Stitching a watch strap by hand
Halfway along the keeper, the thread runs out. Or the stitches wander off the line, or one side looks different from the other. All three problems come from skipping a step before the first stitch. Saddle stitching works well on a narrow strap if you set it up properly.
Why saddle stitch
Saddle stitch uses two threads in alternating running stitches through a single line of holes1. One needle sits on each end of the thread. Tandy says that if a thread is cut on one side but the other side stays intact, the stitch keeps its integrity2. Wikipedia makes the same comparison with the machine lockstitch, where breaking one side of a saddle stitch loosens only one side of the stitch1.
On a watch strap that rubs a wrist all day, that matters.
It's also slow. One maker calls hand stitching incredibly time-intensive3. Don't rush it.
Mark the line first
Set a wing divider to the distance you want from the edge, and run it along for an even line4. On a narrow strap, a small change in that distance is easy to see.
Then use a pricking iron to mark where each stitch will land. Tandy says its purpose is to mark where the stitch will be and cut through the surface of the leather, not to go all the way through2. You finish each hole with an awl as you stitch. Keep the iron's tines lined up with the groove or line, because that's what makes a straight stitch2.
One example from a watch strap maker uses a pricking iron with holes 3.0mm apart3. Pick the spacing to suit your own strap and iron.
Thread and needles
Measure your thread out about five times longer than the length you want to stitch2. It looks like too much, but Tandy points out that leftover thread is better than running out and having to start over2.
Use harness needles, which have blunt tips to prevent splitting the leather fibers4. The maker above stitched a strap with natural linen thread 0.30mm thick3. Thread choice changes how it looks and how the needle passes through, so test it on an offcut.
Making the stitches
Tandy's method has you clamp the work, with the angle of the marks pointing up and away from you, and stitch from the mark farthest away toward yourself2. Make the first hole with the awl, lined up with the angle of the prong mark so the stitches stay at a consistent angle2.
After that, you alternate awl and needle. Each time, pass one needle through, bring the other through from the opposite side, and pull both tight. Tandy's steps also describe looping the thread over the needle to lock it, which gives a consistent zigzag look on both sides2. Follow that source's page for the exact motion.
The keeper
The keeper is the small loop that holds the free end of the strap in place after you buckle it. One maker builds theirs from cordovan, lined, skived and creased3. Because that maker skives the keeper, thin the leather first, as described on the skiving page, before you stitch.
Locking the ends
Loose thread ends unravel. Tandy suggests backstitching, which means stitching back along the same holes without looping the thread. Usually, two or three backstitches are sufficient to keep the thread from coming out2.
For poly thread, trim it close and use a lighter to melt the thread so it can't be pulled back through. Be careful not to burn your project2. Keep the flame well away from your face, and don't do this near the dye or finish you'll use on the edges.
A last tap
Use a smooth-faced hammer to tap and compress the stitches into the leather2. It shows off the zigzag, and it reduces rubbing wear on the thread over time2.
Now the edges. Finishing them comes next.
References
- Saddle stitch, Wikipedia
- Tandy Skills, Saddle Stitching, Tandy Leather
- Behind the scenes handcrafting a cordovan leather watch strap, namokiMODS
- Essential Leatherworking Tools Guide, Tandy Leather