What marking out conventions do you use when marking out the workpiece?

· Always work from established Datum edges, as this will ensure greater accuracy

· When marking out for cutting always cut to the outside of the line to allow for finished filing

· If an internal profile is required always cut to the inside of the line to allow for finish filing

· Circles and Radii can be marked out using steel dividers and then cut and filed to establish the correct profile (Radii can be checked using radius gauges)

· Pitch Circle Diameters (PCD) are a series of holes marked out around a given diameter. The holes can are generally equally spaced (angularly) and reference books such as a Zeus book can be used to establish the hole positions

· Holes on a linear axis can be marked out using either ABSOLUTE or INCREMENTAL

· Absolute dimensions are marked from a datum edge to a singular point meaning that all holes originate from the DATUM

· Incremental dimensions are marked from point to point/hole to hole (using this method means that there is a greater chance of error)

· Angular dimensions can be marked out using a Vernier Protractor or a Combination Square

· When producing tapped holes, allowance should be made for the Tap and we can use reference charts to give us the relevant drill size. For example an M6x1.0 internal thread requires a 5mm drilled hole.

The M before a thread size means Metric and the figure i.e. 1.0 is the pitch