This knob (PM258A) is for the Ascaso Dream espresso machine models.
Your steam valve stem should have a screw hole for the included Allen key screw to thread into. Otherwise, without the hole, it may not hold as well. The wood is now re-enforced with a ring as pictured.
The screw included with the knob will not thread into the wood it will thread into the metal piece that will sit inside the knob.