You can also use small machine screws if you grind the nuts down to clear and use high strength Locktite. I'm not a big fan of those cheap spot welders as they often either stick or fail to get a good weld.
don't trust those cheap spot welders like jjk308 says. you need at least 2.0mm at best 3.0mm range and they just won't cut it. many body shops(good ones) are buying spot welders to use in collision work. they are pinch type welders that will handle 3.0mm steel. this is what we have where I work and in my opinion and experience would be the only sutable welder for this work. you may want to find a sheet metal shop in your area that has a spot weld setup, they may be able to help you.
That's good to know. I've been looking at a cheap spot welder, but even el-cheapos are $150. I might be able to locate one to borrow locally. This particular one is a screw build, so I'm not adverse to the screws, but I would like to get the spot weld practice in for one I rivet. Thanks for the help. Any more comments are appreciated as well.
the 110 ones dont give good welds, my buddy has one and its a POS. i bought one of the harbor freight 220v ones and i have not had a rail tack pop off of the 10 ak's and a psl ive built and my buddys have used it for their 6. all of my ak's get pounded hard. the lowest round one of mine is well over 500 down the pipe