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Old 01-17-2012, 07:45 PM
Lemmingman's Avatar
Lemmingman Lemmingman is offline
Join Date: Jun 2010
Location: McKinney, TX
Posts: 689
Default Shop Safety

Saturday I decided to do some maintenance around the shop. I wanted to get my big top skin attached to my right wing, but my wife (and main riveter) had gone to St. Louis for a hockey tournament with my son. My daughter is getting better with a rivet gun, but I'm not quite comfortable letting her rivet a skin yet. So I decided to put my left wing skeleton on my wing stand and make sure there wasn't anything that was going to need modification for the left wing. As it turned out my homemade bracket that holds the outboard rib to the wing stand needed trimming since it was going to interfere with the skins, so I broke out my die grinder and a 3" cutoff wheel.

I've never had an incident with a die grinder but, the die grinder / cutoff wheel combo scares the fire out of me. Not as much as the drill press / fly cutter, but in the ballpark. For what I was doing, though, it was the right tool for the job. To prepare for the task I needed to assemble my safety gear. I went inside and put on another long sleeve shirt. I reached for my safety glasses but decided on the face shield instead I also put on my dust mask and hearing protection. At the last second I decided that my gloves couldn't hurt either. Now I was set and ready for action. I was grinding away for about 30-seconds and it happened in an instant.


The cutoff wheel exploded sending shards all along the plane of travel of the wheel. Miraculously (or maybe it was physics) none of the pieces hit me. Small pieces did hit the leading edge of the right wing, my table and the ceiling of the garage. I disconnected the air and took stock of my appendages to make sure they were all there and look for shrapnel wounds. All clear. I picked up all the pieces of the failed wheel I could find and noticed that a large chunk was missing. I couldn't find it anywhere. I assumed that it was traveling so fast that it tore a hole in the space time continuum and would erupt from a worm hole a million years in the future.

I replaced the wheel and got back to work finishing without incident. I got to thinking about my preparation. I am sure pieces hit my face shield. Had I put my safety glasses on instead I might be nursing some wounds on my face or forehead right now. My hands were really close to the action too. I don't think anything hit them. I am very glad I took the 20-seconds to walk across the garage and get them and put them on.

What really scares me though, and the real lesson that I took away was the violence of the failed part and the force that the pieces had. If anyone else in the family had been in the garage with me there is a pretty good chance that they would have been standing in the path. I wouldn't have thought twice about warning someone to get out of the way. It just wouldn't have crossed my mind. I was also reminded that I am going to have to think about how my other tools might fail and what damage or injury they could cause. Am I taking the right precautions for the work I'm doing? I'll have a safety stand down on Saturday and see what revelations come up.

Oh yeah. Remember that piece I couldn't find? I found it today while I was on a conference call. I was speaking and saw this. I literally stopped in mid sentence. Everyone thought I my call had been dropped.

For the record, 8' from the point of failure to the point of impact.

From what I can tell by the trajectory of this piece, it missed my wing by a fraction of an inch. Had my daughter been setting clecos in the wrong place, it would have hit her in the face or neck. Granted, this is a cheap interior door that it's embedded in, but that thing would have left a scar in whatever it hit.
Gil Brice
McKinney, TX EAA-1246
RV7 - Working on fuse, fuel, brakes etc...
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Old 01-17-2012, 08:01 PM
fatherson fatherson is offline
Join Date: Oct 2009
Location: Albuquerque, NM
Posts: 427

I've re-learned a lesson from your story that I seem to need to re-learn far too often. Thank you for sharing, Gil. Your safety measures saved you this time, but your story may have saved a bunch of other people too.

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Old 01-17-2012, 08:02 PM
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Walt Walt is offline
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,340

Wow! What kind of wheel are you using and is it rated for 25K RPM? I've been using these wheels for a bunch of years and never seen that happen.
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website:, Email:, Cell: 972-746-5154
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Old 01-17-2012, 08:36 PM
TS Flightlines TS Flightlines is offline
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 2,928
Unhappy me too walt-

But had on explode at my real job the other day. 3 " cut off wheel, wont name the brand ( but purchased at the blue & gray building). It came apart at the metal reinforcement around the arbor hole. Huge surprise---picked up pieces across the shop. It was rated at 25K, and obviously didnt make it.
MUCH more careful now. Even safety glasses would not have helped.
So---be careful.
Tom Swearengen, TS Flightlines LLC, AS Flightlines
Joint Venture with Aircraft Specialty
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7A Tail Kit Completed, Fuse started-Pay as I go Plan, on hold while we develop new products for RV builders
Ridgeland, SC,
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Old 01-17-2012, 08:42 PM
scrollF4's Avatar
scrollF4 scrollF4 is offline
Moderator, Asst. Line Boy
Join Date: Jan 2010
Location: Flower Mound, TX
Posts: 1,631
Default Safety...a culture, profession, and way of life

Man oh man, Lemmingman, am I glad you're OK.

Most of you don't know me, but I am the Director of Safety at Headquarters Air Combat Command in the US Air Force. I deal with flightline, ground, weapons/munitions, and aviation safety mishap prevention on a daily basis at air bases across the US. I am responsible to my 4-star for the execution of the USAF mishap prevention program across HIS major command's 20+ wings and numbered air forces (1st, 9th, and 12th Air Force). My previous job--Chief of FLight Safety at the AF Safety Center--also kept me busy regarding these sorts of events. If there's a way to hurt yourself around airplanes, I've seen it and even written procedures to try and avoid it, and then investigated it when it didn't work. Like when pilots and Airmen don't wear their PPE (Personal Protective Equipment).

Gen Hostage is also an avid soaring pilot...and glider homebuilder. He checks my build site frequently to keep up with my progress (he could also just walk across the street here in officer housing at Langley AFB for a status check). You can imagine how surprised I was one day recently when he pointed out I was working some alclad without eye, hand, and ear protection. Que the thunderclap, a rock-solid reminder to me: Stick to the basics, wear my PPE, and don't slack off when it comes to Safety. It just wouldn't do if his top Safety Officer hurt myself pursuing this dream of ours, when I could have easily prevented it.

I enjoy the VAF's recurring and deeply ingrained culture towards safety. Heck, as a Safety Professional, I'm proud of it. Face it: We're amateurs (well, most of us, with a nod to Iron Flight), but we're working hard to help each other get it right and build airplanes as safe as their design potential promises. I see fellow builders discarding parts and component assemblies that just didn't meet their expectations or standards. We're tough on ourselves and our handiwork. I think we get it, and I urge the VAF to maintain our high standards of discipline, of personal and peer accountability. This is how I hope to trust my aircraft enough to take my wife and boys up as "crewmembers" in my 7A. And maybe my dog.

Lemmingman, you did it right, and I sure am glad. Thanks for the example, and for sharing the experience. Nothing like a good Safety brief to keep things in perspective. So sez the Safety guy.

Sid "Scroll" Mayeux, Col, USAF (ret)
52F NW Regional/Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper
Catch her on YouTube's "Because I Fly!" channel

Exemption waived.
Proud and grateful 2021 -=VAF=- Contributor

PS: I am not an influencer. I have no influence. Just ask my kids.

Last edited by scrollF4 : 01-17-2012 at 08:46 PM.
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Old 01-18-2012, 09:31 AM
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woodmanrog woodmanrog is offline
Join Date: May 2005
Location: Florida
Posts: 781

I have had similar experiences with cutoff wheels. Primarily the arbor hole fails leading to catastrophic failure of the entire wheel. Really dangerous. I find that for this kind of a cut an air powered hacksaw is a much better choice. I also love my vibrating multi tool for doing these types of cuts. I find that a rotating cutoff wheel tends to have problems when the material is first penetrated because even the slightest twist will cause the wheel to bind and shatter. I suspect that is what happened to you. Glad you ar OK and no real harm was done.
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Old 01-18-2012, 01:35 PM
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CPSONE CPSONE is offline
Join Date: Nov 2010
Location: BC Canada
Posts: 219
Default Safety

Thanks for posting your incident. I too try to go out of my way to be extra safe with face shield for even using my big scotchbrite wheel to keep dust out of my eyes. I'll even wear hearing protection for using the drill.
Using cut off discs I'll wear safety glasses under the shield. They have the bifocal lenses in them so help me see what I'm doing anyway.
Been thinking of getting a die grinder that has the half shield to semi-contain failures of cutting disks. I think I'll go out and buy one now!
As you mentioned, for the time it takes, put on the safety gear!
...many years ago I was at the dentist and the grinding bit failed while the dentist had the tool burried in my mouth. Flying bits everywhere, cut my lip etc...ouch. Be safe.
RV-6 emp, done-sold,
RV7A QB. Passed pre-cover and sold!
Disclaimer: Everything I say can be presumed to be wrong. Don't try this at home.
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Old 01-18-2012, 01:36 PM
Lemmingman's Avatar
Lemmingman Lemmingman is offline
Join Date: Jun 2010
Location: McKinney, TX
Posts: 689

Wow! What kind of wheel are you using and is it rated for 25K RPM? I've been using these wheels for a bunch of years and never seen that happen.
Walt you really got me wondering. I thought for sure when I bought those wheels that I specifically checked the RPM rating. I checked this morning and sure enough they are rated for 20,000rpm. As I thought about it I think I know where in the chain of events things went wrong.

I haven't used that cut off wheel in at least 4 months. It's been sitting in a drawer, attached to the arbor, where I store many of my pneumatic tools. I could have dropped a tool on it, or it may have been scored or cracked anytime in the last few months.

My new process is going to be to use a fresh wheel with each new job. They aren't that expensive and come in multi packs.

Sid thank you very much for you your comments. Coming from a professional in the business it means a bunch.
Gil Brice
McKinney, TX EAA-1246
RV7 - Working on fuse, fuel, brakes etc...
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Old 01-18-2012, 01:53 PM
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ppilotmike ppilotmike is offline
Join Date: Jan 2010
Location: Denver, CO
Posts: 2,013
Default Me too.

I had the same thing happen with a small rotary tool and cutoff wheel. It turns at about 22,000 rpm and the cutoff wheel was rated for 25K. It exploded and luckily, I was protected enough to avoid injury. Best as I can figure, it could have something to do with cranking down on the arbor bolt too hard. Or, perhaps I just got a dud wheel. Either way, with more of these toolsm blades, wheels, etc coming from places in the world with lax QC standards, it's better to be safe. Nice pics!
Mike Rettig
EAA Chapter 301
VAF Dues Current
RV-10 - Working on engine / prop installation
F-14 (Pedal Plane - Daughter's Project) "Flying"
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Old 01-18-2012, 02:32 PM
krwalsh krwalsh is offline
Join Date: Nov 2009
Location: San Francisco, CA
Posts: 380
Default Gloves

Lesson learned from a 4 1/2" angle grinder with a zip-wheel. Make sure the gloves your'e using can handle the zip wheel. The pair of leather gloves with synthetic uppers I had would have been fine if the wheel hit the leather. It hit the upper and I now have a nice 2" scar between the thumb and forefinger on my left hand.

Leather gloves for me from now on.
Kevin R. Walsh
Cozy Mk-IV
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