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watch the @%@!#!@ing belt and keep your mind on the job...


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Graphic content below, so go away now if you're squeamish.  No blood, that came about ten minutes later...

 

So we all know that a belt grinder is capable of removing body parts  (I didn't lose anything but skin and dignity) faster and even more easily than they remove steel.  This means we usually treat them with the respect they deserve.  A 36 grit belt at high speed will lay your knuckle open to the bone with a single slight touch.  A 400 grit J-flex can slice you open like a bandsaw if you touch the edge of a slack belt at speed.

 

Up until today, I'd never been mauled by a micron grit Gator belt, they've always been fairly innocuous.  There were two causes to this incident, and a valuable lesson as well.

 

The setup: I was running a Trizact A45 Gator belt at the slow setting on my KMG, about 700 surface feet per minute, or 900 rpm on a 4" drive wheel, doing the next-to-last finish grind on a tiny folder blade in my folder blade jig.

 

Issue #1: Using the jig means using the work rest, which I don't usually use when grinding blades shorter than swords. The jig's baseplate is paper micarta slicked with Renaissance Wax.  The work rest is also polished and slicked with the wax, to keep it from rusting and to keep things moving freely when it's in use.  This also means that it needs to be cleared of swarf regularly when using the jig so it doesn't chew up the baseplate.  I use a paintbrush for this.

 

Issue #2: I allowed my mind to wander from the task at hand just enough to try and grab the jig when it tried to fly off into the water bucket.  I know not to do this. If the grinder grabs something, let it go and jump away.  I got complacent with the slow speed and the very fine belt.

 

Result: The side of my right pinky finger touched the moving belt, which grabbed it and slammed the side of my hand into the work rest very damned hard indeed.  Here is the result while it was still numb, less than 45 seconds after impact (I try to use these as teachable moments...;))

 

20211107_135621.jpg

 

Not too bad, right?  

 

The thing about grinder burns is they are slow to bleed, and the thing about impacts is they numb the injury for a few minutes. I was nearly finished with the grind, so I kept working.

 

Five minutes later, blood was dripping off the end of my finger, and blood will rust your stuff.  So I called it a day and headed inside to clean it up.  One hour later, a bruise is appearing down the entire length of the finger where it hit the work rest, and boy, is it not numb anymore!

 

Lesson learned: ALWAYS keep the belt in mind, no matter what kind of belt it is.  And don't try to catch something if it's falling off the work rest.

 

Corollaries to lesson:  

 

A: If the work rest hadn't been there I'd have gotten away with a tiny nip.

 

B: If I had not, as you always should when using them, had the work rest tight up against the belt, it could have easily broken the finger or even flayed it down to the bone before it bogged down the motor.  

 

Class dismissed, and don't learn this the hard way!

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Thank you for the reminder Alan.

 

One thing I would like to add about your point B:  We have had people where I work with using a disc sander that had the work rest gap to large from the disc.  The work piece got wedged into the gap, taking their finger and pinning it between the work piece and the disc.  Both sanded to the bone and resulted in amputated digits from  grit and metal contamination.

 

While I am sure you already have, please make sure you clean that wound thoroughly.

Edited by Adam Reggie
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19 minutes ago, Gerald Boggs said:

Is this by chance the same hand and fingers?

 

Same hand, different finger from the sledge hammer incident.  Oddly enough, that finger (right middle) works better than the index finger since the psoriatic arthritis set in a couple years ago.

 

And Adam, yes indeed.  I appreciate the concern.

 

Jaro, sorry!

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Sort of related to your issue 

 #1: Using the jig means using the work rest, which I don't usually use when grinding blades shorter than swords. The jig's baseplate is paper micarta slicked with Renaissance Wax.  The work rest is also polished and slicked with the wax, to keep it from rusting and to keep things moving freely when it's in use.  This also means that it needs to be cleared of swarf regularly when using the jig so it doesn't chew up the baseplate.  I use a paintbrush for this.

 

I changed out my steel work rest for a longer and wider piece of 1/4 inch stainless and it has made a very real difference to the rust issue and also to the jig baseplate. My jigs are all made from 8 and 10mm alloy but I sat my work rest back from the belt to where the leading edge of the jig is  over the edge of the rest by an 1/8 or so and there is almost no grindings getting onto the rest to scour the jig base and with the constant dipping the rest is always wet so creates a micro aqua planing so effort is reduced on the larger heavier jigs. If I see any of the grindings on the rest it is a simple matter to wipe with my hand but that is a very rare event.

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I think all the knuckles on my left hand are all scar tissue at this point... little slips here and there and a 24 grit belt ripping through whatever I'm feeding into it seem to, the blink of an eye, take off a little more than the topsoil. Keep your eyes on the prize for sure, even the quickest of slips leave you feeling it for a week of hand washing <_<

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I had a 40 grit belt go in between the nail and the flesh of my left index finger last week, what fun...... 

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Thanks, guys.

 

Gerhard, all I can say is ouch!

 

Today it's in the "stiff, sore, starting to itch" phase. Drinking my tea like a nob, little finger extended! :lol:

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Ouch Alan, glad it wasn't worse.  Like John, my knuckles are quite a collection of scars from minor contact with the belts.  It's doesn't take much with the aggressive belts to make a flesh divot.

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Thanks.  Yeah, we all have the knuckle scars and fingertip divots, the occasional tissue-paper-thin fingernail, and the gashes from the side of the belt.  This was a new one for me, since I rarely use the work rest.   I remain impressed by the force with which the grinder can slam your hand into the rest at a relatively slow speed with about half an inch of head start.

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Mine came with a sound change! My brain is working on wth am I hearing, to kpow bomb blowing up.png. Then wow that hurt, what the, oh the belt broke. Oh, that was the sound change!! It seem like it all happens in slow motion, when it is so fast your brain has to catch up! Mine was up above the wrist and it turned black and blue the next day!! Put some suave on Alan!! May not help the boo boo much but it helps the ego!!

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@Alan Longmire, well your not alone sir. I freehand grind as well mainly because that’s what I got used to doing.

I do want to say that this little jig works great as I took your post to heart and made one to use on these short blades, yes they heat up way too fast to free hand.  

Yep, in a hurry and hand swiped the swarf and put the nicest grind on tip of my middle finger. 

Gary LT

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I'm sorry, Alan, I must have dozed off.  Could you go over issue #2 again, please?:(

20211108_155918[1].jpg

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1 hour ago, billyO said:

I'm sorry, Alan, I must have dozed off.  Could you go over issue #2 again, please?:(

 

 

Issue #2: I allowed my mind to wander from the task at hand just enough to try and grab the jig when it tried to fly off into the water bucket.  I know not to do this. If the grinder grabs something, let it go and jump away.  I got complacent with the slow speed and the very fine belt.

 

I've done that so often with my left index finger there's a permanent flat spot on the side of the first knuckle. :wacko:

 

15 hours ago, C Craft said:

Mine came with a sound change!

 

Did that right before this one!  I was doing the final pass across the sister blade to the one in the jig with a 400 grit J-flex when a loose thread on the edge caught in the choil. It didn't even pull, which is unusual for a belt grab. It just went "POP!" and I was standing there holding the blade and jig against the bare platen with a broken belt draped over my left shoulder, the grinder motor happily whirring away with no load.

 

A friend I was teaching to grind engraving chisels wasn't so lucky.  We were using a 220 J-flex to set the point bevels on small gravers.  I grind those point-down.  James decided he wanted to grind point-up so he could see exactly when it was flat.  Well, when you stick a needle in a moving belt, things happen fast.  The graver got snatched out his hands and thrown hard into the water bucket, and the belt split down the center about halfway, then the break veered to the edge, leaving a loose length of inch-wide belt about two feet long flapping away.  James got smacked down the center of the forehead about five times before he figured out what had happened and stepped back.  

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  • 2 weeks later...

Two weeks later update:  healing is going well. Still a big hole in the finger, still stiff.  BUT! Pay attention to cleaning afterwards if this happens to you.  Like Adam said above, you have to clean this sort of wound very well indeed. I thought I had, but three days later it started going off.  Google "debridement" for fun to see what I had to do.  Basically take a scalpel and scrape it down to clean meat, then sterilize again.  That time did the trick.  

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