Near miss report

C

CDH

Joined
Jun 8, 2007
Messages
283
Well I almost got a trip to the emergency room last night courtesy of my second complete blade getting thrown back at me. I have a serious question st the end of all this, so bear with me.

First, I have cheap equipment. When I started I both didn't know better and couldn't afford more. I still can't afford better, but I'm working on that. I do most of my work by hand with files and paper anyway. I don't think that was the cause of this, but you be the judge.

The knife was basically complete, buffed out, and ready to sharpen. Since I had a good half millimeter of flat edge, I was using a worn 320 grit belt (the finest I have, a Norton Al-oxide 4x36) to do the bulk of the edge profiling. I was using very light cuts and going back and forth to keep the bevels even and the heat down. In order to see, and in keeping with the oft repeated advice, I was grinding it edge up. Apparently the edge caught the seam of the belt.

http://i13.photobucket.com/albums/a297/cdhcmh/Knives/P8200067_cropped.jpg

http://i13.photobucket.com/albums/a297/cdhcmh/Knives/P8200069_cropped.jpg

http://i13.photobucket.com/albums/a297/cdhcmh/Knives/P8200068_cropped.jpg

The knife was thrown down and deflected slightly off the work rest. It happened waaay too fast to see it's path, but it came to rest right beside my right foot. It did not hit me, but with the speed and force it was ripped out of my hand I have no doubt that if it had I would be hurting today. The tip is damaged, but it is salvageable. Dang this knife has been full of 'learning opportunities'.:eek:

Now my question is about the origin of this incident. Should the advice to grind edge up have the disclaimer: "...except when putting the final edge into a blade," or is this a case of a worn belt being pushed too far?
 
Wow I see what you mean,,never worked with a 4" inch wide belt,,i use 2"X72",,
a few years back,,i was doing a final check on a cutting edge i just finished,,
I also sharpened knives edge down,,but there was a slight blimish on the edge,,soooo
I thought it would be ok to lightly touch it to the belt edge up (on the face of a 14"inch rubber face wheel) to keep an eye on it,,,
if I had lifted the tip of the knife up off of the belt everything would have been fine,,
some how the edge caught the left edge of the belt,,
so my added advise is NEVER touch a sharp knife, edge up to a belt over a rubber wheel.
even if you think you know what you are doing,,,,two things,,yes i still have all my fingers,,,and yes Mock-2 is very fast.

but back on point sence then an expert maker showed me how to sharpen edge up on a slack-belt (not over a rubber wheel) and i used an old scrap knife trying to cut the slack-belt but couldn't do it..
I'm glad you are ok,,live and learn,,oh and if the flap of rubber is still attached to the rubber wheel,,then a couple of drops of super glue will patch it if you are quick.
Skip
 
I also grind edge up, sharpen edge down, I think alot of makers do that.

I have also thrown a knife from my grinder...went over my shoulder, missed my right ear by probably less than 2 inches, shattered a flouerscent light 6 feet behind and 2-1/2 feet above me. That day I ordered variable speed motors and controllers for my grinders....
I run only fast enough to get the job done while avoiding much heatup...always have finger or thumb in contact with the steel....

At full speed, things can happen terrifically fast including accidents.....

Somehow, if you can, go variable speed....it is worth saving up to do....
 
I am still waiting for jointless belts since the joint is the culprit many times when it comes to grabbing your balde. Belt hop also is a real PITA.

I also sharpen edge down on the slack belt. I do it real close to the top wheel so the belt does not flex very much. That gives me a nice clean appleseed edge to finish up with a diamond rod or or oilstone.

Glad to see you did not get injured. My neighbor's grandfather was killed from a knife getting shot off a bench grinder. To this day he will not use a knife on my grinder. Can't say I blame him either.
 
Had a trainee that bought a new Square wheel grinder with the serrated wheel. He allowed the point to go into the belt, the blade caught and was thrown, not just into, but through his foot. Boot and all. He had to work the blade to remove it from the wood floor, then from his foot. The point left a mark in one of the serration lands, and he was using a thin belt. It did not catch the seam, it caught the land of the wheel. It was his error, but I have never liked serrated wheels.
 
I've used a 4x36 ever since I started making knives. I've had my 2x72 for a couple of years now but I still use my 4x36 a lot for the final grinding before hand sanding. I don't grind the way you have it set up. I grind with the belt in the horizontal position so turning away from me. It's also the only way to get all the way to the plunge cut. I've never had an accident and I make lots of knives. You can also use this position to grind your handles.
 

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I use a 2x72. I grind edge up and sharpen, initially, edge up. I just use a much lighter touch when sharpening.

Getting the point into the belt/buffer or whatever can be pretty ugly at best, lethal at worst. Bob Engnath once told me about a bowie he made. When he sharpened it he put a little ding in it, so he decided to buff it out. His buffing wheels were 2" wide.

Somehow he managed to get the point into the buffing wheel. It cut 4" out of the buffing wheel. When the knife went past his face it cut the bill off the baseball hat he was wearing.

When the knife quit ricocheting around his shop, he turned the buffer off and sold it the next day. His comment. "You only have to scare me like that once."

Gene
 
Been there done, that, it almost looks like you have what appears to be a craftsman 4x36 sander or something like it with a 6 inch disc on the right side of the machine. In my opinion that sucker is way too fast for sharpening a heat treated and tempered blade at around 3450-3600 rpm. The fact also that the belt is 320 grit makes it even more scary to use that because of how flat the grit is and anything sharp is gonna cut into it like butter! One of the scariest things I have found with that speed of grinder is that if you are grinding edge up, it wants to push that blade down between the crack of the grinder table and suck the blade in! So save your money and buy a 2 x 72" inch grinder and make it variable speed. That way you won't take off as much material at once and the blade won't heat up as fast. I had a couple of belts fly completely apart on me back in the day and that was enough for me. That thing is good for rounding off your handle where nice thick material is still there and isn't gonna get sucked in under the table rest. Be careful if you're still going use it that way. Just takes one more accident and possibly lose and eye or a finger, etc etc. Save your money and buy a coote! about 400 bucks and a motor would be around 150 for a 1 hp tefc with step pullies to variable speeds and very very well made if you're not willing to pay the money for a bader or KMG or etc etc....
 
I definitely plan on upgrading...but I have what I have (Good eye, BTW, it is the Delta 4x36+6" disk) and my budget is tight with 2 little ones and a one income household. For handle work (which is what I started out doing) it worked okay. For metal work it is, as you say, touchy. Good stainless wears out files and arm muscles in a hurry though. :D

Thanks for the well wishes. I'm just glad it didn't go back and put a hole in the wife's car on the other side of the garage. That might have been serious.:foot:
 
Make sure to remove the cars out of the garage first! lol. Glad to hear you are okay. As I always say, you can ever be too paranoid or preventative with your own safety. I'm guessing I don't even have to mention safety goggles and a good respirator when grinding anything! If you aren't using one, I recommend the 3M 6000 Half mask respirator with P100 particulate cartridges. I got mine on ebay for CHEAP!

I grind with the belt running upwards on a jig (which keeps the blade from being sucked into the jig if the belt was doing in a downward position)...I know, I know, most people would think i'm crazy to do that as metal particles are shot into my face....(well not really)...but I wear heavy goggles and a respirator....lol....but then again my grinder is moving around 900 SFM and not 3600 and will not throw the blade out of my hand into my face even if I were to let go of the tang. DO NOT TRY THIS AT HOME!!! lol. The actual only real bad part when metal particles are thrown everywhere is with a fresh belt cutting into a fresh piece of steel.
 
Is the belt on backwards?

I do the rough sharpening on a 10" diameter low RPM wet stone wheel rather than a belt.
 
From the photo, it just looks like a belt that has been beat all to hell and that is probably why it split apart. Used one two three times too many.
 
I too started out with a 4x36 grinder. I also have caught a belt while sharpening like you did. The next week I bought a 1725RPM (3/4hp) Dayton TEFC motor and a 3 position drum switch (Square D - to make it reversible). I made a a shaft mount 9" disc grinder and have used it to sharpen and finish every knife I have made since. This is actually a very versatile solution that not a lot of guys seem to use. I set my secondary edge bevels on a 400 grit sheet and can polish up to 1200 grit. I glue a piece of 1/8" - 3/16 cork backing onto the disc which allows me to get a very slight convex edge. The depth of the cork determines how convex your edge bevel will be.

The disc runs vertically (facing the user). I sharpen edge down at the bottom of the disc and stand to one side so that if the blade grabs, it will shoot away from me rather than into me. The drum switch allows you to change the direction of rotation for sharpening either side of the blade.

The disc sander was the first serious piece of equipment I had. I've tried sharpening on the 2x72 and find myself always going back to the disc. It may not be the most popular method, but it's the one I'm the most comfortable with and it gives me good, consistent results.

I'm with Leu on the old belt theory. Once they stop cutting properly, chop em' up and toss em'. Old belts and abrasive sheets will burnish rather than sharpen, causing a lot of heat buildup - nothing pisses me off more than a heat-blued tip on a near-finished knife (especially since I sharpen after finishing handles and making sheaths).

Nathan
 
CDH

Thanks for sharing the near miss it is always good to have reminders of the dangers. I had a similar event on a buffer after making hundreds. I got a bit tired or lost concentration. I don't quite know what it was but I certainly was woken up in a hurry. I did not have to sell the buffer but the underpants had to go.
 
I sharpen edge down
personally I think if you tempt fait it will get you in time..
just an over looked tear in the edge of the belt is all it will take. and that could happen to a belt before you get the belt into your shop.

I watched a show one time where a mobile Knife sharpener was sharpening edge up, but his belt grinder was geared so low he could do that with out fear of impaling yourself..
I mean slow as an auto honing stone..
be safe guys this isn't kiddy stuff..
 
I sharpen edge up on my 2 x 72 on the slack above the wheel. I need to stress I sharpen with the machine DEAD SLOW! You can read the writing on the back of the belt as it turns. Never had a problem.

I just bought a reversing switch for the VFD specifically so I can sharpen in the same position with the belt going away. Haven't tried it yet.

Rob!
 
I will add that MOST accidents happen when attempting to do things faster instead of smarter.
Dan's note about a professional sharpener having his belt at a crawl is exactly the point. If you sharpen at 1FPS belt speed it will go slow, but have little chance of a slip or catch. Over grinding is not much of a risk either.
If you sharpen at 100FPS it will go faster, but you lose control and safety.
When hogging steel while profiling I can see the speed, when sharpening the final edge, make your machine as slow as it will move. Some makers do the final strops with the belt stopped.
Stacy
 
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