How to measure a screw

TobyGilliam534

Quite new to all this so this is probably quite a dumb question..

I have to put up a little bracket to hold a small three step stepladder. It's going in a masonry wall. I did it once before using screws that were about 2cm long and I I think they were too short, the thing just came off the wall after a while.

So I'm going to try again with some longer screws of about 6cm long.

However I'm a bit confused about the diameter.

I've got the widest screws I can which fit through the holes, and the diameter of the shank is 3mm which I understand is a 4 gauge. This is how I understand you measure a screw from what I've found online.

But I can't believe these screws are that gauge - this would mean using a yellow wall plug and the screw doesn't even vaguely fit into that size of plug. Also it's usually the lowest one on any chart of sizes and this screw is comparatively chunky.

Am I measuring the screw in the right way? If not how should I?

ariba10

You need a suitable screw to take the weight of whatever you are going to hang.

You need a plug to suit the screw.

You need a drill bit to drill a hole to suit the plug.

--Get to a D I Y shop or outlet and ask them for advice.--

TobyGilliam534

I'm pretty comfortable with how to match the screw size, wall plug and drill bit size.

As I say I'm just not sure how you measure what gauge a screw is if it's in your hand. I did get them from a DIY place yesterday and they told me they were 5mm screws, but I just can't see how they could be, unless you were measuring across the thread.

Maybe that's the answer - it's just odd as everything I've read says that you should measure the shank.

anotherbaldrick

Look at the packets of wall plugs, each will tell you on the box or packet the size of drill to give you a hole to suit.

TobyGilliam534

OK - I guess that's a good way of doing it .

One question about the holes - when measuring a screw with the hole, are you supposed to be able to get the whole thread of the screw comfortably through the hole? I.e. does the diameter of the hole reference the diameter of the inner shank or the width of the whole thread of the screw?

getmore4less

Google screw size table

The important thing is matching the load

If any lateral (pull) you need the right grip in the wall

Norman_Castle

A 5mm screw measures 5mm on the outside of the thread. Its a 10 gauge in old sizes.

TobyGilliam534

@Norman - thank you! I searched for a good half an hour and couldn't for the life of me find that one sentence - that solves my problem completely.

@getmoreforless - I did do that and do have screw size tables, but nothing actually tells you how to measure the screw!

paddyrg

Also, if you snip the heads off matchsticks they can help pack and adapt what you've done.

southcoastrgi

2"x10, brown raw plugs, 7mm masonary bit

wallbash

Red use size 8 and a 6mm drill

Buy rawplugs, yellow/ blue/ Lots of red / Brown
The section that holds the plugs together comes with the gauge and all the info required.