Bolt size

On Wednesday, August 14, 2013 6:15:55 PM UTC+1, snipped-for-privacy@gmail.com wrote: (but didn't get it quite right) _trYing_ to connect

In message , asalcedo writes

Once you have decided just what thread it is,

It's the same thread as a camera bush, 1/4 Whit 20 tpi.

Bill

I have looked at the charts

If the screw is between 5 and 6mm then yes it could be 7/32 BSW or #12 UNC but those are not stocked anywhere

I have posted a spare to a specialist. We'll see if they can find it.

Thank you.

Ford / Austin / Morris in the 60's certainly used UNC on the block end of head studs (non crossflow Ford used in the Lotus twincam, A Series, B Series) The threads used on the A series were more or less unchanged for the entire production run of four decades or so.

Not sure about it now but until a few years back all seatbelt anchorages wordwide were 7/16 UNF even on a vehicle where every other fastener was metric.

No, about one country is American, one or two minor ones are maybes, and the rest of the planet went metric for all practical purposes decades ago.

Yes and no. It was built in an entirely different way by Rover, so changing thread type would have been easy. But it was likely all American threads originally anyway. And Rover at that time was using unified.

Since nobody on the Net has ever done it, I made my own chart for unknown threads:

Type Size Dia Inch TPI Dia mm Pitch mm BSW 1/16 0.0625 60 1.59 0.42 M 1.6 0.063 72.57 1.6 0.35 M 2 0.079 63.50 2 0.4 BSW 3/32 0.09375 48 2.38 0.53 M 2.5 0.098 56.44 2.5 0.45 MF 3 0.118 72.57 3 0.35 M 3 0.118 50.80 3 0.5 BSW 1/8 0.125 40 3.18 0.64 M 3.5 0.138 42.33 3.5 0.6 BSW 5/32 0.15625 32 3.97 0.79 MF 4 0.157 50.80 4 0.5 M 4 0.157 36.29 4 0.7 BA 3 0.1614 34.84 4.10 0.73 M 4.5 0.177 33.87 4.5 0.75 BA 2 0.185 31.35 4.70 0.81 BSF 3/16 0.1875 32 4.76 0.79 BSW 3/16 0.1875 24 4.76 1.06 MF 5 0.197 50.80 5 0.5 M 5 0.197 31.75 5 0.8 BA 1 0.2067 28.25 5.25 0.90 BSW 7/32 0.21875 24 5.56 1.06 BSF 7/32 0.2188 28 5.56 0.91 BA 0 0.2362 25.38 6.00 1.00 MF 6 0.236 33.87 6 0.75

What about tapping a new thread?

For M6 (standard 1mm pitch), what is the recommended tap drill size in steel? Is it 5mm or 5.4mm? I have seen both.

If it is 5.4mm since the existing hole is already about that diameter, tapping for an M6 screw might be successful

If it should be 5mm then I might need to tap for an M8 screw which is not an ideal solution

Very useful, thanks.

The fastener specialists that got the sample, believe it is 7/32 Whit

Anybody knows where I can find that type of screw?

I would look for a larger countersunk bolt and re-tap the hole to match. I would guess that an old whitworth threaded countersunk machine screw like that will be near impossible to find.

Tim

It's a non standard size now almost impossible unless you want to commission a production run from a specialist.

However UNC 12 24 is close enough, the diameter is as near as dammit the same, the pitch is the same, the thread form is 60 deg rather than 55 which makes little difference in your application.

One source, unfortunately in stainless and expensive.

?? heres more info on that Diameter Inches T P I Pitch inches Core Diameter Tapping Drill Size

I couldnt find anyone who makes such things apart from the above BUT plenty of die and tap sets around, so you could could take an existing bolt, cut off the thread and stick a whitworth thread on it.

I found em in other sizes but not that one.

Allen socket countersunks..

But what about asking Crittall? IIRC they still exist?

You could, but it's a 7/32" diameter countersunk, maybe 5 threads in length.

If they could do what you suggest then they wouldn't be asking in here, even holding a CSK head in order to perform any thread cuttting or thread replacement operation isn't easy.

I'm rather surprised they used other than a stock size. The Tenable Screw Company in Merton will make some for you. But it would probably be better to drill/tap for a stock size.

That is really helpful.

I agree that screw is very close indeed.

I will order it.

I had actually searched that website but did not see it initially because I was restricting my search too much by looking for slotted screws.

Many thanks again.

This house was built by Charles Voysey in 1935, may be that explains it.