[JustGus]

I'm about to buy a magnetic earth clamp, as often I'm welding surfaces where a normal clamp just can't grab hold, or will damage the surface. My assumption is that I should get a clamp that matches, or is just above the amp rating of my machine, a Cigweld Weldskill 185. So, all other things being equal (e.g. build quality) a 500amp would be overkill and a 300amp clamp would more than do the job. Thought I'd reach out and check whether that's right. Any advice would be greatly appreciated.

[Louie1961]

I don't use magnetic clamps, but I always size my work clamps to match or exceed my machine's max output. Bigger can't hurt you, except maybe in the pocket ($$$).

[Spartan]

300A should be plenty and with room to grow. Checkout Magswitch if you haven't already. They have a few in their product line that serve both as a magnetic ground and as a magnetic fixturing tool. Little more bang for the buck with that added versatility since these things aren't cheap.

https://magswitch.com/products/?swoof=1 ... on&paged=1

[homeboy]

I have a 300A Magswitch on a 250A mig that never gets warm. Get the one with the cooling fins as the body is a one part casting from the wire lug to the base. The 2 part, non finned style that's bolted together can corrode between the parts, short a bit and get hot which requires occasionally taking it apart and cleaning. I use them on 2 welders and a plasma cutter and would never go back to a ground clamp. Make a little handle from 1" flat bar bolted to the switch lug and the cable bolted behind it, tape it up and just flip it around. Only time you really need to switch it off is for cleaning.

[JustGus]

Thanks @homeboy, @Spartan and @Louie1961! That's really helpful. The magswitch looks really well designed.

[Oscar]

Yup, thanks for the link. I'mma need that 800A magswitch soon!