Category Archives: Tools

Air Ministry Callipers

Whilst the most common War Department marked tools that turn up are spanners, for Air Ministry marked tools, measuring devices seem to be some of the easier items to find. A few weeks back I was lucky enough to find a pair of Air Ministry marked callipers in a tool box and for the princely sum of £2 they were mine:imageCallipers are mainly used for measuring the diameter of cylinders, although have other uses in light engineering work. This pair have a crown and AM marking on one of the legs, together with a maker’s name of Buck and Hickman Ltd:imageInterestingly they also bear a /|\ mark and an inspector’s code 60 on the reverse:imageUsing callipers correctly requires a little practice and a 1930s engineering manual gives this advice:

Measuring with Callipers

Callipers, either spring or firm joint types, are convenient tools for measuring a number of jobs which are not required to be extremely accurate. Firm joint callipers have two legs fastened together with a rivet or bolt of a special design. To give a smooth joint thin fibre-washers are interposed between the legs, and when purchasing callipers this point should be looked for.

The legs of inside callipers are curved outward at the extremities to facilitate measuring small holes, whilst outside calliper legs have a large curve inward to increase their capacity for large work.

Firm joint callipers are adjusted approximately by the hands and then set to the “feel” of the work by tapping them on a metal surface. It is common practice when opening callipers by this means to tap the top of the joint. It is better, if possible, to tap the inside of the legs, as repeated blows, though light, tend to burr the edges of the joint. Care should be taken when using callipers to hold them square across the job, or an incorrect reading will be obtained. The interference between the work and the instrument should be very slight as distortion of the legs occurs if force is used. The application of callipers for good results calls for a certain amount of practice.

The book also illustrates another use for this instrument:image

Soldering Iron

A soldering iron is used to join two pieces of metal, or electrical contacts, together by melting a metal solder that joins them together when cool. Today solderin g irons are powered by electricity or an internal gas but in the past it was more common to have an external heat source that the iron was held in until it was hot enough to work with. Tonight we have an example of one of these early soldering irons as used by the British military:imageThis iron is huge, being over 12 inches long, and very heavy, easily weighing a couple of pounds. The tip is made of copper, to better retain heat, and is marked with a /|\ stamp and a date of 1946:imageA second /|\ mark and number 83 is stamped on another face of the iron and is possible an inspector’s mark:imageThe copper tip is attached to an iron handle with a large pair of rivets:imageAnd this in turn is firmly fixed to a wooden handle that protects the user’s hand from the extreme temperatures:imageSoldering in the 1940s was a laborious process and as most of us are unfamiliar with the methods needed to heat up these old style soldering irons, I thought these instructions from a period handyman’s book would be instructive:

An atmospheric gas burner, Bunsen type, is the best for heating the soldering bit, or for applying heat to work to be sweated. Unfortunately a certain amount of oxide is deposited on the bit, so that it requires frequent cleaning by wiping with a rag. Occasionally, after hearting, it will need to be filed clean with an old coarse file (whilst still hot)…

The old fashioned method of heating the bit in a clear fire has much to recommend it, but the worker must guard against too prolonged heating which will burn away the faces of the copper. When using a gas ring, choose one with a small ring of jets close together; cover the bit with a bent piece of sheet iron put on top, to conserve heat…

Heating the soldering bit- Light the gas ring, and put the bit across so that the middle of the copper as well as the pointed end gets the flame. Presently the flame will turn a vivid green, and when the colour is very pronounced remove the tool. Avoid overheating the bit, otherwise the solder may not adhere. Wipe the working faces of the bit on a thick, clean (non-greasy) cloth, and immediately put the bit in the tray, on the end of the stick of solder. The solder will run, and flow over the working faces of the copper bit, which is then ready for use.

Needless to say, when electrically powered soldering irons became reliable this method was quickly dropped as it was far from convenient. Today these old soldering irons are often scrapped for the copper content in their tips, so it has been nice to save this example and add it to my collection of military tools.

Air Ministry Marked Feeler Gauge

Feeler gauges are used to check the clearances of fittings within precision machines such as engines. A set of feeler gauges consist of a set of different metal fingers, each of a different width. Each finger is marked with its thickness, and by trying each in turn, or a combination of different ones, the correct clearance can be set. These have been in service for many decades and tonight we have an Air Ministry marked set dating back to 1939. Folded up the feeler gauge is just a small metal bar:imageA cut-out is provided on one side that allows the gauges to be pushed out from their housing:imageFanned out it can be seen that a wide range of thicknesses are housed in the tool:imageEach gauge has its thickness in thousandths of an inch etched into its surface:imageThese gauges go from 3/1000″ up to 15/1000″ and the gauges are flexible enough that multiples can be held together to make up different thicknesses.

The gauge itself has a crown and AM stamp along with a date of 1939 indicating it was produced for the RAF:imageThis tool was manufactured by Moore and Wright of Sheffield. The company is now part of the Bowers group, and their website gives some history:

Founded in 1906 by innovative young engineer Frank Moore, Moore & Wright has been designing, manufacturing and supplying precision measuring equipment to global industry for over 100 years. With roots fixed firmly in Sheffield, England, the company began by manufacturing a range of callipers, screwdrivers, punches and other engineer’s tools.

The uses for feeler gauges included setting the tappet valves in engines, as explained in a 1953 army handbook on basic mechanical principles for tracked and wheeled vehicles:

Clearance between the valve stem and tappet is tested with a feeler gauge. If the appropriate feeler just pushes through the gap with little force the setting is correct. To make certain try the next size up, this should not go.

Air Ministry 6″ Steel Rule

Steel rules are essential measuring devices in any workshop. The properties of metal allow a worker to score along the edge of the ruler without any fear of damaging the rule itself, a common problem with wood or plastic rulers. Metal rules have been used for the marking out of sheet metal for many centuries and it is therefore unsurprising that examples exist that are marked up to show they belong to the military. The RAF especially relied on fitters and mechanics to keep aircraft serviceable, right form its inception. These men needed extensive tool kits and amongst these would be a steel rule. Tonight we have an Air Ministry marked example to look at:imageThis 6” rule is stamped with the crown and AM mark of the Air Ministry and has a date of 1939:imageDating from the 1930s, this rule is predominantly set up to measure fractions of an inch, however the reverse does have a metric scale as well:imageThe use of a steel rule was viewed as so important that the US actually produced a thirteen minute training film on its use for metal workers! This film can be seen here.

The role of the aircraft fitter was essential to repair aeroplanes and get them back into the sky. John Morris served as a groundsman in World War Two:

Each transport took us to the aerodrome which was about 5 miles from Setif, it was the French Air force and had one or two hangars in which to work on the aircraft. Aircraft were brought to the unit when they had flown a large number of hours, which was called a major inspection. They would be jacked up on large metal jacks in what was known as rigging or flying position, the engines were removed, petrol tanks dropped, hydraulics checked, metal replaced with rivets between the engine nacelle and the fuselage where heavy boots walked over the wing when re-fuelling, the metal got stretched. When all of this had been done, the aircraft was re-sprayed, placed in a pool ready for the next squadron that required a replacement aircraft. It was mainly Bristol Beaufighters that were worked on. A twin-engine, two crewed night fighter, fitted with radar, later used for anti-shipping. It was also converted to carry a torpedo or eight 60 lb. rockets.

One repair job I shall always remember was a Beaufighter that had been built with countersinking too large and the rivets sunk below the level of the outside skin. Two of us replaced a thousand oversize rivets making the fuselage smooth. Later it was mentioned that this aircraft had gone out with other planes from the squadron and pumped 55 rockets into the Rex, a 55,000 ton Italian liner just below the water line and sinking the ship just off Trieste.