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  1. #1
    Join Date
    Jul 2007
    Location
    Inkerman, Ontario, Canada
    Posts
    405

    Warning about Routers

    I am posting this as a public safety announcement.
    I am not looking for a discussion on my practices.

    So i have used my Makita router for internal and external grinding.
    The router has electronic speed control from 8000, -24,000 adjustable by a graduated wheel.
    I have done ID grinding with the small grinding wheels 1/2" - 1" dia max rated rpm 30,000 with with speed dial set to full speed 24,000rpm.
    And i have done some external grinding with a large 4" diameter wheel with the speed dial set at 8000 rpm.

    I haven't used it for some time (many months)
    I went to use it the other day and got injured quite seriously.

    I had the dial set to 8000 for the larger wheel, turned the router on to let it warm up for a few seconds before using it, it was running fine for a while, i turned away to get something and the router ramped up to full speed for no apparent reason, the noise startled me and i turned around just as the wheel exploded. I didn't have any time to do anything, i got hit in the face with a piece of grinding wheel.
    It hit me on the left side of my nose, below the cheek bone, broke my palate and pushed a couple of teeth and the bone that holds them into my mouth, split open my face, cut up my tongue, and bled profusely, inside and outside my mouth. I have had the first emergency surgery to do the initial patchup to remove the chunks of grinding wheel that embedded inside my mouth and had my face sewn up. I have to go to another surgery to get my palette repaired and my teeth put back where they belong, when the swelling goes down. For now i eating through a straw.


    So other than the normal safety procedures you may follow, the take away from this is;
    1. Routers electronic control are not to be trusted.
    2. The can and do randomly change the speed without warning.
    3. Don't run anything in the router that is not rated for the full speed of the router.
    4. Electronic controls can and do malfunction when operating under normal circumstances.

    From the manufacturer:
    Variable Speed Control Dial Enables User To Match The Speed To The Application And The Electronic Speed Control Maintains Constant Speed Under Load

    1-ID grinding.jpg

    1-ODgrinding.JPG

  2. #2
    Join Date
    Apr 2008
    Location
    East Virginia
    Posts
    710
    Whoa, sorry to hear of this bad news. Thanks for warning the forum. I've had (non-speed-adjustable) angle grinders go insane with changing rpm speed...definitely will watch the router with big bits now that you mention it.

    I won't run a grinder without guard and a face shield, as I've heard of bad injuries and even deaths due to wheels breaking and arteries getting severed...maybe I'll start using a face shield when running routers, too.

    Hope you heal up back to 100%. Take care.
    Last edited by Jacob Reverb; 06-07-2019 at 11:54 AM.

  3. #3
    Join Date
    Mar 2003
    Location
    Upland CA
    Posts
    4,274
    I hope you get well quickly Mark. That must have smarted.
    Rick Potter

    DIY journeyman,
    FWW wannabe.
    AKA Village Idiot.

  4. #4
    Join Date
    Jul 2007
    Location
    Inkerman, Ontario, Canada
    Posts
    405
    Thanks guys, i am doing well, a little shaken as i have about a dozen routers, all electronic speed control, and will now be a little nervous using them. Everything in my shop is dangerous and can seriously hurt you; i am okay with danger as long as long as it is predictable, this caught me by surprise.
    The funny thing is i saw this video a month ago.

    https://www.facebook.com/Dandjprecis...=2&theater

  5. #5
    Quote Originally Posted by Mark Hennebury View Post
    Thanks guys, i am doing well, a little shaken as i have about a dozen routers, all electronic speed control, and will now be a little nervous using them. Everything in my shop is dangerous and can seriously hurt you; i am okay with danger as long as long as it is predictable, this caught me by surprise.
    The funny thing is i saw this video a month ago.

    https://www.facebook.com/Dandjprecis...=2&theater
    Holy $#!^ that counter weight took off like a missile.
    Super lucky.

  6. #6
    Join Date
    Feb 2015
    Location
    Beantown
    Posts
    1,702
    Yeah that is just crazy.

    Those of us that use machinery daily to make a living probably take quite a bit for granted.

  7. #7
    Mark, just read the whole post. I guess I guessed it was the end of a finger. Some of us will now be using full face shields.
    Thanks for reinforcing safety by relating what must be a most painful and complex injury. "Rule number 1....Obey all rules!" And that applies to Doctor's instructions. But I believe
    in demanding good pain killers ! Wishing you a full and speedy return to full health and confidence in the future.

  8. #8
    Join Date
    Jan 2013
    Location
    Pittsburgh, PA
    Posts
    756
    I contacted the vendor where I usually buy my router bits, specifically expressing my concern about what might happen if I had a 3.5 raised panel bit in my router and the speed control failed full on. Looks like the bits, regardless of size, are rated for 25,000 rpm and will stay intact if the router speed control fails.

    Our bits are designed to perform balanced at speeds up to 25,000 rpm. That being said, the larger bits are not recommended to be used at that high of an rpm due to high velocity tip speed generated as the cutter gets wider. For that reason, a 3-1/2" bit is recommended to be used at a speed somewhere between 12,000 to 14,000 rpm. At the same time several shallow, incremental depth passes are suggested rather than a single hog out attempt be made.
    Too much to do...Not enough time...life is too short!

  9. #9
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    49,001
    Bill, the big thing with swinging the larger bits with high speeds is the force they generate when they contact the material. So while the cutter might be perfectly fine at the high speed relative to strength and staying together, the effect when/if it grabs a piece of material could have an impact on how many changes of underwear you need to make that day... ...or worse. That's yet another reason why the big cutters must/should be used in a table situation and not with a hand-held router.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  10. #10
    Join Date
    Apr 2017
    Location
    Tucson, Arizona
    Posts
    285
    Quote Originally Posted by Jim Becker View Post
    Bill, the big thing with swinging the larger bits with high speeds is the force they generate when they contact the material. So while the cutter might be perfectly fine at the high speed relative to strength and staying together, the effect when/if it grabs a piece of material could have an impact on how many changes of underwear you need to make that day... ...or worse. That's yet another reason why the big cutters must/should be used in a table situation and not with a hand-held router.
    So the key thing here is the router bit tip surface speed at a particular RPM. Here is a video that explains this in detail. I have also added a router bit speed chart that lists the maximum safe operating speeds for different router bit diameters. I hope that some find this useful.
    David


    https://www.youtube.com/watch?v=qOUF2Cmq2ws

    Router Bit Speeds.jpg router speed chart.jpg

  11. #11
    Join Date
    Dec 2015
    Location
    Cincinnati, Ohio - north
    Posts
    75
    This is just to confirm that switches do sometimes have a mind of their own and are not to be trusted.

    Fortunately my experiences were nowhere near as catastrophic as Mark's, but they are a lesson to be learned. I had my DeWalt RO Sander turn itself on at least twice before I learned to pull the plug whenever I am not standing right by it. On one occasion I turned my back and it started, wearing rings in the plastic surface where it was sitting. Another time it turned itself on while I was on vacation - bounced off the counter, landed upright on the floor, and skittered for some time, leaving worn rings in my concrete floor before somehow turning itself off again. Shame on me, but things do have a way of their own sometimes.

  12. #12
    Join Date
    Apr 2013
    Location
    Okotoks AB
    Posts
    1,164
    That's a known thing with older Dewalt ROS's. Mine has done it too.

  13. #13
    Join Date
    Jan 2013
    Location
    Pittsburgh, PA
    Posts
    756
    Quote Originally Posted by Jim Becker View Post
    Bill, the big thing with swinging the larger bits with high speeds is the force they generate when they contact the material. So while the cutter might be perfectly fine at the high speed relative to strength and staying together, the effect when/if it grabs a piece of material could have an impact on how many changes of underwear you need to make that day... ...or worse. That's yet another reason why the big cutters must/should be used in a table situation and not with a hand-held router.
    I think most of us realize that Jim,

    My concern was whether a large 3.5 bit would come apart or stay together if my router speed control failed like Marks did.

    The answer that the large bits are rated for 25,000 RPM is reassuring. (Looking a different web sites I was unable to find specific speed ratings for the larger bits. Hence the question to the vendor.)

    That was the point I was trying to convey. I was Addressing a safety concern, and in no way suggesting one might want to run large bits at such high speeds...
    Too much to do...Not enough time...life is too short!

  14. #14
    Join Date
    Sep 2010
    Location
    New England
    Posts
    1,726
    Quote Originally Posted by Mel Fulks View Post
    Mark, just read the whole post... Some of us will now be using full face shields.
    Mine just arrived. Appreciate the heads up from the OP. I own 2 PC 7518 VS routers. Plus a shop full of dangerous tools. No point in pressing my luck any farther.

  15. #15
    Join Date
    Aug 2010
    Location
    USA
    Posts
    5,435
    The reason I was asking the questions was to get at the root cause of the problem. Having actually designed and worked with various motor speed controls I thought it would be wise to understand your circumstances better. Not having that, however, I will say that the type of speed control on a router like the one you used is an open loop design. It simply reduces the input voltage supplied to the motor by limiting the peak voltage and / or duration of each of tje 60 Hz voltage cycles. It has no way to monitor the actual speed or do anything to 'control' it. I suspect, in your situation, the rotational speed of the lathe, coupled with the speed of the router itself caused the router to be overcome by the lathe rotational speed. There is no way the router could do anything but "go along for the ride". Effectively the router couldn't keep up and because of the grinding frictional load on the grinding wheel, the wheel ultimately broke. The noise you heard was the wheel fracturing and disintegrating. Again, this wasn't a failure of the router speed control but simply overload due to the conditions that were set up. Maybe this worked for you previously and you were lucky, maybe this time the wheel was degraded enough from previous uses to fail, maybe the load was greater this time, maybe there wad a metal fragment that got into the motor speed adjuster, etc. Who knows.

    Sorry for your injury. Thanks for your initial posting. We can all learn the need for more personal protection when using machines.
    Last edited by Pat Barry; 06-14-2019 at 12:24 PM.

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