Rank: Forum user 
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In discussion with the supervisor of a machine shop at a remote site whilst reviewing risk assessments, I have run into an impasse.
There are a number of grinding machines, mostly of a significant vintage, but reasonably well guarded. The person in control of the workshop considers it reasonable to leave grinding wheels turning under power whilst changing work pieces (universal and vertical grinders). He states: -
"On a batch of 10 shafts I load them in about 80 times.
Grinding wheels are always left running because they will need to be dressed each time the wheel is started.
Some companies leave them running 24hrs a day to keep the size; this is to save time getting the machine up to temperature."
I am struggling to accept these statements based on Reg 11 of PUWER "preventing contact with dangerous parts of machinery" as I see the rotating grinding wheel as such a part and the operator comes into close proximity whilst loading the work pieces onto the machine.
I am of the opinion that this has simply become custom and practice and would welcome the views of those of you who mange issues in this type of environment.
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Rank: Super forum user
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I am a fitter by trade and in the distant past was an abrasive wheels instructor.
I would have to concur with your conclusion that its custom & practise. Grinding wheels do not need dressed every time they are started, only when the stone becomes worn. Temperature has nothing to do with either the efficiency of the motor or the grinding surface.
You need to be very particular as the requirements under PUWER are rigorous and your assessment of Reg 11 is correct.
In any machine shop I have worked, and supervised grinders where never left running.
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Rank: Forum user
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Thanks Jonty.
You confirm my thoughts on the matter.
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Rank: Forum user
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If only life was as straight forward as on/off, black/white.
There is a huge difference between the operating requirements of a precision universal grinding machine and, say, a bench or pedestal grinder. The pedestal grinder should alwys be switched of when not in use, but a precision machine needs to maintain speed, temperature, balance and is frequently dressed in order to achieve the required surface finish. The safe operation of such machines is vital and can be achieved by a range of measures such as keeping the wheel at a safe distance from the workpiece while changing it, automatic guarding arrangements when the wheel is retracted, operater skill and training, etc.
Hope this helps.
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Rank: Super forum user 
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Jonty,
Whilst you may well be correct with as Alistair suggests off hand or pedestal grinders, this is not quite so with all grinders.
Think of it this way.
You drive your car around, you stop the engine before getting out. Pedestal grinder.
The bus driver drives around on his route, he does not stop the engine to allow passengers on and off the bus.
As Alistair suggests, some precision grinding machines, especially those with hydrodynamic spindle bearings should really be left running.
Adams, you really need to look deeper than this for a solution.
Production precision grinding machines are designed to be left running.
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Rank: Forum user
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Thanks for the views guys.
Looking Deeper!
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