[50mhz] cushcraft question

[Bill W5WVO]

Besides the formulation of the SS, there is the question of the quality of
the bolt and nut threads. To quote from the SS paper I referenced earlier,

"Another factor affecting thread galling in stainless steel fastener
applications is thread roughness. The rougher the thread flanks, the greater
the likelihood galling will occur. In an application where the bolt is
galling with the internal thread, the bolt is usually presumed to be at
fault, because it is the breaking component. Generally, it is the internal
thread that is causing the problem instead of the bolt. This is because most
bolt threads are smoother than most nut threads. Bolt threads are generally
rolled; therefore, their thread flanks are relatively smooth. Internal
threads are always cut, producing rougher thread flanks than those of the
bolts they are mating with. The reason galling problems are inconsistent is
probably due largely to the inconsistencies in the tapping operation.
Rougher than normal internal threads may be the result of the use of dull
taps, or the tapping may have been done at an inappropriately high RPM."
[http://www.estainlesssteel.com/gallingofstainless.html]

I think this could be a large part of it. The stainless U-bolts and nuts
supplied by Cushcraft with the antennas I've built felt "rough" right out of
the box while spinning the nuts up and down the bolt threads. There were
many rough spots where you could feel the nut almost catch, even with no
load on the threads at all! I don't experience this no-load roughness with a
lot of other SS bolt/nut combinations, even stuff I can buy at Home Depot or
Lowe's.

So, maybe partially the grade, maybe partially the thread quality. But
again, all problems associated with this behavior are alleviated by
pre-lubricating the threads with Penetrox (or practically anything else).

Bill W5WVO


----- Original Message ----- 
From: "Ray Brown" <kb0stn at sbcglobal.net>
To: <50mhz at mailman.qth.net>
Sent: Saturday, July 08, 2006 7:31 PM
Subject: Re: [50mhz] cushcraft question


>   It may well be that the Cushcraft stainless steel is of a different
composition
> than what we're used to. There's 3 or 4 versions, it depends on the amount
> of nickel and chromium in the mixture. There is one version of stainless,
I
> think 304, that is still magnetizing, that is you bring a magnet up to to
and
> it's attracted to it. I think there's also a 306, a 307, and a 312.
>
>                 _Ray_        KBØSTN
>
> Moderator: Ray Brown, KB0STN