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For what it's worth:
1. Not all "line filters" do an equally good job cutting out line spikes, and compared to what they're designed to block, NONE of them is really supposed to be highly effective at this particular task (actually somewhat LOWER FREQUENCY than they're really good at)! I would look closely at multistage line filters to see if you can find something more effective.
2. Nobody (so far) has mentioned whether the limit switches are designed to be used in "dry circuits" (with practically zero current going through them). The right switch for this has a tiny amount of gold (or WE alloy #1) at the surface of either contact, the concept being that gold is so unreactive that it practically never forms "gold oxide", but tin oxide forms on the contacts of all the other switch types, and once the oxide forms YOU NEVER REALLY KNOW whether you're detecting a circuit closure or not (and this would readily form over time in the shop environment, and without current to cause "burnoff" it stays where it formed)! This goes quite a ways toward explaining why the lashup worked well for a couple of years and then started misbehaving. Since nearly all of these limit switches are in one of a small handful of form factors, you should have no difficulty finding something that fits, so I would strongly try replacing the switches with something designed for this type of service, it might cost a couple of bucks more but the reduction in aggravation is certainly worth it.
1. Not all "line filters" do an equally good job cutting out line spikes, and compared to what they're designed to block, NONE of them is really supposed to be highly effective at this particular task (actually somewhat LOWER FREQUENCY than they're really good at)! I would look closely at multistage line filters to see if you can find something more effective.
2. Nobody (so far) has mentioned whether the limit switches are designed to be used in "dry circuits" (with practically zero current going through them). The right switch for this has a tiny amount of gold (or WE alloy #1) at the surface of either contact, the concept being that gold is so unreactive that it practically never forms "gold oxide", but tin oxide forms on the contacts of all the other switch types, and once the oxide forms YOU NEVER REALLY KNOW whether you're detecting a circuit closure or not (and this would readily form over time in the shop environment, and without current to cause "burnoff" it stays where it formed)! This goes quite a ways toward explaining why the lashup worked well for a couple of years and then started misbehaving. Since nearly all of these limit switches are in one of a small handful of form factors, you should have no difficulty finding something that fits, so I would strongly try replacing the switches with something designed for this type of service, it might cost a couple of bucks more but the reduction in aggravation is certainly worth it.
