Look, leatherwork is just plain slow. If you're good at it, especially if you have your patterns already and a proper machine for sewing, it's only a bit slow. If you don't do it very often, your workshop is a shambles and you're hand-sewing, it's unbelievably slow.
I'm slower than that but I can do it. I like to do it, when I can find the whacking great chunks of time even a slipshod job requires. And I have, by gosh, studied up.
Here's a tip from the pros:* You don't sew across the width of a load-bearing strap. It's like the perforations in a postage stamp: rrrrip! Plus, the load's on the thread; the more loops of thread between the two parts, the stronger the connection will be. The fix is to do a long, converging pattern, pointing away from the stress point. Yep, those shield-shaped terminations on the straps for your saddlebag buckles are not that shape just for decoration and if they are also sewn straight across, you didn't get what you paid for. Properly done, there are more stitches to carry the load and the grain of the leather isn't as stressed.
I have owned all manner of purses, from fashion items to serious carry-purses made by well-respected holster companies. Most have been leather and every last one of them had the straps sewn right across. Many have failed at just that point, too. You can go shop fancy-name bags and 99.99% of them will have the straps sewn right across. Hey, here's a wild idea: charge me a buck more and do it right for flippin' once!
In my closet, I have all or nearly of the parts for Al Stohlman's "Super Gadget Bag," a pocket-laden purse of the sort that appeals to me, all cut out and ready to sew. It's about time I did some more with that.
*Al Stohlman, a born teacher and skilled leatherworker. Between the linked book (The Art of Sewing Leather, you should go to Tam's Amazon link and buy a copy already) and both volumes of The Art of Making Leather Cases, if you don't end up learning a little, you're either unteachable or you're Al Stohlman. He and his wife and occasional co-author Ann ought to have statues to them someplace, or at least carved-leather portraits. It turns out the Universe may be just a tiny bit more just or fair than you have suspected: you'll find the Stohlman Leather Museum and Gallery in Fort Worth, Texas!
6 months ago