Sandy, I forgot were you live,1/2"=13mm. This machine has a hopping foot that lifts up & travles foward as the needle goes in the leather,as you sew thicker you need to turn the screw in the front in more so it will clear the leather,the problem is the thicker you sew & more lift you need the foot can hit the bottom of the needlebar unless you put in a longer needle.
Take your 16mm of leather along & try it out.
Bob