Printed from www.nzmeccano.com
About bossesA boss is the central part of a wheel, where the axle passes through. Through the years of Meccano production, many different types of bosses have been produced and these are referenced in the parts pages. This page describes most of the different types you will come across.
"Feather key" bosses, 1901-1907At the beginning, when Meccano was called Mechanics Made Easy, bosses were integral parts of the wheels and pulleys. Brass parts were initially cast, with gradually better finishes until they were entirely machined from solid brass. The parts from this period are not marked Meccano, but this unique key fixing makes them easy to identify.
This type of boss is referred to as a "Feather key" boss, it is always an integral part of the wheel, and dates from 1901 to early 1907. There are two serious problems with this design. One is that slots are required in all the axles, making them more expensive to manufacture, and the second is that the feather keys are very delicate. Very few feather keys have survived intact; most have had their feather broken off. The design of the feather key did change to have a shorter and deeper feather in order to prevent this, but it wasn't the right solution.
"Tongue key" bosses, 1907-1911The solution came with the 'tongue key' fixing method. Hornby found that it was possible to fix wheels to axles very satisfactorily using an indentation in the boss and a key with a curved 'tongue', which lies against a plain axle.
"Feather and tongue key" bosses date from probably no earlier than June 1907, the very end of the MME period. The word "Meccano" was trademarked in September 1907, and from around this point on the wheels were "Tongue key" only, through to 1913.
"1911 patent" bossesUp to the end of 1910, all brass parts were made from solid cast or milled brass. This was a very wasteful process, and in January 1911 a patent was filed for a new design of boss separate from the wheel or gear. The idea was to stamp the wheel from sheet brass with a hole in the middle around 3/8" diameter, then insert a boss through the hole. The boss was a cylinder of brass with an indentation all round the outside. A circular press tool then compressed the inner edge of the wheel, forcing metal from the face into the indentation in the boss and locking them together.
"Patent boss" parts thus have the circular mark around the boss, but are not stamped with "1911". The photograph to the left shows the patent boss in a 1920's gear wheel.
Tapped bossesDuring 1912, Meccano was involved in a lengthly court battle with American Model Builder, who had copied large amounts of the Meccano system. However, instead of the tongue key fixing, they used a tapped boss (that is, with a screw thread across the boss and a small set screw to fix the part to the axle). Whether by coincidence or not, in early 1913 Meccano dropped their tongue key fixing method and tapped all the bosses -- a much better solution to the fixing problem.
The 1911 patent method only worked well for thick brass gears, and other parts where there was a substantial amount of metal that could be squeezed into the indentation on the boss. For small pulleys and parts that Hornby wanted to make from thin plate, it didn't work. The "standard boss" was designed with a sharp flange at the end of the boss, which was 'peened' over the wheel face using a two or three-stage press, distorting the sharp flange over and trapping the wheel face between this and the rest of the boss. This method worked well, and more importantly was also suitable for use with steel faced wheels and gears. During WW1, the shortage of brass meant that most wheels, pulleys, and gears were eventually made with steel faces.
"Economy" WW1 bossesThe shortage of brass became more acute, and a temporary 'utility' boss was designed in early 1916. The patent for the utility boss was approved in early 1917, coinciding with dramatic restrictions on the availability of brass for the manufacture of toys. This utility boss was seen on many parts, including the small pulleys and cranks, although there was still enough brass for standard bosses to be used on gear wheels and larger parts, although their faces were now steel pressings plated with nickel.
Large bossesSome parts had a larger boss installed, always peened over as with the standard bosses, but these can appear either single-tapped or double-tapped. They were on the 3'' pulley part 19b in the early years, have always been on the 6'' pulley part 19c, and were introduced to the 2'' and 3'' sprockets part 95/95b in the mid-20's.
Double-tapped bossesStarting around 1927, bosses became double-tapped. That is, they gained a tapping for a set screw on both sides of the boss. It is often thought that this was in order to use two set-screws to get a better grip on an axle, although this has been shown to be incorrect. Two set screws allow the builder to ensure that the part is precisely centred on an axle, particularly important in complex geartrains. The tapping was not made in two separate stages but is run directly through the boss and thus the threads are 'in sync' with each other. This allows a long bolt or threaded rod to be run completely through a boss.
By the end of 1927, many common parts such as bush wheels, small pulleys, and small sprocket wheels were double-tapped. The stock of gears and other parts made perhaps less often and on different production lines were slower to change. By the middle of 1928, most parts were double-tapped, although some very rare parts such as the 25b and 26b pinions are known to exist single-tapped although they weren't introduced until 1929. It does seem to depend on the part.
This type of boss was the standard all the way through to the end of production in 1979, and is by far the most common boss of all.
Mazac bosses in WW2Many previously brass parts were already being made in enamelled steel in the 30's, such as bush wheels, small pulleys, and flanged wheels. The shortage of brass got more acute in the last couple of years before production finally stopped in January 1942. The bosses of some parts changed to Mazac, a very low-quality alloy of aluminium and zinc.
Pummels on plastic partsEarly bosses attempted to peen over a circular section of brass, as with the softer Mazac version shown above. Later, it was discovered that making the peened-over section less circular allowed the brass boss to close better on the face, preventing the boss from coming loose.
This type of boss is referred to in the parts pages as a "Pummel" boss, and dates from 1979 onwards.