sandmanred

I have a 31-15 and think it's great. There's tons of them out there and you can still get most of the parts you'd ever need. I don't think you'll get a 135x17 to run as it's probably too long. I didn't try but I did a quick length comparison I think by the time you get the eye where you need it for hook timing you'll be crashing the needle clamp into the body at the top of the needle stroke. Here's a picture of the needles I run below. They are cheap and readily available on ebay. A suffix of LR indicates for leather. I don't see a bobbin case or bobbins in your pics. I think it's a class 15. You should be able to get from ebay pretty easy. You just have to watch the little arm that comes off the case to keep from spinning, I had to trim mine shorter for it to fit. If it was heavily used you'll probably have to replace the hook and the little pin you will find inside the tension assembly. If worn the hook won't run smooth, you'll be able to tell by the sound. Also check it for any burrs or sharp edges where the thread slides on it. The new ones I got on ebay have both needed some filing on the end opposite the hook to get them to fit. There needs to be a little play between the hook and hook driver to let the top thread pass. The little pin in the center of the tension assembly pushes the outer disc out a bit when the presser foot is up. They get shorter with wear and stop working all together when worn too. If your tension stays high when you lift the presser check this first. I also agree on getting the smaller pulley on the motor, I run a 45 or 55 mm drive pulley. I also added a pulley the fits over the stock handwheel that increases the diameter to about 5.5 inches. That gets me down to as low as about 1 stitch per second.

To your question about round needles in leather, maybe okay if it's soft leather but if its hard leather probably not so well. The leather needles I've seen have a wedge or chisel shape that cuts through tough leather. I just tried a round point vs a leather on some veg tan leather that is about 3/16 inch thick. The round needle took a lot more force to punch through and then actually pulled out of the needle bar on the very first up stroke. The leather needle punched right through and sewed without a problem.

What's the best kind of grease to run on the miter gears that drive the rotary hook?

Here's a picture of what I meant. You can see the original point the connecting rod attached on the right. And you can see the blank hole to the right of the current attachment point, I tried it but it was too short. You can see ended up about midway between the original point and the axle. My connecting rod is adjustable in length so easy to adjust to accommodate the connection point changes.

I'm facing the same challenge of speed control on a clutch motor. In asking around someone suggested greasing the cork on the clutch. I was reluctant to try it because it's not easy to undo but I went ahead anyways. I polished the metal face of the clutch and put a light coat of grease on cork and it does help get a bit more control. The other thing that help is to modify the linkage from the foot pedal to the clutch motor. Either extend the lever on the clutch motor or shorten the foot lever throw. Looking at your pics a new hook on the foot pedal about half way between the axle and the existing rod that connects to the clutch lever would be a good start. This shortens the throw at the clutch to give a bit better control as well.

I just picked up these machines and both have only 1/4 inch welting feet. Any body know where I can get set of regular feet?