BA sizes

I have nut spinners for 0BA, 2BA and 6BA but I have NOT been able to purchase a nut spinner for 4BA (at a reasonable price).

I have looked at the data, and that suggests that 4BA is very similar to 1/4 inch A/F

Is this a reasonable inference?

MC

Have you got a caliper? If so measure it.

4 BA is 0.248, so near as you can get

Across flats for 4BA hexagon is 0.249", so fairly close to 1/4" .

Looks like ±1 thou according to sources...

I'm a bit surprised you could not find BA nut spinners or similar. Have you tried Chronos or ModelFixings? They may have them.

[This posting has been removed]

Get an imperial Allan head bolt with 1/4" socket.

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... or just use the handle from a 1/4” hex drive screwdriver set

MichaelG.

I have tried both; Chronos does NOT sell nut drivers and Model Fixings do NOT have BA sizes in their range - only metric.

But Very many thanks for the suggestion.

I have tried using a 1/4" screwdriver bit handle but the 4BA nuts do NOT seem to be a consistent size. Some fit but others do not, even though they all have a 4BA thread.

Can anybody tell me what size Cap head screws have a 1/4" socket in the head, please?

Some 5/16" UNC and UNF have a 1/4".

Make your own up, bit of tube (drilled out to the suit), heat it up and force some steel 4BA nuts down the tube, adjust the fit by hammering to shape. That way, you can make them "deep" to accommodate nuts that are spun onto threaded rod further than the "normal" amount.

I have used car radio Ariel telescopic tube for 8 and 10 BA tubular spanners.

Bob

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If some of the hexagons are over-size, then it seems you are ‘on a hiding to nothing’

... You need to find whatever wrongly sized socket happens to fit them.

MichaelG.

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Edit: __ maybe useful link

https://www.ba-bolts.co.uk/faq.html

Edited By Michael Gilligan on 11/05/2021 06:51:42

Get a 4BA box spanner and Loctite or solder on your own extension handle.

4 BA socket and a 1/4" drive "screwdriver" handle work for me in most cases changing to a box spanner if room is tight.

Edited By JasonB on 11/05/2021 07:15:45

Here’s another useful reference page: **LINK**

https://www.fastenerdata.co.uk/fasteners/nuts/hexagon-full/ba/ba-hexagon-full-nut-brass-bs57.html

Note that there is a common theme emerging :

Anything greater than 1/4” AF is not compliant with BS 57:1951  and is therefore ‘out of spec.’

There, of course, is no law against making ‘specials’ ... but you must expect to need a special spanner.

MichaelG.

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Ref: https://shop.bsigroup.com/ProductDetail?pid=000000000000010735

Edited By Michael Gilligan on 11/05/2021 08:11:25

Thank you for taking the time to post.

Actually the nuts are smaller than the 1/4 driver.

The BA-bolts data is interesting - on both of the sites for which links are provided, the figures are in inches - but I was told years ago that BA is actually defined in Metric.

When I find useful data, I like to print it, laminate and keep in workshop. Sadly both the tables are NOT in an easily printable format.

With best wishes and thanks again.

MC

Ebay has plenty of 4BA nut spinners. However if you have hex heads that do not conform then check that you have a genuine BA bolt. You may find that some of todays suppliers fo bolts are using a more readily available metric or Imperial A/F hexagon bar. I have 4BA open ended, ring and box spanners and they all are perfect fits on genuine 4BA hex heads. If you find nut spinners do not fit then try a long reach box spanner which will probably be 4BA one end and 2 BA the other.

BA threads are originally based on the Swiss or Thury thread with a thread included angle of 47 degrees and 30 minutes. Thus the thread depth is less that the 55 degree Whitworth thread form. HTH.

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Apologies ... I misunderstood your “Some fit but others do not ...”

It is not uncommon for BA nuts and bolts to be supplied with under-size spanner flats.

As regards the BA system calculations: Yes, the calculation was derived from an existing metric system; but the British Association for the advancement of Science was Imperial to the core !!

MichaelG.

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P.S. __ BS 57:1951 actually tabulates all the values in both systems of units.

Edit: this is worth a look:

https://en.wikipedia.org/wiki/British_Science_Association

Edited By Michael Gilligan on 11/05/2021 13:19:57

Are some of the nuts made with the one size smaller hex bar to make the nuts look more in scale. So a 4BA nut would be made with a 5BA hex size. Kennions still sell these and also bolts.

Cheers

John