Delrin Specifications — ASTM D6100, Sizes & Tolerances
Delrin (POM-H acetal homopolymer) stock shapes are governed primarily by ASTM D6100, which specifies requirements for polyacetal (polyoxymethylene) rod, sheet, and tube. This page covers the applicable standards, dimensional tolerances for stock shapes, standard stocked sizes, and procurement specification language for engineers writing drawings and purchase orders.
At a glance:
- Primary specification: ASTM D6100 — Standard Specification for Polyacetal (POM) Plastic Rod, Sheet, and Tube
- Property test methods: ASTM D638 (tensile), D790 (flexural), D256 (Izod impact), D648 (HDT)
- Standard rod diameters: 0.125" to 12.0"; standard sheet thicknesses: 0.062" to 4.0"
- Rod diameter tolerance: typically ±0.010–0.015" for standard stock; tighter to special order
- Sheet thickness tolerance: ±10% of nominal (ASTM D6100 default); ±5% to special order
- FDA grades (150SA / 500SA) comply with 21 CFR 177.2480
Governing Standards
ASTM D6100
ASTM D6100 is the primary specification for polyacetal stock shapes (rod, sheet, tube). It covers:
- Material identification and classification (Type I for unfilled, Type II for filled)
- Dimensional tolerances for rod, sheet, tube, and plate
- Required property certifications and test methods
- Marking and labeling requirements
All standard Delrin rod, sheet, and tube from reputable distributors should be produced and certified to ASTM D6100. When specifying Delrin on a drawing or purchase order, call out ASTM D6100 along with the grade (e.g., "Acetal (POM-H), Delrin 150, ASTM D6100 Type I").
ASTM D638, D790, D256, D648
Individual property tests reference these ASTM standards:
| Property | Test Method |
|---|---|
| Tensile strength, modulus, elongation | ASTM D638 |
| Flexural strength and modulus | ASTM D790 |
| Izod impact (notched) | ASTM D256 |
| Heat deflection temperature | ASTM D648 |
| Compressive strength | ASTM D695 |
| Water absorption | ASTM D570 |
| Hardness (Rockwell) | ASTM D785 |
ISO Equivalent
ISO 9988 (Plastics — Polyoxymethylene (POM) moulding and extrusion materials) defines POM material classification per ISO. For European procurement, DIN EN ISO 9988 is the applicable standard. ISO 11470 covers tolerances for extruded POM rods.
Regulatory Compliance Standards
- FDA 21 CFR 177.2480: Food-contact compliance for Delrin 150SA and 500SA
- NSF/ANSI 51: Food equipment material standard
- NSF/ANSI 61: Drinking water system component standard (applicable to some Delrin grades)
- RoHS Directive 2011/65/EU: Compliant (Delrin contains no restricted substances)
- REACH SVHC: Not listed as a substance of very high concern
Stock-Shape Dimensional Tolerances
Rod Dimensional Tolerances
| Diameter Range | Standard Tolerance (ASTM D6100) | Tighter Tolerance (Special Order) |
|---|---|---|
| Up to 0.500" | ±0.010" | ±0.005" |
| 0.501" – 1.000" | ±0.010" | ±0.007" |
| 1.001" – 2.000" | ±0.015" | ±0.010" |
| 2.001" – 4.000" | ±0.020" | ±0.015" |
| 4.001" – 6.000" | ±0.030" | ±0.020" |
| Over 6.000" | ±1% of diameter | To quote |
Straightness: rod is supplied straight within 0.050" per foot for standard stock; precision-straightened material to 0.010" per foot is available on request.
Centerline porosity is a characteristic of Delrin (POM-H) rod in diameters above approximately 3.0 inches. It is not a defect under ASTM D6100, which acknowledges this characteristic of homopolymer. If centerline-porosity-free material is required for large-diameter applications, specify acetal copolymer (POM-C) instead. See the acetal copolymer specifications page.
Sheet Dimensional Tolerances
| Thickness Range | Standard Tolerance (ASTM D6100) | Special Order |
|---|---|---|
| 0.062" – 0.250" | ±10% of nominal | ±5% |
| 0.251" – 0.500" | ±10% of nominal | ±5% |
| 0.501" – 1.000" | ±10% of nominal | ±7% |
| Over 1.000" | ±10% of nominal | ±7% |
Sheet flatness: standard sheet flatness is 0.025"/ft over the sheet length; precision-ground sheet is available to ±0.005" total thickness variation for precision machining applications.
Standard sheet sizes stocked:
- 24" × 48"
- 48" × 96"
- 12" × 12" (cut-to-size; not an extruded size)
Tube Dimensional Tolerances
| OD Range | OD Tolerance | Wall Thickness Tolerance |
|---|---|---|
| Up to 2.000" | ±0.015" | ±10% of wall |
| 2.001" – 4.000" | ±0.020" | ±10% of wall |
| Over 4.000" | ±0.030" | ±12% of wall |
Tube concentricity (wall variation): ±15% of wall thickness for standard stock.
Standard Stocked Sizes
Delrin Rod — Standard Diameters
| Diameter | Grade Availability | Standard Length |
|---|---|---|
| 0.125" (1/8") | 150, 500, natural/black | 4 ft |
| 0.187" (3/16") | 150, 500, natural/black | 4 ft |
| 0.250" (1/4") | 150, 500, natural/black | 4 ft |
| 0.375" (3/8") | 150, 500, natural/black | 4 ft |
| 0.500" (1/2") | 150, 500, 150SA, natural/black | 4 ft |
| 0.625" (5/8") | 150, 500, natural/black | 4 ft |
| 0.750" (3/4") | 150, 500, 150SA, natural/black | 4 ft |
| 1.000" (1") | 150, 500, 150SA, 100AF, natural/black | 4 ft |
| 1.250" | 150, 500, natural/black | 4 ft |
| 1.500" | 150, 500, 150SA, natural/black | 4 ft |
| 2.000" | 150, 500, natural/black | 4 ft |
| 2.500" | 150, 500, natural | 4 ft |
| 3.000" | 150, 500, natural | 4 ft |
| 4.000" | 150, natural | 4 ft |
| 5.000" | 150, natural | 4 ft |
| 6.000" | 150, natural | 4 ft |
| 8.000" | 150, natural | 4 ft |
| 10.000" | 150, natural | 4 ft |
| 12.000" | 150, natural | 4 ft |
Delrin Sheet — Standard Thicknesses
| Thickness | Grade Availability | Sheet Size |
|---|---|---|
| 0.062" (1/16") | 150, 500, natural/black | 24×48", 48×96" |
| 0.093" (3/32") | 150, 500, natural/black | 24×48", 48×96" |
| 0.125" (1/8") | 150, 500, 150SA, natural/black | 24×48", 48×96" |
| 0.187" (3/16") | 150, 500, natural/black | 24×48", 48×96" |
| 0.250" (1/4") | 150, 500, 150SA, natural/black | 24×48", 48×96" |
| 0.375" (3/8") | 150, 500, natural/black | 24×48", 48×96" |
| 0.500" (1/2") | 150, 500, 150SA, natural/black | 24×48", 48×96" |
| 0.625" (5/8") | 150, 500, natural/black | 24×48", 48×96" |
| 0.750" (3/4") | 150, 500, natural/black | 24×48", 48×96" |
| 1.000" (1") | 150, 500, natural/black | 24×48", 48×96" |
| 1.500" | 150, 500, natural | 24×48" |
| 2.000" | 150, 500, natural | 24×48" |
| 3.000" | 150, natural | 24×48" |
| 4.000" | 150, natural | 24×48" |
Writing a Delrin Specification for Engineering Drawings
Recommended purchase specification language:
Material: Acetal Homopolymer (POM-H), DuPont Delrin 150 or approved equivalent, ASTM D6100, Type I. Natural (white/ivory) color. Certifications required: manufacturer's certificate of conformance with grade, lot number, and ASTM D6100 compliance statement. [Add "FDA 21 CFR 177.2480 compliant" if food-contact grade required — specify Delrin 150SA.]
For applications where grade equivalents are acceptable (non-branded POM-H from other manufacturers), add: "POM-H acetal homopolymer per ASTM D6100 Type I, with tensile strength ≥ 10,000 psi (ASTM D638) and heat deflection temperature ≥ 250°F at 264 psi (ASTM D648)."
Avoid writing specifications that simply say "Delrin or acetal." This language allows substitution with acetal copolymer (POM-C), which is a different material with different properties. If POM-H is required, say so explicitly: "acetal homopolymer (POM-H)" or "Delrin 150/500 specifically."
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