I supose it depends if a screwdriver is a tool that is available to the operator using the machine -
i.e do they use screwdrivers in that area as part of their job (readily available) or will they need to go fetch one from an engineer to overide the interlock?

You could always use hex screws or another odd shaped head to deter this action even further.

But to give my opinion, using just screws is cutting it a bit fine, even if screwdrivers are not readily available in the area - I'd choose another type of fixing, just to further reduce any potential possibility / liability.

If a member of staff did overide an interlock with a tool from his work bench, your defences may be limited, as under the PUWER regs the liability to prevent access is absolute (PUWER 11.1 Every employer shall ensure....)

I would expect it more likely they would tape over the switch than try to remove it.

I'm sure this subject was discussed on my diploma course and that the outcome was that the fixings should not be easily removed using normal easily accessible everyday tooling.

Problem is I have a small cheap tool set in the back of my car that has a screw driver with interchangeable bits (which includes torque and hex type bits). Extract From the HSE report below indicates people may be assisted by their managers or perhaps instructed by same to overcome such devices ( and gather necessary tools at back of desk to do so). Those who have been in engineering will now what I mean ( they were once the maintenance guy etc). There are special fixings which are one way or have snap off heads, so the only way to remove would be grind or drill, as these devices should not normally need to be removed once fitted.


From HSE report RR974 dated 2013

Common activities associated with defeating were setting, proving, swarf removal and deburring . Semi-CNC machines were identified as being commonly defeated in the sample used in this research. Managers and operatives/supervisors perceived this practice to be the ‘norm’.


Chris

Sometimes you need guarding for the routine stuff but need to be able to acess for maintenance (by designated, competent staff) What do you do then?

You need to tghoroughly consider why somebody would want to defeat the interlock.
Does the are need regular cleaning; resetting; unjambing etc. I spent 17 years in the aggregate industry and employees were extremely innovative in creating tools they could use with guards in place to remove spillage (dust, stones). The business incorrectly made the guards bigger, stronger and heavier to both contain the spillage and stop access.
The secret is to remove the need to bypass the guarding on a regular basis.

I would risk assessed the operation with the gaurd removed. Include the control measures in the permit to work. Have the engineer sign off the PTW once the gaurd is re-instated. It is better to allow the operation to happen in a controlled manner than to find out that it was done off the radar or out of hours.