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Numbered woodscrew sizes

E

Eric the Viking

Nordic Pine
Joined
Dec 10, 2020
Messages
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Location
In the downstairs shower, trying to fix the leak.
Size​
Major Thread Diameter*​
​
Decimal​
Nearest Fractional Measurement​
#0​
.060"​
1/16"​
#1​
.073"​
5/64"​
#2​
.086"​
3/32"​
#3​
.099"​
7/64"​
#4​
.112"​
7/64"​
#5​
.125"​
1/8"​
#6​
.138"​
9/64"​
#7​
.151"​
5/32"​
#8​
.164"​
5/32"​
#9​
.177"​
11/64"​
#10​
.190"​
3/16"​
#11​
.203"​
13/64"​
#12​
.216"​
7/32"​
#14​
.242"​
1/4"​
#16​
.268"​
17/64"​
#18​
.294"​
19/64"​
#20​
.320"​
5/16"​
 
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Not wanting to guess an unusually large size, I found the above and thought it worth sharing.
Sorry the table is a bit silly - I was amazed that I could simply copy-paste from a spreadsheet, and it saved a lot of typing.

And I should add that the original table came from here.

Enjoy, or something!

E.
 
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I usually work on the rule of thumb that the diameter is the screw number divided by two: no lookup tables involved. For example, #8 is 4 mm.
 
Steve Maskery said:
Has anybody, in the history of the universe, encountered a No7 screw?
No7 Belongs on a shelf in Boot's the Chemists and that's that.
Click to expand...
No but No5’s are very handy, I’m thinking brass slotted countersunk as they usually fit cabinet hinges a lot better than 6’s.
I must be getting old as I can’t seem to get my head around shank sizes in metric, show me a screw and I’ll tell you it’s a 6 or an 8 etc but metric? Not yet and probably never will as the metric aren’t available over here.
Ian
 
Steve will surely say, "I'm not in the least surprised!" but I do have a small box of #7 screws somewhere, 3/4" csk., if I recall. They were bought for some small butt hinges many years ago, but I only had two hinges to fit, rather than 25.

My interest in measuring screws this time was because of the hinges on our front door: they are 5" rising-butts (the door is big!) and because we've changed the floor height in the hall, they now need some careful adjustment.

After faffing about in an attempt to avoid damaging the screw heads, it dawned on me that I might find some replacements at our local traditional ironmongers, and so could replace the hinge in question using completely fresh screws.

They turn out to be #12s, which I'd guessed but not confirmed. The ironmongers not only have them, but in several lengths also, so I intend to get some that are 1/4" longer, thus ensuring a good grip (I will cautiously pilot-drill the extra length).

And If anyone knows where 5" rising-butt hinges are to be had, I'm all ears. The present ones are probably 100+ years old and have been carefully rebuilt by me once already in the 1990s, but there's little scope for doing it again. It is quite impossible to fit anything else*.

At the time, there were no architectural ironmongers on-line, and I couldn't find anybody who stocked anything similar. I doubt I'll have better luck now, so the 'mended' hinges will have to serve, albeit with their new, longer #12 csk. screws (steel this time also, not brass).

E.

*(well maybe 6" rising-butts but that's getting absurd, and they certainly wouldn't be easy to fit).
 
Decimal inches! That way lies madness...........
 
Dr.Al said:
I usually work on the rule of thumb that the diameter is the screw number divided by two: no lookup tables involved. For example, #8 is 4 mm.
Click to expand...
Indeed. I think the fact that it is so easy in metric explains why 5 minutes of searching hasn't turned up a single table of metric woodscrew sizes.......but literally dozens of imperial ones.
 
I don't think we need a look-up table or a conversion to metric.
Measure the diameter of the head in sixteenths of an inch, double the number and subtract two.

For example: a no 10 screw has a head 3/8" across, which is 6 sixteenths. Double 6 to get 12, subtract 2 to get 10.

Or if the head measures 9/32", double that to give 9/16", subtract 2 to get the result that it's a no 7.

What does seem odd is that I can't see any relationship between the numbering of screw gauges and any of the various wire gauges, even though screws were presumably made from wire.

But here's a twist. Imperial, Birmingham and American wire gauges all used a similar system of numbers. At one extreme were 0000, 000, 00 and 0, (referring to similar but slightly different diameters) then a run of all the whole numbers up to 50, 36 or 40.

Screw gauges used a similar set of numbers, from 0000 up to 50.

But with wire, the higher numbers denote smaller diameters. With screws, it's the opposite way round!
 
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I bought a job lot of boxes of screws some 45 years ago. there were 2s, 3s, 5s and 7s, strange combinations like 7/8th x 5 and 3/8th x 3. Brilliant for repair work where you just need to go one gauge heavier or 1/8th longer.

^^^^^^^^^^^^^ that's what I was taught.
 
Steve Maskery said:
Has anybody, in the history of the universe, encountered a No7 screw?
Click to expand...

No, but I've got some 3.5 mm screws (e.g. these), which are the same size as a #7.

Mike G said:
Decimal inches! That way lies madness...........
Click to expand...

It's one of the (many) reasons I abandoned imperial. Yes, believe it or not, I used to work exclusively in imperial. Then I realised (a) how much you have to look up in imperial - sheet metal thickness (in AWG or SWG), tapping drill sizes, even thread diameters (e.g. what's the diameter of a #4-40 screw?) ... and (b) how inconsistent the measurement systems used in imperial are. I've seen CAD drawings where a single part has some hole sizes specified in fractions (e.g. 3/8"), some in decimal (e.g. 0.125") and some that use letters or numbers (e.g. #56 or "S"). In metric it's all just millimetres.

AndyT said:
I don't think we need a look-up table or a conversion to metric.
Measure the diameter of the head in sixteenths of an inch, double the number and subtract two.

For example: a no 10 screw has a head 3/8" across, which is 6 sixteenths. Double 6 to get 12, subtract 2 to get 10.

Or if the head measures 9/32", double that to give 9/16", subtract 2 to get the result that it's a no 7.

What does seem odd is that I can't see any relationship between the numbering of screw gauges and any of the various wire gauges, even though screws were presumably made from wire.

But here's a twist. Imperial, Birmingham and American wire gauges all used a similar system of numbers. At one extreme were 0000, 000, 00 and 0, (referring to similar but slightly different diameters) then a run of all the whole numbers up to 50, 36 or 40.

Screw gauges used a similar set of numbers, from 0000 up to 50.

But with wire, the higher numbers denote smaller diameters. With screws, it's the opposite way round!
Click to expand...

I rest my case m'lud.
 
Dr.Al said:
I rest my case m'lud.
Click to expand...
I didn't say it was easier! :)

What's more, whenever a series of sizes are given serial numbers, it obscures the fact that, in the small sizes, you need a smaller increment than in the larger ones. So for slim screws, 3.5mm is useful, between 3 and 4. I expect tiny screws have even smaller intervals.
Old fashioned series of numbers, such as the various wire or screw gauges mentioned, obscure this difference. Just using plain millimetre sizes makes it nice and clear.
 
Eric the Viking said:
*(well maybe 6" rising-butts but that's getting absurd, and they certainly wouldn't be easy to fit).
Click to expand...

Not absurd at all - here they are in the Buck and Hickman catalogue:

IMG_20250222_110326034.jpg

But sorry - that's from 1935 so it might be out of date. Let's see what we get in a more modern edition, 1971:

IMG_20250222_110534382.jpg

Well that's not progress! 4" maximum and much dearer. I blame the accountants.

Trying harder to help, I found that B&H are no more:

"In 2011 Brammer acquired Buck & Hickman thus becoming what is known today as Brammer Buck & Hickman. "

...and a quick search at what is now Rubix.com led to the message:

Nothing found for “rising butt”​

not-found.svg

There's nothing related to rising butt inside the database​

Sorry!
I suggest that you mainly use the back door and reserve the front door for VIP visitors to save wear and tear. ;)
 
AndyT said:
Sorry!
I suggest that you mainly use the back door and reserve the front door for VIP visitors to save wear and tear. ;)
Click to expand...
We did that last time - battened the door in place and used the back... for three months. I got away with it, but certainly wouldn't be popular repeating it. Then there's the problem of her bath chair -- the crane at the front* still isn't finished!

[edit] * of the house. Putting one on a bath chair would be silly, obviously.[/]
 
I'm coming late to this, apologies, but in partial answer to EtV's original post (et al) I have always found the little table from "The Stanley Tool Guide" helpful:

https://archive.org/details/StanleyToolGuide1952/page/n23/mode/2up page 24.

I do, of course, use Zeus tables too, because my Wadkin, ML4 and other antique (but lovely!) 'stuff' necessitates it, but for wood, the table in the Stanley guide is first class.

Edit: That Bolt Depot set of charts is also dead useful, especially the red "Metric" gen at the back. I have printed and laminated some of it. Laminating is brilliant for use in oily/grimey scenarios DAMHIKT...
 
Last edited:
Eric the Viking said:
Steve will surely say, "I'm not in the least surprised!" but I do have a small box of #7 screws somewhere, 3/4" csk., if I recall. They were bought for some small butt hinges many years ago, but I only had two hinges to fit, rather than 25.

My interest in measuring screws this time was because of the hinges on our front door: they are 5" rising-butts (the door is big!) and because we've changed the floor height in the hall, they now need some careful adjustment.

After faffing about in an attempt to avoid damaging the screw heads, it dawned on me that I might find some replacements at our local traditional ironmongers, and so could replace the hinge in question using completely fresh screws.

They turn out to be #12s, which I'd guessed but not confirmed. The ironmongers not only have them, but in several lengths also, so I intend to get some that are 1/4" longer, thus ensuring a good grip (I will cautiously pilot-drill the extra length).

And If anyone knows where 5" rising-butt hinges are to be had, I'm all ears. The present ones are probably 100+ years old and have been carefully rebuilt by me once already in the 1990s, but there's little scope for doing it again. It is quite impossible to fit anything else*.

At the time, there were no architectural ironmongers on-line, and I couldn't find anybody who stocked anything similar. I doubt I'll have better luck now, so the 'mended' hinges will have to serve, albeit with their new, longer #12 csk. screws (steel this time also, not brass).

E.

*(well maybe 6" rising-butts but that's getting absurd, and they certainly wouldn't be easy to fit).
Click to expand...
When the weather gets better I'll have a root in me ironmongery stash for 5" risers as this rings a bell.
Don't bank on it but stranger stuff is in there.
There was an amazing big set on an 8ft internal door in The Dower House Market Bosworth with a mid point after which it would drop to open.
Another person to talk to is https://www.antiques-atlas.com/oldbakeryantiques he has some unusual stuff in his back room.
Cheers, Andy
 
The other place you could try is a little place near Derby. Loads of old stuff. I forget the name, but it is in a sort of Vintage Village kind of place. ABC Ironmongery, or somesuch. Helpful guy.
S
 
Steve Maskery said:
Has anybody, in the history of the universe, encountered a No7 screw?
No7 Belongs on a shelf in Boot's the Chemists and that's that.
Click to expand...
AFAIK they used to be quite common in the days of 2-1/2 and 3in sheet steel hinges. Similarly, I've seen no.9 countersunks sometimes supplied for 4in hinges

In terms of suppliers, over the last couple of years I've been busy on a grade 1 refurb where it was necessary to "replace" several hundred countersunk semi-raised slot head brass screws which were used to fit T-shaped push plates. Many of the original screws were either missing or had been replaced by "inappropriate" modern screws over the last 150 odd years. Best source for ex-stock metric screws turned out to be Westfield Fasteners. A lot of the decorative washered butt hinges in the public areas were on no.14 or no.16 screws, again a lot were missing or had been replaced by oddball screws over the years. They really were a problem to get hold of, being that there are generally no readily availably (off the shelf) modern metric equivalents
 
Last edited:
I use and like Westfield a lot.

Not the cheapest, but efficient and their stuff is excellent quality, amounting to good value.

They also sell unusual things like small (#7-ish sized) torx-drive, countersunk-head stainless screws (for oak, etc.), which are unobtainable for me elsewhere (I rarely need a box of 1000!).
 
I've not needed to use them myself, and I probably heard of them on here, but just in case anyone does want some no 7s (or 1s or 14s) they are available as new old stock here

Steel Wood Screws / Countersunk Head / Slotted

Buy Steel Wood Screws online from Screwsline. Free delivery on orders over £35. Contact us for specialist advice and bulk orders.
www.screwsline.co.uk www.screwsline.co.uk
 
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