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Acetal is one of the most common types of Plastic used in CNC Machined applications. Acetal provides high strength and stiffness coupled with enhanced dimensional stability and ease of machining. As a semi-crystalline material, acetal is also characterized by a low coefficient of friction and good wear properties -- especially in wet environments.


Because acetal absorbs minimal amounts of moisture, its physical properties remain constant in a variety of environments. Low moisture absorption results in excellent dimensional stability for close-tolerance machined parts. In high moisture or submerged applications, acetal bearings outperform nylon 4 to 1. Acetal is ideally suited for close tolerance mechanical parts and electrical insulators which require strength and stiffness. It also offers resistance to a wide range of chemicals including many solvents.


Here a few things to take into consideration when designing with Acetal:

1) Acetal has a Maximum Service Temperature of 180°F and a Heat Deflection Temperature of 220°F. If your part is going to be in a highly stressed environment, be sure that your application temperature is 180°F or lower.


2) Acetal comes in many different grades, including homopolymer (Delrin®), copolymer, and various filled grades such as Delrin® AF for increase bearing and wear capabilities.


3) Acetal has been known to move substantially after machining if proper techniques are not used. This is due to Center Line Porosity and a Coefficient of Thermal Expansion (CTE) of 5.40x 10-5 in./in./°F.


If you are looking for Material Data Sheets, need a Material Sample or have any questions about Machined Acetal Parts you can do so at



Posted on May 25, 2016 3:07:13 PM by Tom Gilfillan in Designing for Machining

Tom Gilfillan

Written by Tom Gilfillan