Rivets and eyelets are generally dictated by the thickness of kydex you use. Personally, I prefer .093" thick kydex, which means I use #8-9 eyelets that are 1/4" dia. Eyelets also double as rivets, so I don't purchase rivets. As far as belt loop attachments....there are a ton of them available, each with thier own hole sizes and spacings. I tend to use Tek-Lok belt attchements, both the large and small varieties. I use the existing holes in the Tek-Lok and a silver pencil to mark where I drill for the eyelets. Setting eyelets by hand is an art unto itself.....for me it was always hit-n-miss....but then again I'm a picky bugger too.
I use an arbor press and a set of the eyelet dies, and almost never have to deal with splits on my rivets.
Something that I feel is worth mentioning about kydex sheaths...... not all knife designs are compatible with a kydex sheath. Kydex holds a knife in place via pressure points.... a knife with a large guard, oddly shaped guard, or a knife with a neoprene handle are simply not good candidates for kydex...... with the larger guards, the knife is often held securely, but can be a real pain to get out of the sheath.....those with neoprene/rubber handles often have a molded in finger guard.....which will, over time get torn off by the kydex sheath. There was a time when I swore I would never make kydex sheaths.....but as more an more requests from clients came in, I changed my thinking.
Although kydex sheaths are much quicker to produce, and generally more durable when compared to the traditional leather, they have their own unique drawbacks..... for example, dirt and grit inside a kydex sheath is the quickest way to scar up a knife..... they are sensitive to higher temps..... such as being left inside a hot vehicle, or even laid in a sunny window. As with most anything we do in the knife shop..... it will take a bit of experimenting, but kydex is fairly easy to work with.
