Bench grinders

Hi Folks,

Q1---  do diamond grinding wheels require a guard as per a stone wheel?

Q2--  any tricks to hold spindle when tightening nuts, there is nothing obvious 

          On the Spindle and holding one end nut whilst tightening the other just                undoes the held nut, I suspect there is a simple way but I'm too daft to                see it

Mick

Sorry these A's keep appearing, I have no control

Mick

Well, here's my take on this:

Q1 - Yes

Q2 - hold the wheel with your hand at the periphery. You can now do up the nut. Don't tighten it more than your hand resisting the force at the periphery of the wheel can resist, the nut mustn't be over tightened. The blotters will compress and stop the nut loosening in service, provide the wheel runs without vibration. It jolly well must, so the first action after mounting the wheel is to dress it true.

Actually, my thought is that Q1 is a lot deeper than this. The Abrasive Wheel Regulations say that an abrasive wheel cannot be run without an adequate guard under any circumstances, so one would argue that no guard can't be adequate. In reality we need to do a risk assessment and ask what guard is adequate for the foreseeable risks of running a diamond wheel. The same goes for CBN.

There are two obvious hazards, neither of which is that of the wheel bursting spontaneously or because of an undetected fault in its structure as is the most dangerous risk of a traditional stone wheel (dangerous as in worst consequences and entirely possible, therefore highest risk).. With a diamond wheel you've still got the hazard of a catastrophic dig in, and the shrapnel that could ensue. The second hazard with a diamond or CBN wheel is that of the hot metal particles cut off the work piece being expelled away from the wheel. The action of the guard should be to control where they go. Amongst other things you definitely don't want to see them reappear at the top of the wheel and be thrown off directly into your line of sight.

So my simplistic risk assessment seems to confirm that a guard is necessary. What is adequate? - well why not fit the guard that the manufacturer has provided and for which the CE certification is valid (!) There would be no defence under a prosecution for negligence (or worse) to say that the guard wasn't fitted because we thought we knew better than the manufacturer.

In a home work shop environment you take a chance with your own life if you want to. But invite the neighbours in and damage someone else, and the ensuing court case when your home insurance refuses to pay out against a claim for third party liability is going to make for some sleepless nights and serious aggro.

I was once in the same room as a grinding disc which exploded off the shaft of an air powered angle grinder. I'm very pleased to report that the bits went the opposite way to the three of us watching. It exploded because the chap who mounted it fitted a disc with an oversized centre hole, carefully doing up the centre nut so the disc was concentric but it wasn't adequately located. Predictably enough, as he pulled the trigger the wheel slipped, went eccentric and burst. My friend and I had already taken cover. The gent holding the tool got away scot free - but only because the grinder guard was in place.

Thanks Simon for your detailed reply, I have a white cup 4" at one end and fit diamond cups at the other, the supplied guards are awkward to fit around the cup so have made my own not sure if it is adequate,will take a pic

Mick

Perhaps I should add a guard to front, in mitigation I always wear a full face visor

Mick

Thanks for the picture, and of course any guard is better than none. But please please please bear in mind that most full face guards are not impact rated. If you do get hit full in the face a typical face guard won't be enough.

That gets us into another subject being the impact rating of eye protection, goggles etc. I don't feel competent to offer advice here, even though my risk assessment was incomplete without identifying remedial action and the effectiveness of those measures. I only did half the job!

Any one able to comment on how eye protection is rated?

Good luck! Simon

Fair comment will see if I can improve the guard. Will be interesting to see comments on impact ratings we,do put our faith in them

Mick

My initial worry in the photo is the distance between wheel and toolrest in the background. Now that is scary.

Never, ever use a grinding machine (or any workshop machine) without safety glasses. They are cheap and nowadays usually comfortable .

And as for having a machine thats not bolted down, thats another story. You will be telling me next, you hold the piece being ground in gloves. Ahhhhh

The toolrest is adjustable and can be slid nearer the wheel, it just happens to pulled back and would be advanced when grinding, it is just a mock up design for a more robust rest which I am making, thanks for your concern though,not sure about bolting down because it is to the bed which weighs about a hundredweight, anything else to criticise? Always keen to learn and I'm sure you have my welfare at heart

Mick

Simon, it seems to be based on the speed of the object hitting the lense.

http://www.seton.co.uk/how-to-choose-safety-glasses

 

I did a grinding course with SMEE and they INSIST on B rated eye protection.

Most safety glasses are F rated and are not suitable for grinding.

As an aside I thought that full face visors were mostly B rated or above.