It is a long shot I'm afraid.

Tried Emkay, for example?

Or possibly, ModelFixings (though that company sells mainly metric sizes)?

If you end up having to convert the design to metric, you'd be looking at M3, 3.5 or 4, whichever would be the more appropriate, but for which cap-screws are readily available… e.g. from above?

Alternatively, try UNF cap-screws. These are still fairly easily obtainable (e.g. Westfield Fasteners, possibly those above), and if the engine is in Imperial sizes, at least the UN series is as well.

'

If you have already drilled and tapped the holes you would have to assess whether the replacement is close enough for re-tapping as-is to trim the thread, though that's a horrible practice leading to loose threads; or would need re-drilling and tapping for the nearest size M or UNF above. You might need re-cut the counter-bores as well.

One immediate barrier to the horrible practice is that although actually metric the BA diameters are integer mm in only some sizes, and the thread angle is about 47º whereas M- and UN are of 60º. It might just work for 5BA as that is very close to 3mm dia, (like 0BA / M6, allegedly) but I have not tried it, and would not recommend it for anything critical.

I think you are going to have to consult detailed thread-tables carefully to find a replacement, but the risk is ending up (as I have), with an inelegant mix of thread standards in one machine.

Err, Do you know, I am not sure now!

Ah, I think I saw a very similar enquiry maybe on another thread, that does relate to 5BA studs or screws on an engine, so I probably mixed the two up.

Anyway it's not important to the point of the question.

If you have tapped for them already then tapping the existing hole out to 4BA would keep the same thread forms and even numbers are available.

If not drilled then go with M3

the GPO used odd sizes of BA both to deter theft and make it more awkward for unauthorised access – likewise many electrical suppliers – the choice of the M3.5 for domestic electrical outlet fixings is a hangover from the use of 5BA

Brian

Did you find some screws?

I have a few 10mm long ones, are they long enough, how many do you need?

Rod

Brian,

I recently got some 8BA SHC screws from Howard Lee & Son Ltd,. a good old engineers suppliers based in Birmingham. They actually sent me some 9BA initially by mistake so it appears they do have an extensive stock of BA SHC screws. Their lengths started at 1/4" and went up in 1/8th increments to 1". No connections other than a satisfied customer.

My contact was Karen Gracie – email: karen.gracie@howard-lee.co.uk

Martin

Have you considered using 4BA socket screws and turning the thread down to the outside diameter of 5BA and then cutting a 5BA thread on them using a die?

Fiddly but it's NOT a large number

MC