Tap for M3.5 Screws

Apr 28, 2022 Last reply: 4 years ago 44 Replies

I agree, those type do help a lot but it is still possible to cross thread them.

Another tip - if the back box was in the wall while the wall was being plastered it is possible that a little plaster ends up (partially) blocking the threaded hole in the back box lug. Clean out the hole by poking a nail into it and before trying to put a faceplate/socket/switch on try one of the screws in the back box lug. It can save a lot of hassle :)

Why are 99.9% of the M3.5 supplied with socket and switches slotted headed rather a cross head? I've only purchased one (no-name) brand with cross head screws.

Because electricians screwdrivers have always been "-" type.

You do sometimes see the odd cross head screw forced into one.

Some newer BT faceplates use "woodscrews" rather than machine screws, they're crosshead and just look wrong.

He cant help it.

The electrical size is M3.5. not M3. And the correct screws generally have raised heads and are chrome plated, or bright zinc. Commonly only two lengths - switch and socket. With long available for use over tiles, etc.

Because a slot head - neatly lined up to vertical - looks so much better than cross head.

Yes, sorry typo should be M3.5. I have just received an order of  25, 35,

40, 50, 60 and 75 mm lengths from eBay, 20 of each, that should help!

But where that used to be important for assembly they use nail guns these days

For a decorative screw, the drive on the head, barely has to work. The cheapness of the screw, is part of the equation.

But there are screws with better drive characteristics. The screwdriver doesn't slip out of these.

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I made a table yesterday, and those screws hold the flange that holds the leg to the table.

Paul

You're welcome to use a nail gun to fit your sockets if you wish.

I tighten them until they feel right but they rarely end up vertical.

You need a better feel.

Well, I cracked the nuts out of plastic boxes (just surface-mount, I think) a few times, so I'm cautious about over-torquing the screws.

Just back them off then. They're not like a terminal screw which needs to be tight.

Although I never use surface mount plastic. Flush metal box type have quite a bit of flex.

Robertson head, defacto standard in Canada.

Possibly it makes a big difference if you are trying to force half a km of wire into the back box or if the back box is barely deep enough for what you are trying to put into it. When I fit a back box into a wall I always select 35mm deep.

True.

TBH I don't think I've ever looked at a switch or socket and noticed the screw head orientation.

Those fixing screws generally have a raised head in a bright finish. To make them attractive as possible? If looks don't matter a plain CSK would be cheaper? And do the job perfectly?

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