Since I have yet to see a tutorial with acceptable spot welds, I started this thread to help builders achieve good spot welds. I will edit it and add pictures as I think of new things to add. When I first tried spot welding, my welds were terrible, so anyone who is having problems can do it. Keep in mind that this is the same cheap 115V Harbor Freight spot welder everyone else is using; however, a quality 110V or 220V Miller spot welder with a timer will achieve even better spot welds. With some reading, patients, and practice, everyone can have excellent spot welds. If anyone needs any help, post pictures of your welds and spot welder setup, and I will help you fix the problem(s). Also, if anyone else has pictures of good spot welds that they would like to contribute to this thread, please do so. Here are some excellent resources for spot welding: Miller Owner's Manual, Handbook for Resistance Spot Welding, Spot Welding Guidelines, http://www.gunco.net/forums/f43/spot...dimples-37801/.
Keys to achieving good spot welds:
- File upper tong tip to ~0.150-0.180" diameter; lower tong tip to ~0.180-0.210" diameter.
- Adjust tong pressure so that lower tong flexes slightly even without any workpieces between tips. Be sure hex jam nuts are tight and hand lever stop is set.
- Be sure tips are flat against workpieces when clamped together.
- Be sure tips are properly aligned when clamped together.
- If possible, plug spot welder directly into outlet.
- Chamfer ends of lower rails where they meet trunnion. Use receiver stub as reference. This will allow for smoother operation of bolt and bolt carrier.
- Be sure workpieces are free from dirt, grease, and oil.
- Be sure workpieces are clamped properly. If spatter is expelled from between workpieces, they are not clamped properly.
- Use correct number and placement of spot welds. Refer to the picture below and make reference marks on receiver. (There can be 2 or 3 spot welds above magazine well on right side.)
- According to a professional I spoke with, weld time should be about 0.5 seconds to 1 second. I recommend about 0.7 seconds for 0.040" + 0.040" combinations and about 0.9 seconds for 0.040" + 0.0625" combinations; however, it may be easier to look at the size of the area of discoloration. Excessive weld time may warp your receiver.
- Notice the area in the center of the spot weld is not discolored. If a portion of the area in the center is severely discolored, the tips were likely not flat against the workpiece, or there was not enough pressure.