The invention relates to a valve with a magnetic or magnetisable pilot valve body and a main valve body for a vacuum System in a wood processing machine, whereby the wood processing machine comprises a clamping table running in at least one vacuum zone, with at least one drilling for mounting the valve such as to sit below the clamping table surface, between the vacuum supply Channels and the clamping table surface, whereby a suction adapter supporting the workpiece is arranged on or in the clamping table, which, on the side thereof facing the clamping table surface, is at least partly made from a material, or has a device, which opens the valve, closed in the idle State, by a magnetic interaction and hence sucks the suction adapter to the clamping table and/or the workpiece to the suction adapter. According to the invention, a valve is developed, permitting an opening with applied vacuum, which rapidly closes on unexpected pressure rise and which guarantees a secure functioning in all operating conditions.