Luckily, Mazda used a self cutting bolt on the 1st gens and this really helps when rebuilding these cars.
When the car was built, Mazda welded in blank captives into the shell and then used 6mm hex head 'taptites', a self cutting bolt that was driven into the captives, cutting its own thread as it went in. This saved Mazda pre-threading the captives first. It has a slightly triangular shank that cuts the thread.
I bought a big bag of these from my local fixings specialist and they just swap like for like with the existing bolts. I have swapped loads of mine and everytime I work on the car and remove one, I replace it with a new taptite and put a bit of copper grease on the thread before I screw it in to make it easier to remove in the future.
The taptite bolt...
The great thing about these is that if/when you snap the head off a bolt, just drill a 5.5mm hole through the snapped off bolt and then drive in a new taptite.... most of the time it'll pick up on the original threads and the jobs a gud'un. You don't even have to clean out all of the old bolt back to the threads. The bolts also look 'factory' with the same 10mm head.
I drive mine in with a cordless drill...
I bought 500 for a few quid.... well worth the money!!
