[ARC5] Parts needed for ARC-5/274-N - splines...

[J. Forster]

Very unlikely,IMO.

Mike, is the outer thread the same as is used on studio mike stands. I ask
because pipe threads are almost universally tapered, but electrical
threads are not.

-John

================


>> ...since the thread is actually 1/2-27.  1/2-28 makes an interference
> fit, and with fresh aluminum to aluminum contact
>> may weld the two parts together through galling action.  I'm not sure
>> how
> the powers that be, or were, came up with the
>> odd thread count per inch, as I discovered for the flex cable article on
> my website that the 27 T.P.I. thread came from
>> a 19th century standard for gas light fittings! It persisted in
> electronic hardware in a number of places, including coax
>> microphone connectors with the center soldered button.  You can buy a
>> tap
> with that thread, but it counts as a "special
>> thread" that is more expensive.
>
> Any chance that the thread is British/Euro?
> Many decades ago I scouted around the hardware stores and vehicle parts
> stores here in Auckland and found a pipe fitting that could be screwed on
> by hand, so the threads were either identical or very close.
>
> The fitting was of brass and of the type that connects fuel line to
> carburettor in vehicles. I can't remember whether I had to drill out the
> hole or not, but do remember that the shaft was eventually a snug fit
> inside it.
>
> Since we in the still subservient (-; Brit colonies tend to have more
> Brit/Euro stuff, maybe the thread was Brit/Euro?
>
> 73 de Neil ZL1ANM
>
>
> On Tue, May 27, 2014 at 8:06 AM, Mike Hanz <aaf-radio-1 at aafradio.org>
> wrote:
>
>> On 5/26/2014 1:55 PM, hwhall at compuserve.com wrote:
>>
>>> Tom Kneitel's Surplus Conversion Handbook, 1970 edition, had a short
>>> note
>>> on an ARC-5 RX tuning adapter that seemed the best I've seen. It
>>> provides
>>> mechanical support for the coupling joint, which seems to be key to
>>> getting
>>> a good feeling control and one that places minimal strain on the
>>> coupling
>>> material.
>>>
>>> It requires making a short (3/4 inch) cylindrical fitting of brass or
>>> aluminum (could probably do it in modern hard plastics or composites,
>>> too),
>>> drilled & tapped 1/2 - 28 at one end to screw onto the RX tuning ring,
>>> with
>>> a 1/4 inch hole continuing through the other end. Making that is the
>>> hard
>>> part.
>>>
>>
>> Trudat.  :-)   Tom must have misread his thread gauge as well, since the
>> thread is actually 1/2-27.  1/2-28 makes an interference fit, and with
>> fresh aluminum to aluminum contact may weld the two parts together
>> through
>> galling action.  I'm not sure how the powers that be, or were, came up
>> with
>> the odd thread count per inch, as I discovered for the flex cable
>> article
>> on my website that the 27 T.P.I. thread came from a 19th century
>> standard
>> for gas light fittings! It persisted in electronic hardware in a number
>> of
>> places, including coax microphone connectors with the center soldered
>> button.  You can buy a tap with that thread, but it counts as a "special
>> thread" that is more expensive.
>>
>>
>>
>>  A 1/4 inch dia short shaft extension goes in with enough length to
>> touch
>>> the spline shaft when installed, and a piece of plastic tubing makes
>>> the
>>> coupling from shaft to spline (could use brass or copper, too, I
>>> suppose).
>>> Then just attach your favorite knob to the 1/4 shaft.
>>>
>>
>> In a way, it is simply a home brew variation of the retention nut part
>> of
>> the command receiver local control at the bottom of http://aafradio.org/
>> garajmahal/flex_drive_cables.html
>>
>> It is certainly a more sound way to make the connection than having the
>> shaft cantilevered out from the tuning capacitor.
>>
>>     73,
>>  - Mike
>>
>>
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