Safety device...

Overmountain

Overmountain

Joined
May 2, 2013
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Richard J has a shop safety tips thread below, but its locked... I had an idea though, and may try it on this new grinder build.

Has anyone tried connecting a pressure or other type of switch to the tensioner of their grinder, hence acting as a kill switch when a belt lets go? I have had a belt do a split and parial shear, leaving a nice 3 foot or so whip flying around....

I know foot switches are common, but I move my body, not my arms when I grind. That means I take steps and a foot switch would be more of a pain than a benefit.

Thoughts? Any examples?
 
LucyCustomKnives said:
Richard J has a shop safety tips thread below, but its locked... I had an idea though, and may try it on this new grinder build.

Has anyone tried connecting a pressure or other type of switch to the tensioner of their grinder, hence acting as a kill switch when a belt lets go? I have had a belt do a split and parial shear, leaving a nice 3 foot or so whip flying around....

I know foot switches are common, but I move my body, not my arms when I grind. That means I take steps and a foot switch would be more of a pain than a benefit.

Thoughts? Any examples?
Click to expand...

I don' think that is fast enough.


Bader sells enclosures for their grinders, they just sit over it.

You can copy that.
 
I saw a device that was simply two poly wheels that the belt ran through above the platen. Supposedly keeps the belt from whipping.

Count- I think that's what I will do. Simplest fix, or precautionary measure. Just was curious if a sort of 'dead man' switch would work. But in the instance of a split belt I don't guess it would release as the belt still has tension...
 
If the belt is still partially whole, the pressure switch would not actuate.

I can't remember who did it, but I saw a photo of a bar of steel with a semi-sharp edge on it ( facing backward) mounted rigidly above the idler wheel. It would shear off or catch any belt that broke before it could come around and get you.

No ones reaction time is faster than a broken belt, so foot switches or any sort of dead-man would not work. Using new belts, and storing them properly is the best prevention. Safety glasses or a face shield is also just plain good sense. While an exploding belt may make you need to change underwear, it rarely does much harm.
 
I had a "puckered up" experience, had a 400 grit Trizact belt on my 2x42 ans was using a gator belt cleaner, well I applied too much pressure and POP! the belt exploded on me, scared the living kaaaa-rap outta me. No harm done to me except for my underwear
 
They now make a setup that will stop a table saw blade so fast it won't cut your finger so anything is possible.
 
anyone that has a safety tip can send it to me and i'll add it to the list if it is a good tip. (i locked the thread to keep it from being cluttered up)
 
mccandmatt said:
I had a "puckered up" experience, had a 400 grit Trizact belt on my 2x42 ans was using a gator belt cleaner, well I applied too much pressure and POP! the belt exploded on me, scared the living kaaaa-rap outta me. No harm done to me except for my underwear
Click to expand...
i put up plastic to try and keep the dust maintained where i sharpen and one day when grinding i had a belt start to come apart so i moved to the side. the belt came loose and the end shot right through the heavy plastic which was 2+' away :eek:. you can usually tell when a belt is getting ready to go, you will see it start to snake side to side before it breaks (if you are lucky :D)
 
i just thought of a safety switch that woud be easy to make that would turn off a grinder if a belt partially breaks. i'll have to try and draw up some plans when i feel like drawing.
 
My concern isn't so much a belt going ballistic, that seems to just give you a startle. But, my reaction is broken, so I don't jump... much. With the face mask, apron, long sleeves, not really a worry.
My concern was this, I had a partial split once with a long tail that was whipping about. I know its rare and probably more related to what I was doing at the time, but that tail was whipping like a mad ninja daring me to stop the grinder without getting whacked...
But yeah, like I said above a pressure switch wouldn't work in that instance anyway.
Thanks Richard. I figured that was why you locked it. I know how those threads can get...
 
SteelSlaver said:
They now make a setup that will stop a table saw blade so fast it won't cut your finger so anything is possible.
Click to expand...

That's right. It stops instantly when a finger actually touches the blade itself. Can't remember exactly how it works, but it's neat technology, so neat that the guy who invented it had trouble with the big manufacturers of some sort.

I had a belt (60 grit zirc) pop the other day. I was wearing ppe, but it was indeed frightening. Also had a belt split and whip but that made me mad more than anything. Cut the tail off with the knife I was grinding.

We have laser bars (curtains) at work. They e-stop the machines when you break the beam. I'm sure you could program it to stop when you step back and a tail wouldn't be enough to trigger the curtain if you set the sensitivity correctly. Not sure how much they cost though.
 
what i have in mind would work no matter how much of the belt would stick up. i need to try to draw this up today before i forget. all it will take is 2 pieces of stiff rod or wire and a regular 110 light switch. if someone has cad, i'll send them a picture of the drawing and they can make it look good.
 
Stopping the motor won't stop the broken belt from continuing its flight path. You need to stop the belt. The motor can spin all it wants to without any problem. Partial shearing as the OP mentioned are pretty uncommon in my experience. Even if some sort of switch disconnected the power to the motor immediately upon the belt partially shearing, the grinder would freewheel for several whacks of the belt.

The saw stop systems use a fast acting switching circuit to detect a path of conduction between the saw blade and the user. If this path closes, the circuit actuates a VERY fast and hard solenoid that locks the motor shaft. With the torque of the high sped motor turning a 10-12" saw blade, this isn't exactly good for the saw, but it is good for your finger.



Just a bit of engineering info:
To make a disconnect safety switch, the pressure switch would need to be in a control circuit with low current draw. It could no be directly in the motor circuit. A control circuit uses low current and usually low voltage to control a much higher ( and more dangerous) voltage/current.

The SSR foot switch I designed a few years back is a good example of a control circuit. It can run on a 9V battery if you want, but an old charger transformer will work perfect.
http://www.bladeforums.com/forums/s...-footswitch-see-posts-10-13-14-19-29-45-51-52
Those who have built one say it works really well. It is nice to have both hands in place when starting a belt grinder, disc grinder, drill press, etc.
 
Strigamort said:
That's right. It stops instantly when a finger actually touches the blade itself. Can't remember exactly how it works, but it's neat technology, so neat that the guy who invented it had trouble with the big manufacturers of some sort.

I had a belt (60 grit zirc) pop the other day. I was wearing ppe, but it was indeed frightening. Also had a belt split and whip but that made me mad more than anything. Cut the tail off with the knife I was grinding.

We have laser bars (curtains) at work. They e-stop the machines when you break the beam. I'm sure you could program it to stop when you step back and a tail wouldn't be enough to trigger the curtain if you set the sensitivity correctly. Not sure how much they cost though.
Click to expand...

We have those laser light curtains as well, and they work great for the most part, but they go out pretty often and need replacement, I don't know the cost , but I know they aren't cheap at all. They are pretty much idiot proof though we have 4 of them per station 2 at the bottom about 2 inches off the floor and 2 sideways blocking the entrance, the only way you can mess up is if your too far in the station and you do something to get your feet off the ground, and I've seen some bad situations due to that, however they can be programmed at my job , to do certain things again not cheap at all , so I dont know if they would be a good investment for a small shop, I work in metal fabrication so those light curtains are a must have, FWIW I've been popped with some 80 grit belts a couple of times, nothing major , It will scare the crap out of you and the times I have been hit with the belt it just felt like a light slap...Anything is possible, We have auto mig robots and the jig you sit the metal in to be welded is ful of sensors , as well the robot has a few as well, If the temp gets off on the automig, It will shut down before it blows through the metal, off topic I know, but just showing anything is possible, I have also seen say blades that will cut through metal, but won't cut flesh, I didn't believe it and I wasn't going to be the crash test dummy to try it out but my superiors swear it's true...
 
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I have actually used relay incorporating flashlight switches for high current apps that draw only .03v... I could do wonders with a 9v... lol.

I have only ever had the one belt split. A broken belt just gets that one good swing at you and lays down... like a paid off prize fighter. I split it grinding vertically against the spine of a clip point and when i got to the tip it dug in. Belt was pretty much toast anyway.

And yes, you can kinda see when one is about to go. Well, I can't cause I'm grinderless again for the moment, but will again soon enough.

I may incorporate a foot switch with a bypass on this one. Foot switch when I'm stationary, bypass when I'm not...

Cheers. Surprised this thread generated so much feedback. Thanks. And Richard, if your new design gets you some moolah, I'm gonna have to ask for a kickback of some sort... lol.
 
I welded 3 bolts to my grinder after my first belt broke , hopefully one will catch the belt if it breaks again??

013.jpg
 
Allen R. said:
We have those laser light curtains as well, and they work great for the most part, but they go out pretty often and need replacement, I don't know the cost , but I know they aren't cheap at all. They are pretty much idiot proof though we have 4 of them per station 2 at the bottom about 2 inches off the floor and 2 sideways blocking the entrance, the only way you can mess up is if your too far in the station and you do something to get your feet off the ground, and I've seen some bad situations due to that, however they can be programmed at my job , to do certain things again not cheap at all , so I dont know if they would be a good investment for a small shop, I work in metal fabrication so those light curtains are a must have, FWIW I've been popped with some 80 grit belts a couple of times, nothing major , It will scare the crap out of you and the times I have been hit with the belt it just felt like a light slap...Anything is possible, We have auto mig robots and the jig you sit the metal in to be welded is ful of sensors , as well the robot has a few as well, If the temp gets off on the automig, It will shut down before it blows through the metal, off topic I know, but just showing anything is possible, I have also seen say blades that will cut through metal, but won't cut flesh, I didn't believe it and I wasn't going to be the crash test dummy to try it out but my superiors swear it's true...
Click to expand...

We've only had ours for a couple of years. Haven't had many problems, and nothing that I couldn't fix. Only thing is, they are controlled by PLC. I imagine they sell a controller, but yeah, probably cost prohibitive.
 
You can usually buy surplus light curtains and controllers cheaply from sellers like HGR ( ebay) and other surplus sellers. I have played with them, and found them not really suited for knife work in a small shop. About the only use I found was turning on the work light on a tool area when you stepped up to the tool. A proximity detector did that equally well and enormously easier.
 
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