Bolt size

[asalcedo]

I need to find bolts like the one in the picture. (Slotted countersunk

10mm long)

The bolt will screw into existing threads on an old steel window frame to fix the hinges.

I have tried M5 and it does screw but loosely, it does not tighten.

I have tried M6 but it does not screw in, it is a bit too big.

I guess the thread is imperial

How and where do I find the right bolt?

+-------------------------------------------------------------------+ |Filename: hinge bolt.jpg | |Download: |+-------------------------------------------------------------------+

[Bill Wright]

It looks as if it might be the Whitworth size that was used for many camera tripod bushes. 1/4"-20tpi (threads per inch) British Standard Whitworth (Whitworth or BSW).

Bill

[The Other Mike]

Someone, maybe even a nuts screws washers and bolts supplier will need to measure it and use a thread gauge to determine the correct size. Look in the yellow pages or search on google.

Anything further said in here on the basis of your posting will be just guessing.

[charles]

between M4 & M5 is possibly 2BA but it could be a BSF or a BSW. And then again it might be an American thread. I certainly don't recognise the thread - it looks very deeply cut. Your best bet is to take another one out and go to a good stockholder to get a match.

[Dave Plowman (News)]

If you do a bit of Googling you'll find out the thread diameter of M5 and M6 and the threads per inch. Now look up BSW and UNC - those are the most likely ones used on a UK made window - with BSW being the most likely.

Or just take it to a decent bolt supplier for matching.

[Nick]

Do you know if this is Crittall window? I rebuilt some a few years back. I *think* the screws were BA. If you contact Crittall, they should be able to tell you.

Nick.

[Muddymike]

Sent: Wednesday, August 14, 2013 10:30 AM Newsgroups: uk.d-i-y Subject: Bolt size

Could be UNC. Available from

Mike

[The Natural Philosopher]

Crittall almost certainly Whitworth, if from the olden days. Especially tapped intocast metal.

UNC rarely seen in UK pre 1970s when it started to appear in imported goods and goods made for the US market.

[Dave Baker]

Ummmm, you measure the bolt diameter and thread pitch and look it up on a thread chart unless that's beyond the wit of a reasonably intelligent hominid.

Measuring the pic as best one can the thread pitch appears to be exactly 20% of the diameter which would fit either a 1/4" x 20tpi BSW (Whitworth) thread or a 1/4" x 20 tpi UNC (Unified Coarse) one. However the thread angle appears to be steeper than the 60 degree UNC angle and therefore is more likely to be the Whitworth 55 degree one.

It clearly can't be either metric, BA, BSF or UNF with those relative measurements as they all have finer thread pitches vs the o/d.

[Muddymike]

I worked as an assembly fitter for Crane Fruehauf from 1969 well into the

70s and all we used were UNF and UNC threads (mostly UNF) we even measured everything in inches for most of that time.

It was only at the end of my time there that metric threads first appeared.

So UNC was anything but uncommon. Did the OP give an age for his window frames? I don't recall.

Mike

[The Natural Philosopher]

IIRC there was almost no difference between BSF and UNF...

the UK started with Whitworth, BSF, BA and lord knows what else, and THEN went metric.

metrication of screw threads started in 1960, and so a lot of stuff right up to the 70s and 80s still used whatever they had used before.

Certainly a lot of cylinder heads studs were whitworth into the block and UNF/BSF on top of it. where the nuts went.

I think we never went UNC much - by the time whitworth was out of style, we were on the metric trail.

Of course disk drive retainer screws are UNC where they go into the alloy castings thereof..

Half the world is now American standard, and the other half metric.

Its hard to find definitive info though.

[charles]

not quite true. Ford (the Ford Motor Company) introduced UNF/UNC to the UK. My Cortina (1971) used UNF/C - I had to buy a new socket set. In teh

80s I bought a Peugeot and so went metric - French metric.

[Dave Baker]

Actually, if you're thinking of things like early A and B series Leyland engines they were always UNC into the block and UNF for the nuts. I think you'd have to go an awful lot further back than the 60s, 70s or 80s to find anything Whitworth in an engine block or head.

[Muddymike]

You are quite correct. Not only fords but BL in their may incarnations were all UNF/C for many years. My 1972/4 Land Rover hybrid is all UNF/C apart from the new bolts joining the exhaust together. I owned a 1954 Austin Champ years ago, the Rolls Royce B40 engine cover of that was clearly marked UNF.

Mike

Mike

[Dave Plowman (News)]

Unified threads were the norm in the UK car industry after WW2, on new products. Engines etc carried over from pre-war days might have stayed with what they used then. The same sort of thing carried on after the changeover to metric - the Rover V8 in my '85 car has unified threads, although most of the rest of the car uses metric.

[Dave Plowman (News)]

The closest threads to unified are American Fine (UNF) and American Coarse (UNC). Some imperial threads are of course close. but then again so are some metric and UNC.

You missed out unified - used on most post WW2 cars until metrication.

Thought you had a Midget or Spitfire? Both used unified threads near exclusively.

[Dave Plowman (News)]

Some engines designed before WW2 and carried on afterwards didn't change to unified. Things like the genuine Riley twin cam fours. Think their transmissions too. The MG XP engines also used some odd threads - notably the big end bolts.

[Bob Minchin]

I agree with earlier reply that it is almost certainly whitworth. I'd have expected a common size like 1/4 BSW. the tapping drill for this is

5.1mm but if you could not get a M6 in that has a core diameter of 5mm, it might be a really odd size like 7/32 whit. If you have a sample old screw, then try measuring the pitch and then looking up the wiki on whitworth threads and see what matches. 1/4BSW is 20tpi , 7./32 is 24 tpi so should be easy to tell them apart

[Tim Lamb]

In message , "Dave Plowman (News)" writes

Er.. Didn't that Rover V8 originate with Buick?

>

[The Natural Philosopher]

the thing is, that company was making metal windows in essex from before art deco. And before UNC. And would have seen no reason to interoperate with anyone else. My guess they would only have switched to metric when the taps wore out :-)