"Inside every project are a bunch of smaller projects, trying to get out." - anon
Damfoolishness first. I had a careless/clumsy moment, the drive box hit the floor, and the power switch broke its fall:
The toggle switch is a strange one from Tektronix, because I now perceive the baton was hollow plastic, not metal. Sheesh. Fortunately, the switch type is nothing special, and they are cheap.
Next, the buttons. I've been thinking about safety a lot lately, started making small tweaks around the shop. Everything short of putting guards on my machines, heh-heh.
One of the things that came to mind is this: suppose your spouse or neighbor hears you hollering for help (because your lathe has grabbed your hand, and wrapped your arm around the work, breaking it in seventeen places). They rush in and want to help. How do they turn off the machine? Maybe they've never seen a machine tool in their life, or maybe its your spouse but they just never made a study of the thing.
You know what all those buttons, knobs and levers do - they don't - but you're busy. There's eighteen of them on the average mill. And you're probably hollering (I'm being optimistic) so your rescuer is panicky.
OSHA and other agencies worldwide solved the access-to-dangerous-spaces (where the whirling bits are) the best they could with movable shields, light curtains, NO FOOT PEDALS, dual hand buttons and so on. But just in case, every machine has an Emergency Power Off which is larger than all the others, it is orange or bright red, and typically on a yellow background close to "eye level" for an average person.
I bet your machine doesn't have shields or light curtains. Mine sure don't. ^_^
Well, my lathe had a red mushroom-head stop button when I bought it, but it could use better labeling. It's a bit of a reach too because they put all the buttons at the back of the headstock instead of the front somewhere. That appears to require a major re-structuring of the headstock, so it's a toss-up whether it will happen in my remaining forty (I'm being optimistic) years. <_<
I originally installed a turn-to-select knob to control power to the rotary phase converter (which feeds power to the mill motor, if it's turned on) specifically this one:
I wanted to change it to a modern EPO type mushroom head. These were my options from what I had in my parts drawers:
super easy to install, change parts on, change functions...
The next one to the right was no good because it's a momentary button, which is no good - only useful in telling a relay to drop out, but that's not what we want. We want positive actuation of the actual switch contacts.
The next one is exactly what we want; when it is pushed in, it positively holds the contacts open, and it stays firmly in either position. Pull to run, and it too is a drop-in replacement.
But the complete replacement from Itek on the far right has one thing going for it, which I like: you don't turn the power back on by pulling, you reset it by turning. Howsomeever, I would need to buy new contacts for it, I would need to embiggen the hole slightly, and right now, the Telemecanique block is the ground for the whole box, very convenient, its jack screws dig through paint into the metal, no extra holes. So the Itek doesn't seem worth the trouble.
In the end, I went with #3. To change it, the switch/lamp panel mounting body has to be loosened but not removed - two straight bladed jack screws on the inside of the panel. Then the switch/lamp/whathaveyou bayonets out, the new actuator/lamp/whatever bayonets back in, re-tighten those two jack screws and you are done. Voila:
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| I wish it had better labeling; at least my block printing is legible. |
I had to change the contacts too (from NO to NC) but I had spares. It's one mounting screw per pole, and BTW they have good, easy to access wire clamps. AFAIK, none of their kit is made the same way any more, more's the pity.*
By the way, the reason this switch is in such a rugged, sealed, flanged box is that the available fault current from this circuit is several hundred amps before the breaker (motor time delay type) trips, which translates to a released power of 43,200 watts minimum. That's a lotta calories while that breaker decides whether this new load is a big motor or a short cirtcuit. If something shorts in that box, the flanges direct any arc flash or other ejecta away from the operator. That's the downside to not having some relays in a box somewhere far from the operator. OTOH, this is more failsafe. The box is also gasketed, don't recall what NEMA equivalent, but it'll keep out splashes of cutting fluids.
Those familiar with industrial controls know that panel switches are only good for "pilot duty" which in most cases, including these Tele contacts, means 240VAC @ 10A. The phase convertor pulls about 3A when idling, 5A when the motor is running. Load or no load is nearly the same. The actual increase in electrical load when machining is very low on this machine, the way I run cutters with low CPT loads.
That said, those contacts could, in theory, over a long time, weld together. I think I will install a pair of these QuenchArc components I just happen to have lying around (bought for air compressor), across those two contacts, eliminating arcing and extending their life past the life of the mill, in all likelihood. As soon as I remember where I stashed them. >_<
It's not paranoid to try to do a good job while keeping a weather eye on potential misfortunes.
______
* I believe this entire line of products was rendered obsolete by a Euro-initiated safety standard which disallows any conductive parts passing through the panel, which describes most of the old series Telemecanique devices. D'oh!
~≈{👁}≈~
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