Hollow Bar in PEEK SX 1000 mm beige

A hollow bar in PEEK SX is the format with a hole in the middle, so you avoid boring out a whole rod when the part is ring shaped anyway. That saves time and expensive chips. The material is the same friction optimized PEEK as in sheet and round rod, with lubricating additives in the stock that let the surface slide dry. The bar handles 260 degrees long term and briefly close to 300 degrees, which makes it an obvious choice where lubricants would burn away.

Mechanically the tensile strength sits around 110 MPa and the ball indentation hardness around 240 N/mm², enough for a bushing that has to carry load without deforming. The density is about 1.31 g/cm³ and the water uptake negligible, about 0.03 percent, so fits hold in both damp and heat and a mounted ring sits firmly. The flammability rating is V0. The thermal conductivity of around 0.27 W/mK means the friction heat is led away slowly, which you allow for at high sliding speeds by keeping margin in the fit. The broad chemical resistance covers oils, many acids, bases, hot water and solvents, so the ring handles the medium it works in.

The format shines in ring shaped sliding components. Large bushings and sleeves with a coarse inner diameter where a solid rod would have cost an unreasonable amount of turned away material. Thrust bearings and wear rings in pumps and compressors that run dry. Liner sleeves and guide rings in hot process machines. Slide washers with a large hole diameter in conveyors and rotary tables. You start closer to the final geometry, and the friction properties are exactly the same as in the other SX formats, so choosing a hollow bar is only about saving material and turning time, not about any compromise on function.

When turning, you clamp the bar on a mandrel or in soft jaws so that you do not squeeze the stock and lose the roundness. Sharp carbide tools, moderate feed and cooling give a clean surface and stable dimensions. Check the wall thickness against the drawing before you rough, so you have material left for finishing and do not turn straight through. The friction additives make the surface somewhat softer than pure PEEK, which finishing cuts appreciate and which gives an even sliding surface. Thin walled rings may need a support mandrel throughout the machining to hold their shape.

The biggest gain with a hollow bar is economic and shows most clearly at coarse inner diameters. When the hole is already in the blank you avoid both the time it takes to bore out a solid rod and the cost of the material that would otherwise have ended up as chips on the floor. For a large wear ring the difference in raw material cost can be significant, since PEEK is an expensive material per kilo. You pay for the stock that actually becomes a part, not for what is turned away.

The function of the finished ring is the same as for SX in other formats. It slides dry against steel, starts smoothly without jerking and handles the process medium. Remember to give the fit clearance for thermal expansion, since the plastic moves more than the metal it sits against. A smooth mating surface gives the longest service life. The color is typically brown to black from the friction additives. Always check that the wall of the bar is thick enough for your final geometry before you order, so that you have material left for finishing, and get in touch if you are unsure which inner and outer diameter gives the least waste.

A practical point in ring making is to hold the roundness throughout the machining. Thin walled rings tend to spring out when stresses in the stock are released, so take light cuts toward the end and measure the roundness before you release the part from the machine. An even, finely turned sliding surface on the inside gives lower friction and quieter running than a rough surface. Plan in a light chamfer on the edges as well, so that the ring is easier to fit and does not damage the mating surface on insertion.

The hollow bar in SX at 1000 mm is pre-bored and holds the ultra high purity, for turned rings and sleeves in semiconductor equipment.

Hollow bars come in combinations of outer and inner diameter and are cut to length as needed. Not sure whether a hollow bar or a solid round rod gives the lowest material cost for your particular bushing? Send the inner and outer dimensions and we will work it out together and point you to the format that gives the least waste.