Looking For Help Removing Damaged Speaker Screw

breadfan

The head broke off a speaker screw as I was trying to remove it from my old Marshall 4x12 cab.

It was difficult to turn & a little rusted. Unfourtunately, there's nothing left to grip with a pliers - it's all below the baffle.

Any tips on getting it out?

I was thinking the best thing to do is to remove & replace the t-nut but I'm hoping to minimise the damage to the cab & also hoping not to have to remove the baffle - it's a '68 or '69 cab!

slacker

The usual way is to drill and tap, is it big enough area to do that?

breadfan

I'll add a picture.

I was hoping I could just push the grill cloth out a little and tap out the t-nut but I've just realised that there's a piece of wood on the baffle covering the front of this particular t-nut - the piece where the '100' logo attaches. It's a 1982 cab. 

breadfan

 

ICBM

breadfan said:

I was hoping I could just push the grill cloth out a little and tap out the t-nut but I've just realised that there's a piece of wood on the baffle covering the front of this particular t-nut - the piece where the '100' logo attaches.

It’s always that bloody one…

When I’ve had to fix this - more than once - I’ve simply got a separate speaker clamp (the sort you find on front-loaded PA cabs) and a large self-tapping screw, and screwed it to the wood next to the broken bolt. Yes, it means one new hole in the cabinet. But I’d rather that than try to drill out and re-tap an extremely rusted T-nut.

breadfan

@ICBM The other 15 screws came out fine!

Would you mind posting a pic or a link to tjat speaker clamp? I'm not familiar with them.

ICBM

breadfan said:

@ICBM The other 15 screws came out fine!

I think the extra piece of wood on the front traps moisture and causes the bolt to rust. I’ve had to do two or three exactly like yours, where none of the others were a problem.

breadfan said:

Would you mind posting a pic or a link to tjat speaker clamp? I'm not familiar with them.

Something like this -

https://www.flightcasefittings.co.uk/g0726-plastic-speaker-clamp.html

There are simpler metal ones too, but mostly only seem to come in sets of four.

https://www.ukdj.co.uk/stands-cases-c4/accessories-self-build-c345/fixings-c352/eagle-altai-set-of-4-heavy-duty-speaker-clamp-kit-inc-t-nuts-and-bolts-p5048

(Ignore the mounting bolts and just use a big wood/self-tapping screw - you have the advantage of double thickness of the plywood there, so it can be quite a big one.)

I have a number of spare ones if you prefer!

CampbellH

Have you looked at reverse drill bits? Sometimes called left-handed or screw extractors.

Basically it drills in and if it gets a bite of the screw shaft it will start to turn out the screw.

ICBM

CampbellH said:

Have you looked at reverse drill bits? Sometimes called left-handed or screw extractors.

Basically it drills in and if it gets a bite of the screw shaft it will start to turn out the screw.

Given how solidly it will be rusted in, there's a real chance you'll break the screw extractor instead. That's why I gave up after trying to remove the first one I came across like this - just wasn't worth the risk.

I think the best bet if you are determined to get it out is to drill as much of the bolt away as you possibly can, then see if you can get a tap - it's 2BA (not M5) to follow the thread in the T-nut and clean it out. Bearing in mind it's now a blind hole because of the wood across the far end.. although you could go into that a bit if you have to.

breadfan

@ICBM Thanks for the links - I'll send you a PM

@CampbellH As ICBM has said, I can't see the screw coming out - it was very difficult to turn. 

I may as well try to drill out as much of it as I can & then tap it, but I'm quite sure I'll be using the speaker clamp method above!

CampbellH

If you can run some very thin oil into the thread without making a  mess that will help keep the drill bit and the old bolt cooler and prevent any expansion from making it a little more challenging. FYI My experieince has been with metal (classic cars, bikes) not wood so I am aware oil cooling may not be possible, Good luck whatever you try.