For leather carving, you do indeed open quite a can of worms with this, and mighty tasty Gummi-Worms they be, too.
There are two basic leatherworking techniques: carving and stamping. Either may be called "tooling."
If you're going to do freehand carving, it's worth throwing the extra bucks at a higher-quality swivel knife, and get all shapes and sizes of blade, too, as they are made to adapt them to different jobs. The ceramic swivel knife blade is a good idea for anyone who does a lot of swivel knife work, and a pretty good idea for anyone who only does some of it. The steel blades, well, you're forever having to strop them, as they work much better when they are kept at a high polish. You can feel when a steel blade needs a lick at the strop you've charged with white tripoli -- it starts to drag. Ceramic blades cost a lot more but you don't have to stop and strop the things.
I like the marble slab for tooling, even if the masonite board is adequate to the task. The marble is heavy and very smooth, and works better. A hard rubber mat is best for punching holes with the Mini- and Maxi-Punch sets. The rotary hand punch should be the expensive sort, not the stamped-metal budget version. Buy the Mini/Maxi-Punches first.
There are definitely two levels of quality in stamping tools -- some of them just look cheap and blurry, and then there are the ones with crisp detail. Sometimes its a matter of taste. You will eventually accumulate a lot of stamping tools of all kinds; get them as needed. I try and start out with a cross-section of what's available and then fill in gaps as required. Beveling and backgrounding tools will be natural complements of your swivel knife, since this tool basically draws the line between figure and background. You'll want styluses and deerfoot tools of every shape. A plain stylus is easy to use well and invaluable for transferring patterns, preliminary layouts, and all those pencil-like tasks.
Something I've always felt blessed to have is a strap cutter -- you can always make belt blanks and straps, absolutely any width you desire. A stitching awl is also a must. Dishwashing gloves for dyeing are a good idea too -- dye that gets on your fingers doesn't so much wash off as wear off; remember too that stuff is designed to color dead skin layers, so it colors your epidermis about as well as it colors leather -- just with less penetration!
You'll be wetting the leather as you work it pretty often: I like a sponge stuck in a jar, with most of the water sucked up into the sponge -- cuts the chances of spillage.
For some reason, practically every knife for leather cutting and trimming that I've seen included in leatherworking kits from the factories has been, well, utter crap. No edgeholding at all; they are too soft. Use Ex-acto knives or something else that suits you better.
For really excellent hand stitching with an unimpeachably period look, don't make stitch holes with thonging chisels -- use a stab awl, and get one made of good metal. I have a bad one, and it goes dull and drags -- the same old curse of the metal being tempered too soft. Tandy/Leather Factory may have introduced a good one in their #3209-00 4-In-1 Awl set. The Stitching Awl, or Awl-for-All, that I mentioned above can get along without a stab awl doing its advance work in lighter leather weights, but heavy leather is too much for it. Its thread is nylon, very strong, prewaxed, and comes in three colors to match your project. The only thing to beat stitching-awl thread for strength is artificial sinew. A reel of that stuff lasts a long time and can be used to generate a thread of any thickness. The recipe for quality hand stitching goes like this: run along the stitch line with the rowel of a pouncing wheel, making little pricks in the leather with its points. Stab each pouncing wheel mark with the stab awl, angling its cutting edges about 45 degrees to the stitch line, so as not to have the leather tear on the dotted line. Sew the seam, using any of the several ways to stitch from a single needle, to double needles for saddlestitching, to a stitching awl. Then go back over the stitches with the same pouncing wheel and roll the thread down into the stitch line for a very neat and professional appearance. This works even better if the stitch line has been grooved beforehand to sink the thread below the grain surface of the leather.
For some leather cutting-out, leather or household shears work better than knives, and for other cuts, knives better than shears. I have both a leather and household shears, and I like my household shears best. These are expensive; they are Cutco #77 Super Shears and they cost $77 + shipping. For all this money, you get a pair of shears that are unf**q***ngbelievably durable and are guaranteed literally forever. I've used them to snip all kinds of tough substances, and, well, the only right adjective is
unchanged. Those
http://www.cutco.com guys make some incredible stuff!
The leather people will sell you how-to books on about any kind of leatherwork and carving. The emphasis is pretty heavy on Western-type stuff, all the way up to making your own saddle, but the Hispano-Western foliate motifs and suchlike carvings (swivel knife is about the best tool for Celtic interlace) will teach you mastery of sculpting and figuring leather.
When I'm finished with my current project I will write one up.
