Cut off wheel explosion

[benupton]

Hi,
Has any one else had this problem where a 100mm x 1mm cutting wheel is cutting and exploded sending chunks of blade everywhere? Only leaving what is under the nut left.
Thanks Ben

100 mm diam x 1 mm x 16 mm Flexovit Ultra-thin Inox Cutting Off Wheel | The Sandpaper Man This blade

[Gaza]

worse i had the 14in chop saw blade do it, dam shtt my pants

[BobL]

I have used many many (maybe hundreds) of those thin cut off wheels in a wide variety of ways and I do not recall one ever completely exploding. They are not designed to be used with ANY side pressure but invariably this happens even when you try hard for this not to happen. When side pressure has been applied some have snapped off at the arbor but the wheel itself has remain integral - they whizz around the arbor a few times and stop moving in a fraction of a second - pretty much a non-event really. They do not fly off like a friszbee decapitating everyone in the vicinity. Several times when pushing these wheels too hard up to cm size pieces of wheel have broken off at speed but this size piece of wheel has too low a mass to do much damage to skin. One piece hit me in the arm and it barely drew blood. The high air resistance to such a light mass slows it down very quickly so you need to be close up and personal.

Nevertheless I wear a full face shield and try to remember to wear buttoned up long sleeves when working with them. I normally wear thin leather gloves except when I am cutting tool steel and I like feel the temperature of the steel alongside the cut. If I am doing a lot of cutting I wear a leather apron but that is more to reduce the risk of setting my clothing on fire from the sparks than worrying about the wheel breaking up.

The same cannot be said for thicker cutoff or grinding wheels or chop saws.

About 6 months ago I bought a used metal band saw for $150 and even though it is slower I much prefer using it to any cut off wheels

[Chief Tiff]

G'day Ben,

Yeah, a bit scary when it happens eh? Personally I prefer it when they completely shatter into tiny pieces rather than breaking off big chunks and having to contend with a hugely out of balance machine. Now you know why it's important to have the guard fitted and adjusted properly, and use that side handle too!

Possible cause #1 cheap&nasty manufacture. Cutting and grinding wheels spin at ludicrously high speeds and have huge centrifugal forces acting on their edges, the cheaper brands can't always cut the mustard but if the wheel was a genuine Flexovit it shouldn't happen. Too often.

Possible cause #2 damaged disc. Discs can be damaged by dropping them or having things dropped on them, causing tiny cracks. Store them away from damp too. When you've finished using the tool, take the disc off. If you store the tool with the disc on it is possible to rest the tool on the disc which will cause the disc to warp slightly.

Possible cause #3 bad fitting. Check the fit of the disc on the spindle, it should be a slip on fit but with no slop. Check that the holding down nut is on the right way round too!

Possible cause #4 wrong disc. Check that the disc is appropriate for the material your cutting, using steel discs to cut ally or brass is a big no-no.

Possible cause #5 general ham-fistedness. Were you trying to force the wheel into a curve? The don't like that. Were you trying to cut thin material edge on? They don't like that. Did the tool bite and then shoot away from you? They don't like that. Were you trying to force the disc to cut quicker than it wanted too? They don't like that either.

Hopefully that little lot will help, and I suspect now you'll have a greater appreciation for your personal safety. When I see tradies using these machines one-handed with no guard or side handle and using the "safety squint" method of eye protection I almost wish they do come a cropper.

[benupton]

I was not using the grinder, it was being used on the roof where it was cutting off screw heads. When it shattered I through that the screw head went flying but it was a part of the blade.

[BobL]

. . . Store them away from damp too . . .

For most (some are designed to run under water) other grinding wheels I agree but in the case of 125 mm thin kerf wheels I have used dozens of them over the last 4 years in a small table table saw under a water drip feed to cut tool steel. Just running them for 30 seconds after cutting and they are bone dry.

Admittedly the TS is also only 2850 rpm but once these wheels are down to ~80 mm they are too small to use in the TS so they are then handed down to use on angle grinders.
Because they are smaller radius the side torques are less and these are far less likely to break from side pressure than new bigger ones.

[wheelinround]

9" grinder wheel many years ago

[Tools]

I was not using the grinder, it was being used on the roof where it was cutting off screw heads. When it shattered I through that the screw head went flying but it was a part of the blade.

Sounds like the blade was being flexed to do this.

Tools

[Grommett]

I just assume they will fly apart and wear ALL the safety gear. I have had larger wheels fracture and throw bits about and have not noticed till I turned it off and whoops, where dit that bit of disc go

[Jim Carroll]

I was not using the grinder, it was being used on the roof where it was cutting off screw heads. When it shattered I through that the screw head went flying but it was a part of the blade.

Just as my guess like others have indicated the blade has been flexed.

These are great disc for straight cuts but cutting the tops of roofing screws means you would have to flex the blade, not a good thing to do with these discs.

[Lumber Bunker]

yep.

[BobL]

these are great disc for straight cuts but cutting the tops of roofing screws means you would have to flex the blade, not a good thing to do with these discs.

+1

[Loco1960]

I have done the same, caused by a flexure of the disc cutting off bolts or screw heads. Like a hand grenade going off.

[Denim]

My uncle was using a 9" cut off wheel without a guard about 15 years ago. The disc exploded killing him instantly. Safety is always on my mind when using them.

Regards,

Denim