Model Engine Maker
Supporting => Tooling & Machines => Topic started by: arnoldb on August 01, 2014, 03:16:17 PM
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I make a point of regularly inspecting the grinding wheels on my bench grinder. Today I came across something unexpected and thought I'd share with you.
I noticed what looked like a ding on the rim of the one wheel. I know that I didn't ding the wheel and nobody else was in my shop unsupervised, so this warranted a closer inspection before simply dressing down the wheel:
(http://www.nam-engineering.com/cm/albums/userpics/10004/normal_IMG_6150.JPG)
Examining the side of the wheel, I noticed a "defect" mark running through the wheel and joining up to the ding on the rim - in the photo it's visible just above the black line I'd drawn in:
(http://www.nam-engineering.com/cm/albums/userpics/10004/normal_IMG_6151a.JPG)
That means the wheel is now potentially very dangerous, and it got removed immediately and whacked with a hammer to break it in two before heading into the trash:
(http://www.nam-engineering.com/cm/albums/userpics/10004/normal_IMG_6155.JPG)
There's a fair amount of dumpster diving happening in Namibia, and I wasn't prepared to let someone find that wheel and try to re-use it...
I got a new high quality grinding wheel from a reputable supplier, together with the required and certified bushes to mount it to my grinder:
(http://www.nam-engineering.com/cm/albums/userpics/10004/normal_IMG_6152.JPG)
According to the supplier this wheel is just the thing for grinding HSS, and is certified for side-grinding too, which will be extremely useful.
That was mounted on the grinder, and let run for two minutes, before stopping the grinder and doing a thorough inspection. That passed fine, so it got a proper dressing-down:
(http://www.nam-engineering.com/cm/albums/userpics/10004/normal_IMG_6154.JPG)
Now that's ready for some more toolbit grinding.
Kind regards, Arnold
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A good reminder Arnold, and something we should all do far more often I suspect. The other key thing in your post is buying from a "reputable" manufacturer. Even that won't guarantee 100% reliability, but as we all know, with the lax quality control of importers, grinding wheels are not a wise place to save money...the potential consequences are just too great! Thanks for the post...good catch by the way!!
Bill
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Well spotted Arnold - that could have proved very nasty indeed.
We have a well known local (Norfolk / Suffolk UK) accident story that used to be used as an example on grinding wheel mounting courses .....
A guy had in his home workshop a wheel on a plummer block type spindle driven by belt from a remote motor - no guard was fitted - at some point the wheel shatters and a lump of it tears into his arm severing an artery - he did not survive dying, I think I'm correct, at the scene
Some years ago I sold a Clarkson T/C grinder and prepared paperwork relevant to fitting guards as sold. When I gave it to the buyer he gave a wry smile and explained who he was - he turned out to be none other than the very Doctor who had attended the scene and death of the victim above.
The sting in the tale was that the victim was allegedly employed as a grinder and was well versed with grinding wheel dangers and safety requirements ::).
As a matter of interest (apologies for any egg sucking ;)) are you familiar with 'ringing' a wheel? Holding it on one finger through the mounting hole and tapping it gently with the handle of a hammer it will produce a bell like 'ring' - the slightest crack in the wheel and it will sound quite dull and should never be fitted.
Changing and mounting of grinding wheels was at one time something that occurred frequently and regularly throughout the day, everyday - a wheel was always rung before fitting to the mandrel no matter how many times it was changed.
Regards - Ramon
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So, Arnold, did you ever puzzle out how the wheel was damaged in the first place? Looks like a fair blow from something.
Has Shrek been sneaking into the shop and using your tools to sharpen his beak?
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Did you do a ring test to hear what a bad wheel sounds like?
Greg
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Thanks for checking in all.
I did "ring" the old and new wheels. The old one still produced a slight ring, but with that flaw in it I was not going to take chances. The new one had a nice "tinnnngggg" to it.
Marv, the mark was caused by the flaw in the wheel; it appears the abrasive compound was "soft" in the flaw area; I could scratch it out with a fingernail.
Shrek doesn't need to get to the shop to sharpen his beak; he's got his own nail file - actually a small flat needle file - lying around the living room. He likes to play with that, and it seems to keep his beak rather blunt compared to other African Greys. He does sharpen his toenails to needle tips though. Quite ingenious; he takes a bath, and then sharpens the nails with his beak. Then I have to file the needle tips off with the file to prevent lots of tiny holes in my hands, arms and shoulders...
I'll soon be ringing a lot more wheels; priority #1 right now in the shop is to get my tool & cutter grinder in operation.
Kind regards, Arnold
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Good job on avoiding something that could just ruin your day. Now, on the Shrek subject, to quote Jimmy Buffet; " Have you sat him on your shoulder and opened up your trusty old mind, have you taught him how to fuss, taught how to cuss, and pull the cork out of a bottle of wine". Hey, I am a Parrot Head.
Whiskey
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:) :) :) :ThumbsUp: Good comment Eric
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Good advice, always useful to be reminded of such dangers.
I notice that the label on the old wheel clearly shows "The Peoples Republic of China". I don't think I've seen that anywhere else, in those words. Usually it just says "China" or "Made in China". How old was that wheel? And did it break along that "fault line".
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Good observation :ThumbsUp: I've always done the ring test on any wheel I changed over the years, plus if it was a floor mounted grinder - balanced it as well
George
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Once I got the Kalamazoo 1x42 belt sander and laid in an assortment of Trizact belts, the grinder has seen virtually no use. It seems that the Trizact belts cut HSS much faster and flat.
I've put a glass pressure plate on the Kalamazoo (I was a bit concerned about this but Chuck Fellowes assured me his was fine.)
Just my way of grinding HSS bits.