Round Rod in PTFE 2000 mm natural

Round rod in PTFE is the raw stock you bring in when the part is to be turned out of a solid block and the material has to handle chemical attack, high temperatures or dry running. PTFE has the lowest friction figure among engineering polymers, is inert to practically all industrial chemicals and keeps its mechanical properties from minus 200 to plus 260 degrees. Few materials span such a wide temperature window without losing shape or properties, and even fewer combine it with such broad chemical resistance.

Turning is PTFE's natural machining operation. The material is soft, so inserts should be sharp and feeds moderate, but the chip releases cleanly and the dimensional tolerance is predictable as long as the blank is allowed to warm to workshop temperature before the work starts. Thin walled sleeves, gasket rings, piston seals, valve guides and bearing bushings are typically taken out of round rod. For longer parts with tight dimensions it is important to support the workpiece; PTFE is dimensionally stable during turning but yields under radial pressure, so clamping and steady rest have to be matched to the dimension. The chip is feather light and needs to be directed with extraction or air so it does not fall into the machine.

Chemically, PTFE works as the reference value when other plastics are judged. The material resists concentrated acids, alkali, organic solvents and oxidizing process chemistry. That means the same round rod diameter can be turned into an O-ring for a sulfuric acid pump and the next day into a slide block for a food line, without the material choice having to be reconsidered. The low surface energy means process media do not stick to the surface, which both gives clean seals and simplifies cleaning between runs.

In tribological applications unfilled PTFE is useful at low loads and moderate speeds. The material creeps under load and the static PV figure is limited, so plain bearings for heavier loads are often chosen in a compound with carbon, glass or bronze. For seals, valve seats and guides where friction matters more than mechanical load, unfilled PTFE is the right choice. It handles both dry running and operation without lubrication, which is valuable in food, pharmaceutical and lab equipment where traces of lubricant would be a contamination risk. The impact toughness is good down to very low temperatures, so parts turned for cryogenic use keep their function even in liquid nitrogen class operation.

Thermally, PTFE is rated V0 according to UL 94 and does not start to give off smoke until very high temperatures. That makes the material suitable in process parts that can be exposed to thermal shock, in electronics that have to survive fault conditions and in high temperature gaskets for flange joints. The material also has stable dielectric properties, which makes thin turned parts useful as insulators in high frequency equipment.

The diameter is chosen according to the part's outer diameter plus at least 2 to 3 mm machining allowance, and for parts where eccentricity in the blank can become a problem, count on a larger allowance. Long rods are useful when several identical parts are to be turned in series, since the raw stock is fed through the spindle. Short lengths are ordered when only a few parts are to be taken out and you want to minimize material waste. The natural color is PTFE's own white, semi-opaque shade; there is no transparent version in unfilled PTFE.

PTFE is not glued or welded with ordinary methods. Parts are mounted mechanically, clamped or joined with TIG welding where that is possible. The surface can be etched to take adhesive if a combination with other materials is required, but in the great majority of industrial applications the fastening is solved with screws, flange or press fit. In screw joints, metal sleeves are used to take up the preload so that the creep in the PTFE does not tear the joint loose over time.

For contact with food or pharmaceutical media there are PTFE qualities approved according to FDA and EU 10/2011. Specify the quality when ordering if the part is to sit in product contact; the specification is not visible on the raw stock itself.

In handling, keep in mind that PTFE has relatively high thermal expansion; long turned parts change length noticeably between room temperature and operating temperature, which has to be included in the fit calculation. The material is also soft enough to be scratched by sharp handling tools, so parts that are to keep an intact surface are stored hanging or on soft padding.

Do you need to discuss diameter, length, or whether a filled PTFE compound would be a better choice than unfilled? Write to us and we will get back to you.

In double length, 2000 mm in natural, the rod is enough for several bushings and sealing blanks without a joint.