My Knob keeps falling off

[OliverBlackman]

The tone knob on my mex p bass sometimes becomes loose and every time I tighten the screw and it stays on for a while, bu then comes off again. Anyone else got a loose knob and/ or an idea to fix it?

[KiOgon]

If it's a grub screw knob onto a split/splined shaft - line up the screw so that it goes in in line with the split & tighten fully!

[BobVbass]

put a bit of nail varnish or threadlock on it as well

[discreet]

Just stop fiddling with it.

[Number6]

A tiny drop of threadlock / loctite on the grubscrew.

[OliverBlackman]

[quote name='KiOgon' timestamp='1428573773' post='2742496']
If it's a grub screw knob onto a split/splined shaft - line up the screw so that it goes in in line with the split & tighten fully!
[/quote]

I've tightened as much as I can on several occasions and eventually it comes loose. Will try to get hold of some thread locker.

[Number6]

[quote name='OliverBlackman' timestamp='1428575578' post='2742519']


I've tightened as much as I can on several occasions and eventually it comes loose. Will try to get hold of some thread locker.
[/quote]

A dab of nail varnish will do it. Try to avoid superglue because sods law says you'll need to take the knob off as soon as you secure it with that.

[pfretrock]

My mex p has a solid brass pot shaft and solid metal knob.. Have they gone cheap?

[organic]

Had this problem with my Gretsch Tennessee Rose, it was still under warranty and shop's workshop reckoned the problem was the spindle so they replaced the pot.

[KiOgon]

[quote name='pfretrock' timestamp='1428576077' post='2742525']
My mex p has a solid brass pot shaft and solid metal knob.. Have they gone cheap?
[/quote]Not 'gone cheap' if they are CTS pots, solid or splined shafts are the same price but require different knobs to suit. The OP doesn't say what shafts his has. Other pots are available of course

The split shaft splined type are not designed for knobs with a grub screw fitting, they are generally a internal splined knob with a push on fit.

[MarkG3]

My knob was always falling off my old pbass so I left it off then eventually hid the pot under the scratch plate

[OliverBlackman]

I'm not sure on the different types of shafts so I've attached some photo's.

[PlungerModerno]

Looks like a tiny drop of clear nail varnish on the grub screw as BobVbass suggested, will work just fine.

Should hold it still in the knob.

[HowieBass]

Solid shafts sometimes have a flattened face that the grub screw makes contact with so there's greater surface area to work with; I wonder too if the end of the grub screw is pointed which makes for even less metal to metal contact. Have you compared the tone knob with the volume knob to see why one stays put whilst the other doesn't?

[uncle psychosis]

I'd be tempted to put some paper or blutack into the knob to make it grip more tightly, as well as using nail varnish on the grub screw.

[OliverBlackman]

The end of the grub screw is only what I can describe as a crater, so then point of contact is just the edges which is very thin. I am hoping my girlfriend will pick up some nail varnish for me to try over the weekend. I'm nervous about touching the volume knob incase I make that loose to. I rarely have to use that compared to the tone pot though.

Thanks for the suggestions BC's.

[pfretrock]

Hmmm... aluminium pot shafts, don't take a grub screw as well as old fashioned brass. When was the bass made? Mine is around 2012. Years ago when I used to work in electronics, we always swapped the 'set' screws that came with knobs for hex drive grub screws, they tended to hold better, having a better designed point. Then collett knobs came out. But too expensive for guitar makers. Nail varnish may help, but if the aluminium is giving it may not.

[grenadilla]

You might file a flatish section on the pot shaft where the grub screw touches. That will give it more to tighten against. Also a grub screw filed flat at the end may hold better. Wipe any sweat/oil off the pot shaft and clean out the knob too. Or get some new knobs that will stay tight.

[ianrendall]

I had the same issue with the volume knob on my Mex 50s Roadworn. The grub screw wasn’t quite long enough for the amount of thread in the knob. I tapped the knob with a 0.8 thread tapper so the thread goes all the way through. All is now well with my knob. 

Edited October 11, 2018 by ianrendall

[TheGreek]

If it's a split shaft you could gently pry the shaft apart (a bit) with a flat head screwdriver thus making it a tighter fit...

[songofthewind]

What Mick says, but be really careful! Split shafts are made of cheap metal, and can shear very easily at the stress point at the bottom of the slot. I’ve buggered up quite a few!

[TheGreek]

4 minutes ago, songofthewind said:

What Mick says, but be really careful! Split shafts are made of cheap metal, and can shear very easily at the stress point at the bottom of the slot. I’ve buggered up quite a few!

Really??? (note the sarcasm)

Note how I used the words "gently" and "(a bit)"....sometimes the best way to learn is to get it wrong....I did (more than once)!!

[songofthewind]

I did indeed note that you said “gently“, Mick. Just adding my two pence worth, and not suggesting you were off the mark.

[BreadBin]

If the split shaft is already bent then it may have been weakened enough to break - I have bitter experiences to confirm.

Packing out the socket of the knob with foil works as an alternative 

[ianrendall]

It’s ok guys. The shafts on my pots are solid brass. Or a brass coloured metal at least.