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Engineering Parallels

Transfering precision

Engineering Parallels are up there with dial indicators and Morse Tapers when it comes to simple straightforward principles that are set down to bemuse and confuse the beginner.

A parallel is simply a lump of (usually) metal which has a very carefully prepared surface. Usually in the form of a rectangular block, the parallel will be carefully constructed to make sure all the sides are at right angles or parallel to each other. You can trust the accuracy of the engineering parallel beyond the accuracy of your machine usually.

The main use of parallels is mounting work so that you can machine it using a mill or lathe. Think about your expensive milling vise. The floor of the vise is supposed to be parallel to the bed of the mill. Thats is good. Use the egineering parallels to mount a small piece of work in the vice.

Use the parallels when you are mounting a part onto the bed of the mill, but need to raise it up so that you can mill the edge perhaps.

A pair, or better still, a set, of engineering parallels is a vital tool in the home metalworking workshop. Adjustable parallels are often commonly available, but I do not know how good they are - sounds like a compromise to me.

On ebay, engineering parallels tend to get snapped up for quite a high price - and do not come up very often. Grab them when you can.

Again, the principle involved is always that of TRANSFERING PRECISION - transfering the precision of the milling table to your workpeice.