PTFE Specifications: ASTM Standards & Stock Sizes

PTFE stock shapes are governed by a family of ASTM standards that specify resin composition, processing requirements, and dimensional tolerances for each product form. Procurement teams and engineers specifying PTFE sheet, rod, tube, or film should reference these standards on purchase orders to ensure material traceability and consistent mechanical performance. This page covers the applicable standards, standard stock sizes, and tolerance ranges for each form factor.

At a Glance

• Resin specification: ASTM D1457 (molding and extrusion materials); ASTM D4894 / D4895 (granular / fine powder)
• Sheet: ASTM D3293 — thicknesses from 1/32 in. to 4 in.; planks typically 12×12 to 48×48 in.
• Rod: ASTM D3295 — diameters from 1/4 in. to 12 in.
• Tube: ASTM D3296 — OD from 1/4 in. to 6 in.
• Film / skived sheet: ASTM D3308 — 0.001 in. to 0.060 in. thick
• Thickness tolerances: ±5–10% depending on form and dimension
• Color codes: white (virgin), black (carbon-filled), off-white/beige (glass-filled), bronze/gold (bronze-filled)

Applicable ASTM Standards

ASTM D1457 — PTFE Molding and Extrusion Materials

The master specification classifying PTFE resins by type, class, and grade based on molecular weight, processing method, and intended use. Understanding D1457 classifications is useful when procurement calls out specific resin grades:

• Type I: granular PTFE (compression molded)
• Type II: fine powder PTFE (paste extrusion)
• Type III: dispersion-coated PTFE (coatings and impregnation)

Most machined stock shapes (sheet, rod, tube) are produced from Type I or Type II resins.

ASTM D3293 — PTFE Sheet

Covers flat sheet produced by skiving from compression-molded cylindrical billets or by molding directly to sheet form. Specifies thickness, width, length, density, tensile strength, and elongation requirements by material grade.

ASTM D3295 — PTFE Rod

Covers round rod from 1/4 in. to 12 in. diameter, produced by ram extrusion (smaller diameters) or compression molding (larger diameters). Specifies diameter tolerances, straightness, and surface condition requirements.

ASTM D3296 — PTFE Tube

Covers seamless tube produced by ram extrusion or paste extrusion. Specifies OD, wall thickness, and concentricity tolerances.

ASTM D3308 — PTFE Skived Film

Covers thin film produced by skiving (lathe-cutting) from cylindrical billets. Specifies thickness, width, surface finish, and physical property requirements. Skived film is the form used for gasket tape, release film, and electrical insulation wraps.

ASTM D4894 / D4895 — Granular and Fine Powder PTFE Resin

Powder specifications for raw resin used by compound manufacturers when blending filled grades. Not directly relevant to stock shape procurement but cited in resin certificates for traceability.

Standard Stock Sizes

Sheet

Rod

Tube

Skived Film

Military and Industry Specifications

In addition to ASTM standards, PTFE stock shapes may be called out under:

• MIL-P-19468 — PTFE resin and compounds (legacy aerospace and defense specification)
• FDA 21 CFR 177.1550 — food-contact compliance for virgin PTFE
• NSF/ANSI 51 — food equipment materials (select grades)
• USP Class VI — biocompatibility for medical device applications (requires certification testing)
• 3-A Sanitary Standards — dairy and food processing equipment (certain fittings and seals)

When calling out military or FDA specifications, include the specification number on the purchase order and request a certificate of conformance (C of C) and, where required, a material test report (MTR).

Dimensional Tolerances — General Notes

PTFE has a high thermal expansion coefficient (~5.5 × 10⁻⁵ in/in/°F). Tolerances stated above are measured at 73°F (23°C). Parts that will be installed at a significantly different temperature require adjusted clearances:

• A 1-inch PTFE rod at 300°F will be approximately 0.012 inches larger in diameter than at 73°F
• A 12-inch-long piece will grow approximately 0.028 inches over the same temperature rise

Design clearances for housing fits accordingly — typical practice is to specify clearance fits rather than interference fits for PTFE-in-metal assemblies.

For machining tolerances and surface finish expectations, see the PTFE machining guide. For stock grade selection, see PTFE grades.

Ordering Information

Standard stock is stocked at common sizes in virgin and major filled grades. For custom specifications:

• Precision-ground rod and sheet (tighter-than-standard tolerances): available with lead times of 1–2 weeks
• Custom colors (other than standard grade colors): not available — PTFE color is determined by filler type
• Certifications: ASTM C of C, material test report, FDA certificate, and RoHS compliance statement available on request

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