Being new to spot welding, I'm learning about a few of the issues with this new, old, spot welder.
The first is getting replacement electrodes. With my machine being ancient, I can't seem to source the exact electrodes, which comprise 5mm copper rods which have a thread at one end, the thread screwing into a copper holder, which has a 6mm shank that is held in the welder arms by a grub screw. Not an insurmountable problem - I can just buy 6mm rods (I think) and plug them directly into the welder arms, eliminating the holder completely. Alternatively I can add a thread to 5mm rods with a die.
The next issue is the fact that new car panels come with a tough, electro-deposit primer (EDP), which interferes (as I discovered) with the circuit between the two arms of the spot welder, rendering it useless. This necessitates the removal of any paint, which itself can cause opportunities for rust formation at the joints at a later stage, which is not so much of an issue inside the car, but certainly is on exterior parts. However, I've discovered that you can coat the work area where the paint has been removed with what's called weld-through primer, which is rich in zinc and enables a circuit to be made through the paint.
You don't get these problems with arc or MiG welding - so long as there's a good earth, an arc will jump across almost any paint barrier, providing it's not too thick. Spot welding, on the other hand, is resistive welding and requires a complete, unimpeded circuit.
On another issue, I was trying to get an air connector for my new sheet metal nibbler and got really confused. Why is 1/2" BSP not half an inch when measured?
A 1/2 inch BSP thread actually measures more like 3/4 inch with a ruler. Apparently the size was originally based on the inside diameter, measured in inches, of a steel pipe for which the thread was intended. How bloody crazy is that?
It wouldn't be so bad if all the adverts for my Sealey 28A nibbler said it uses a 1/4 inch BSP, when it obviously doesn't (I have a bunch of 1/4 inch connectors and they're too small). It's a 1/2 inch. It's a bloody wonder that the British with their weird measurement systems ruled the automotive world at one time. It's probably also why they lost that position.
No comments:
Post a Comment