Heartbroken!

As is the 8BA Plug tap that is broken in a 1/8" inch deep blind hole!

Any (sensible) suggestions welcome, as is an offer of spark erosion near Mansfield with a financial contribution from me.

Please don't suggest heating it to red (it's a carbon steel tap) because it's in a silver soldered assembly!

Brian

Edited By Brian H on 16/08/2019 15:25:43

You do not say what metal the tap is in.

I broke a 7 BA tap in a blind hole the other day, I managed to grind away the tap using a small diamond coated burrs with a Dremel. I basically ground away the centre portion of the tap after initially grinding the top surface reasonably flat to get a good start. I used a fine pointed burr and a very small spherical burr, alternating between the two.

I did this with the aid of a desk illuminated desk magnifying glass.

It took 15 - 20 minutes and I was surprised how well the it went. 8ba is a little smaller though but I think manageable by this method.

Nigel

Take the offer of spark erosion and cough up the money.

My suggestion would be either carbide drill from M A Tooling on Attercliffe in Sheffield on 07973843152 or a carbide burr from J B Cutting Tools in Dronfield on 01246 418110 . I got some minature burrs from J B at last year's Midlands show , and they are very good . Also , if you visiting Meadowhall in the near future , Took Shed in The Lanes has a small stock of Proxxon carbide burrs . Hope t all helps . Please post your progress so we may all learn . Trevor.

Many thanks for the suggestions all. The material that the broken tap is in is a mixture of brass and gunmetal.

I seem to remember that there is a chemical solution that has been mentioned before on here, that disolves the steel, but I can't remember what it is.

Brian

Memory suggests that the chemical is alum, as used in cooking, but I can't remember the details. I seem to remember it takes quite a long time.

With respect, you wouldn't need to heat the fabrication up to red heat in order to soften a carbon steel tap. Tools are usually considered to be spoiled if they get to blue, which is about 300C. You've another 300C to play with before the silver solder starts to soften - and that's ignoring any liquation effect which will raise the solder melting temperature even further.

Cheers,

Rod

Brian,

The chemical you mention is Alum, however, I managed to get a broken small drill (1.5mm dia) out of a brass item by leaving it soaking overnight in citric acid. The next day the drill had basically turned to rust and could be poked out with a scriber.

If you use clean citric acid, rather than some which has had copper in it, you won't get a deposit of copper on your item.

Good luck.

Regards Tom

If you need Alum it is readily available on the internet, when I ordered some it took only a day to arrive, can’t remember where I ordered it from but there are plenty of suppliers..

Dave W

recently I broke a No. 50 drill in a block of Aluminuim . Some time ago I bought a product called BTR-10-broken tap remover, (Translunar technology Ltd , Bucks) it contains 33% aluminum sulphate.

The instructions say to dissolve a quantity in water in a aluminum /glass container and simmer the part . It states no action occurs at a lower temp.

After approx 1 hour enough of the drill had been dissolved and it just fell out.

the chemical I use is hydrochric acid it dissolved carbon taps the problem is tirying to buy these days regards norm

Is alum safe on copper alloys?

BrianH, whereabouts in Derbyshire are you?

If you're in easy reach of Buxton, I had some Alum arrive a month or so ago off ebay, You're welcome to a bit.

I bought it ready for when I brake a tap in a bit of motorbike one day.

Bill

Alum is usually available in garden shops, and the cooking dept of the super market.

Ian S C

Have you an option to move the hole and drill and tap elsewhere?

You can see the attempted expiation of my sin in the position of the LH bearing strap retaining bolt (also due to a broken 8BA tap) here:-

Hi Norman. Hydrochloric acid is the main constituent of B&Q's Brick Cleaner.

Many thanks to all on here for the suggestions and offers. I've now managed to secure a small amount.

I first came across alum as a young apprentice with Crossley-Premier Engines. One of my first jobs was to pressure test valve guides which where hollow cast iron castings with water passages to cool the valves on diesel and gas engines.

They were tested to 25psi (as I remember) and any porosity or leaks were fixed by the addition of a teaspoonful of alum which VERY quickly rusted any defects so that a second pressure test could be carried out to ensure no leaks.

Brian

Just discovered that I needn't have made the holes blind! They will just go through without leaving a witness in the mating parts.

Also realised tht the two holes that I broke a tap in,needn't have been put in at all.

Must get my brain in gear next time.

Brian