH may also cause heat checks, hardening the surface and not very effective.
All wood can have flaws that we can't see; that's why we need to use protective equipment. A lesson or two from some experienced turners may reduce that risk.

[robert hainstock]

A little scary! an understatement I guess.. I've never been hit, (yet!). but I make it a habit to stand out of the line of fire. Makes it a little more difficult sometimes, but I've become attached to my various body parts, and do not want any part of your mishap. THANK YOU FOR SHARING, and heal up soon. OUCHY!:eek::eek::eek:
Bob

[Bruce Smith]

Good morning and Merry Christmas Alex, certainly glad to know that you are on the mend. Lots of good information so I won't repeat it other than
my thoughts are that speed was a big factor, just like on the highways. I personally use a Triton Respirator when I'm turning and as you no doubt know it is equiped with a hard hat (not hard to get used to) that protects the head but doesn't offer much for other parts of the body. I'm not sure how one could offer protection to the chest area other that keeping out of the line of fire. If I were you, I would take that large portion of the broken bowl and screw to the wall by the lathe as a reminder as to what might happen when excessive speed is implemented. Anyway glad to know that you survived the event, as it must must of certainly been scarry.

[Pete Jordan]

Yes, thanks for sharing! I made the mistake of not using a steady rest making a bat and wound up on the floor with a shiner before I knew what happened!

Safety first.

[Paul Douglass]

Holy Cow! Hope you recover completely. Maybe an outfit like a baseball catcher wears would be appropiate!;) With out the glove of coarse.

[Jason Roehl]

Glad to hear you'll be okay.

Here's my take on why it came at you instead of away: you were sanding, probably without the tool rest in place, right? Anyway, when you get a catch with a tool, using the tool rest, the tendency for the object is to climb at the point of the catch, then whatever break happens propels it up and away from you due to the "thrust" of the wood letting loose. Sanding is a different story because the tool rest is out of the way, and you're likely putting some pressure on the top or nearest to you. So, when the item broke out of the chuck, it dropped onto and bounced off of the ways of the lathe, where it got some traction and came your way off the rebound.

Just my theory.

[Jeff Nicol]

Alex, As said by all it is a great thing that you are alright and will be back turning soon! I too had a bad thing happen to me but the out come was a bit more grusome than yours I will be the man like you have been and post my own war story. Basicly the same thing with a little higher impact point! Take care and again glad you are O.K.

An EXTRA MERRY CHRISTMAS TO YOU!

Jeff

[Reed Gray]

A couple of comments here. The wood failure/bowl coming off the lathe does look to be caused by a failure at the recess of the bowl. Using a recess was not the problem. A PROPERLY made recess or tenon will hold fine, and I have turned thousands of bowls in sizes up to about 22 inches using a recess. As far as I am concerned, there is no mechanical advantage to either method. The only real difference is that a tenon must be turned off, where a recess can be a part of the design. From the metal stains on your recess, it looks like you expanded a small chuck into a big recess. If properly done, for 2 1/2 inch jaws when closed, you want a recess that is 2 5/8 in. max in diameter. You want the sides of the recess to match as exactly as possible, and you do not want your recess so deep that the bowl sits on the face of the chuck. Depth wise, 3/16 inch is sufficient for a bowl that size. Also, you can over tighten to the point where you break the recess, or tenon. Some times you get it tight to the point where there is a lot of stress on the fit, but not enough to break anything, then a little extra stress it put on the recess by sanding or cutting, and the bowl will fail at the point of the most stress. Another cause of stress is wobble. If the bowl is unbalanced at all, this will add stress, and seldom is a bowl ever perfectly balanced. At slower speeds there is less stress, and at higher speeds, there can be a lot more stress.

For sanding, you want slower speeds, for hand sanding, 500 rpm max. The bowl is never perfectly round, and at higher speeds you will bounce over the low spots, which always seem to be where the tear out is. Funny how that happens. Even lower speeds work as well. If you power sand, you can go lower still. I power sand at about 20 rpm because my bowls are all warped, and there is no way I could keep the sander or my hands on the bowl at speeds over 50 rpm. With a power sander, you can also stop the lathe and work on those problem spots. When I did hand sand, I would stop the lathe, and hand sand the tear out spots, then blend it in with the rest of the bowl with the lathe on.

Glad you survived. Borrowing a quote from some one, "Good judgement comes from experience, and experience comes from, well, bad judgement".

robo hippy

[Alan Trout]

Alex I am glad you are ok. Don't feel to bad we all do stupid stuff. Just like the night in September that I decided that I did not need to use push pads when using my jointer I was Joining a a piece of acrylic that I had cast about 6x6 the part kicked out with my hand over the cutter head. Now I live with a finger 1/2" short and no feeling in another.

There was a good part of my accident. I can honestly say that this will never happen again. I am much more alert in the shop and use any safety device or precaution I can for a given operation. I also realize that most of the tools we use have the potential to be deadly. I was very fortunate I could have lost all my fingers, hand, or my life. These stories need to serve as reminders to all of us that most of these accidents are preventable by our own actions and we need to take appropriate precautions.

Merry Christmas to all

Alan

[Scott Conners]

I learned this same lesson with my first winged bowl - recesses are inherently not as strong as tenons. Luckily there was nothing but a bruised ego and a much healthier fear of sticking my gouge where it doesn't belong after that incident.
I also try to follow the rule of thumb given by Stuart Batty and Mike Mahoney - the tenon should be ~1/3 the diameter of the piece. That means on a 12" piece it's a 4" tenon. I have turned 10" bowls on 1.5" tenons without incident before, but I now try to avoid that. Thanks for sharing your story, and I'm glad you're alright!

[alex carey]

thank you for all the advice. I am going to put the piece on my desk as a reminder just like you said Bruce. That will be my reminder of the dangers of turning.

Wilbur thanks for that equation, I had no idea it was moving that fast. Now that I see it that way I am shocked how fast the outside was moving.

Jason I think you are absolutely right. That makes complete sense. Every time I have broken other bowls it has been while the tool rest was there and I was cutting not sanding.

Thanks for all the kind words and I think in a week or so I will be back to turning. All this advice has been really useful, thanks for that.

Alex

[Bernie Weishapl]

Alex sorry to hear about the accident and glad to hear you will be ok. I do wear a leather apron which has saved me a couple of times. Everytime I lost a bowl it has been with a recess. My problem was like Reed said. I was making the recess to big and I wasn't making it properly for the dovetail jaws and I cranked down way to hard so was probably cracking the whole time I was turning. Sit down, rest a while and enjoy Christmas.

[Jack Mincey]

Alex,
Glad your OK!! Things can go bad on the lathe quick. A random orbit palm sander can be used to get the bad spots at low RPMS or even with the lathe off.
Happy Holidays,
Jack

[Jon Lanier]

Ouch. (probably bigger than that). I'm glad to see you are okay. I use to stand 'in the line of fire' until I had one go off. Fortunately, mine was smaller and was not traveling as fast. It hit my chest and and rolled straight up my face shield and hit a rafter.

Take everyone's advice here. Mine is to stay out of the danger zone, your not Maverick from the Top Gun Movie.

[Rob Mathis]

Glad your ok enough to post!

[Dean Thomas]

I'm with Rob. Glad you're well enough to post. Glad you're in one piece and sorry that your bowl is not.

Wilbur has given you the formula. There are other ways to determine safe speed, but this one is the one I find to be best and most reliable. Most of the others are touchy-feely and rather subjective. Give me hard numbers that I can crunch and stay safe every time!

I did a little Excel spread sheet using that formula and have it posted in several places around my shop. I've also got it in a PDF if you'd like a copy. If ANYone would like a copy, email me through SawMillCreek and I'll send it to you. I may talk to Keith to see if there's a way to pin it to the top of this forum. It really is that important. There are two truisms about turning: Speed is your friend; Speed kills. Both very, very true.

Good story to keep us mindful of the need to use those safety items, not merely own them.

[Harvey Schneider]

I just want to add to this excellent post based on my experience designing high speed centrifuges.
Imbalance generates forces which drive vibration. A rotating body at low speeds rotates around it's geometric (based on dimensions) axis. a rotating body at high speeds rotates around its mass (based on balance and weight distribution) axis. There is a critical speed at which the forces from imbalance overcome the stiffness of the work and the work moves from one axis to the other. Critical speed increases with stiffness (high stiffness => high critical speed) and decreased with mass ( high mass => low critical speed).
As work is reduced in mass the critical speed increases and if you are working above that critical speed the work will become unstable.
When enough material has been removed to weaken the work and reduce the stiffness, the critical speed is reduced and unless you increase stiffness by providing support or decrease speed the work will become unstable.
Without exceeding the rules of safe speed, increase speed until vibration just starts, and then decrease it until the work becomes stable again. This is a good working speed for the piece. Speed can be adusted up as the critical speed increases when material is removed, but stay within the safe range and below the critical speed.
I hope this isn't to technical sounding, but I think it is important to understand what is going on.

[Larry Edgerton]

As a guy that has been bit by many of the tools in my shop, and one that is just collecting parts so I can start learning my lathe, I read this thread with great interest and really appreciate all of the theory, experiances and suggestions.

I'm really tired of having parts sown back on......

Thanks,Larry

[Jim Becker]

'Glad you are OK, Alex.

[Dick Strauss]

I'm glad you are okay!!!

Here's some other food for thought...
Whenever you are chucking up a piece of wood in either expansion or compression mode, try to mount it so that the jaws are not perpendicular/parallel to the direction of the wood fibers. This helps to prevent shearing of the tenon or wood surrounding the pocket by dispersing the force applied by the jaws along two axes of the grain structure (assuming a standard side grain orientation used for bowls). In your case it looks like you had the jaws exactly perpendicular/parallel to the grain.

[Mark Rios]

Hey everybody, I've just finished reading through this thread and I'm not so sure that Alex is telling the WHOLE story about how he got his "catch". I kinda think that it might have bee a little more like this...............

http://www.youtube.com/watch?v=tnSQa0eoGc8
















:D:D:D



Glad you're okay Alex.

[Steve Trauthwein]

Glad you are going to be ok and thanks for sharing this accident. I think it is easy to become complaisant after many hours of turning. We start to feel as though we have control and then a slight oversight can really be dangerous. I am speaking of the oversights that I have made, naturally.

I agree with the consensus opinion that speed was probably the biggest problem. While I am not a huge fan of a chuck in the expansion mode it seems from the picture that the shoulder on your inset was quite deep, according to what kind of chuck you are using this can make seating the chuck properly a problem.

The thing is that tenons can break off too. One has to carefully examine the wood for any weakness and discard or adjust a piece that is not useable. This is very difficult for me to do, as my German ancestry comes in to play and I feel like I am wasting wood. Usually something I got for free!

I would advise using a faceplate when turning a large piece that you have any doubts about the stability of. A lot more stable and forgiving. Slow down.

Regards, Steve

[Keith Christopher]

Alex,

as others have said I am glad you are ok! Scared and still bruised but ok. As a side note, I did some math.

13x4.5x.75 (dimensions of the piece) total area in cubic inches 43.78 LxWxH.

This is ~.189 cubic gallons liquid, converting this to weight equates to about 1.512 lbs (based upon the specific gravity of the eucalyptus of 1.01 and determing the weight of water in this cubic volume.

so you had almost two pounds hitting you in the chest at approx 80mph.

to determine the exact force is hard to do as it is unclear as to how much energy was applied over the area of impact (work energy and displacement) , this can double or triple the actual work energy.

Very lucky indeed.

[Toney Robertson]

Keith,

That is impressive but you got WAY to much time on your hands!!!:D

Toney

[Keith Christopher]

Keith,

That is impressive but you got WAY to much time on your hands!!!:D

Toney

yeah but I stopped before determing its kinetic energy but here's the formula

E = 1/2 * (m*v^2)

Where m is mass (in this case weight) and v is the velocity (at the center)

this will be in joules and 1 joule is equal to ~ .74 ft lbs of force.
1.512lbs in kg .69
80mph in meters per second 35.8

So.....(sorry I can't resist) E= 1/2 ( .69 x 35.8^2)

E= 442.1658 (joules)

442.1658 * .74 = 327.202692 ft lbs.

In comparison, a 10lb weight dropped from 20ft, hits with about 249ft lbs of force.

in other words.....ouch.

[alex carey]

I wish I could have said something like that every time someone asked me what happened to me while in the hospital.

[Jeff Nicol]

Alex, Great to see you still posting and no ill effects from the bowl bashing! When I got whacked in the head and went to get the stitches, the doctor was a pretty woman and the nurses very symathetic! I love numbers and stuff but a smile and witty remark goes a long way! To bad I was already in love with my wife!

I love this forum as one never knows what genius and compasion will be experienced!

Have a happy new year!

Jeff