A heavy gauge needle is needed for your sewing machine to stitch leather. Using a heavier weight thread than normal is also advisable. An old trick to help the leather advance smoothly with the stitching is to put a piece of waxed paper both on top and under the leather.
Maybe; modern machines intended for home use aren't powerful enough, even with very heavy needles. Commercial makes/models (Juki, etc.) are ideal for sewing sailcloth, denims, upholstery, and leathers.
