ARGUS oscillator

If the part is in aluminium then send it for anodizing will remove any broken taps or steel parts including helicoil inserts.

I found that out the hard way.

> >

P Riedie

The Ferric Chloride solution will work in bronze, brass and gun metal.  It also works in Spherical cast iron. Back to lower level school chemistry (or ‘stinks’ as we called it)! The reason it will work is that in brass etc the alloy has a lower (less reactive) position in the electro chemical series than iron. The hard steel of the tap reacts with the Ferric Chloride in the same way that the ‘Wasting Anode’ protects your central heating system. What you are really doing is making a battery where the iron is the wasting anode and gets eaten away (dissolved).  In cast iron, the carbon in the matrix protects the iron in the casting so that the broken tap is dissolved preferentially.  It can also work in mild steel where the materials in the tap tip the reaction towards the harder material –the tap-. Do not try it if you are using free cutting mild – think how badly this rusts-.

In an ‘etching bath’ dissolving copper on a printed circuit a different reaction is occurring.

Edited By Ramon Wilson on 21/08/2010 10:26:16

To do the tap removal trick: -

1.    Degrease the tap and hole. This is important!

2.    Build a little dam around the hole using wax/modelling clay/shellac/PCB resist. Do not let any go down the hole.

3.    Use an eye dropper/pasture pipette or W.H.Y. drip in your reagent.

4.    Make sure you do not get air trapped in the hole.

5.    Let the reaction start. Wash out and refresh as needed.

Do not use acids they will not work well in this way.

Selotape (Durex for those who live upside down where the Cross hangs in the sky)  I have never used it. (U.K. stuff has semi-water soluble glue).

The last time I had to pull this stunt was in 1996 on a 12 BA tap (or there about) I used some candle wax (from a real ‘Frankie Randall’ not one of those smelly things the S.W.A.M.B.O’ have in the bathroom).  I like good old Carbolic anf a lump of bath brick -to get rid of any clinkers- my self

For small taps It works! And is cheaper than building a ‘Sparky’.

Good luck

Dick

Edited By Richard Parsons on 21/08/2010 12:55:08

Edited By NJH on 21/08/2010 15:39:13

Edited By Richard Parsons on 21/08/2010 15:43:07

It's called 'Sods Law' Norman -  surely it has to be one of our biggest 'stress raisers' on a job - a long worked at component with oodles of tapped holes and just one more left to do

Talking of Sods Law - after two days of searching for a set of car keys where I looked everywhere I found lurking in the back of a drawer the Dickson tool holder spanner which I was convinced I had thrown out with a pile of swarf several weeks ago. The keys? in a jacket pocket - where else

Edited By Ramon Wilson on 21/08/2010 18:28:20