Round Rod in PBT GF30 3000 mm gray

The round rod in PBT GF30 is polybutylene terephthalate with 30 percent glass fiber by weight, made for turned and milled parts where dimensional stability and stiffness carry real weight. The material is a welcome middle ground when PA6 GF30 takes up too much moisture and POM gets too expensive or overqualified.

PBT is a semi-crystalline thermoplastic polyester with low moisture absorption. The difference from nylon shows up most clearly where tolerances are tight: a turned PBT GF30 sleeve barely moves between summer air and winter air, while PA6.6 GF30 can swell several tenths per hundred millimeters of diameter. The glass fiber lifts tensile strength, flexural stiffness and dimensional stability at elevated temperature, and the material creeps only a little under constant load. Heat resistance is enough for continuous service well above room temperature, but a check against the manufacturer datasheet is wise before higher temperatures are specified.

Friction against mating steel is low and wear resistance is good in dry to lightly lubricated conditions. The glass fiber raises wear resistance against abrasive wear, but it also wears on a softer mating surface; remember to pair PBT GF30 with a hardened or at least tempered mating surface in plain bearings and guide sleeves. Chemically the material does well against mineral oils, greases, fuels, aliphatic solvents and weak acids. Hot steam and strong bases break down the ester backbone and should be avoided.

Typical parts turned from the rod are plain bearing bushings, spacer sleeves, guide studs, pivot sleeves, intermediate shafts in fixtures, valve pistons and coupling bushings. For gear drives that have to take shock loads there are other materials that suit better, but for stiff loads and small angular movements PBT GF30 is stable. Machining calls for sharp carbide inserts, moderate feed and good chip clearance. The glass fiber is abrasive, so count on shorter tool life and more insert changes per shift than with unfilled PBT.

In the choice between PBT and POM C it is often moisture and cost that decide. POM C has lower friction and better impact strength, PBT holds its dimensions better in a damp environment and does not burn as readily. PA6 GF30 has higher impact strength but grows with moisture, which is a recurring source of trouble. The list of trade-offs is worth a look before you choose: what is the operating environment, how tight is the fit, how much shock load does the part take?

We stock the common diameters and cut the rod to blank length on order. Full rods go out as well, if the workshop would rather do its own cutting. If material and batch certificates are needed, we get them from the manufacturer.

Are you unsure whether PBT GF30 is the right grade for your particular part? Get in touch with a drawing or a description of the function, and we will go through fit, mating surface and operating environment together.