What imperial sizes are close to M6 metric?
- Thread starter Dowser
- Start date
I'd use M6, IME they fit well enough for light duty. You are only locating a light loudspeaker on a frame. If it were a car's suspension, no. But a speaker? Go on then.Thanks again all - so you reckon 1/4 BSF Steve? I'll probably order a small quantity of a few just in case.
Please remember - I left England in 1995 never to return...I have been living in mostly metric lands every since, and find all these thread pitch differences as confusing (and frankly, unnecessary!) as hell
I agree with you on the logic, there's a reason why these threads are obsolete!
2.54. Exactly.OK, thanks - I actually have some calipers
It wasn't really, but the metre is now defined as so many million light wavelengths and the foot was never so defined, so it was set to 25.4 mms precisely because that was what it measured and it made the maths tolerable.
As for not having inches in Switzerland, what size are TV screens there, and car tyres?
Dowser
Learning to bodge again..
Thanks...and f*ck off
Actually, TVs now have both inches amd cms in their Ads...but wheel diameter & width still exclusively inches...while offset is in cms Even that confuses the hell out of me!I understant zat even ze Tchermans still use inches ven specifying the size of water pipe fittings. I thought they were supposed to be engineers.Thanks...and f*ck off
Internationally I think brass bar is sold in inch diameter and metric length, or is it the other way around, or is that steel?
Stainless steel pipework however is still specified by inch internal diameter.
BA threads are intriguing, they use all imperial measurements but the thread pitch is metric. This was something invented in, when, the 50s?
Whitworth is the daddy though, it was the first standardised UK thread. Prior to that it was a right bugger's muddle.
You will excuse me, I'm going to sort through my collection of British Standard Coarse No. 3 Universal (not Birmingham) Cycle Thread fittings.
Barrymagrec
pfm Member
BA
Bit before that in fact - 1884. It is actually an entirely metric based thread scaled from 0BA being 6mm major diameter by 1mm pitch though the dimensions are normally shown as imperial.
https://en.wikipedia.org/wiki/British_Association_screw_threads
Bit before that in fact - 1884. It is actually an entirely metric based thread scaled from 0BA being 6mm major diameter by 1mm pitch though the dimensions are normally shown as imperial.
https://en.wikipedia.org/wiki/British_Association_screw_threads
Thinking about it, of course it predates the 50s. It was at its heyday then. I hadn't realised though that it was *intended* to take over from BSW and BSF in the small sizes. I didn't know it was *entirely* metric either. How odd.
In our hobby, BA is likely important, since it was/is used a lot for electrical connectors (and until VERY recently was the thread of the screws holding the cover plates of wall switches and sockets in place).
And the connections in DUALIT toasters
BugBear
Depends what you mean by recent. Changed 20? 30 years ago? Certainly WAY over 10 years ago. But the metric equivalent will do as good a job.
Not really when you consider what BA stands for and what that institution is about. The threads are also linked to the number scale drills, although I have always assumed that the UK version is not the same as the US.
How are the BA threads linked to number scale drills? (Oh, and number/letter drills are a can of worms on their own, of course. Many different systems in both UK and US).
BugBear
Barrymagrec
pfm Member
I don`t think there is a direct connection between number drillls (I only know and use the British number and letter drills) and BA threads.
It is a convenient feature of BA threads that the tapping drill for most sizes is also the clearance drill for two sizes smaller, i.e. tapping size for 4BA, number 33 is clearance for 6BA.
Mostly only even BA sizes are used, I only once have found a 3BA thread, on the pendulum of a Victorian clock.
It is a convenient feature of BA threads that the tapping drill for most sizes is also the clearance drill for two sizes smaller, i.e. tapping size for 4BA, number 33 is clearance for 6BA.
Mostly only even BA sizes are used, I only once have found a 3BA thread, on the pendulum of a Victorian clock.
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LOL, far too long ago, but the engineers in the tool room would always shout a number whenever we asked for the tapping drill for ?BA (usually 2 or 4). I would assume that logic would be right and that The BA defined a number and letter twist drill "set" that correlated to threads.
That means (only) that number drills are finely gradated enough that there exists a number drill that is near enough to fit the spec, which is certainly true.
(My 1976 Zeus table only gives drill sizes for BA tap and clearance in metric and decimal inches)
BugBear
The screws holding my Britool ratchet together are 3BA. I had quite a task finding a replacement, since one of them was missing...
BugBear
How do you work that one out?
In a workshop with imperial, metric, number and letter drills, it just happend to be the number drills that were a best fit to BA tapping drill requirements.
What you are effectively saying is that there are no drills at tapping sizes for BA threads, just lucky happenstance that number drills do the job. That would be insane.
Barrymagrec
pfm Member
I can`t see a date on my £1.60 Metric Revision Zeus tables. There is a number and letter drill conversion table sideways down the edge of the first page. - only noticed it today!
Barrymagrec
pfm Member
Number and letter drills have a graduated size system and give a much greater selection of sizes than drills sized in fractions of an inch, particularly in the smaller types.
There is a BS recommended tapping size which gives a particular percentage of thread depth, it is common to adjust this figure according to the material and thickness to be tapped. thus two or three different adjacent number drills could be the appropriate tapping size for different applications.
Absolutely so, but that does not affect the fact that there is a nominal. See the link.