I purchased a used Miller MSW-41T 110 volt spot welder. I've downloaded the manual. There is an illustration of several tips. Most I understand.What is the difference in useage of the standard tips (040 211) and the flat tips (040 212)?
Also a question on supply wiring. The manual calls for 10ga wire on a
30 amp circuit breaker. My receptical is 14ga 20 amp 3 feet from the breaker panel. It hasn't tripped the breaker. Can there be any significant voltage loss in 3 feet?
I do not have a code book handy, but as I remember normal practice is to use 14 gauge with a 15 amp breaker and 12 gauge with a 20 amp breaker. So you might have another look and see if you have 12 gauge wire.
The code has some special rules on circuits for Welders. Someone here can probably quote it. I just remember there is an exception for welders.
There won't be significant voltage loss in three feet. If the spot welder needs to be on a 30 amp circuit then it likely draws more than twenty amps. Breakers don't blow instantly like fuses because they need to be used in circuits that have high loads for short periods, like motor starting. Your spot welder so far may not have been on long enough to pop the breaker. But doing lots of welds may cause the breaker to warm up enough to pop. The real issue is the reason the 10 gauge wire is called for, this is to prevent the wire from getting too hot in the wall. It may be that the reason your breaker doesn't trip is because it is faulty. You should really either connect it to a properly wired circuit. Failing that you should at least put an amp clamp on the spot welder supply wires to see how much current it really is drawing. If you have a faulty breaker then the 14 gauge wire in the wall may heat up and start a fire. Wouldn't you feel pretty stupid then? Eric
Never used that particular spot welder or seen those tips, but in general spot welding is a balancing act between the current your welder can supply, the thickness and thermal conductivity of the material you are welding, how big the pieces are, and how much strength you need. For thin low conductivity material (30 ga. stainless steel, for example) you can weld a bigger spot so using the flat tips would give you that, compared to thicker
16 ga. mild steel where you need the pointed tips to concentrate the limited current your welder can provide into a small enough spot to get it hot enough to weld. If you are sticking large flat sheets together big spots are nice because you can make fewer welds and still have the same square inches of weld and thus approximately the same tear-away strength, compared to lots of tiny spots that take longer to make. On the other hand, joining bent strips to make some delicate little bracket where the strips are already narrower than the flat tips requires the pointed ones just to get in where you need to make the weld and not blow out the edges of the material. Just depends on what the shapes of your pieces are and what you need. The pointed ones are more "general", the flat ones better in some circumstances.
----- Regards, Carl Ijames
It is in the shop. Wire is inside surface mounted metal conduit. Thanks for your concern though.