bolts

I have some miniature brass door knobs that take a threaded rod which measures 1.85 mm or .073 inches across the threads. I need to order some more of the rod , anyone know who would stock this size . Not sure if this is a BA size or not.

Mike

possibly 9 Ba ! Thread gauge would be the answer, 65 Tpi Or 1.8mm X .35 Good luck, Noel

Depends on the provenance of the miniature door knobs., UK , possibly Europe, or North America.

9 BA is 1.9 mm OD, 0.39mm pitch, or 65.1 tpi So, 1.85 mm could be a gnat's undersize. (0.025 mm is not much, 0.002" in old money )

1 - 64 ANC is 0.073 OD

1 - 72 ANF is 0.073 OD,

So you need to measure the pitch of the thread . The ANC /ANF threads will be 60 degree thread form

The BA thread will be 47.5 degree thread form, so they are not interchangeable!

If that is any help

Howard

If it turns out that the thread is BA then I could let you have some pieces. I've been cutting down some 9BA x 1" screws to 1/4" long and have saved the cut off pieces.

Brian

As Howard said, could be #1-72, if made in USA.

Thanks for replies. I tried my thread gauge, but the thread size is so small its not easy for me to see. It seems to fall between 0.6 and 0.7 in metric.

Mike

Just musing but it ought to be possible to determine whether it's a 47.5 or 60 degree thread by eyeball through a reasonably powerful eye-loupe (or whatever).

Oh, woe .... the passing of the shadowgraph.

could it be M2? 9ba is unlikely, it has been a 'non preferred' size for many years

Hi Peter,

The shadow graph hasn't passed. I have one in my workshop and for jobs like this, you can't beat it!

Andrew.

0.6 mm pitch is 42.33 tpi 0.7 mm pitch is 36.2 tpi Both too coarse to be 1 ANF or 1 ANC, and certainly not 9 BA

48 tpi would be 0.529 mm pitch. 60 tpi would be 0.423mm pitch

The thread could be special, or maybe one of the lesser known ones used in watches and clocks?

Howard

M2 Coarse has a 0.4 mm pitch, and M2 Fine has a 0.25 mm pitch, So both too fine for a pitch between 0.6 and 0.7

Taking the coward's way out would it be feasible to drill and tap out to

8 BA? 2.2 mm OD, 1.68 mm core 0.43 mm pitch Tapping drill 1.85 mm

7 BA 2.5 mm OD, 1.92 mm core 0.48 mm pitch Tapping drill 2.1 mm (Non preferred size )

6 BA is 2.8 mm OD, 2.16 mm core, 0.53 mm pitch Tapping drill 2.35 mm

Howard

(0.025 mm is not much, 0.002" in old money )

There's inflation for you - 0.025mm used to be 0.001"

Nigel B.

Absolutely right Nigel.

Do you know of a good proof reader?

Howard

It did cross my mind to drill and tap, this is what I would normally do. But the parts are so tiny and I do not have a watchmakers lathe. They are only door knobs so not critical. I will just fit in what I can with loctite and leave it at that.

Cheers Mike