Delrin / POM Weight Calculator
Calculate POM acetal sheet, rod, and tube weight — copolymer, Delrin homopolymer, glass-filled, and PTFE bearing grades
POM / Delrin Weight Calculator
Calculation Results
Grade Quick Reference
Formula Used
POM / Delrin Grade Specifications
Density values per ASTM D792 / ISO 1183, referenced against ASTM D4181 (POM material specification). Tensile strength per ASTM D638. Hardness per ASTM D785 (Rockwell M scale). Maximum service temperature for continuous use in air.
| Grade | Density (g/cm³) | Tensile Strength | Elongation | Flexural Modulus | Hardness (Rockwell M) |
|---|---|---|---|---|---|
| POM-C — Acetal Copolymer | 1.41 | 62–65 MPa | 25–40% | 2,600 MPa | M80 |
| POM-H Delrin® — Homopolymer | 1.42 | 65–70 MPa | 25–40% | 2,800 MPa | M92 |
| Glass-Filled POM — 20% GF | 1.56 | 90–110 MPa | 3–5% | 7,000 MPa | M92 |
| PTFE-Filled POM — Bearing Grade | 1.42 | 48–55 MPa | 15–25% | 2,200 MPa | M75 |
Standards: ASTM D4181 (POM material specification). Density per ASTM D792 / ISO 1183. Tensile strength per ASTM D638. Hardness per ASTM D785 (Rockwell M scale). Flexural modulus per ASTM D790. Delrin® is a registered trademark of DuPont (now Celanese).
POM-C vs POM-H: Which Grade Should You Use?
Delrin is the most recognized brand name in the POM family, but it is specifically DuPont's (now Celanese's) trade name for POM homopolymer. Understanding the distinction between POM-H and POM-C — and the filled grades — is essential for correct grade selection and accurate weight estimation.
POM-C — Acetal Copolymer
The general purpose acetal grade made by copolymerizing trioxane with a comonomer. POM-C exhibits lower centerline porosity than POM-H in thick cross-sections (over 50 mm), making it the preferred choice for large-diameter rod and thick plate machining. Available in natural white and black. Widely FDA compliant for food contact.
- Density: 1.41 g/cm³
- Best choice for: thick rod, large plate, food contact parts, general precision machining
- Lower centerline porosity — critical for thick-section machining
POM-H Delrin® — Homopolymer
Delrin is DuPont's brand name for POM homopolymer, made exclusively by polymerizing formaldehyde. It offers slightly higher tensile strength (65–70 MPa vs 62–65 MPa) and hardness (M92 vs M80 Rockwell M) compared to POM-C. The preferred grade for precision gears and parts where maximum mechanical performance is required. In thick cross-sections, centerline porosity can be a concern — use POM-C for sections above 50 mm.
- Density: 1.42 g/cm³ — effectively the same as POM-C for weight calculations
- Best choice for: gears, high-load bearings, precision components, thin-section parts
- Higher hardness and strength than POM-C
Glass-Filled POM — 20% GF
20% short glass fiber reinforcement dramatically increases stiffness (flexural modulus from 2,600 to ~7,000 MPa) and reduces thermal expansion. Density increases to 1.56 g/cm³ — parts made from GF POM will weigh approximately 10% more than unfilled grades at the same volume. The trade-off is brittleness (elongation drops to 3–5%), poor self-lubricating properties, and abrasive wear on cutting tools. Not suitable for sliding contact without additional lubrication.
- Density: 1.56 g/cm³ — heaviest POM grade
- Best choice for: structural parts, pump components, dimensionally critical parts requiring low thermal expansion
- Use carbide tooling — glass fibers are highly abrasive to HSS tools
PTFE-Filled POM — Bearing Grade
PTFE particles dispersed through the POM matrix significantly reduce the coefficient of friction and enable dry-running (unlubricated) operation. Used for bushings, wear pads, and sliding guides where oil or grease lubrication is not practical. Tensile strength is reduced compared to unfilled POM because PTFE does not bond to the POM matrix. Density remains approximately 1.42 g/cm³.
- Density: 1.42 g/cm³ — same as POM-H for weight calculations
- Best choice for: dry-running bushings, sliding wear pads, conveyor guides, food processing slides
- Lower strength than unfilled grades — verify load requirements
Standard Stock Sizes
Common stock dimensions for POM sheet, rod, and tube. POM is available in natural (white) and black in most grades. Confirm availability with your supplier before ordering.
S Sheet Stock
Standard sheet size: 24" × 48" or 24" × 96". Available thicknesses:
Metric equivalent (approx): 3 mm, 4.8 mm, 6.4 mm, 9.5 mm, 12.7 mm, 19 mm, 25 mm, 38 mm, 51 mm, 76 mm, 100 mm
R Rod Stock
Standard rod length: 2 ft, 4 ft, or 6 ft. Available diameters:
Metric equivalent (approx): 6 mm, 10 mm, 12 mm, 19 mm, 25 mm, 38 mm, 50 mm, 75 mm, 100 mm, 150 mm
T Tube Stock
Standard tube length: 2 ft or 4 ft. Common OD × wall thickness:
Custom bore tube is often machined from solid rod. Confirm tube availability in your grade — not all grades are stocked as tube.
POM / Delrin Applications
POM is one of the most widely specified engineering plastics for precision machined components. Its combination of high stiffness, low friction, excellent dimensional stability, and moisture resistance makes it the standard material for mechanical parts that must perform reliably without lubrication.
Gears & Precision Components
- Spur and helical gears
- Worm gear wheels
- Ratchet mechanisms
- Cams and pawls
- Sprockets and timing wheels
Bearings & Wear Parts
- Plain bearings and bushings
- Thrust washers
- Wear pads and slides
- Conveyor chain guides
- Rollers and pulleys
Food Processing & Medical
- Food contact conveyor parts
- Cutting board inserts
- Pump impellers and housings
- Valve bodies and seats
- Medical device components
POM vs Nylon: Which Should You Use?
POM (Delrin) and Nylon are the two most common engineering plastics for machined gears, bearings, and sliding parts. The key differentiator is moisture: Nylon absorbs water and changes dimensions, POM does not. This single factor drives most material selection decisions between the two.
| Property | POM (Delrin) | Nylon 6/6 |
|---|---|---|
| Density (g/cm³) | 1.41–1.42 | 1.14 |
| Moisture Absorption | 0.2% (very low) | 1.5–3.0% (high) |
| Dimensional Stability | Excellent | Moderate (varies with humidity) |
| Tensile Strength | 62–72 MPa | 75–85 MPa (dry) |
| Impact Resistance | Good | Excellent |
| Surface Finish (Machined) | Excellent | Good |
| Max Service Temp | 90°C / 194°F | 100°C / 212°F |
| Chemical Resistance (Acids) | Poor | Moderate |
| FDA Food Contact | Yes (natural/unfilled) | Yes (selected grades) |
| Relative Cost | Moderate | Lower |
Choose POM when:
- Tight tolerances must be maintained in humid environments
- Gears and cams require a hard, smooth running surface
- Excellent machined surface finish is required
- Contact with water or wash-down conditions
Choose Nylon when:
- High impact or shock loading is expected
- Weight savings matter (Nylon is ~20% lighter than POM)
- Running against rough mating surfaces
- Budget is the primary constraint
Need Nylon weight? Use our Nylon Weight Calculator.
Machining POM / Delrin
POM is considered one of the easiest engineering plastics to machine to tight tolerances. It produces short, clean chips, holds dimensions well, and achieves excellent surface finish with standard tooling — all without requiring flood coolant.
Best Practices
- Sharp HSS or carbide tooling — POM cuts cleanly with either; carbide essential for glass-filled grades
- No coolant required — dry or air blast only; water-based coolant acceptable but unnecessary for unfilled grades
- High surface speeds — 200–400 SFM typical; produces excellent surface finish
- Anneal before finish machining — stress relieve at 150–160°C for 1–4 hours to prevent post-machining distortion
- Hold tight tolerances consistently — POM's low moisture absorption means dimensions do not change after machining
What to Avoid
- Avoid strong acids and bases — POM degrades rapidly below pH 4 or above pH 12; use neutral cutting fluids only
- No chlorinated solvents — methylene chloride and similar solvents attack POM; use IPA for cleaning
- Do not use HSS on glass-filled POM — 20% GF is highly abrasive; switch to carbide immediately
- Avoid excessive heat during cutting — POM degrades above 200°C producing formaldehyde gas; ensure adequate ventilation
- Do not use alkaline cleaners — caustic cleaning solutions cause stress cracking and surface degradation
Standards & Certifications
POM is governed by well-established ASTM material standards, and natural unfilled grades carry FDA food contact listings that are required for food processing and medical applications.
ASTM D4181
Standard classification for acetal (POM) plastics. Covers material designation by type (homopolymer vs copolymer), grade, and class based on mechanical and thermal properties. The primary specification for engineering POM grades used in sheet, rod, and tube stock.
FDA 21 CFR 177.2470
Natural (white) POM-C copolymer and unfilled POM-H are listed under FDA 21 CFR 177.2470 for repeated food contact use. This regulation covers polyoxymethylene (acetal) resins intended for repeated use in contact with food. Black, glass-filled, and PTFE-filled grades must be individually verified — confirm food contact compliance with your material supplier.
RoHS & REACH
Natural and black unfilled POM grades are RoHS compliant and free from SVHC substances under REACH. Glass-filled grades using standard E-glass are also typically RoHS compliant. Confirm compliance documentation with your supplier for regulated markets and medical applications requiring full material traceability.
Frequently Asked Questions
What is the density of Delrin (POM)?
POM-C (acetal copolymer) density is 1.41 g/cm³. POM-H (Delrin homopolymer) is 1.42 g/cm³. For practical weight calculations, both are treated as 1.41–1.42 g/cm³. Glass-filled POM (20% GF) is 1.56 g/cm³ — approximately 10% heavier than unfilled grades at the same volume. PTFE-filled bearing grade is 1.42 g/cm³. All POM grades are significantly denser than water and will sink.
What is the difference between Delrin and acetal?
Delrin is DuPont's (now Celanese's) registered brand name for POM homopolymer (POM-H). Acetal copolymer (POM-C) is the generic alternative produced by multiple manufacturers including Celanese (Hostaform), BASF, and others. Both are polyoxymethylene (POM) resins with very similar properties and densities. POM-H has slightly higher tensile strength and hardness; POM-C has lower centerline porosity in thick sections and is the preferred grade for machining thick rod or plate over 50 mm.
Is Delrin (POM) food safe?
Natural (white) unfilled POM-C and POM-H are listed under FDA 21 CFR 177.2470 for repeated food contact use. POM is widely used in food processing equipment, conveyor parts, cutting surfaces, and pump components. Black, glass-filled, and PTFE-filled grades are not automatically FDA approved — each must be individually verified against the regulation. Always confirm food contact compliance with your material supplier before specifying for direct food contact applications.
What is the maximum service temperature of POM / Delrin?
POM has a continuous service temperature of approximately 90°C (194°F) in air. Short-term exposure up to 120°C is manageable, but sustained use above 90°C causes oxidation and gradual property degradation. POM should not be used in contact with strong acids (below pH 4) or strong bases (above pH 12), as these cause rapid chemical attack. For applications requiring temperatures above 90°C, consider PEEK, PPS, or polyamide-imide (PAI) as alternatives.
How does POM compare to Nylon for machined parts?
POM is stiffer, dimensionally more stable, and absorbs almost no moisture (0.2% vs 1–3% for Nylon 6/6), making it the preferred choice where tight tolerances must be maintained in humid environments or wet service. Nylon has better impact resistance and performs better against rough metal mating surfaces. POM machines to a better surface finish and holds tighter dimensional tolerances. For gears, bushings, and precision sliding components in controlled environments, POM is generally preferred. For shock-loaded or outdoor applications, Nylon (especially oil-filled Nylon) is a strong competitor.
How do I calculate Delrin rod weight?
Delrin rod weight = π × (diameter ÷ 2)² × length (mm) ÷ 1000 × density (g/cm³). For a 50 mm diameter × 1000 mm POM-H Delrin rod (1.42 g/cm³): π × 25² × 1000 ÷ 1000 × 1.42 = 1,963.5 × 1.42 = 2,788 g (2.788 kg). For POM-C acetal copolymer (1.41 g/cm³), the same rod gives 2,769 g. Select Rod shape in the calculator above and enter your diameter and length in metric or imperial units.