It helps to know what materials to use when you know what you are using them for. Why are you making a sheath for a knife? And we will assume that this is a user type of knife rather than one that sits in your vault. This sheath now is determined to protect the user of the knife from cuts to his person rather than protecting the knife from scratches and the weather. The secondary need for sheathing the knife is to carry the knife in a position where it is readily available. The sheath is not used to strengthen the knife, it is only used to carry the knife which involves tensile strength not thickness. Thickness of the leather is involved in order to reach the necessary stiffness to maintain the mold or fit of the sheath. It is common knowledge that the average man's belt is often asked to support a 250 pound belly and the belt is less than 8 ounces in weight. Why would it be necessary to use 11/12 ounce leather to support a knife weighing less than three pounds and that would be one big cutter? I have actually made thousands of knife sheaths and have found 7/8 ounce to me my maximum thickness required for the job. I some times (on blades over 10 inches in length) might sew a full length stiffener on the back of a sheath to limit bending. Unless you make a lot of sheaths, I would not buy the leather by the side or back but would opt for the double shoulder in carving cowhide which is vegetable tanned. Bellys, which is part of the side, are too stretchy, rarely are clean and smooth on backside and would not be used on quality merchandise. Horse butts, in soft rolled type, are excellent for sheaths and carve well, but are better left to the more experienced leather worker. SUMMARY---5/6 OZ for small sheaths for folders and small straight blades and 7/8 OZ for all other knives!
