How to remove bath pop-up waste knurled knob?

[Widgets]

In order to solve a leak with my bath overflow I need to remove the chromed knurled rotary knob that controls the pop up waste. The knob has a hole in the side through which with the aid of a torch I could see a brass screw, so I assumed it would be a simple matter of undoing the screw and then pulling the knob off the end of the shaft it is mounted on.

Well, I now have a loose screw rattling around inside the knob, but the knob is still stuck resolutely to the shaft. Before I break something I have stopped and decided to ask here for help. I can't see a circlip to release and don't want to start applying more torque to the knob (the whole overflow assembly starts rotating as it is in normal use, hence the leak) until I know whether it is likely to be threaded on to the shaft, and if so whether it will be a left or right hand thread.

I have no idea of the make, but would described it as a "common standard UK building industry fit" in a gazillion houses and hotels up and down the country, with pop-up control being by the normal cable route.

Many thanks for any help you are able to give,
Widgets

 

[Bahco]

Should only be a screw holding it on. Might be worth spraying WD 40 and leave to soak in. Keep gently trying to prise it off.

 

[swidders]

Yep, it was that screw. Sounds like it's rusted on - try WD40 but you may have to force it off and replace the whole thing I'm afraid

 

[Widgets]

Thank you, Bahco and swidders. I feared that corrosion might be the cause, though hoped it would be something else such as the threaded assembly I mentioned.

I'll try the WD40 route, and if necessary, some sharp shocks from a carefully used club hammer with the overflow assembly braced against the wall behind with a block of wood (the fibreglass bath flexes too much otherwise)

Will post the outcome

Cheers,
Widgets

 

[Widgets]

Tapped with moderate force working on the side of the knob using a 12"x2"x3" offcut of softwood timber.
Repeated tapping on the diagonally opposite side, then through 90 degrees, and then opposite that. Imagine torquing up four car wheel nuts 1-3-2-4 to get the idea.
After doing this a dozen or so times the knob pulled forwards on the shaft enough for me to get a flat bladed screwdriver shaft all the way between its reverse face and the front face of the nylon overflow assembly.
Prying on the screwdriver handle whilst tapping with the wood had the knob creep along the shaft (splined I could see by then) and eventually come free.

Yes, I did ensure that the plug was removed and replaced with wide sticky tape across the aperture to ensure I didn't lose the screw

Thanks again for your help; you gave me the information I needed to persist with reasonable force rather than find a design aspect I'd missed.

The splined shaft has light surface corrosion so I will clean it up, along with the mating part on the knob, and reassemble with a little coppaslip.


Cheers,
Widgets

 

[swidders]

Nice one. Glad it didn't open a can of worms!