Screw size..?

[bobsammers]

Hi,

I'm trying to replace a set of wood screws (old ones gone rusty) from my front door handle. I can't work out what size they are! Can anyone offer advice?

The main problem is the gauge - there's no shank to measure. Shaft diameters according to my cheap callipers:

• without thread:~2.3mm
  with thread: ~3.5mm

I'm guessing these are no 4 screws, based on the non-existent shaft being between the inner and outer diameter of the thread. Can anyone confirm or refute this?

Thanks,
Bob

 

[big-all]

4mm is no7 as in 3mm= no4 3.5mm= no6 4= no7

 

[bobsammers]

Thanks for your reply, Big-all.

I'm aware of these sizes, but they refer to the shank diameter, don't they?

The screws I'm trying to measure don't have a shank, which is my problem! I don't know what to measure instead (or what to do with the measurement once I've made it).

In case my question isn't clear, the two measurements are diameters of the same part of the screw but one is the width including the thread and the other the width of the solid part of the shaft I can see through the thread (I think this might be called the "root diameter").

 

[big-all]

yes
the metric sizes are the metric screw size you need as in 4mmx 40mm equivilent to imperial no7 x 1 1/2"

 

[bobsammers]

Thanks, Big-all.

As I said, I understand how the metric shank sizes correspond to the gauge no.

But I'm still no nearer to identifying the shankless screws I have!

Anyone?

 

[denso13]

Screws are sized by gauge number and length. The gauge number was thought up by someone with a weird mind, if the gauge is not known, simply measure the diameter of the head in sixteenths of an inch, take away one and double - that is the gauge number.
Example:

if the head is a quarter of an inch, that equates to 4 sixteenths;
take away 1 equals 3;
double that equals 6, so it is a 6 gauge screw.

Or take an old one to the ironmongers who will match new ones for you.

 

[big-all]

aaahhh got you i just call them fully threaded no7s are usually fully threaded as they are common for door and window furniture[fittings] that are generally only 2 or 3mm thick so give maximum grip

are the screws slotted or star??

 

[bobsammers]

Thanks guys, that's helpful. I'll measure the head later and see.

I'm not aware of any ironmongers near where I live (Loughborough). Presumably I could find one in Leicester or Nottingham, though. A guy is selling what I need on ebay, providing I can get the sizing right...

I've taken one to B&Q, Wickes, Screwfix & Homebase. Our B&Q in particular is massive but they have a fantastic selection of screws you wouldn't want to look at and virtually none that are even vaguely decorative.

In answer to your question, big-all, it's a slotted, raised countersunk I've got, in black. But if it's got no rust on it, I'm happy with slotted, cross, starred or anything. "Fully-threaded"is a much better term than "it's got no shank". I'll use that from now on!

 

[big-all]

just measured a no7 and the head was 7.5 mm across but thats a pozi screw
i have some brass screws slotted will measure the head off them----


ok the heads seem to be 0.5mm bigger than the number size dont have a no7 brass but the no6 is 6.5mm and the no8 is 8.5mm

 

[bobsammers]

Well, my head is just over 7mm, so it falls between the gaps with what you've discovered, big-all.

However, denso13, your system seems to suggest the screw could be a no 7 (as big-all suspected). It's nearly 4.5 16ths, so:
(4½ - 1) x 2 = 7

But no 7 shanks are massive compared to the thread diameter I've got...

I think I need to take it into a shop, as you suggested!

Thanks for all your help.

 

[big-all]

a number 7 shank will be slightly smaller than the outer thread at around 4.75-5mm ish

 

[aveatry]

I think you are also looking for "dome head"
Try here, down the road from Loughborough I believe.

Door Furniture - Broughtons Lighting & Ironmongery

Shop for door handles, door knobs and other door furniture at Broughtons - the period ironmongery specialists. Choose from brass, bronze, chrome, nickel, iron and much more. Free delivery on orders over £100.

www.broughtons.com

 

[carmanmemoranda]

After 11 years ?

 

[aveatry]

Ooops didn't notice that, just trying to help others a little after I have been helped on this forum.
Its the way that the forum delivers you "similar threads" just below and I don't notice the date. I was on the tiny screws thread.