Delrin is the brand name for acetal homopolymer resin, which is a very hard, high-strength engineering plastic. It can withstand temperatures from -40°C to 120°C (-40°F to 248°F), and it holds its shape well over time. Despite being hard, it mills easily and gives a really nice finish with the right settings. It’s also self-lubricating (aka slippery), which allows it to be used for parts that slide against other parts, without wearing down or sticking.
From the manufacturer: Delrin is used for high-load mechanical applications, such as gears, safety restraints, door systems, conveyor belts, healthcare delivery devices, and components across a diverse range of products and industries.
A number of the Bantam Tools Desktop CNC Milling Machine's parts are made of Delrin, notably the bearings and anti-backlash nuts used in all the carriages. Among the Bantam Tools community, Delrin is mostly used to make mechanical parts.
We sell pre-cut pieces of both black and white Delrin in our store. They’re the perfect size for many projects, and they fit nicely on our milling machine's bed.
In general, larger tools like 1/4”, 1/8", and 1/16" end mills are better because they cut through material the fastest and are least likely to break. For 3D shapes, a 1/4”, 1/8", or 1/16" ball end mill produces the smoothest contours. For best results, keep a set of end mills specifically for Delrin and other plastics, and never use them to cut metal. This allows for increased milling speeds and a better finish.