I make my own studded tires as well. I think the key is using screws just long enough to penetrate through the tire lug 1/8 of an inch or so. I've found through trial and error that any longer than that and they tend to fold the lug over when you ride on them. I use a cordless drill and predrill the lugs from the outside first so the studs penetrate where I want them to. Than I use philips head #6 sheet metal screws, put a bit into my cordless, and drive the screws into the inside of the tire. I take on old tube, cut the valve out and slice it around the inside, lay it into the tire, then put my tube in. You don't need a ton of studs, too many makes a really heavy tire, and this type of studding is good for offroad only.