[Elecraft] K3 KNOBS
Ron D'Eau Claire
ron at cobi.biz
Mon May 18 12:21:12 EDT 2009
Cookie has it right. It seems to me another issue is that many of the knobs
have tight threads. Not terribly tight, but requiring more torque than I
normally see on such a small screw. I had some like that on my first set.
Lube didn't help. That makes it difficult to tell how hard they are binding
against the control shafts.
Also, I wondered if the fact they were tight wasn't due to a slightly
undersized hole, so the set screw acted like a wedge pushing outward on the
surrounding area as it was screwed in. A wedge like that can exert huge
force on the knob even though it's not very hard to turn. That could be the
source of stress cracks before the knob was even tightened.
The Aptos folks have been very clear for a long time that they got a bad
bunch of knobs and have replaced them as quickly as cracks have been
reported. So far, my second set, received almost a year ago, has been fine.
Ron AC7AC
-----Original Message-----
Posts like this are no doubt well intentioned and good advice in general.
For these knobs with built in stress cracks normal care is not adequate.
Use the short handle for leverage, just tighten barely enough that the knob
does not slip on the shaft, expect the knob to fail while you are adjusting
the knob at some point in the future. If can keep spare knobs on hand.
Elecraft are taking steps to get us better knobs and I am confident they
will succeed soon and do something that is appropriate, but it takes a while
to accomplish these design changes. I am sure they will let us know soon.
But don't assume that those of us who have had failures are ham-fisted
klutzes who don't take normal precautions. That could be the case
sometimes, but certainly not the general situation in this case.
Willis 'Cookie' Cooke
K5EWJ
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