grub screw

A solution in water of potassium alumium sulphate, commonly known as alum, will dissolve the steel without affecting the brass.

Cliff Coggin.

How long will it take Cliff? I tried the equivalent of sulphuric acid to get a piece of 3mm drill out of Aluminium and gave up after a long weekends worth of messing about.

It depends how warm it is, how often you replenish the alum as it is exhausted, how well you de-grease the screw, etc. but about a day should do it.

Cliff.

"Cliff Coggin" schreef in bericht news:RFyqk.21064$ snipped-for-privacy@newsfe19.ams...

Cliff, can this "alum" by accident be found in fertiliser? Dirk

Or you could try a carbide drill, rigid setup, drill at af size plenty of coolant so you drill the centre of the screw out, then you have a chance with a square tapered punch in the hole and turning or just collapse the remains of the screw. Peter

I don't know about fertiliser, but it is used to turn change the colour of pink hydrangea to blue.

Cliff.