Bar mixer shower - unable to adjust temperature

[miketurner201]

I have a concealed 3 valve thermostat mixer shower which is around one year old.

I realised that the middle mixer that sets the temporary is just going around and not changing the temperature. I’ve removed the knob and found the grub screw has created a groove all around the spindle and the knob is not gripping. I have tried tightening the grub screw but it did not help

I am now looking to drill the spindle a little so the grub screw can sink into the spindle and make a firm grip.

Would this solution be ok or is there any danger of me causing a further problem ?

Any help much appreciated.

 

[JCplumb]

Go gentle and be sure to get all the swarf, should be fine.

 

[ShaunCorbs]

You could put a flat on the shaft where you want the grub screw to tighten onto

 

[miketurner201]

Go gentle and be sure to get all the swarf, should be fine.

Hi, I'm assuming the spindle is solid so no risk of puncturing anything. Will do, thanks and take care.

 

[miketurner201]

You could put a flat on the shaft where you want the grub screw to tighten onto

Hi Thanks for the info. I'm sorry for being a bit dumb but what do you mean putting a flat on the shaft ?

 

[ShaunCorbs]

Hi Thanks for the info. I'm sorry for being a bit dumb but what do you mean putting a flat on the shaft ?

like a or b would do

 

[miketurner201]

Hi Thanks for the info. I'm sorry for being a bit dumb but what do you mean putting a flat on the shaft ?

like a or b would do

View attachment 43238

Hi

Many thanks for the diagram, I will definitely consider doing that, thanks again.