PO Series 1000 / Ericsson lever key switches - what screw thread?

[Simondm]

I've just been on a voyage to the past (2013) in an earlier thread about the fantastic prices these switches were on sale for before they finally stopped being made.

I have some I want to use (recycled and NOS), but for some stupid reason when I salvaged them I didn't keep the machine screws to fit them to a panel. Does anyone know what pitch they were?

It's possible they were metric, but the PO used them in such huge quantities it's also possible they were imperial.

Anybody who remembers, please say - I can probably get the right screws, but I don't know what to look for.

Many thanks, S.

PS: if anybody who doesn't know these is wondering, the nuts are captive on the switch frame.

[M0FYA Andy]

Are they BA?

Andy

[Tim]

Hi Simon

The trouble is, the PO used ODD(literally) BA sizes. Eg, 1Ba, 3Ba,5Ba etc) so you never know.If you are really stuck PM me.

[Simondm]

Originally Posted by Tim

Hi Simon

The trouble is, the PO used ODD(literally) BA sizes. Eg, 1Ba, 3Ba,5Ba etc) so you never know.If you are really stuck PM me.

Thanks both.

I tried a small UNC machine screw last night (I think intended for 20-way EDAC shells - can't remember). The thread seems to fit, which is an encouraging start, however the screws themselves, otherwise perfect, have a strange cheesehead top (they're really hard to get here, as there's no alternative for that size of EDAC). I need to find my Zeus tables and see what's close. To achieve a neat finish on a panel, they really need to be countersunk heads (or domed, at a pinch).

If they are BA, I may well have some squirrelled away somewhere.

In the interests of those following on, I'll report back what I find, if I do nail it (or someone else knows!).

[peter_sol]

They were 6BA countersunk head.

[Simondm]

Originally Posted by peter_sol

They were 6BA countersunk head.

Those I do have... somewhere!

Many thanks, S.

[peter_sol]

A correction I meant to type 8BA contersunk head.
Sorry for misleading you.

[Simondm]

Simply knowing they are definitely a BA size is very helpful.

If I remember correctly, UNC and BA threads are similar pitch circles and pitch (I think the actual thread form is different though).

I shall go hunting in tins this w/e...

[m0cemdave]

I have just checked some I have.

They are 8BA x 1/2" CSK, used in conjunction with a plastic spacer behind the panel.

The spacers are 1/4" diameter and they measure 2.7mm thick, so probably meant to be 7/64" (which would be 2.778).

[yestertech]

I think they changed over to metric at some point. The earlier ones were definitely 8BA and these screws in c/s raised head chrome look great on panels.
I have some later ones which 8BA didn't fit so presumably M2/2.5 ?
Does anyone have a good mounting template for these ??

Andy

[Simondm]

Chronos carry stock of 8BA 1/2" csk in either brass or unplated steel. They're not expensive, either.
I did find some in a tin (inherited from my dad), but they're much longer than necessary, and hex-headed, so wouldn't look terribly tidy.

Regarding a template, I use a piece cut from an old equipment panel. I don't have a small enough Q-max cutter, so usually drill the corners and Abrafile-out the rectangle (neater than a Dremel-type cut). It looks neat enough on die-cast boxes. I'm fairly certain the mechanical workshop back in the day used a fly press and a punch+die set to do everything in one go.

I think the spacers are because the mounting was usually behind the visible panel, on a sub-panel, with the countersunk screws flush. If you used a switch guard, obviously then you did need to drill the mounting holes all the way through though.

[ScottBouch]

I have some here, and have just tried an 8BA screw in one, and yes, the ones I have here are definitely 8BA!

Cheers, Scott

[m0cemdave]

There was actually a Q-Max style rectangular punch for the cutouts, 13.7 x 11.1 mm.
Mine came from RS under their type Nr. 545-317, but that was about 40 years ago...