C3 Mini-Lathe Metalworking Beginners

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Copper makes a useful hammer in the home metalworking workshop - here is how

Copper is not a material we find ourselves machining in the home metalworking workshop on a regular basis. Nine times out of ten a piece of aluminium will do fine. The first property of copper that most home machinists will identify is the extremely high thermal and electrical conductivity of copper. This makes it very useful as a material for constructing heat sinks. One occasion, many years ago, I modified a webcam for astronomy use by mounting the CCD sensor onto a copper finger.

This is all very interesting, but there are some other properties of copper which make it more useful in the home metalworking workshop – especially when we are using the mini-lathe. Essentially copper is soft. It is softer than steel, and, crucially for use in the home workshop, softer than aluminium. This allows us to hit bits of aluminium with lumps of copper and it is the copper which gets dented, and not the aluminium.

When mounting parts in the mini-lathe, it is often necessary to use a dial indicator to align the part in the mini-lathe. During this adjustment we need to move the part very slightly relative to the chuck jaws, before tightening the jaws completely. If we hit our nice, half completed aluminium part with a regular hammer, it will dent the part, we will swear, and then start over. If we used a rubber hammer, then even less progress is made – the rubber mallet simply bounces off the part!

It is possible to go shopping for a copper headed hammer for just this purpose – tapping parts into adjustment. However, in the interests of economy I use a small bit of copper rod I picked up for a few pence in the off-cuts section of the local metal supplier.

The advantage of this is two-fold. The narrow rod allows me to direct blows exactly where I want them – this helps a lot when centering a part in the mini-lathe.

The other advantage of using a small single piece of copper is that I am able to re-soften the copper rod when I want to.

Copper has a curious properly – the more you work it (i.e. bash it against other things on the mini-lathe) the hard it becomes. This is known a work hardening and is a common property of metals.

The more we use the copper rod to knock aluminium parts into alignment on the mini-lathe, the hard the copper rod becomes. Of course, this increases the chance of denting or scratching our precious aluminium part.

The copper rod can be re-softened by using a blow torch. I have a nice blow torch I purchased from B&Q for a reasonable amount. I can use this blowtorch to heat up the copper rod until it is very hot – i.e. Glowing cherry red. Then I just leave it to cool.

This process of heating and cooling will undo the prior effects of the work hardening on the copper rod. Because the copper rod is quite small and of low mass, it does not take long to heat it up with the blowtorch. Please be careful – it will hold its heat for a long time!

Of course, you are always welcome to use copper to make parts. It adds a nice touch to add a small amount of copper parts into a project for decorative effect – with some sandpaper and metal polish you will be a splendid finish to copper parts made on a mini-lathe.