I have made quite a few different studded tires during the last 5 years or so.
There are different ways to studd a tire and they have their pros and cons. I have mostly used two types of studding.
Method #1 is the way you guys are talking about, screwing screws in the knobbies from the outside, using the heat of the screw for traction. This method i havent found working as good as i want, either the screws pull out or provide too little traction. Its possible it can provide enought traction and durability with kold kutters but then the whole idea why i started making my own tires dies - it had to be cheap.
The other method, #2 i have used is made of normal bolts from the inside of the tire and a nut on the outside. This method is alot more work than the other method. The good thing is when its made properly i have archived AMAZING traction, its almost impossible to spin the tire on pure ice.
I have made a new tire this winter that i yet havent put on but its method #1 but quite different so i call it method #3. I dont know what the screws are called in english but they are used to screw the big quite heavy non burning boards you probably have on your walls behind the wallpaper. Well you can see how it looks on the picture page. I have screwed two or three in each knob making a total off 410. Then cut off the head, giving them a lenght of about 45mm if i remember right, about 10mm are sticking out.They are 2.9mm thick. Its screwed just as deep as you cant feel the tip on the inside of the tire. I will use protection for the tube, usually i use a few layers of carpet. Since there are no head as you usually use its less likely that the screws will pull out, although i recommend using a very little worn tire for this method since its using the rubber to hold on, if you have a worn tire i suggest using method #2. If you want more info on that tire i can give the specs on the screws and more.
It will become more clear when you look on the pictures on the link below, picture pict0079s.jpg if method #3. Also have pictures on a very well working set on my ktm, using method #2.
It should be this url:
http://int.pixum.com/viewalbum/?id=1536536