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Small set screws
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Tue Oct 06, 2015 2:48 pm    Post subject: Small set screws Reply with quote

Help again required.

I am looking to replace / supplement a number of small raised countersunk set screws but am having a bit of a time identifying the thread type and size.

They are from a prewar windscreen so should be Whitworth or BA of some kind but I cant seem to match them.

They measure on average 3.84mm across the thread (maximum diameter) but 5BA is 3.2mm and 4BA is 3.6mm and 5/32"BSW is 3.969mm

Any ideas ladies and gents before I re-tap them larger?

Many thanks,

Tim Green
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goneps



Joined: 18 Jun 2013
Posts: 601
Location: Auckland, New Zealand

PostPosted: Tue Oct 06, 2015 9:58 pm    Post subject: Reply with quote

This is not going to be easy with so little information to go on. How many threads per inch? That might give us a clue.

You say "They measure on average 3.84mm across the thread". More to the point would be the diameter of the largest (ie, least worn/corroded/damaged) screw.

What vehicle do they belong to? Is the windscreen frame from a proprietary maker such as Auster?

Important point—if they are raised CSK they must be machine screws. Set screws are fully threaded hex headed bolts.

Richard
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Wed Oct 07, 2015 12:54 pm    Post subject: Reply with quote

Hi Richard,

Yes, the measurement I gave of 3.84mm is the widest point of the threaded section i.e. maximum diameter. They are quite consistent in this dimension and are hardly worn having been in the component since manufacture in the 1930's
They are very short but I will try to get a thread gauge on them. You are also correct in that they are threaded for their whole length and are therefore machine screws.
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Wed Oct 07, 2015 12:56 pm    Post subject: Reply with quote

Also, the screws hold the adjustable stays on an opening screen from a Morris 8 but I am not familiar with the make
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PAUL BEAUMONT



Joined: 27 Nov 2007
Posts: 1279
Location: Barnsley S. Yorks

PostPosted: Wed Oct 07, 2015 1:03 pm    Post subject: Reply with quote

Weren't Morris an early convert to metric? Is it not feasible that these are M4?
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Penguin45



Joined: 28 Jul 2014
Posts: 321
Location: Padiham

PostPosted: Wed Oct 07, 2015 2:13 pm    Post subject: Reply with quote

Morris engines built at the old Hotchkiss works were metric. The company as a whole wasn't.

P45.
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Wed Oct 07, 2015 4:13 pm    Post subject: Reply with quote

I just cant see that these screws are that worn. The screen would have been assembled and there would have been very little reason to take it apart and certainly not regularly enough to wear them down. I have a long time served engineer down the road, I might pop them in to him for an opinion.
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Wed Oct 07, 2015 7:15 pm    Post subject: Reply with quote

Well, I have now measured the thread and it looks like 32tpi which suggests a 5/32" bsw thread. Just don't understand the undersized diameter but maybe they were made with a truncated thread ?
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goneps



Joined: 18 Jun 2013
Posts: 601
Location: Auckland, New Zealand

PostPosted: Thu Oct 08, 2015 12:18 am    Post subject: Reply with quote

Tim,

It seems it's a saloon windscreen, which unfortunately I'm not familiar with since my car's a Tourer. However, at least some threads on that are BSW, so if your screen was also made by Auster (quite likely, I would think) then possibly what you have is, as you suggest, 5/32"BSW.

If so, the screw diameter is undersized by only 0.12mm, possibly at the limit of manufacturing tolerance at the time.

In the absence of more definite information your best bet might be to get hold of a new 5/32"BSW fastener and try it in the female thread. Finding one might be a challenge, though.

Richard
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1414
Location: Above the snow line in old Monmouthshire

PostPosted: Thu Oct 08, 2015 10:08 am    Post subject: Reply with quote

goneps wrote:


In the absence of more definite information your best bet might be to get hold of a new 5/32"BSW fastener and try it in the female thread. Finding one might be a challenge, though.

Richard


Not necessarily. A quick look on fleabay - often a good bet for odd bits of hardware - suggests that 5/32" BSW is a thread commonly used in the world of Meccano, for which there are many enthusiasts.
See http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X5%2F32%22+BSW.TRS0&_nkw=5%2F32%22+BSW&_sacat=0
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Thu Oct 08, 2015 3:46 pm    Post subject: Reply with quote

Richard,
What you say has been echoed by my engineer friend this morning. He said that data chart dimensions are 'ideal' and are usually not 'actual' particularly for less vital fittings where going together easily is more important than perfect technical fitting. I have now ordered a small number of 5/32" screws and will see how they go.
Bitumen Boy
I did notice that about Meccano in my research but unfortunately don't have any of the stuff any more so couldn't try it
Thank you everyone
Tim
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goneps



Joined: 18 Jun 2013
Posts: 601
Location: Auckland, New Zealand

PostPosted: Fri Oct 09, 2015 3:03 am    Post subject: Reply with quote

Bitumen Boy wrote:
goneps wrote:


In the absence of more definite information your best bet might be to get hold of a new 5/32"BSW fastener and try it in the female thread. Finding one might be a challenge, though.

Richard


Not necessarily. A quick look on fleabay - often a good bet for odd bits of hardware - suggests that 5/32" BSW is a thread commonly used in the world of Meccano, for which there are many enthusiasts.
See http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X5%2F32%22+BSW.TRS0&_nkw=5%2F32%22+BSW&_sacat=0


Excellent point, BB—that useful fact had slipped my mind. During my years in the engineering fastener business we had occasional requests from Meccano enthusiasts. Also, I think the screws securing the fuel gauge sender to the tank on the Morris Eight are 5/32"W, though it's 30 years since I've had to tinker with that.

Richard
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Fri Oct 30, 2015 1:38 pm    Post subject: Reply with quote

The 5/32" screws were perfect (thankfully as they were very expensive) and have done the job well which is good for a number of reasons, not least of which is for originality. Also, a relatively cheap 5/32" tap means that I can also put them in other locations if the need arises in the future. I have found that the occasional investment particularly in small tools even if I don't need them at that moment can be very beneficial in the longer terms. A word of warning though, if you ever do this, make sure you put them away in the most logical place right away to avoid repeating the exercise further down the line. Also, if you buy a small quantity of an obscure sized screw or bolt for example, make sure that you label any that you have left over. It can be really very frustrating not knowing the thread size of something that could be very useful and having to buy it again - I have done this on too many occasions unfortunately !
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