Engineers designing UHMWPE parts the first time often specify metal-grade tolerances and wonder why the quote is double, or the part comes back warped. UHMWPE has 13× the thermal expansion of steel and 1/100 the stiffness, so machining rules are different. This reference covers standard tolerances, design rules and what to send for a fast accurate quote.
Why plastics need different tolerances than metals
UHMWPE expands 200 µm per metre per °C. A 1 metre part machined at 20 °C and used at 60 °C grows by 8 mm. This is why bolt holes are slotted, why bushings have running clearance, and why metal-grade IT6 tolerances are physically impossible to hold over the full operating temperature range. The DIN 16742 plastics tolerance standard exists exactly to address this — use it as your starting point, not ISO 2768 metal tolerances.
Standard CNC tolerance ranges for UHMWPE
DIN 16742 plastics tolerance class TG6 — typical for production parts.
| Feature size | Milling tol. | Drilling tol. | Turning tol. | Notes |
|---|---|---|---|---|
| Up to 30 mm | ±0.10 mm | +0.15 / 0 mm | ±0.10 mm | Standard production |
| 30–120 mm | ±0.20 mm | +0.25 / 0 mm | ±0.15 mm | Most common range |
| 120–400 mm | ±0.30 mm | +0.40 / 0 mm | ±0.20 mm | Large bushings, plates |
| 400–1000 mm | ±0.50 mm | +0.60 / 0 mm | ±0.30 mm | Sheet cutting, large covers |
| 1000–2000 mm | ±0.80 mm | +1.00 / 0 mm | n/a | Sheet panels, mat sections |
Design rules to avoid expensive surprises
Apply these rules at the CAD stage and your quote drops 20–40%.
- Minimum wall thickness 3 mm for milled features, 6 mm for drilled holes (avoids tear-out)
- Hole spacing ≥ 2× hole diameter (avoids inter-hole crack on torque)
- Bore tolerance H10 standard; H8 only if essential and length < 3× diameter
- Counter-bore depth = bolt head height + 2 mm (allows for thermal expansion compression)
- Surface finish Ra 1.6 µm standard; Ra 0.8 µm available but adds 30–50% cost
- Avoid sharp inside corners; specify R0.5 minimum for milled pockets
- Slot bolt holes 0.5 mm oversize per metre of part length to allow thermal growth
- Specify TOP and BOTTOM faces if surface texture matters — rolled-in marks differ from machined
Counter-bored bolt hole design for thermal cycling
Critical for chute liners, ground mats and bollard pads exposed to 60+ °C delta.
Specify counter-bore deeper than bolt head
Bolt head height + 2 mm. The 2 mm gap allows the polymer to compress during thermal expansion without bolt tension loss.
Use Belleville washer or T-bolt capture
Belleville washers maintain bolt tension as the polymer flows. T-bolt capture systems eliminate the bolt-head problem entirely by hooking the polymer over a steel rail.
Slot the hole in the direction of expected expansion
For sheets > 1 m long, slot bolt holes 1 mm × length oversize in the long direction. Use round holes only at one anchor point.
Specify torque, not turn angle
UHMWPE creeps under load. Spec maximum torque (typically 50% of equivalent steel torque) and re-torque after first heat cycle.
Provide stainless or zinc-plated bolts
Carbon steel bolts will corrode and stain UHMWPE. We supply A2 stainless or HDG zinc bolts pre-fitted on request.
How to send DWG / DXF / PDF / STEP for fastest quote
We accept DWG, DXF, PDF and STEP files. Send via email to claire@jsltupe.com or WhatsApp to +86 189 6300 3803. Include: (a) overall dimensions; (b) tolerance class (DIN 16742 TG6 standard if unspecified); (c) material grade (PE-300 / PE-500 / PE-1000); (d) quantity; (e) any food-grade or anti-static requirement. Quote in 24 hours. MOQ from 1 piece. CNC cutting, drilling, counter-boring and milling all in-house. Joining is by mechanical fastening, counter-bored bolting, T-bolt capture, tongue-and-groove or fillet plates.
Frequently Asked Questions
Can you hold ±0.05 mm tolerance on UHMWPE?
On features under 30 mm, yes — at 2–3× standard cost and only over a narrow temperature range. We recommend ±0.10 mm standard; tighter spec adds 30–50% cost and may require post-machining stress relief.
Why is my quote higher than a metal part?
UHMWPE is more expensive per kg than mild steel, machining is slower (lower feed rates), and stress relief is often required between rough and finish cuts. For abrasion or impact duty, the lifetime cost is usually 2–5× lower than metal.
Do you supply assembled parts?
Yes. We supply UHMWPE parts pre-fitted with stainless or zinc-plated bolts, T-bolts, slide rails or fillet plates ready to install on site.
What CAD formats do you accept?
DWG, DXF (preferred for 2D), PDF (for reference), STEP (preferred for 3D). IGES on request. Hand sketches with dimensions also acceptable for simple parts.
Do you provide first-article inspection report?
Yes. First-article inspection report (FAIR) per AS9102 format on request, with measured dimensions vs spec, surface finish, and material certification. Standard 5-piece sampling on production runs.