How can these screws both have 4mm diameter?

[Homervanderjazz]

So one screw has the size 4x40mm and the other is 4x30 I assumed this meant that both diameters (thickness of screws) would be same and it's the lengths that are different. However, when I look at them side by side the 40mm seems a lot thicker. Please see pictures-how can there be this difference? Thanks for any help

 

[Doggit]

Measure them, and see which one is actually 4mm, as they certainly aren't 10mm difference in length. I'd say the one on the right is a 3x25, so it's either in the wrong box, or the box has been mislabelled. Had a grey door turn up in a box marked High Gloss White the other day - it happens.

 

[Homervanderjazz]

Here is the screw boxes

 

[Doggit]

So what are the measurements on a tape measure. It's possible that they are working from two different standards - odd though. I'd be inclined to trust Spax.

 

[Homervanderjazz]

No real idea how to measure it using tape for the diameter to be honest. Does the tape need to wrap around the screw? It's impossible to use this method to get an accurate reading. Any tips?

 

[Doggit]

Just hold the tape in front or behind the screw, and see how thick the internal shaft is, and then with the thread as well. It's possible that Spax measure across the central shank, and Turbodrive are measuring across the complete thread, although having done a quick Google search, it seems as though the measurement should be across the thread.

I think the trick in future will be to stick to the same make of screws for conformity.

 

[Homervanderjazz]

Mystery solved- spoke to my mate who is a joiner and who left the turbodrive screws at my bit. He says there are mixed screws in the box... thanks for your help though mate, thought was going mad there...

 

[lostinthelight]

No real idea how to measure it using tape for the diameter to be honest. Does the tape need to wrap around the screw? It's impossible to use this method to get an accurate reading. Any tips?

May be of use in the future? Either use an adjustable spanner as you would a set of calipers and measure gap or place the screw in the jaws of a drill chuck and tighten to sliding fit, remove screw and see the closest size drill bit that will slide in.....
litl

 

[Homervanderjazz]

May be of use in the future? Either use an adjustable spanner as you would a set of calipers and measure gap or place the screw in the jaws of a drill chuck and tighten to sliding fit, remove screw and see the closest size drill bit that will slide in.....
litl

Thanks mate, will defo be useful in the future!

 

[big-all]

not a hard and fast rule but the head will be roughly twice the screw size so an 8mm head will be around a 4mm screw

 

[rsgaz]

It's impossible to use this method to get an accurate reading. Any tips?

If you've got a lot of drilling/screwing/DIY etc to do then treat yourself to some digital calipers...

http://www.ebay.co.uk/itm/222129314930

There are cheaper ones out there, but they don't come with a case, are plastic instead of steel and you really want one with the thumbwheel. You'll find that you use them SO much and come in handy for SO many things. You no longer need to guess what size pilot drill you want, you can just measure it. You no longer need to try various size spanners/sockets in metric/imperial until you guess the right one to fit a nut, you can just measure it. You can identify bolt sizes and whether they are metric/imperial (be aware metric threads under-read because the tops of the threads are flattened off, so an M6 bolt will read approx 5.88mm for example).

You'll wonder how you ever managed without one!

Gaz

 

[maltaron]

Pity we cant go back to the old imperial sizes. A No.4 was the same in all makes, as was a 6:8:10:12:14 etc and even No.7 to fit 3" butt hinges.

 

[Tigercubrider]

I have a stainless vernier, it' s great and does metric plus imperial as a decimal or fraction