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The Folding Knife (& Switchblade) Forum The materials, techniques and the designing of folding knives.

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  #1  
Old 11-02-2012, 03:02 PM
BillyJack92 BillyJack92 is offline
 
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Exploding belts!

I wasn't sure were to post this so I hope it's fine here, but anyway I just had a belt explode on me and it scared the #### out of me. I was trying to bring the plunge cut back on a flat grind like I normally do and out of no where I hear a loud explosion, it was as loud as a shotgun. The belt grabbed ahold of my hand and slammed it on my workbench where my grinder is mounted on. I then looked down and there was the belt totally shredded. I just wanna know what causes that to happen cause I wasn't doing anything different then normal. So if possible please let me know if you have an idea why this happened so maybe I can prevent it from happening again.
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Old 11-02-2012, 04:36 PM
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Eli Jensen Eli Jensen is offline
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My guess is the belt delaminated. When belts get old or worn, the seam fails. Never all the way of course, just a little peel. When the belt comes around to the edge of your blade that peel goes over the blade instead of under and grabs it real good. It can also happen if the edges of your belt are frayed or otherwise damaged. It happened to me once, VERY SCARY. Even more damage is possible too. When it happened to me it locked up everything including my drive belt. The axle kept spinning and shredded the drive belt good.
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Old 11-02-2012, 05:24 PM
jdware jdware is offline
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I've had it happen on an old belt - the joint failed and BAM!! Nothing damaged but my nerves.... have to just walk a way for a while to calm down. Still afraid to run the belts at anything over about 3000 SFM.
J

JDWARE KNIVES
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Old 11-02-2012, 06:06 PM
BillyJack92 BillyJack92 is offline
 
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O yea it was terrifying I thought it broke my fingers when it slammed my hand down and yes it was a very worn belt. I was actually scared to start grinding again cause I wasn't sure what caused it and I don't want to experience that ever again, and while I'm here instead of starting a new post I'll just ask another question in here lol. I'm doing my first folder and the blade is hard to grind with vise grips do you guys have any other suggestions that are a little more comfortable to hold onto the blade with? Thanx for answering my questions.
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Old 11-02-2012, 06:13 PM
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Don Robinson Don Robinson is offline
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I always make 2 blades at once, back to back. One becomes the handle while I grind the other.
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  #6  
Old 11-02-2012, 06:24 PM
BillyJack92 BillyJack92 is offline
 
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So the tip of one blade is attached to the tang of the other??
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Old 11-02-2012, 06:29 PM
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Don Robinson Don Robinson is offline
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No. Back (tang) to back with enough extra space between to saw them apart after both are ground.
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Old 11-02-2012, 06:47 PM
BillyJack92 BillyJack92 is offline
 
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Ohhh great idea I really like that I'll give it a try after I finish this first friction folder ive been working on. Thanx alot man I really appreciate it.
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Old 03-16-2013, 12:09 PM
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John I Shore John I Shore is offline
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Had one blow out on me last month, slammed my hand and split my thumb to the bone. After 2 years in Iraq and a number of IED's and tons of ordnance going off, needless to say I was rattled for the rest of the day. Finally got back out there and the same thing happened on the next belt, only thing was I wasn't hit by it. I took that batch of belts and threw them in the fire. They both separated at the laminate joint.

I had heard stories about that for years, first time in 30 years of knife making that it happened to me.

John I.


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Old 03-16-2013, 05:48 PM
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How much tension do you guys put on the belt when mounting them up?

I've had belts separate at the joint and the belt goes slack then drops off the wheels. Of course the sudden cease of cutting is shocking but as far as these catastrophic separations I've not encountered and don't want to.


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Old 03-16-2013, 07:13 PM
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Don Robinson Don Robinson is offline
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Quote:
Originally Posted by M&J View Post
How much tension do you guys put on the belt when mounting them up?

I've had belts separate at the joint and the belt goes slack then drops off the wheels. Of course the sudden cease of cutting is shocking but as far as these catastrophic separations I've not encountered and don't want to.
I must use a lot of tension then, because I've had dozens of belts explode suddenly.

They usually separate at the splice, not always. If you nick the edge with the workpiece accidentally, it'll shred sooner or later.

I just use enough tension to keep the belt tracking on center.

I've had my hands hurt occasionally, but they usually just separate and fly off.

I always use the guards on my grinders, a Square Wheel and a Burr King.

Never use an old belt, even though it may not have been used. If it gets too stiff, you can bet it'll explode.
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Old 03-16-2013, 09:01 PM
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I recall a story Bob Engnath relayed about exploding belts. Of course the way he would grind was like an animal to hog the steel out. My memory is fuzzy since this was in the early 90's, I want to say he said it took him 3-4 minutes with the 36 or 60G belts to rough grind the bevels on both sides. He said it was like the 12ga going off.


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Old 03-17-2013, 09:06 AM
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John I Shore John I Shore is offline
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Quote:
Originally Posted by M&J View Post
How much tension do you guys put on the belt when mounting them up?:
I only use enough pressure to keep the belt tracking where I want it. I don't use a grinder that has those Barn Door Springs on it, they are Sh(&6=t in my opinion, the tension should be adjustable, the best setup is an air cylinder with an adjustable pressure valve. So it's not the pressure of the adjustment arm, it (in my case) was belt failure at the joint.

As I stated before, only had two do this in 30+ years of grinding. Putting pressure on the belt while grinding has not caused it for me. I usually take a bar of steel and turn it 14 shades of color when getting it ready for HT/profiling and that has had no effect on the belts.

John I.


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Old 03-17-2013, 08:46 PM
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TexasJack TexasJack is offline
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I got some 'bargain' belts once and they had a number of unique ways of failing. Stuck with quality belts after that lesson and never had a serious problem.


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