What is the difference between machine sewing and manual hand stitching (Saddle Stitching)?

One thread vs. two threads

When you use a machine, that sewing line uses two separate threads that lock around each other in what is known as a “Machine Lock Stitch”.

A hand-stitched line uses a single thread with needles on both ends. The thread runs back and forth on either side of the leather in what is called a “Saddle Stitch”

Difference in Construction

Technically speaking, the hand-stitched piece that uses the “saddle stitch” provides a stronger and more durable construction than the machine sewn piece that uses the “locking stitch”.

A locking stitch by a sewing machine has two threads running the length of the material on opposite sides, if one thread were to snap at a single point, the entire thread could unravel along that side of the material thereby allowing the material to separate.

However in a hand-stitched piece, should the thread snap at a single point, it could not easily unravel the length of the item since it’s passing on both sides of the leather. More importantly, it’s easier to repair the line of stitching.

Difference in Aesthetics

Saddle stitch results in an elegant line of slightly angled stitches when used with a particular set of tools. Decisions like stitches per inch, size and type of thread, and how we set the holes (e.g. pricking iron, diamond chisel) all play a role in the design of a piece.

Machine lock stitches usually look pretty straight on the top and the bottom side would be a usually visibly thinner thread to complete the lock stitch.