[K3} Help, hex key for split knob
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> My experiences are different. For small knobs you need to > use high > quality wrenches. Those .050 do work if you have a good > one. It's > amazing how much twist you can put in a high quality Allen > wrench > while trying to deal with a stubborn screw. I would not ever force the screw. That is just asking for problems. Off the shaft and on the table, run it in until it resists turning and then back out. Do that several times cleaning the threads out. > As an old-timer I dealt with many a slotted set screw. > Nothing but > headaches. No truer words were ever spoken!!! The last thing I would want is phillips, and then second last would be slotted screws. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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My personal rule for torque-wrenching small allen screws (once I know
threads are clear) is "pinky pressure". I turn the allen wrench until it *just barely* runs into resistance. Then I put my pinky on the wrench and let some of the weight of my forearm (no pushing) tighten it up. Should not ever be stripping allen wrenches in K3 RF/AF knobs. The replacement knobs I got for the flawed early batch that came with my K3 have been just fine. 73, Guy. On Tue, May 11, 2010 at 8:21 PM, Tom W8JI <[hidden email]> wrote: > >> My experiences are different. For small knobs you need to >> use high >> quality wrenches. Those .050 do work if you have a good >> one. It's >> amazing how much twist you can put in a high quality Allen >> wrench >> while trying to deal with a stubborn screw. > > I would not ever force the screw. That is just asking for > problems. > > Off the shaft and on the table, run it in until it resists > turning and then back out. Do that several times cleaning > the threads out. > > >> As an old-timer I dealt with many a slotted set screw. >> Nothing but >> headaches. > > No truer words were ever spoken!!! The last thing I would > want is phillips, and then second last would be slotted > screws. > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: [K3} Help, hex key for split knob
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In reply to this post by Don Wilhelm-4
Don,
Wrong answer, guess again. The kit supplied allen wrench strips because it is a cheap, low quality tool that can not support the required torque. The required torque is higher than necessary because of the overly tight, tapered, and/or incomplete threading of the set screw hole in the knobs. The concentric knobs are undoubtedly splitting because they are plastic knobs that have the set screw threaded directly into the plastic. That design is a non-starter from a quality perspective and is bound to fail in one way or another, sooner or later. The engineering dilemma with an all plastic knob is that if the set screw threading isn't tight the set screw will strip out the plastic threads before achieving enough force to secure the knob to the shaft. On the flip side if the threading is tight enough to allow securing the knob, it is also tight enough to tend to split the plastic around the set screw hole via radial pressure when torqued. This is why quality knobs are either all metal or have metal inserts for the set screws. Being an old gunsmith, I'm not intimidated by slotted screws and wouldn't hesitate to swap out the allen drive set screws with slotted ones, and probably will if these knobs ever need to be removed. I realize that this is a good solution only if one actually knows how to properly fit and operate a slotted screw driver. The "pinky" tight approach is OK if you are working with a "D" shaft that provides positive indexing. Otherwise, as in the round shaft K3 concentric pots, the set screw has to be very tight to maintain the knob indexing. 73 Jack KZ5A -----Original Message----- From: Don Wilhelm [mailto:[hidden email]] Sent: Tuesday, May 11, 2010 5:39 PM To: Jack Brabham Cc: '[hidden email]' Subject: Re: [Elecraft] [K3} Help, hex key for split knob Jack, If you stripped out the allen wrench, you were applying more force than is necessary, and excessive force may be the reason some of the newer knobs are cracking (that is just a guess). 73, Don W3FPR Jack Brabham wrote: > Tim, > > I had a similar experience assembling #4169 a few weeks ago. Unfortunately > my stack of assorted allen wrenches didn't include any that small. > > My work around was to grind off the "stripped" portion of the cheesy allen > wrench each time it stripped. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Out of curiosity reading this thread I just removed the knobs on my K3
for the first time since they were installed nearly two years ago. The screws came out easily after the initial stiction was overcome; Twirling the wrench between thumb and index finger is all that is required to drive the screws through the knob. I doubt that even the ceapest 0.05 allen wrench would have a problem loosening them, yet the knobs have remained firmly in place for all this time. The "loose" threads on mine make it easy to adjust the screw tightness by feel. I suppose this would not be the case if the threads were very tight. In that case I would adjust the screws by sight initially then cinch them up a bit against the shafts. If someone is having a problem with the knobs coming loose or cracking, I'd suggest inserting a small "dot" of neoprene-cork gasket material into the threaded hole between the shaft and the screw. The friction will keep the knob on the shaft while the soft seat will perhaps reduce the chance of overtightening and cracking. (I do this for the speed weight on my bug to avoid having to apply a lot of torque to the setscrew; it is very easy to adjust by feel yet holds the weight snugly in place on the pendulum shaft.) 73, Drew AF2Z On Wed, 12 May 2010 10:29:03 -0500, you wrote: >Don, > >Wrong answer, guess again. > >The kit supplied allen wrench strips because it is a cheap, low quality tool >that can not support the required torque. The required torque is higher >than necessary because of the overly tight, tapered, and/or incomplete >threading of the set screw hole in the knobs. > >The concentric knobs are undoubtedly splitting because they are plastic >knobs that have the set screw threaded directly into the plastic. That >design is a non-starter from a quality perspective and is bound to fail in >one way or another, sooner or later. > >The engineering dilemma with an all plastic knob is that if the set screw >threading isn't tight the set screw will strip out the plastic threads >before achieving enough force to secure the knob to the shaft. On the flip >side if the threading is tight enough to allow securing the knob, it is also >tight enough to tend to split the plastic around the set screw hole via >radial pressure when torqued. > >This is why quality knobs are either all metal or have metal inserts for the >set screws. > >Being an old gunsmith, I'm not intimidated by slotted screws and wouldn't >hesitate to swap out the allen drive set screws with slotted ones, and >probably will if these knobs ever need to be removed. I realize that this >is a good solution only if one actually knows how to properly fit and >operate a slotted screw driver. > >The "pinky" tight approach is OK if you are working with a "D" shaft that >provides positive indexing. Otherwise, as in the round shaft K3 concentric >pots, the set screw has to be very tight to maintain the knob indexing. > > >73 Jack KZ5A > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jack Brabham KZ5A
> The "pinky" tight approach is OK if you are working with a
> "D" shaft that > provides positive indexing. Otherwise, as in the round > shaft K3 concentric > pots, the set screw has to be very tight to maintain the > knob indexing. Jack, We used tens of thousands of knobs at Prime, Heathkit, and other places. Plastic knobs without inserts were generally OK except for rare cases. All-plastic knobs without inserts historically have been used in everything from TV's and radios to cars and everything else around us. The set screws in my K3's knobs are a cup point style. That is not a good holding screw, but it should be OK for a small knob if the shaft isn't too hard. It would be great on plastic shafts, or even a very soft metal. It is not a screw of preference for a plastic knob, especially on a hard shaft. Since the knob is pretty well set in one place and not frequently removed, and since it is a plastic knob without a metal insert and tight clearances, it should probably be a sharp pointed setscrew like a cone point. It would take very minimal torque to securely lock a sharp cone point. Cupped screws mainly lock on the raised edges that run parallel with the circumference of the shaft. This means they "slip" with the sharp edge in line with the force, like a saw cutting across a round shaft. They also spread the pressure over a larger area. This all means a great deal less holding power, especially with hard shaft. A cone pointed screw would put all the pressure on a needle point, and even with a hard shaft dig in pretty deep with minimal pressure. They are far better on non-insert knobs. With metal insert knobs they could make it difficult to remove the knob because they would divot the metal and not allow easy removal, so a cone point or even flat point and higher torque is better with a insert knob. The problem is the screw has to turn freely, has to have the right tip, and can't be torqued down on. It really should just take "pinky pressure" or less. This isn't the rear axle-shaft nut in a 1960's Chrysler or AMC, it is a tiny knob on an easy to turn shaft. 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Here's a link I just found....
http://www.radax.com/store.asp?pid=15198 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: [K3} Help, hex key for split knob
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Tom,
Great link, thanks for digging that one up. So far my concentric knobs haven't split and are staying on the radio, and so I'm content to leave well enough alone. I was mostly grousing about the time and aggravation involved in mounting them due to the set screw threading issues with the plastic knobs and cheap allen wrench. If they ever have to come off or eventually split I'll get better set screws before replacing them...or look around for a set of better quality knobs. 73 Jack KZ5A -----Original Message----- From: Tom W8JI [mailto:[hidden email]] Sent: Wednesday, May 12, 2010 5:36 PM To: Jack Brabham; [hidden email]; [hidden email] Subject: Re: [Elecraft] [K3} Help, hex key for split knob Here's a link I just found.... http://www.radax.com/store.asp?pid=15198 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by W8JI
Hi all,
I can't believe all the messages my original post created. Well, today I swung by the local Home Depot and invested in a 13 piece inch kit that promised to include the 0.050" one. I am sure I will never use the 3/8" one, but I could use a new inch kit anyway. It came with a nice yellow plastic holder to hang on my tool wall. I had no problem putting the knob on, no excessive friction or tendency of the tool to slip. Just finger tightened it (them) and don't expect any problem with that one for years to come. Don't know what all the fuss is about. AB2TC - Knut
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