The Nuts and Bolts

Fasteners used for the Locost build can be numerous in type size and material. Normal nut and bolt fixing will be mostly used and in general most will be standard metric coarse sizes. Some suspension parts can be threaded with old imperial threads so it is advisable to take a look at how threads are configured. A good source for tables showing thread types and sizes are engineers' pocket books such as Zeus Charts. These can be bought from tool suppliers or large book stores and cost around £6. I have seen £4.99 on E-Bay.

Metric threads are listed by their outside diameter such as M8, outside diameter 8mm etc. The thread is also listed with a pitch in mm. In simple terms, the pitch is the distance between the tip of two threads, or how much the bolt will move in if turned one complete revolution. A coarse thread has a bigger pitch than a fine thread, so do not get this mixed up as if you try to tighten a nut onto a bolt with the wrong thread it will Pick Up. This means the nut will lock onto the bolt and not turn any more. If you get lucky you will be able to get the nut off again but ruin nut and bolt, or you will have to cut them off and put new nut and bolt in place.

Older imperial threads are listed once again by outside diameter such as ¼ or 1/2inch but another twist appears to make it more complicated. Imperial threads do not have a pitch but instead are listed by how many teeth per inch they have Tpi. This is found by measuring, put a rule against the bolt and count how many teeth there are in 1inch. If the bolt is short then you have to work out how many teeth there are in a shorter distance. If you find there are 4 teeth in the 1/4inch, there are four quarters in one inch. You then use your count of 4 and times it by 4 to be 1inch, so your have 4x4 = 16Tpi.
So a typical example of an imperial thread will be ½ x 13 UNC.

The Data books will list all the thread types and sizes, UNC- Unified National Coarse, UNF Unified National Fine, Whitworth, BA, BSF- British Standard Fine, Metric Coarse, Metric Fine and BSP British Standard Pipe threads. If you need to drill and tap your own thread in steel, the charts also list the drill size to tap the required thread.

Standard bolts are normally strong enough for your needs but once again some suspension bolts that come under stress are bought as HT bolts. HT is the abbreviation for High Tensile Bolt. If I do not need HT bolts, I tend to use mostly Stainless Steel nuts and bolts, which are a little more expensive, but pleasing to the eye and will not rust!

Bolts also come with many different types of head. Hexagon head is the norm but you can also choose , Socket cap head, countersunk head, pan head, cheese head, dome head. Some of these have to be tightened up with an Allen Key instead of a spanner. It is well worth spending the extra few pounds for Ball Ended Allen Keys, if you have hex head screws that are close to anything to restrict movement, the ball end alloys you to angle the allen key to spin up a screw quickly and then finally tighten as normal, saving time.

If you are using nuts and bolts, you will either use a combination of plain washer and nylon locknut, or a spring washer and a plain nut. These combinations will help stopping the nut and bolts working loose.
Your Locost will need bolt heads with a good radius on them and some, nut covers to get it through the SVA test. This is to protect from cuts from sharp edges!