Removal of metal screws in alloy casing 3ph motor

W

wanton dwarf

Member

• Sep 3, 2014

• #1

On a 3ph motor we have an alloy/aluminium casing but metal screws holding the wiring panel.

The casing is old enough to have "white rust" - metal screw refuse to budge, I've even tried using a heavy impact screwdriver - ie the type you hit with a hammer.

The heads are in good order and I've been cautious enough not to disfigure the heads and make them unusable - I've not applied full force but close to, I would guess the impact screwdriver was well in excess of my hand strength.

I've managed to get around the problem of getting the motor to run as I want but the fix is not the preferred method of removing the casing and wiring as I want.

Any ideas on removal of the metal screws ?
Will it stand some heat ?
I doubt easing oil with have any effect ?

Failing that I'm tempted to just buy a 3ph switch keeping some of the old wiring and having the new wiring as required.
Last alternative would be grinding the heads off, stud removal and then new screws - with the obvious problem of losing a serviceable casing altogether.

 

Kevtherev

Member

✓

Location

Welshpool Powys

• Sep 3, 2014

• #2

Can you weld nuts to the heads with a little mig.
Or too small?

 

llamedos

New Member

• Sep 3, 2014

• #3

vinegar/lemon juice mix, put it on with a toothbrush. Worked when I was doing up an old LR, be sure to clean off and neutralise with baking soda after.

 

Mursal

Member

• Sep 3, 2014

• #4

Yes there is a reaction when steel meets aluminium as you probably know.

Try hammering/tapping directly on the screw head to try and weaken the corrosion in the threads.

 

Last edited: Sep 3, 2014

W

wanton dwarf

Member

• Sep 3, 2014

• #5

Kevtherev said:

Can you weld nuts to the heads with a little mig.
Or too small?

Click to expand...

It might be doable but would be last resort before cutting/grinding them off.

 

Thick Farmer

Member

Location

West Wales

• Sep 3, 2014

• #6

Get an electric drill with an impact driver setting.

 

DrDunc

Member

Livestock Farmer

Location

Dunsyre

• Sep 3, 2014

• #7

The triumph stag cylinder head conundrum!!!

See if your local garage mechanic has a snap on induction heater. You touch the screws with it, and it gets them red hot very quickly. A few hot / cooled cycles usually does the trick.

Thick Farmer said:

Get an electric drill with an impact driver setting.

Click to expand...

Do NOT do this. You will definitely destroy the screw heads.

A cordless impact wrench is the tool for the job (it's like the hammer blow you've used, but much more effective).

 

Tonym

Member

Location

Shropshire

• Sep 3, 2014

• #8

I presume it is the lid of the terminal box you want to remove. Why not grind off the heads and leave the remaining bits of the screw as locating pegs then glue the lid back on with polyurethane sealant. It will be waterproof and probably stronger than the screws and can be removed in the future if needed.

 

P

Pennine Ploughing

Member

Mixed Farmer

Location

200 miles N,NW of New York

• Sep 3, 2014

• #9

just heat the alloy with a small blow torch, don't melt it, but alloy will expand more so than steel with heat, use something like a small plumbers blow torch, screws should come out with ease after that

 

spanners

Member

• Sep 3, 2014

• #10

coke

 

DrDunc

Member

Livestock Farmer

Location

Dunsyre

• Sep 3, 2014

• #11

spanners said:

coke

Click to expand...

Snorted


Err, maybe I typed an "N" by mistake

 

G

grumpy

Member

Location

Fife

• Sep 3, 2014

• #12

DrDunc said:

The triumph stag cylinder head conundrum!!!

See if your local garage mechanic has a snap on induction heater. You touch the screws with it, and it gets them red hot very quickly. A few hot / cooled cycles usually does the trick.


Do NOT do this. You will definitely destroy the screw heads.

A cordless impact wrench is the tool for the job (it's like the hammer blow you've used, but much more effective).

Click to expand...

showing yer age there pal.and dont get me started on dolomite sprints.

 

W

wanton dwarf

Member

• Sep 3, 2014

• #13

Thanks very much guys - some good ideas.

I've done what I needed to do in the short term as I had a rats nest somewhere in the carrier, 1 dead rat + nest removed & I've plated over the ends for now.

Will be cleaning some rape over the next few weeks so should be using it again - will get around to trying some of the solutions.

Thanks again

 

Grassman

Member

Location

Derbyshire

• Sep 5, 2014

• #14

A left handed drill set is good for stuff like this but it's very difficult to stop the drill tip wandering in to the alloy. Cut off flush any exposed steel. Centre punch it well and go with the drill. Sometimes works.
If it doesn't buy some 'Quicksteel' www.kalimex.co.uk and just fill the hole and make a new threaded hole with it.