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Delrin and mini-lathes and micro-mills

Delrin and Acetal Engineering Plastic?

There is one major problem with metal work on a mini-lathe and micro-mill. Metal is fundamentally a very hard substance. The lower power tools like mini-lathes and micro-mills require patience from the operator to do a good job. If a mistake is made in the fabrication of a part towards the end of the manufacture, it is exceedingly annoying. You either have to start again, or modify your design.

However, for some situations there is an easier approach. Engineering plastics. Certain plastics make fine engineering materials. They are not as strong as metal and they are much softer than metal. This means the mini-lathe is able to cut the metal away very quickly.

The name Delrin refers to a trade name of an engineering plastic made by Dupont. It has high mechanical strength, stiffness and hardness. Combined this with its good wear resistance and high impact strength, Delrin exhibits good dimensional stability. Delrin is a specialised form of Acetal Resin. Other types of Acetal resin, often marketed as just "Acetal", are available. e advantage of choosing Delrin over Acetal is that:

• Higher mechanical strength, stiffness and hardness
• Better creep resistanceas
• Lower rate of thermal expansion
• Better wear resistance.

The advantage of choosing Acetal over Delrin is Acetal's greater resistance to nasty chemicals, such as alkalis. It does not degrate in hot enviroments so easily.

For me, Delrin is the stuff to use.

• If I do not need to strength of metal for a particular part, then I will consider Delrin.
• If I am making something complicated in metal, I will practise first in Delrin.
• IF I am not sure what my final design will be, I will prototype in Delrin.

Mini-lathes cut through delrin at least 10 times faster than metal. It is easy to quickly knock up a prototype... and often the prototypes stick around!

A somewhat slower speed is required on the mini-lathe with engineering plastics so as to not melt them.

I strongly recommend a stock of Delrin - for those days when the metal is too hard.