Today I've been cleaning off some rust off a backhoe using a wire cup brush on an angle grinder. I thought these brushes would last a fair while, but after about 15 minutes of use it lost most of its wire (depositing quite a bit into my overalls, spear style :-D). Is this the typical lifetime for these brushes? I guess if the angle grinder does about 8,000 to 10,000 rpm, after 15 minutes each wire has probably been flexed enough times to create large fatigue cracks which cause the wires to snap off. I don't have a needle scaler and I can't really justify hiring someone to shotblast the rust, but these cup brushes cost about £5 each, so it's annoying. Maybe I'm using them wrong - I was using the edge of the brush to get into awkward corners, but this might reduce the lifetime of the brush. I guess even if I buy a box of 10 it's still a lot cheaper than blasting. Any thoughts?