'The removal of the broken piece involved the use of a large sauce pan, a pyrex bowl, and 'ALUM', the pyrex bowl was filled with boiling water enough to cover the cylinder with broken tap by about 2'' of liquid, 'ALUM' powder was then poured into the bowl of boiling water until no more powder could be absorbed by the water, the bowl of liquid 'ALUM' was then put into the large saucepan which already had boiling water in it and left to simmer at just under boiling point for 15 hours over yesterday and today, that is what I mean by 'slow but sure', the gunmetal casting was not affected in any way and the remains of the broken tap had vanished.
It was amazing to watch the constant stream of tiny little bubbles erupting from hole where the broken bit of tap was being eaten away with the chemical.
For anyone who has never used this process before [like myself] I would heartily endorse it as an excellent ''MODEL ENGINEERS '' tool.'
The job used only about 200 gms in 3/4 pint.

Alum can be obtained from clockmakers suppliers - e.g. H.S. Walsh

One kind gentleman made an observation....

Giles,your site is very interesting, I have 71/4" myself and considering 101/4" in the future.
A recurring theme in your workshop seems to be the drilling of large holes with light machines. Have you tried 'rotabroach' cutters? I have just been drilling some 24mm holes in 1/2" plate, no pilot hole, and it is easier than drilling 1/4" with a twist drill ( work securely clamped, using my 3mt oerlikon drill). They also work well in a 'stick-on' magnetic drill, which is what they were designed for! nb, I have no connection with rotabroach etc etc.
Kind regards,
Alan.

There is a design currently being serialised in Model Engineer of an 18 inch gauge Manning Wardle in 7 1/4" ('Anna') which has been manipulated by it's designers to also allow a 2 ft. gauge ( actually I think it scales at 2ft 3in.) 'Locke' class loco to 10 1/4 inch gauge. All the drawings are available from the designers specifically for this version, properly representing the increased width, and also length of the specific prototypes. Laser cut components are currently available (frames buffer beams etc) as are shared castings. Specific castings ( frame stretchers etc) are either in the process of being produced, or will be replaced by fabrications from laser cut components. The loco will be 52.5 inches long over buffer beams, c.24 in. wide, with 2.25 x 3.25 cylinders and 8 in. drivers. The designers are certainly using modern tecniques with the development of this loco and are capable of producing as much ( or as little of course) as possible in labour saving form so it might appeal to people looking for a simple build. ( fully cored ports etc on cyl. castings as an example) Both designers have email addresses in ME and are very enthusiastic about the wider gauge options.

I've just been to B & Q, (Thursday 19th Jan), and come away with an electric hoist for £39.99 ! This is the sort I used for powering the rail-rolls - but they're useful for all sorts, as it's a single phase reversible motor..... bargain

Incidentally, Aidan described a jig that his mentor, Tony Grice at Culworth Engineering used to use when sharpening drills. Very simply, it was an old lathe centre mounted on a bracket which has quite a high back to it. The trick is to sit the drill being checked onto the centre (large drills have a centre drilling already...) and then use each cutting edge in turn to scribe an arc on the back plate. If the drill was correctly ground, the scribe marks would be over-laid, but if it had been ground unevenly, you would end up with two separate scribes, which means the drill will cut over-size, and needs grinding true.
This is very easy to make, very easy to use, and improved accuracy no end (on the large drills). I am now resonably happy to sharpen drills over 1" dia with an angle grinder - knowing I can get them pretty good. A useful addition would be an angle gauge tacked on the side so you can check your tip angle...... Up till now I was paying £15 a shot to get them done professionally.

If wanting to put a crisp fold in metal sheet - and you're lacking equipment, try grinding up an old hacksaw blade to theis sort of profile, and use it to cut a deep groove in the reverse side of the metal (using a steel rule or straight edge of course...). It should then fold easily and cleanly. (don't cut all the way through, though....)