A grinding machine has a rotatable grindstone (1) and a support (12), which is generally parallel to an axis of the grindstone. Jig means (1-8) are provided for bringing a knife blade (15) to be sharpened into controlled engagement with the grindstone (1). A jig arm (1) is provided with attachment means (2, 3) for its fixed attachment to the support (12) in a proper position for the sharpening of the knife blade (15) and—at a distance from the attachment means—with resilient holding means (1′) for the knife blade (15).