avo: AVO vcm 163 thread size

Hello, I have a simple question. Hopefully someone can answer. I am looking for the machine screw thread size, that is used on the bulk of the small machine screws that secure the various panels, (back , sides, front, etc). I am wondering if is a currently available, or a now obsolete size. As close as I can tell it is the roughly about 6/32", only it has more threads per inch. I have a 3.5 mm set screw that will go in part way, and then stop. The 3.5mm set screw seems to have more threads per inch than the screws used in this tester. I am only asking because the unit I came across is missing a few, and i would like to make it complete. I'm thinking they might be metric, but are they an obsolete imperial size ? I thought it might be listed in the manual, but the screws are not.

While I am asking, they also used 8 rubber isolation (damper) grommets on the large bolts that secure the corners of this tester. Mine seem to be hard and crumbling, (literally falling apart). I know it isn't a real critical area. Would someone know what size to use as replacements, or just something that is "close enough' as far as rubber grommets go?

Thank-you to all in advance. Tony

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It is very common that british electronic equipment uses BA threads instead of the more common UNC or UNF. In some cases, BSF might also be used.

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Hi Tony.

It's been almost 40 years since I left UK, but as Torbjörn says, BA thread sizes were commonly used well into the sixties when this item was introduced, so I would suggest that the screw type you're looking for may well be 4 BA. If you consult Wikipedia, you'll find that the diameter of 4 BA screws closely resembles the 3.5 mm. type you tried, but the thread pitch is unlikely to be the same. There are still vendors on eBay and elsewhere that can supply various types and sizes of BA thread screws, the common ones being 2, 4 and 6 BA. Let's hope some of our UK members can give you more definitive information.

Kind regards, Stan

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Thank-you Torbjörn and Stan. That is a big help, and certainly points me in the right direction. At least the day wasn't a total loss, I learned something new today ! Looks like it is going to be hard to track down any BA fittings on this side of the pond. EBay does show a fair amount of U.K suppliers with the proper screws.

Tony

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