Hob knob stiff or loose: a small fix with a large safety margin

Knobs are the one part of a hob you touch every day, so a change in how they feel is noticed quickly and then, often, ignored. Neither a stiff knob nor a loose one should be.

Stiff

The valve stem has dried out or gathered residue. Forcing it wears the valve seat, and a worn seat is a valve that does not fully close. The fix is a clean and re-grease of the valve with the correct gas-safe grease — not oil, not a spray lubricant.

Loose or spinning

Either the knob has cracked at its centre and is slipping on the stem, or the stem's retaining pin has gone. A knob that spins without turning the valve can leave a burner slightly open without you knowing.

Will not push in to light

The spring behind the valve stem has weakened or jammed. The push-to-light action is part of the safety interlock; if it is not working, the ignition and flame-failure sequence is not either.

If a knob is loose, check that the burner is fully off by listening for a hiss with the room quiet, then avoid using that burner until it is fixed. Do not remove the knob and turn the bare stem with pliers.

The repair

Knobs are inexpensive and usually available. A valve service or replacement is more involved because it is on the gas side and the hob usually has to come out of the counter. Either way it is a leak-tested job, and worth doing promptly.