Avoiding explosive breakups on the lathe.....

[Steve Tiedman]

27mph. 40mph. 60mph. Doesn't matter.

For perspective, a 7-year-old can probably throw a ball 27mph. Anyone want to take a 27mph 1.62oz golf ball to the face? That'll smash teeth, break a nose, cause permanent damage to an eye... How about a 5oz baseball?

How about a 3oz jagged edge lump of walnut?

I didn't think so.

10" diameter, 750rpm (skip the long hand math) = 22.3mph. Bring it to 1000rpm, 29.7mph.

 

[Kevin Jenness]

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…

I agree, but make sure you do have a realistic estimate of the forces involved. A 12" blank at 1000 rpm has a rim speed of over 35 mph. I don't know how big a chunk might break off nor can I predict where it might wind up after a ricochet. The piece that whacked Lynn Yamaguchi (a very experienced turner) was a large fraction of a10" diameter hollow form turning at 1200 rpm and it made a life-changing impact on her.

 

[Ron Solfest]

@Kevin Jenness - not to belabor a point, but I’m not sure Lynne falls under my ‘mere mortal’ category - spinning a 5-6lb (2lb shard that hit her) chunk at 1200rpm without a face mask (albeit temporarily). If she had a stout goalie mask, but wasn’t wearing that either, it wouldn’t have turned out any better.

Don’t let me talk you into being less careful than “that little voice in your head” suggests, but don’t let others talk you into being inordinately fearful either.

 

[Brian Gustin]

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.

Generally that formula - more of a guideline really, is most applicable when roughing out a bowl blank or other large (I.E. a lot of mass) turning blank Once you have it trued up however, (and know the blank is nice and solid) then generally you'll adjust your speeds for the cuts you're making

The basic thinking behind it is the ejection speed of anything that comes off the lathe (26 MPH might not sound like a lot, but you ever been in a fender bender? Even getting rear-ended at 10-15 MPH can leave you stunned for a few seconds.. trust me, I've been rear ended twice in Miami traffic downtown.. it's a fairly daily routine in big city traffic, I believe) that little projectile moving at 26 MPH at your face (or any other body part) is still gonna hurt (been there done that) - But the trajectory of the piece seems to trend towards throwing the broken off piece downwards and away - higher RPM's tends to eject upwards and towards you - (unscientific really and not even close to 85% true, but still a weighted tendency, but I can see some little logic to it in that if the break happens at the cutting edge of the tool - I.E. a catch - then due to the rotational speed, by the time the piece ejects slower speeds tend to have it coming off near bottom or bottom back of the spin, while higher speeds it may come further around and eject up and out, I suppose..) That's not to say a broken piece isn't going to bounce and ricochet off something back at you! (Been there done that too!)

There are those that will turn larger bowls at up to 1500 RPM or more, and some that turn at much slower speeds - and then there's the ones like me that will adjust RPM sometimes a bit higher when I'm seeing tear-out or uneven cuts , sometimes lower if I feel some vibration (varying grain density, punkiness in wood, etc.) It is really just a sort of guideline to start from, not a hard and fast rule - Most cases when turning a fresh blank to get it trued up, you may even have to have it turned down to as little as 250 - 300 RPM otherwise the out of balance makes your lathe walk across the floor....

 

[Bill Blasic]

I have in my shop the riot helmet noted above and I also have a hockey helmet and experimented with both. Well both would definitely keep you safer but they are awkward to wear. So much so that I don't wear either but rely on good turning practices and wear either my Uvex Bionic or my Airshield pro.

 

[Odie]

I have in my shop the riot helmet noted above and I also have a hockey helmet and experimented with both. Well both would definitely keep you safer but they are awkward to wear. So much so that I don't wear either but rely on good turning practices and wear either my Uvex Bionic or my Airshield pro.

Howdy Billl.....🙂

I went through the same thought process as you. I have a riot shield and a woman's softball mask. The softball mask fits nicely under the bionic shield.

I brazed on a couple extra bars on the softball mask shown in the 2nd photo.

I seldom use them, but keep them for "just in case" some piece of wood scares me! 🙂

=o=

 

[Dean Center]

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…

I agree with Ron--if you need a hard rock miner's helmet to turn wood, you maybe should rethink the project.

However, I did have a section of green 12" bowl rim fly off and put a fist sized hole in my sheet rock. It weighed about 1 1/2 pounds. I'd like to think my faceshield would have saved my face, though not without some damage to me or ruining the faceshield.

 

[Bernie Kopfer]

As an experiment I took a scratched face shield, put it on the floor and struck it hard several times with a hammer. No breakage and barely a scratch. I’m sure if struck with a large piece of wood the helmet frame would collapse and the shield would be pushed into one’s face, possibly giving the nose a hard time. Much better outcome than no shield in place.