Perhaps a bit big for electronics work, but I’ve become a big fan of the Borka adjustable torque wrench for mounting optics.
On Sunday, October 29, 2017, Bob McGraw K4TAX <[email protected]> wrote: > Here is one reliable source for screw torque. > > http://www.mgtd.ca/screw%20torque.htm > > Now, to get the proper torque tools and use them. > > 73 > > Bob, K4TAX > > > > On 10/29/2017 8:34 AM, Clay Autery wrote: > >> It is possible that an explicit torque has never been calculated. It is >> not a particularly hard thing to do however. >> >> I do not have a K2, so I can't do it, but here's the idea: >> >> 1) Fastener size/type, material, thread spec: (e.g. 4-40 x ___ pan head, >> phillips, zinc coated, non-rated steel >> 2) What does fastener anchor in? (e.g. aluminum heat sink, what alloy >> aluminum, thickness of threaded area. >> 3) Thread spec... not JUST the #4, 40 tpi, but the rating for thread >> engagement. >> 4) Check the specs for the RF transistor.... package, et al. Docs >> may/should have a max torque spec for the package.... maybe... package >> material, etc. >> 5) # of fasteners... usually 1 maybe 2. >> >> There are tables that specify general torque specs for fasteners, threads >> in various materials, etc.... The idea is to take the lowest max value from >> the list. This becomes the MAX NTE. >> Then, use some analysis and judgement in what forces are to be imparted >> to the joint.... static tension, sheer, axial, radial, vibration, et al... >> Then in this instance consider the qualities of the mating surfaces.... >> are the flat? What is the run out? Are they smooth? To what grit spec are >> they smooth? There's a difference between flat and smooth. >> What is the interface material being used? Thermal pad? Insulating? >> Non-insulating? Initial thickness? Read the spec sheet for the thermal >> pad/compound. >> >> I suspect here that the RF package has an insulating thermal pad between >> it and the heatsink... It was probably spec'd to keep the RF package >> within its operating envelope under 90% of expected operating conditions... >> knowing Elecraft, probably even a higher spec, and maybe a little extra to >> cover the "cheater". >> >> Thermal pads and MANY top quality thermal compounds REQUIRE a curing >> period. If the package is held with a tension spring/fastener, there is >> usually no requirement/need to re-torque. >> >> IF it is JUST a screw and maybe a locknut, you NEED TO RETORQUE after a >> given number of thermal cycles.... The thermal interface material flows >> under heat and cools when not in use. Eventually it reaches an equilibrium. >> You torque the fastener JUST enough to hold the junction static at this >> point. I'm a freak, I would use a thermally conducting thread >> locking/anti-seize compound (I made one). >> I NEVER torque unlubricated fasteners.... ESPECIALLY steel to aluminum >> interfaces. >> >> The final torque for this application is likely in the relatively low >> inch-pound range.... just guessing. I have 2 inch-pound wrenches... 0-15, >> and 0-70. Most people don't.... >> >> Key... do NOT over-torque. Consider the lever length and force applied... >> >> 73, >> Clay, KY5G >> >> >> On 10/29/2017 8:03 AM, David Woolley wrote: >> >>> As far as I can tell, no torque settings are given for any of the >>> fasteners, wouldn't it be an idea to provide those, for people who do have >>> suitable tools. Generally there are just warnings not to over-tighten. >>> >>> On 28/10/17 20:24, Mel Farrer wrote: >>> >>>> If the people at Elecraft have done their job and mounted the >>>> transistor properly with the correct torque on the mounting hardware >>>> procedure, no additional maintainance is required. >>>> >>> >>> -- >>> David Woolley >>> K2 06123 >>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] >> > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] -- Scott Small ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
