Arm Braces on Hollowing Tool Handles

I felt the same way about parting off a spindle at several hundred rpm. After the first one just dropped down on the ways it seemed less scary.

I use a side handle on my hollowing tool and it feels perfectly natural and have never had any scary episodes. A lot of catches, but none scary. I feel that an arm brace would be fine, but too expensive for me.

How much horsepower drives your lathe? Is the drive geared? The reality of arm-brace tools is that even with fairly long overhang, you have enough leverage to stop the spindle dead, and smoke whatever smokes (belt, motor, etc) on any reasonable wood lathe most normal humans run.

If you have a 5-10 hp geared-drive lathe, that might be different. If you have that lathe, there's not much excuse for using any sort of hand tool on it, actually. Chuck the tools in a toolholder and spin dials or tell the CNC where to put the tool.

please, let me respectfully disagree - I have only 2 hp, and I have used (note past tense) an arm brace type tool for hollowing - things have gone wrong (you can blame the user if you like) and when things bind up the resultant torque is turned into a nice solid twist to your arm, or a lifting moment. If the piece is heavy, say 100 pounds, it can easily lift you off the floor - with a slightly larger piece, I could see it breaking an arm - in either case the result is not up to my standards for comfort and luxury. Some folks use the arm brace for years with no problem, then break their arm with a nasty catch, some never have issues.

I'd be happy to sell my now not-used arm brace tool to someone who would make use of it because I'm not going to.... or I can just let it hang on the wall to impress people

bill

I know of one torn up shoulder as a result of a catch - on a Stubby. And the individual is a very experienced turner, with 20+ years of turning - and has turned just about everything that can be turned on a lathe. The ONE incident required surgery to correct MOST of the damage (shoulders are kind of a complicated joint, with lots of tendons, ligaments and muscles holding the joint together in a somewhat precarious combination of bones - and not easy to repair fully).

He readily admits that he had a momentary lapse in attention - and that's all it took. Personally I prefer tools that, if something goes really wrong, I merely have to change pants and drawers - and not make a trip to the emergency room and subsequent trips to an orthopedic surgeon (they are really EXPENSIVE).

It's good to keep in mind that the energy involved with a moving mass, traveling at velocity V is not mxV but mxV^2. If you double the rpms, you impart FOUR times more energy to the turning mass.

Here's the energy for a 12" diameter piece, weight 5 pounds, spinning at 1500 rpms - 30,843 LBs-(ft^2/sec^2). For comparison, a 2000 pound little sports car, traveling at a bit over 2 1/2 MPH's energy is 29,645 LBs-(ft^2/sec^2). Can you stop that little moving car - almost instantaneously - with just your arm?

I'm going with the physics - and err on the side of caution - and therefore avoid attaching a tool to ME.

BTW - the energy of the spinning mass is what you have to stop/ overcome, not the horsepower of the motor that's spinning it at the speed it's traveling when the catch occurs. The belt(s) might slip AFTER you've stopped the piece from spinning - but by then, the damage is already done.

I've bought (and made) an arm brace because several turners whom I respect use one. John Jordan who used to check in here used one, sells one and I presume teaches its use. I don't use mine, mostly because I don't need it for what I turn, but I've wondered about its safety.

What does an arm brace do for me? I assume it helps prevent lateral motion of the tool's longer lever by "locking" to my right forearm and therefore to my arm and shoulder girdle. If the brace's walls are shallow so that my arm safely slips out when a strong lateral force suddenly occurs then what's the use of the brace? Do I need it for weak forces?

I don't know if vertical downward motion is impeded by an armbrace, but upward impedance seems unlikely. Seems that the more efficient the armbrace, the greater the risk of injury. Maybe it's just another of dozens of trade offs between usefulness and injury. The risks we incur and accept every time we turn wood.

This is all armchair thinking by a non-user and I may have it wrong. Lets hear from some users since the armbrace has been used without injury by many competent turners for a long time. The old rational vs empirical reasoning thing we learned about in school and promptly forgot. :)

Charlie notes the only accidental injury by a good turner that I know of and he (not Charlie) admitted to inattention. If I don't pay attention while turning with or without bracing my arm, I'm likely to get hurt. What are the risks of an armbrace used properly? I sure don't know.

Turn to Safety, Arch Fortiter

This is a frightening recounting of anecdotes:

snip

Accidents, by definition, are not intentional. And the phrase "Nobody's perfect" is true. And yes, like so many other things in life, mounting a chunk of wood to a motor, spinning it at 500 to two or three thousand rpms and applying a steel cutting tool to it involves some risk of injury. And yes, many accidental injuries could have been prevented by better prior choices, one of which is being risk assessment BEFORE acting in a potentially risky manner.

I drive a little Miata - convertible - often atfreeway speeds - on freeways of course. It has an airbag and I added a real (as opposed to cosmetic cause it looks cool) roll bar, I ALWAYS wear my seat belt, my rear and side mirrors are adjusted so I can readily and often see what's around and behind me, I don't play with the radio or use a cell phone while driving and whenever possible, leave myself space to maneuver should that become necessary. I also don't drink and I never drive when I'm stressed out or angry. I've had two fender benders that were my fault - in 40+ years, neither involving injuries and only one other accident - caused by another driver, going in the opposite direction hitting another car also driving in the opposite direction - and spinning that car into my stopped vehicle.

Given the math and physics vs the anecdotal evidence - I choose to err on the side of caution - and the math and physics - be it when driving - or turning. Captured Systems readily available, and at least for me, affordable make the potential risks of a hand held, arm braced hollowing tool unnecessary.

For those getting into hollowing who haven't seen this before here's a compendium of captured hollowing systems available - and I bet more are out there now.

Consider alternatives to arm brace hollowing tools and then make a risk assessment.

In message , charlieb writes

Never trust statistics, Never trust fact Statistically speaking the odds can be 100 Million to 1 Facts may show no evidence

But unless it can be guaranteed something can never happen, then it can, so does anyone want to be the first ?

Their are many areas of life where their are risks, we try to control / limit them as best we can, but their are no guarantees, and the risk may be catastrophic.

I had a mitre saw that failed in use, and it was a design fault. The only reason I know was I had a second identical machine, and it also failed, but safely, and leaving the evidence. When the first machine failed, not only the blade guard was destroyed, several Tungsten Carbide teeth also and a large chunk of aluminium casting. What was the cause, quite simple no screw lock, or spring washer, on a plate attached to the guard. Vibration caused the screw to come loose fall into the guard as it had just reached maximum speed..... and the rest was history. When the second one failed I had the blade tilted and the screw fell on the floor, the design has since been modified

For me I prefer the idea of not being attached

I do hope later this year to start building my own design hollowing system, though I suspect it will include a combination of feature from many of the designs seen already

There are 3 kind of lies; lies, damned lies and statistics. Mark Twain

If some one invents some thing that is idiot proof, then some one else will invent a better idiot. unknown

robo hippy

I agree, Charlie... "hands down"

I looked at those things and my first thought was something like "those things are for folks a lot younger than me"...

mac

Please remove splinters before emailing

When I make a mistake, and I KNOW I will, I don't want the tool attached to me.

I wnat my grip of the tool JUST precarious enough that I am going to DAMNED WELL PAY ATTENTION in "iffy" situations when I'm pretending I'm that little Engine saying "I think I can..."

I'm not a cyborg.

I couldn't agree more... Most of my gouges are ground "swept", so the tool handle is much lower than the tip.. If I get a catch, (not that any of US ever do), I want the tool to be pushed down and on MY side of the tool rest..

mac

Please remove splinters before emailing

The problem with making things foolprof is that fools are so ingenious.

I like my arm braces for hollowing. By the way, an arm brace is only attached by holding it with your hand. The extra control comes from "resting" the arm in a holder, not strapping it in. The chances of the force of a catch breaking your grip are a lot better than the forces breaking your arm.

true enough, but after some rough work with such a tool, I had a very very sore shoulder and forearm