It might be conceivable to cut on a CNC machine if the carriage moved by it's
own power and not a lead screw using an encoder to tell where it was at.
Special threads like multi-lead screws are generally used only in worm
gearboxes and a few jacks using acme thread for speed rather than weight
carrying ability. Fast speed worm boxes like ratios of 10:1 use multi-lead
worms, some two, three leads. Worms are generated on special worm gear hobs.
Most of the CNC lathes I've seen though still used some sort of screw to drive
the carriage for threading, but that's not saying they're all like that as I'm
not sure. Fast machining using CNC is a whole horse of a different color where
everything is automatic and is ran from a program. The carriage on them could
use a rack and pinion drive like for turning, and use an encoder. In a small
lathe, it comes with two sets of back gears, one for inch, and one for metric.
The larger ones have both sets built in. Now in Jennings place, they cou
ld have had a custom screw machine(s) made for this purpose. However. military
contracts dont like folks using anything out of the norm, and that would
certainly fit the bill. One would think they would want that screw in some even
number so it could be used with the ratios that turns counters have. I'd say
one could buy a tap and die to match it, but it would have to be a custom from
somebody who makes them. Custom stuff is highly expensive. Thing is, Jennings
had to pay extra too just to use an odd-ball size.
Best,
Will
*********** REPLY SEPARATOR ***********
On 3/13/06 at 9:46 AM Gary Smith wrote:
>Fwiw, its not whitworth thread either. If my aged memory is correct all
>whitworth was 18 tpi regardless of the diameter of the bolt or cap screw
>in
>question.
>This is a new one on me too.
>73,
>Gary...wa6fgi
>
>
>----- Original Message -----
>From: "Will Matney" <craxd1@verizon.net>
>To: <amps@contesting.com>
>Sent: Monday, March 13, 2006 9:35 AM
>Subject: Re: [Amps] Proof of idiocy
>
>
>> I've never seen nor heard of a 1/4-23 thread. The standards are 1/4-20
>NC,
>> and 1/4-28 NF. I don't know of a lathe that would turn that either
>without
>> a special gear being made for the feed, if that's even possible over the
>> ratios. If it was odd-ball size, the thread dial might not be usable to
>> know when to throw in the half-nut lever. Most lathes are set up to turn
>> either standard inch or metric threads. I would think that the shaft of
>> those caps would be turned in a lathe or a screw machine. I did a google
>> search for 1/4-23 and came up with nothing.
>>
>> Best,
>>
>> Will
>>
>> *********** REPLY SEPARATOR ***********
>>
>> On 3/13/06 at 8:50 AM R; Measures wrote:
>>
>>>On Mar 13, 2006, at 4:43 AM, HAROLD B MANDEL wrote:
>>>
>>>> It is possible that the threads are bunged on the
>>>> leadscrew or the collar, but good luck locating
>>>> a tap or die!
>>>>
>>>> These threads are Jennings proprietary pitch
>>>> and once fouled there is no way to chase them
>>>> or to re-cut.
>>>
>>>The threads are 1/4 - 23 -- for which taps and dies are available.
>>>>
>>>> The alternative is to substitute pieces from
>>>> another vacuum variable and hope for the
>>>> best.
>>>>
>>>> If the junction that pulls the bellows on the
>>>> room-pressure side is gone and the threads are
>>>> still good then the piece can be used for the collars
>>>> and lead screw threading.
>>>>
>>>> Allen Bond and Economy sell very decent vacuum
>>>> variables to the amateur. I have bought several
>>>> ceramic and glass types from each. The most important
>>>> feature is that both of these businesses HiPot each
>>>> item before it ships and will not send a DOA or
>>>> leaky variable.
>>>>
>>>> Buyer Beware: Things seeming to be too good to be
>>>> true often are.
>>>>
>>>> Hal
>>>> W4HBM
>>>>
>>>>
>>>>
>>>>
>>>> On Sun, 12 Mar 2006 19:35:08 -0500 "Will Matney" <craxd1@verizon.net>
>>>> writes:
>>>>> $148 and gowing on! The only usable piece looks to me like would be
>>>>> the flange on the rear. The high bidder now looks to be an
>>>>> engineering firm......
>>>>>
>>>>> http://cgi.ebay.com/Jennings-Vacuum-Variable-Capacitor-5-kV-9-500-
>>>>> pF_W0Q
>>>> QitemZ7597842893
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>>>
>>>
>>>
>>>
>>>Rich Measures, 805.386.3734, AG6K, www.somis.org
>>
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
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