Most leather suppliers sell a tanning kit, I know Tandy does. Check into that. My partner on the ranch wanted to build a reata. A reata is a rope made out of braided rawhide. There is a renaissance in using them here in parts of CA and other areas of the Pacific Slope. Good ones run about $7.50- $8.00 a foot and no self respecting reata guy would dare show at a branding with less than 60-65 feet. More is better, if you can handle it, and I've seen em to 110 ft. Mine is 75 ft and they are temperamental and finicky, requiring very gentle and artistic handling in use as they are not very strong or durable. Roping with one is just like roping with a poly rope but completely different. However, I digress, sorry, reata roping can get under your skin. My buddy had a cowhide from one he'd butchered. The work getting the hide to the rawhide stage was so overwhelming and time consuming and fraught with potential catastrophic (to the hide and thus the reata) screw ups that part way through, he bought a hide already processed. This was just getting the hide to the stage where you would start tanning. I'm not trying to discourage you in the least, just letting you know its a lot of tedious work. I did a couple of rabbit skins when I was a kid that came out pretty good. Even those little guys were a lot of scraping. For a sheath you are gonna want a firm leather which means veg tan. I've heard of guys dumping a hide in an old oak stump that was hollowed out and full of water. You might investigate that. Good luck. I too would be interested to see how your efforts turn out.