Switch mounting hardware search 1

[BetaGamma]

I have a vague memory, from too many years ago to count, that many toggle switches came with a special lock washer. For the typical 1/2" dia. threaded bushing with a keyway, an external star lockwasher was provided with an internal tab to fit the keyway. This allowed the switch to be mounted in a round hole with a positive lock to prevent rotation, instead of just tightening onto a plain lockwasher.

I hadn't thought about it for a long time, until I got into a project where such a lockwasher would be very convenient.

Has anyone seen such a lockwasher and maybe a source? I haven't been able to find them anywhere and it's really bugging me ....

 

[VEBill]

The ones I've seen require a little panel hole beside the big panel hole.

I used the search terms toggle switch lock washer and then looked at Google Images.

 

[Comcokid]

Such parts are stocked as switch accessory hardware. Quick check at Mouser Electronics shows they are stock under a variety of names in the data sheets and catalogs.
Carling and C&K list them as "Locking Rings" in their catalog. EAO calls it a "Anti Twist Ring". Grayhill terms it a "Non-Turn Washer". NKK list is as a "Locking Ring". Lots of different sizes out there for rotary and toggle switches, both English and Metric sizes, up to sizes for industrial control panel switches.

 

[BetaGamma]

This isn't it - you missed my point about it being an external star lockwasher.

I've used these "anti-twist" tab washers inverted with a plain internal star lockwasher between it and the panel. Torqued down tightly, the lockwasher will dig into the backside of the (preferably aluminum) panel. The tab washer itself is usually pretty hard and really doesn't secure as well when using this method, but at least it doesn't require the second hole. Unless there's a cover over the panel, that second hole looks like crap.

The whole point of the part I've been looking for is that the mechanical load goes straight to the panel via the tab in the keyway.

 

[mcgyvr]

Many panel mount toggle switches either have the tab integrated into the body of the switch and have standard lock washer or other method to prevent rotation now.

 

[BrianG]

BetaGamma - you are supposed to counterbore the REAR of the panel for the anti-rotation tab. That way all you see from the front panel is one neat hex nut (or a round knurled ring depending on the switch type)sitting flush on the first few turns of the thread. The other (lock) nut, the star washer and the tabbed washer are tightened from the rear of the panel to secure the switch.

 

[BetaGamma]

Yes, we typically have an indent machined into the back side of a panel for the anti-rotation tab on thicker panels which are also structural. This presents 2 issues: The machine shop has to set up for the milling the indent, at extra cost, and there may not be sufficient thickness on a given panel to mill the indent.

Having an extra hole punched adjacent to the switch mounting hole is somewhat cheaper than milling, but leaves a perforation. If a panel cover is used, such as a self-adhesive polyester sheet with switch legends, etc., the holes may be acceptable. But this adds to the cost and not all jobs use such a cover. We typically use painted panels with silkscreened legends.

The workaround method of installing the tab washer inverted gets the job done, but is not the best method. My whole point is that with the lockwasher tying the switch bushing to the panel, the extra metal fab cost goes away.

 

[BrianG]

I'm surprised you say the indent is an extra MILLING operation and of extra cost - are you into mass production of panels?. If you are not into volume panel production then your machine shop is probably 'hand-crafting' the panels and has probably drilled the hole for each switch bush; then the small extra indent hole in the rear of the panel for the lock washer tab is only one change of drill size and hardly a major cost driver overall.

If you are into mass production then the proper way to do this is to throw away the lock washer method altogether! Invest in a punch / press tool that pierces the bush hole, with a locking tang on the inside of the hole, all in one operation. (The tang engages in the same groove in the switch bush that the lock washer would have used)

 

[telecomguy]

Using the google image search as mentioned above (which is one of my favorite/most productive ways of finding things), I ran across this one. Is this what you're describing?

http://www.ereplacementparts.com/bearing-lock-washer-p-771372.html

-tg

http://xternal.me