WG flanges are brass or aluminum. Dowel pins are case hardened steel. For all practical purposes, they do not wear.
-John ================ > Robert, > > > Many apologies for giving you the "big snip" (!) - replying to TN postings > when receiving via "Digest mode" leaves room for such mishaps. > > I'm not familiar with 5/32" dowels or how well they fit in WG mounting > holes. One major problem is European IEC & US-MIL spec'd flanges have > varying size holes! 5/32 is 0.156 - this dowel may/may not fit WR75 > (0.144 or 0.161) but will be "loose" on WR90 (0.169). Then there's metric > & imperial variations ... > > What I can say with confidence that if you're building a WG run with 20-30 > flanges (ie an HPA hybrid combiner) using disparate makes of hardware and > don't take anal care with tapered pins on each and every joint, you <will> > end up with dB's of ppk ripple when the assembly is swept end-end. This > is well-nigh impossible to reduce without re-aligning every flange. If > the system has only a few mating flanges, other methods may be OK. > > I can appreciate how shoulder screws reduce the degree of craft assembly > skill and assembly time required - certainly less messy than pins ! Thick > flanges don't seem to be in common use in satellite earth stations. (BTW > - do dowels wear with use?) > > Rgds, > > > Kit > VK2LL > > ***************** > > Message: 4 > Date: Mon, 20 Sep 2010 18:44:37 +0000 (GMT) > From: Robert Atkinson <[email protected]> > Subject: Re: [time-nuts] WG mounting h/w (2) > To: Discussion of precise time and frequency measurement > <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=iso-8859-1 > > I think you are a snip too soon. My original post said "If you have to use > screws, at least align two diagonal holes with 5/32" dowels while nipping > up the ?first two screws". Taper pins are also OK of the taper is slight > and flanges are not too thick. Don't tighten the first two screws too > tight at first to aviod warping the flange.?In aircraft installations I've > designed have used shoulder screws because they were specified by the > equipment manufacturer. > ? > Robert G8RPI. > > > --- On Mon, 20/9/10, Kit Scally <[email protected]> wrote: > > > From: Kit Scally <[email protected]> > Subject: [time-nuts] WG mounting h/w (2) > To: "[email protected]" <[email protected]> > Date: Monday, 20 September, 2010, 9:19 > > > > Hi, > > > Well, still not strictly, strictly true !? > In Ku & K? band earth stations I've worked in, I've never seen shoulder > screws used, although the equipment used was mainnly from the USA.? > Next to you precision adaptors, SMA torque wrenches etc in your personal > goodie box are sets of tapered pins, about 35-40mm long - that fit various > diameter WG mounting holes (the old metric vvs Imperial issue again). > > You insert a pair of pins on diagonal corners then add bog-standard SS > hardware to the opposite diagonals & tighten.? The tapered pins are then > removed and replaced with another pair of screws/nuts.? This ensures > absolute (?) internal WG slot alignment.? There are a few variations on > this theme if you must have absolutely minimum RL within that section of > guide or if one guide face is threaded.? Hex-headed bolts are usually > used. > > That may explain why shouldered bolts are seldom seen. > > Tapered WG pins fall into the 99.9999% unobtainium class of materials. > > > Kit > VK2LL > > Message: 2 > Date: Mon, 20 Sep 2010 14:58:41 +0000 (UTC) > From: [email protected] > Subject: Re: [time-nuts] WG mounting h/w (2) > To: [email protected] > Message-ID: > > <324993853.1018422.1284994721127.javamail.r...@sz0110a.emeryville.ca.mail.comcast.net> > > Content-Type: text/plain; charset=utf-8 > > Another mystery solved! > > My (late) father-in-law spent most of his career at Varian-Eimac, mostly > working on TWTs, BWOs, and the occasional magnetron. In one batch of his > goodies, along with the H&S SMA torque wrench, was a little box with some > tapered metal pins! I've wondered what those were for, and now I know! > > He was very happy when his daughter brought home someone who knew what > vacuum tubes were, even if he did think that the RF work I did as a ham, > even the 144 and 440 MHz stuff, was still practically DC... > > Bob K6RTM > ------------------------------ >>>snip > ------------------------------ > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
