Rawlplugs

[Dave Plowman (News)]

What matters if numbered screws are Imperial sizes? They might be, but since they're yonks old it matters not. What can be easier than a 4 6 8 10

12 sequence rather than 3.0 3.5 etc etc? And a drill with the same number for the wallplug?

Convert? But you don't have to with woodscrews and their wallplug drills - it's been done for you. That's the *whole* point. Metrication has some good points but has thrown some of the best babies out with the bath water.

Perhaps it's because those continental cousins forced to use metric only for DIY can't work to a millimetre either - so why bother making it accurate? ;-)

[Christian McArdle]

Yes, I got a couple from France last time I was there, but have trodden on both of them now. I'm now using the Tesco cheapies until next summer! I'm particularly missing my decent Stanley 8m tape.

Christian.

[tinnews]

How is that different from diameters in mm for the screws and similar diameters in mm for the drills?

A no 8 drill and a no 8 plug and a no 8 screw or A 4mm drill and a 4mm plug and a 4mm screw

[Dave Plowman (News)]

Ah - obviously wearing metric glasses. ;-)

[Christian McArdle]

The fact is that the number on the screw isn't the same as the number on the drill bit, unless you manage to locate some imperial drill bits marked both in fractions of an inch and number.

Meanwhile, I can pick up a 5mm screw and I know I need a 5mm drill bit. No need for conversion tables on paper or in memory. I can also pick up a 200mm core bit and know it makes a 200mm hole. No need for a change in units when the size gets too big.

What size bit do I need for a "number 12" screw? Who knows? Who cares? I just buy metric, so I know it will fit.

Christian.

[Clive George]

Fair enough for non self-tappers. But woodscrews is a different matter. Eg the size of hole required varies from 0 (no pilot hole) up to big enough for a rawlplug, and isn't critical anyway. So the 6/8/10/whatever system works well.

cheers, clive

[Dave Plowman (News)]

Well, yes. I was moaning about metrication for the sake of it when it ends up with a worse system.

For what? Clearance? Pilot? Wallplug? Tapping a thread? For all these you'll need to do some sums. And you won't end up with conveniently sized metric drills like whole numbers or even those +0.5mm.

Of course you're changing units - singles, 10s 100s, etc. It doesn't take many brain cells to remember how many feet to an inch, etc.

Fit what?

You obviously don't remember or have used the old fibre Rawlplugs. A number 8 woodscrew needed a number 8 Rawlplug which needed a number 8 masonry drill. The rawlplug being parallel sided would go through the screw hole in the part to be fixed.

[Aidan Karley]

Measuring off the bottom ? Oh, you're a right hander, aren't you? Must be difficult.

[Frank Erskine]

Metric sizes aren't logical at all. To tighten an M6 nut do you use a

6mm spanner? No, it's 10mm (I think!). At least a spanner to fit a 1/4" BSW nut would be marked 1/4 BSW...

[Dave Plowman (News)]

Unfortunately my favourite, the unified threads, aren't that simple. ;-)