Rock-Ola Newbie Attemping to Refurbish

Hi
Ron, yes the imperial would be the same as the American SAE sizes using the older historic type measurements
I took a look at the amp I have and a 4.5mm head takes it off, other times I have used pliers to take it off, maybe a little WD40 to help it on its way and I wouldn't undo the shield
clones

Hi Mike,
I shouldda answered this better, earlier--
Do NOT remove the shied from the tone arm--it is wrapped around the audio wires, which if disturbed, will cause tracking problems later.
If you are un-able to remove that screw, you may cut the shield, leaving enough room on both sides of the cut, to solder it back together later, when the amp is returned. Ron Rich