Deadly lathe switch and replacement. Exposed 120 volts on the contacts. - Page 1
Forum section: electronics / general

author: Mysion
author_rank: Regular Contributor
timestamp: December 13, 2017, 11:03:38 pm
content: I thought some of you might get a kick out of this. I bought a used lathe a few months back and it came with and "interesting" setup.Yes sir that's exposed 120 volts on the contacts. Up is forward and down is reverse. There's no off position either. To switch it off you have to balance the switch vertically.I bought it from the second owner. More of a collector than any thing so I have no idea what the brain dead idiot that made this was thinking.Probably thought electricity would grown some hair on his chest.I didn't have much of a choice so I replaced the whole electrical system. It was tedious figuring out what the motor wanted for forward and reverse. Other than that it was easy enough to rewire it.Here's what the new one looks likeOn the left you can see the new system. The 3 position switch on the top is Forward-Off-Reverse. The estop button is the primary switch when the machine is in use. No exposed wires and a dual switch system.Nice little lathe now that's it's safe to use. For any one interested it's an Atlas 6-18 lathe.Whats the most dangerous piece of shit that you've stumbled upon?

author: jmelson
author_rank: Super Contributor
timestamp: December 13, 2017, 11:35:21 pm
content: Wow, I think that knife switch is several (human) generations older than the lathe!Using it on 120 V is just NUTS! Especially on a lathe with metal chips flying about the place.Jon

author: james_s
author_rank: Super Contributor
timestamp: December 13, 2017, 11:43:27 pm
content: It's funny how at one time a switch like that was considered perfectly acceptable, although not within the life of that lathe. While it wouldn't bother me to operate a switch like that in general, I wouldn't want to use it around a metal lathe.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 14, 2017, 02:00:31 am
content: Quote from: jmelson on December 13, 2017, 11:35:21 pmWhat? I have seen them on generator switchboards. The switchboard was made of marble and the round instruments had handmarked scales. We call them Frankenstein-style switches.

author: rhb
author_rank: Super Contributor
timestamp: December 14, 2017, 03:13:30 am
content: That was probably a rotary switch that died and got "repaired" with what was readily to hand. The one on my Clausing gives me fits. A plastic cover would have fixed it properly, such as a scrap of PVC pipe with a slot for the handle.Given the potential need to shut down a lathe quickly, leaving the contacts exposed like that was asking to have a bad day.

author: Mysion
author_rank: Regular Contributor
timestamp: December 14, 2017, 06:12:53 am
content: jmelson it certainly looks old enough! It's got the corrosion to match!To Neomys and blueskull nothing wrong with knife switches in the proper environment. On a wall some where so that I'll never have to touch em!I'm a clumsy bastard I don't need help hurting myself!rhb that's not a bad guess at all. When I installed the new switch the price of a proper drum switch was over 50$, probably even more at the time.Funny enough the original builder took the time to earth ground the metal shell.

author: james_s
author_rank: Super Contributor
timestamp: December 14, 2017, 06:31:42 am
content: A pair of 3-way light switches could have been ganged together pretty easily to get DPDT, still not exactly correct, but cheap and safer than an exposed knife switch.

author: rhb
author_rank: Super Contributor
timestamp: December 14, 2017, 02:45:38 pm
content: I've not seen a drum switch under about $70 which is why I keep putzing with mine rather than buy a new one. Most of my problem is caused by the way the handle is mounted to the switch. The set screw takes a 1/16" allen wrench! It's also very difficult to align it correctly because of the way it's mounted to the spindle housing. In all fairness, I have not taken the time to rework it. I just reset it when it gets loose.I should probably replace it with relays with buttons for forward and reverse and a big "STOP" button.