FILES. Apart from the well known file cards, another method of cleaning files is to take a strip of rubber (from an inner tube) roll it into a cylinder, securing with fine wire. When rubber along the line of the teeth, the metal particles will be drawn out.
Hardening Copper. Copper hardens as it is worked. If you need to harden copper, wire and thin sections can be hardened by stretching. Even a small amount of elongation, insufficient to significantly change the cross-section, will harden it.
10 Minutes. You have ten minutes spare in the workshop while waiting for something to dry, or cool down. What to do?
Make some more soft-jaws for the vice, and for the machine vice. You don't want to mark a completed job, so protection is vital.
It is often useful to have an assortment of vice-jaw covers to suit different work, and to ensure that unmarked ones are available for that "special" job.. Aluminium and copper are common materials. Thick lead jaws are useful if you need to grip a thread. Vinyl tiles are ideal to fit to jaws, and other surfaces which might mark the work. The self-adhesive ones can be fitted and removed in seconds , and non adhesive tiles can be fastened with double sided tape.
Holes in spring steel. (1) To make a hole in spring steel, take a piece of copper tube, slightly smaller in diameter than the required hole size. Fix in drill chuck and keep the end charged with carborundum paste, whilst rotating at slow-medium speed. (valve grinding compound works well.)
Holes in spring or hard steel. (2) To make a hole in spring or hardened steel, such as a hacksaw blade, get a carbon rod from a torch battery, connect one end to the positive post of a car battery, and the negative to a steel plate to which the spring / blade should be clamped. Press the carbon rod firmly on the point where the hole is required.
Lubricants for tapping.
Cast Iron. Paraffin is a good lubricant. Stainless steel Neatsfoot oil. Aluminium. Beeswax or tallow. Magnesium alloys. Engine oil or tallow. Copper. Lard.
Rivets. The diameter of the head of a round-head rivet is 1.5 x the diameter of the shank.
WEIGHT OF PATTERNS.
Weight of pattern in well-dried pine, gives following weights of casting in stated metals.
There have been several recent articles in the model press about the use of PTFE in models. I can make no worthwhile additions to the published information, but would add one note of caution, make sure you keep the PTFE away from flame or heat, especially during manufacture. If you are a smoker, DON'T smoke whilst machining it. The fumes are poisonous, and even the small amount which may be ingested through a cigarette can be harmful.
----------------------------------------------------------------------------------------- NOTE. On querying the reasons for this I have been told that:-
Burning PTFE will emit HYDROFLUORIC ACID fumes. Ingested into the lungs, this will cause irreversible damage to the lining and any absorbed past that will cause damage to the nervous system. Skin contact will cause lesions that are virtually impossible to cure/heal.
Smoking is / used to be banned in machine shops when working with PTFE.
The first aid treatment for hydrofluoric burns is the use of Calcium Gluconate Gel
(Thanks for information to Dick Clements, Peter Gearing, Tim Rickard & John Ray .)
In the workshop.
I was always taught never to leave a job unfinished, so I always tried to complete the item I was working on before the end of the days work.
I have now learned that this is the wrong way to do things. ( For me, at any rate.) Late in the evening, which is when many model engineers do their work, one can easily get tired and careless and a moments inattention can ruin an almost-completed part.
Nowadays I leave the end of the day for roughing out, tidying up, and other non-critical work, and leave all the final cuts and finishing until the next day when I am fresh
Silver soldering and heat treatment is on the next page