Micron Belt break - Looking for experienced feedback

LifeBlade.net

LifeBlade.net

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Mar 18, 2010
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Hello all and happy Friday,

I was just attempting to put the finishing touches on my first attempt at a full convex grind blade before sending off for HT and the belt snapped on me (just a friendly reminder, ALWAYS wear your full face shield, even when you're "just touching something up". I wasn't and while it didn't hurt like I'm sure a Y weight Blaze would, it smarted pretty good).

I was slack grinding about midway between the platen and the idler pulley on a Coote, wasn't at all "leaning into the grind" (just touching up some grind lines). The cutting edge of the blade is still as thick as a dime and was trailing, so I didn't catch an edge and I had only made 3 passes on this side, so no heat build up to speak of. The observant will also note that it didn't turn loose at the joint, it appears to have simply "ruptured", for lack of a better word.

I'm stymied and wanted to see if any of you more seasoned fellers might be able to tell me what I did wrong so I don't repeat this incident. Any and all feedback would be most welcome!

Thanks in advance,

Taylor
 

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If your belt snaps, it should just fall limp not bite you..... what's up with that?

Are you grinding with the blade forward... I mean, are you grinding into the edge or away, like a strop?

Edit to add*******

I just noticed the pic with belt and grinding guard on the blade.... are you grinding with that on? If so, I think the edge of the belt caught a hold of that. The belt looks like it was torn from the edge. I would not grind with the guard on.



Rick
 
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I have had a couple of those "explode" on me also. As always, when a belt explodes, I have to stop work and see if all my parts are still attached. Then, if I still have all my fingers, eyes, etc., I have to go and change my drawers.

They are so thin, and even though you might think you are putting niece even pressure on them, just blink your eye once, and "KABOOM", the world seems to end.

You can glue a piece of leather on your platen and run it SLOW. This will help, but no guarantees. Did I say run it SLOW ?

Robert
 
Hi guys,

Thanks for the quick replies.

Rick, when I wrote "the edge was trailing", I was trying to describe that the edge was at the tail end of the grind, or like you asked, the way you would strop a blade.

I think the reason it bit me, was that I installed a DPDT switch on my motor and was grinding in reverse (the belt was traveling upwards) so I could monitor my edge thickness. When it broke the portion of the belt that was still in contact with the drive wheel and the tool rest had enough friction to be thrown up into my face. Scared me more than it hurt.

Carl, I think you and Rick both have solved the mystery for me. I think you're right. That film that the Micron belts are made of just aren't made to resist the edge of my plunge line guide.

Here's the reason I have it in place. With flat grind, after I've established the plunge with a 36 grit Blaze, I take it off and use the plunge I've established as the guide from that point on.

Being that this is my first attempt at a full convex grind, I'm having trouble keeping the plunge line square and straight, thus the guide being in place.

Anyone have any hints or suggestions for keeping your plunge line straight when full convexing a blade?

Thanks again guys,

Taylor

EDIT: Man talk about a bunch of stand up Gentlemen! I couldn't even reply to Rick and Carl before you added your input Robert. I've said it before and I'll say it again, this forum is outstanding.

Robert, I hear you loud and clear. I was running it at my slowest setting on a ceramic platen and REEEEALLY going easy on the pressure. I think the culprit is the sharp edge of the hardened guide. The corners are pretty sharp and I feel like an idiot for not recognizing that right off.

Guess I was still too busy "changing my drawers":D You got that part right. Nothing like being extremely focused on minute details when a belt turns loose!
 
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Rick Marchand said:
If your belt snaps, it should just fall limp not bite you..... what's up with that?

Are you grinding with the blade forward... I mean, are you grinding into the edge or away, like a strop?

Edit to add*******

I just noticed the pic with belt and grinding guard on the blade.... are you grinding with that on? If so, I think the edge of the belt caught a hold of that. The belt looks like it was torn from the edge. I would not grind with the guard on.



Rick
Click to expand...

Rick, i thought that when a belt snaps it is normally violent and hits the user, because it is travelling fast the momentum and elastic recoil whips it out. I caught a tape on a 80 grit norton about to rupture this week, very glad it did not let go and hit me before i got the machine stopped.
 
ernestrome said:
Rick, i thought that when a belt snaps it is normally violent and hits the user, because it is travelling fast the momentum and elastic recoil whips it out. I caught a tape on a 80 grit norton about to rupture this week, very glad it did not let go and hit me before i got the machine stopped.
Click to expand...

I can only speak from my experience. I have had 2 belts break on me. The first was a 240grit and it literally just went limp. The second was a 38grit... Although it really didn't snap completely apart, it popped the piece out of my hand but ran off the side rather uneventfully. The tear was 3/4 of the belt width. I use a Grizzly grinder. It only has two wheels and no guards, aside from one small one at the top wheel.

Upon searching the internet, I have now seen that torn belts can be very dangerous at times. I also noticed that most of the violent incidents happened on "KMG" 3+ wheel types... some with guards. I wonder if that has something to do with it?

Rick
 
A breaking belt can and will hurt you if your not careful. I have been fortunate enough to escape about 30 breaking belts. Some have slapped me silly and some have not. Many times the tape lets go in the middle of the splice and I can feel a bump against the flat platten and a strange noise. If this happens I turn off grinder and inspect the splice. Many times if the splice starts to let go on the right side or the left side of the belt and it will start to track irregularly, because the belt is tight on one side and looser on the other. I again immediately turn off grinder and inspect the splice. I also never have my head directly in front of a belt, I am always slightly off to the right or left so that my shoulder gets the slap and not my face. I also always wear a hat to help lessen a impact if i get one. I guess I have been lucky up to date but when a belt lets go it is possible for it to come off the drive wheel and with momentum go up torwards the ceiling and then hammer its way down onto your head/face/shoulder etc.
But many times it is a non-frightening affair also.
Chris
 
I should have never read this thread....

I feel like a Looney Tunes character who's hovering off the edge of the cliff bececause nobody has told him about gravity, yet.
 
I have had a few break over the years. Usually there is a warning when the seam starts separating making it bump. I stop the machine and if the belt has some life I cut it up for hand sanding. When they break while in use they usually just go 'pop' and drops dead. Nothing too startling.
 
first belt i ever broke was a 220 grit gator belt, sounded like an m-80 going off in my face. i understand the changing drawers. luckily it just flopped down to the ground.

the micron belts look like they're awfully susceptible to heat, with the thin plastic backing. i have a couple and haven't had them break but i've been really careful not to put any thermal load on them, especially on the edges. i mention this because it kind of looks like one of the sides has shrunk a bit, like hs tubing, maybe that was a contributing factor?

glad you're ok, and the face shield is something i might have to pick up hah!
 
In my experiance the cheaper belts break more often. I think I have broken a blaze belt but can remember several of the belts that only cost a buck or two break on me. I still like to use the cheap belts on wood though.
 
nobody has asked this yet . You were running your machine in reverse , was your belt directional ??
 
Make this a habit; move your face to the side when starting any grinding machine. You will retire with a lot less scar tissue on your face.

The fine micron belts I am familiar with tend to become brittle as they age and get used. The brittleness is found mostly along the edges of the belt.

Fred
 
Fred.Rowe said:
Make this a habit; move your face to the side when starting any grinding machine. You will retire with a lot less scar tissue on your face.
Fred is Right on.
Make this a practice weather you start a belt grinder a bench grinder a lathe or any machine with motion. Keep your self out of initial line of fire.
Click to expand...
 
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Fred.Rowe said:
Make this a habit; move your face to the side when starting any grinding machine. You will retire with a lot less scar tissue on your face.

The fine micron belts I am familiar with tend to become brittle as they age and get used. The brittleness is found mostly along the edges of the belt.

Fred
Click to expand...

I do this routinely to avoid the puff of dust that comes with startup.
 
Bufford said:
I do this routinely to avoid the puff of dust that comes with startup.
Click to expand...

I had an new 80 grit trizact belt that moved sideways, on start up and catch the edge on a piece of metal along the side of the grinder. It smacked me across the face from forehead to nose across my left eye.
Thats all it took for me.

Fred
 
Fred do you use a Wilton square wheel 2 X 72, because mine does that on start up too? Over the years the belts have worn down alot of metal on the sides of the machine.

To reduce this effect I start up the machine at a slower speed with the variable speed control, and it helps save the belts from getting damaged on their edges.
 
ONeill said:
nobody has asked this yet . You were running your machine in reverse , was your belt directional ??
Click to expand...

Hi Jack,

Thanks for taking the time to make such a great observation.

I don't know whether the 3M 100 Micron belts are directional or not (there's no marking indicating such).

I do, however, always try to remember to run my belts, regardless of whether they've got a directional indicator on them, in the same direction that I ran them the first time I mounted them on my grinder. I don't know if this matters, but I've found that they seem to track better if I do. What I do is mount the belt with the label reading "left to right" from bottom up, if that makes sense.

When I reverse the direction, I'll flip it around, so in effect, it's running exactly 180.

Correct me if I'm wrong, but I believe most directional belts are "lapped" at the joint rather than butted and have to be run that way so you're not peeling the joint back every time it hits your work.

Thanks again for chiming in and asking "the question not asked",

Taylor
 
Fred.Rowe said:
Make this a habit; move your face to the side when starting any grinding machine. You will retire with a lot less scar tissue on your face.

The fine micron belts I am familiar with tend to become brittle as they age and get used. The brittleness is found mostly along the edges of the belt.

Fred
Click to expand...

Howdy Fred,

The belt I was using was brand new, along with it's user; I've never ground with the things. I made this post hoping someone could tell me what I'd done wrong, so that I could use them in the future without the fear of breathing on them wrong.:D

Yeah, I'll never forget watching Harvey Dean's "Flat Grinding Blades" video and how he discussed the importance of standing clear of anything when you spin it up. Stuck with me from day one and actually saved me from eating a cheap Harbor Freight angle grinder cut-off wheel one day (Side note to anyone interested: DO NOT BOTHER WITH HF CUTOFF WHEELS; THEY'RE A CHEAP FORM OF SELF MUTILATION).

BTW, you may have recognized that guide in the picture I included at the beginning of this thread.;) It, along with your bubble guide jig, have really come in handy. I truly appreciate it!

Taylor
 
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