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My upcoming preamp project will need a long shaft extension from the rear-mounted selector switch. From past experience, I know that 1/4" panel bearings often don't hold the shaft in position very well. They tend to create more side play than when a switch or pot is mounted directly to the panel, and sometimes they even rattle if the knob is "flicked" with a finger. I'm wondering if anyone has found an alternative to these bushings, maybe something made from hard-wearing plastic or other material? I have the machinery to DIY a solution, but I'd rather spend my time doing circuit design or wiring.
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Buy Chinese. Bury freedom.
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Remove the tip contact, and these make excellent shaft bushings.
I have used #11 jacks for this, and also the nylon version (#111N?).
while roller-bearing might be nice considering mechanical feedback and such you might find a simple phosphor-bronze bush with a oring groove might be the best solution. A bronze shaft with grove in it might be simpler still and the heavier the moving mass I suspect the better it will feel. Do a small cnc run and ebay the other half.
I'm not quite clear on what your are trying to accomplish. A support for a switch with a long shaft or an arrangement to extend a shaft through the panel. In the latter case they are common in electrical switchgear and the coupling should provide enough play that your concern should not be a concern. I'm off on a road trip so I don't have the time to search. If you could elaborate further I'll check in periodically. Or it might spark Eli's or someone else's imagination. I did find the link below.
Edits: 07/11/17 07/11/17
Keystone in the US also manufactures parts like that. The fit between shaft and hole is somewhat variable, and it often gives the knob a clunky feel that I dislike. I suppose there are a couple reasons this doesn't happen directly at the shaft of a switch or pot. For one thing, the manufacturer has control over the dimensions of both the shaft and hole, so tolerances can be tighter. Also, the parts are usually designed to be greased, which cushions the effect.
When I assembled the front panels for my SETs a few years ago, I bushed the holes for push switches with press-fit Delrin inserts. That worked really well, but it requires additional time that I was hoping to avoid in this case. Maybe there's no choice. I could use a 3/8" panel bearing and bush it down to 1/4", or maybe turn down the 1/4" shaft where it passes through the standard panel bearing and add an internal plastic sleeve. Like I say, was just hoping I could buy my way out of doing this. :)
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Buy Chinese. Bury freedom.
The original RM-5 from Music Reference used bearings as you mentioned in the OP and onece we solved certain issues -below - they worked quite well-
the only issue we had was galling then the bearing and shaft were the same material-
The comment above regarding sizing is appropriate and will - if addressed properly - make a difference in the Knob feel-
Delrin or PTFE (Teflon(r)) make excellent bearings but can be a challenge to machine correctly-
Happy Listening
Perhaps an additional support at approx. the mid-point of the long shaft, in addition to the panel bearing will solve the problem. Check this at McMaster-Carr out. I'm thinking that part # 5912K1 will do nicely. Aluminum standoffs can be used to get the pillow block's location just right.
Eli D.
Thanks for the suggestion, but I don't see how that could be relied on to reduce end play at the front panel. A live bearing doesn't necessarily improve the fit between the shaft and hole, and any free play at the pillow block would be angularly magnified several inches away at the front panel. Do you know of a particular bearing/bushing intended for panel mounting that might exhibit a tighter fit than the usual offerings?
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Buy Chinese. Bury freedom.
it is a lot tougher than Delrin. It threads well too. I use it for firing valves in 3650 psi air rifles...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
PEEK is tough stuff. The flange mount for the ball bearing I mentioned is made of PEEK.
Eli D.
McMaster-Carr part # 4575N33 is a 2 bolt, flange mounted, double shielded, ball bearing. Mount that item on the inside of the front panel.
Eli D.
That looks interesting, I hadn't thought about using a press-fit bearing. That would definitely hold the shaft in place. I wish the specs listed end play, but it's probably pretty good on a greased and sealed bearing. I'll order one of those as soon as I make up a larger order (shipping cost and all that). Thanks!
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Buy Chinese. Bury freedom.
First make sure your not using a 6mm shaft 0.240" in a 0.250 bearing mount. If that looks good maybe use some high viscosity grease or silicone damping fluid on the shaft.
BillWojo
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