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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 9th Nov 2021, 6:09 am   #1
Radio1950
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Default Making Holes For BNC Solder Pin Type Panel Sockets

Making Panel Holes For BNC Solder Pin Type Panel Sockets.

I use quite a few of these sockets for homemade Workshop Test Equipment.
I use this type of BNC panel socket, as the connector never normally loosens.

The four screw type socket is functional but, on a panel face, shall we say, ... ugly.

I have always made attempts to make the “truncated, or bicut circle” holes perfectly, but, shall we say, it sometimes ends up being a porcine breakfast.

I was reading another Vintage item, “Mathematics For The Million”, by Lancelot Hogben, when one of his drawings, a multi inscribed polygon on page 150 of the 1966 edn, gave me an idea.

Works well every time.


The method is so simple that it hardly bears writing about it, as probably everybody in the whole world knows about this, ... except me.

First get the socket with two flats on the threaded section.
Use a machined metal type, as the cast metal sockets have poor threading, and cannot be tightened up securely.
If your socket is impoverished, and only has one flat, file another, to the same thread depth, and with care.
If you do file, thread the nut on fully before you file, to act as a thread nut to cleanup your, ahem, ... “filing”.

Measure the dimension “across flats”; mine are 8.80 mm.
Measure the dimension “across the fully threaded section”; mine are 10.0 mm.

On your panel to be drilled for the BNC socket, mark out a drill point with a centre punch, with an offset equal to (10-8.8)/2 mm from the exact socket hole centre.
It can be left or right, up, down, offset.

As Lancelot would say, Offset = (Dia major – Dia minor)/2.

I now just use about 1.50 mm for BNC, but I show the principle, in case it is need for “N” Type Sockets, inter alia.

Use a starting drill of say 2.00 mm dia, then a final drill of slightly smaller than the "dim across flats" say 8.75mm. Ream or tidy up to 9.00 mm.
Using a round file, lengthen the hole towards the imaginary actual socket centre.
File only along the imaginary centreline, until the hole length is the BNC socket major dimension, ie, across the threaded section.

Then, file a little in the corners of the squashed circle to blend the minor (drill) radius to the major radius of the threaded section. Clean up with flat and round files to fit, but with care.

For the really obsessive, like me, the sockets were UG1094/U with imperial dimensions (ie in “bananas”) originally, but commercial sockets can now be very slightly different in dimensions.

Kewpie dolls are available for correct detailed analysis of that type number.

Even larger Kewpie Dolls are available for the first correct mathematical equation of the hole shape.
As normal, dolls are pickup only.

The attached will assist with visualisation.
There are variations.
The UG657 is a special for front panel use, but has nice drawings; the original UG1094 was for general use.
.
Attached Files
File Type: pdf BNC UG1094 1680589.pdf (284.0 KB, 122 views)
File Type: pdf Amphenol BNC Solder Jack UG657, C31-102.pdf (366.9 KB, 108 views)

Last edited by Radio1950; 9th Nov 2021 at 6:18 am. Reason: Usual old age blunders
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Old 9th Nov 2021, 7:46 am   #2
mole42uk
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

I like it! I didn't know how to set those holes out either.
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Old 9th Nov 2021, 7:55 am   #3
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

Yes, been doing that for years when fitting sockets that have flats to stop rotation. Just drill a hole to match the socket's minor width (across the flats), then use a large rat tail file to extend the hole upwards and downwards, then clean up using a small round jewellers file or as appropriate.
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Old 9th Nov 2021, 1:39 pm   #4
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

I use Loctite.
 
Old 9th Nov 2021, 2:40 pm   #5
G6Tanuki
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

Fascinating insight into a problem I have had on a number of occasions.

Personally I like the four bolt type but fit them from the rear of the panel so you only see the four screws not the whole flange.
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Old 9th Nov 2021, 8:31 pm   #6
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

Quote:
Originally Posted by G6Tanuki View Post
Personally I like the four bolt type but fit them from the rear of the panel so you only see the four screws not the whole flange.
Good idea .

B
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Old 13th Nov 2021, 8:53 am   #7
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

If you have access to a 3D printer, here's a technique which I've used for BNC connectors, binding posts, or anything else with flats. Make a small bezel, a couple of mm thick, to fit the connector and at least one other component on the panel. The holes in the bezel can of course be printed in whatever size and shape you need.
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Old 14th Nov 2021, 3:14 pm   #8
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

Yes, it's really annoying when BNC connectors rotate in round hole in a metal box. I've been there many times. I'll give this method a try.

I sometimes solder the flange to the enclosure if the enclosure can be soldered. For really high performance stuff I sacrifice looks for performance and make up an enclosure using tinsnips and solder it to the connectors to make a quick and dirty (but very tight) RF enclosure.

The image below is my rather ugly collection of RF protection limiters to protect test equipment from overload. The limiter circled in yellow uses 4 x 1N4148 diodes and is good to about 433MHz and several watts of RF power. From memory the insertion loss is <0.1dB and the VSWR better than 1.1:1 up into UHF. It is soldered together, no need to drill any holes but a decent soldering iron is needed.

I have some 50 ohm AF low pass filters to design soon. I was going to use Teko boxes and solder the BNCs to the enclosure. It seems a waste to use Teko boxes at audio frequencies. I do also have some diecast boxes so so I'll have a go at R1950's method.
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Old 14th Nov 2021, 6:15 pm   #9
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

It would make for a great youtube video if you wanted to demo this method.

Alternatively a step by step visio drawing of each stage would be helpful I think. I can have a go at the visio drawing if it helps but other people will do a better job of it than me...
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Old 14th Nov 2021, 6:26 pm   #10
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

The flats are there to speed up the manual production line by ensuring the orientation is correct and to provide a reaction to the nut tightening torque. After that the flats don't do much. The few loose BNCs I've ever come across have all been in commercial equipment, in 'properly' shaped holes, but presumably inadequately tightened on assembly.

If the connector body can be held firmly in position while tightening the nut then it's perfectly possible to apply sufficient torque that it's never going to come loose, flats or no flats.

I've fitted many, many BNCs over the years into plain drilled holes and I can honestly say that not a single one has ever worked loose. I've posted this before, but the trick is to align and hold the connector body securely using a home made 'BNC spanner':-

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It's just a collar removed from a BNC, soldered to a brass washer and bolted to a piece of aluminium shaped to fit a file handle. The collar is adjusted so that the pips on the connector are in line with the handle, which makes it much easier to see when the connector is nicely aligned with the panel.

It probably took less than an hour to make some 30 odd years ago. I wonder how much filing and fettling time it has saved since?

Cheers

Last edited by Trigon.; 14th Nov 2021 at 6:53 pm. Reason: typo
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Old 14th Nov 2021, 10:50 pm   #11
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Default Re: Making Holes For BNC Solder Pin Type Panel Sockets

Have you noticed though, that these days, things that used to come with a "shake proof" washer no longer come with them.

Makes tightening things up a little harder these days.
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