A device for producing piped openings in flat base material, for instance welted pockets, comprising first workpiece clamping means for securing a workpiece to a workplate, piping patch holding and folding means, sewing machines for sewing said folded piping patch on said workpiece with two stitch rows cutting means for cutting a slit and V-shaped tab slits at the ends of said slit, and a second workpiece clamping means which is displacable into said first workpiece clamping means and said piping patch holding and folding means, to receive said flat base material together with said folded piping patch and to feed them through said sewing machines and said cutting means.