Acetal Homopolymer

Also known as Delrin or POM, this is our favorite choice for plastic gears. Acetal naturally has low friction, high wear-resistance, high strength, and high stiffness. Use this material for gears, lightweight bearing surfaces, fixture blocks, and more.

Overall Sizes
Largest Outside Diameter (ODmax)	2.91 in
Max Length (L), no bored features	9.5 in	Limited by machine clearance.
Max Length (L), with bored features	6.25 in	Features cut into the face of the part require more room for the tool to move into the part, subtracting from available room in the machine.
Minimum Wall Thickness	0.04 in
Max L:D ratio with no Tailstock	4.5	If the part is too long compared to its diameter, the cutting forces will push the part away, causing inaccurate dimensions. Allowing for a Tailstock can help exceed this limit.
Max L:D ratio with Tailstock	10	Even with a Tailstock supporting the end of the part, cutting forces near the middle of a long part can cause deflection and inaccurate dimensions.

Feature Sizes
Maximum Radial Step	0.826 in	0.119 in minimum groove width
	0.629 in	0.060 in minimum groove width
Maximum Boring Depth	0.890 in	For hole diameters 0.133 in and larger
	1.340 in	For hole diameters 0.196 in and larger
	1.790 in	For hole diameters 0.258 in and larger
Minimum Groove Width	0.119 in	0.826 in maximum depth
	0.060 in	0.629 in maximum depth
Internal Threads
External Threads

Gears
Minimum Number of Teeth	12	Our gears are made by hobbing or single-tooth cutting, both of which have limitations under a tooth count of 12.
Maximum Helix Angle, Helical Gears	45°	Limited by machine clearance.
Available Tooth Sizes	0.5 mod hob	20° pressure angle
	0.6 mod hob	20° pressure angle
	0.7 mod hob	20° pressure angle
	0.8 mod hob	20° pressure angle
	1 mod hob	20° pressure angle
	1.25 mod hob	20° pressure angle
	1.5 mod hob	20° pressure angle
	12 DP hob	14.5° pressure angle
	16 DP hob	14.5° pressure angle
	20 DP hob	14.5° pressure angle
	1 mod hob	14.5° pressure angle
Maximum Gouge	3 times module	The maximum allowable distance for the gear cutting tool to enter the part. Features nearby to the gear surface will get gouged if they are too close.
Maximum Number of Gears per Part	4	Be aware of gouging when combining gears in one part. See: How to Make Stacked Compound Gears and Herringbone Gears

Tolerances
Diameter Tolerance	±0.005 in
Length Tolerance	±0.005 in
Thread Tolerance
Gear Class

Material Properties
Not tested or guaranteed. Use appropriate safety factors in design.
Density	1.41 g/cc
Yield Strength	66 MPa
Ultimate Strength	69 MPa
Elastic Modulus	3 GPa
Hardness	95SD