UHMW and PTFE CNC machining covers the two lowest-friction plastics most shops will see, and both reward careful handling more than machine horsepower. Ultra-high molecular weight polyethylene (UHMW) is extremely tough and abrasion resistant and is the workhorse for wear strips and conveyor parts. PTFE, often called by the brand name Teflon, offers near-universal chemical resistance, a very low friction coefficient and good electrical insulation. Wexmar machines both, including glass, carbon and bronze-filled PTFE, at our shop in Canastota, New York.
Machinability of UHMW and PTFE
Neither material is rated on the AISI 1212 steel scale. Both cut freely with little tool wear, but both are soft, and the limits are heat, stress, clamping and dimensional stability. Thermal expansion is the main challenge. UHMW and PTFE expand roughly 5 to 10 times as much as aluminum for the same temperature change, so a few degrees of heat from cutting or a warm shop can move a dimension measurably. PTFE also has a phase transition near room temperature, around 66 to 77 F, that produces a small but real volume change right in the range where parts are usually measured.
Tolerances and surface finish
For machined UHMW parts, plus or minus 0.005 in. is a practical typical tolerance, with tighter values possible on small features. PTFE typically holds plus or minus 0.002 to 0.005 in. depending on size, with the measurement temperature agreed on critical parts. Surface finish is typically 63 Ra, and 32 Ra is achievable on PTFE sealing faces with a sharp tool and light finishing pass. UHMW finishes slightly fuzzy by nature and is rarely specified to fine Ra values.
Tooling, heat and handling gotchas
- Razor-sharp tools. Polished, high-rake carbide or sharpened high-speed steel shears cleanly. A dull edge pushes the material aside and leaves fuzz and burrs.
- Cool, steady cutting. Air blast or light water-soluble coolant keeps the part near shop temperature. Parts are allowed to stabilize before final measurement.
- Clamping pressure. Both materials compress under clamping and spring back after release. Soft jaws, vacuum or full-contact fixtures and light pressure keep bores round and faces flat.
- Cold flow. PTFE creeps under sustained load. Seal and seat designs should allow for it, and parts should not be stored clamped or stacked under weight.
- Filled PTFE. Glass and carbon fillers improve creep and wear resistance but are abrasive to tools, so tool life is tracked closely on production runs.
- Burrs and chips. Long continuous chips and soft burrs are common. Finish passes and programmed chamfers reduce hand trimming.
Stress relief and finish options
Stress-relieved stock is recommended for tight PTFE parts, and annealing or stress relief of PTFE or UHMW, when specified, is performed through qualified outside processors. Neither material bonds or paints easily, and parts almost always ship as machined. Surface etching of PTFE for bonding, when required, is arranged through qualified outside processors.
Common UHMW and PTFE parts
- UHMW wear strips, chain guides and slide rails (horizontal machining centers)
- UHMW star wheels, timing screws and change parts for packaging lines (horizontal mills and lathes)
- PTFE seals, gaskets, backup rings and valve seats (CNC lathes)
- PTFE electrical insulators, bushings and spacers (Swiss-type, to 32 mm diameter)
- Filled PTFE bearing pads, piston rings and slide bearings (lathes and horizontals)
- Chemical handling components and laboratory fittings
PTFE rings and seals are turned on our CNC turning lathes, while UHMW plate parts run on pallet-changing horizontals through our CNC milling department.
Cost index vs 6061 aluminum
| Material | Approx. machinability (1212 = 100) | Cost index vs 6061 | Notes |
|---|---|---|---|
| 6061-T6 aluminum | ~180 | 1.0 | Baseline |
| Delrin / acetal | Not rated; cuts freely | 1.0 | Stiffer, more stable |
| Nylon 6/6 | Not rated; cuts freely | 1.0 | Tough, absorbs moisture |
| UHMW | Not rated; cuts freely | 1.1 | Abrasion resistant, high expansion |
| PTFE | Not rated; cuts freely | 1.4 | Chemical resistant, cold flow |
| PEEK | Not rated; cuts freely | 4.5 | High heat, stiff, low creep |
These values are typical and illustrative for a comparable part; actual quotes depend on geometry, quantity, tolerances and mill pricing. Where a seal must resist creep at high temperature, PEEK machining is a common upgrade.
Applications and industries
UHMW parts serve food processing, packaging, bottling and bulk material handling equipment. PTFE parts serve fluid power and pump OEMs, chemical processing, instrumentation, and electrical and connector makers. FDA-compliant grades of both materials are available from the mill with documentation. Parts ship nationwide from our shop in Central New York.
Getting a quote
To price UHMW or PTFE parts, upload a drawing for an instant estimate or call (315) 400-2654. A human estimator confirms every quote and checks the grade, filler and stock form required.