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around the fixing, whereas sockets meant for impact use have much thicker walls. High quality impact sockets are usually made from chromium molybdenum alloyed steel, as the molybdenum has a higher level of elasticity, which allows the socket to withstand higher shock loads. Impact sockets are normally chemically blacked, a treatment that provides increased corrosion resistance and doesn’ t materially affect the socket’ s dimensions. With chrome plated sockets, the chromium isn’ t very flexible and can split and peel under the increased forces used.
How do you get an accurate fit on the nut / bolt head? On the testing side, Go-NoGo gauges are used. These are measuring tools used to check parts against their allowed tolerances. The doubleended gauge has two tests, which involves the socket having to pass one test( Go) and fail the other( NoGo). The hex shaped( or Go) end is engineered to the relevant standard levels, and this is pressed into the socket and should fit. The other rectangular shaped( or NoGo) end shouldn’ t fit into the socket. But it isn’ t just a matter of seeing if the socket fits: the gauge doesn’ t return a size measurement in the normal sense but rather a state, which means to be of an acceptable state, the socket must be within the specified tolerances. When you use a socket and you feel‘ sloppiness’ over the nut / bolt head, this can be traced right back to the cold forging dies. If the dies aren’ t set up correctly to start with, they can produce sockets that are very slightly out of alignment, leading to that sloppier feeling.
Which part of the fixing should sockets ideally grip? Preferably on the flat, not on the corners. Some sockets grip on the corners,( the thin part of the fixing) which can lead to rounding off, and you can also get a slight side to side movement. If the socket grips on the flat then you get higher torque levels on the fixing plus there’ s less chance of slippage, which also helps prolongs the life of the fixing, especially those that are regularly being undone and done back up again. This is even more important if you’ re working on classic machines, as certain fixings aren’ t readily available. Exhaust studs are a good example of where you need good grip and the necessary drive onto the fixing, as they’ ve normally been through many heating / cooling cycles and the heat can effectively weld them in, making them hard to undo without damage.
What about‘ biting’ faces? You’ ve normally got either hex or bi-hex shaped sockets with six or 12 points. Metric and AF( across flat) measure across the flats, whereas Whitworth / BA measure thread size, not bolt head, so you really need to make sure you are using the right socket for the right type of fixing. 12-point sockets are useful in hard to access areas with limited turning space as the 12 points double the number of places where the socket will locate over the nut. Six point sockets generally provide better grip and are less likely to slip or round corners off.
What about different socket depths? Sockets come in various lengths / depths, and the usual ones are standard( or shallow) and deep. Standard sockets make it easier to access fixings in confined areas and have a lower profile. For deeply recessed fixings, deep sockets are needed. Vortex sockets are also available: these have no middle to the socket( they are hollow), which are ideal for long fixings. It drives around the outside( edge driven) which supplies more torque and allows a fixing to pass through the head, avoiding any depth restriction issues.
Next time we’ ll look at the next thing you need to use your sockets, a quality ratchet.
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