Miniature Plastic Ball Cages: N500 POM Replacement for Mahr
A customer sent in a plastic ball cage with a part number printed on the end: N500. It came off a Mahr linear guide in a metrology stage. The original is no longer available in their size, and they need a replacement that drops into the same bore without redesigning anything.
N500 is Mahr’s standard plastic ball cage — an acetal (POM) cylindrical retainer with steel balls in molded pockets, designed for light-load, quiet-running linear guidance. We machine and assemble equivalent N500-style cages in POM to the same envelope.
What the N500 plastic cage is for
The N500 is not a heavy-duty part. It is the opposite: a miniature, non-corroding, self-lubricating ball guide that runs dry. The typical uses are metrology stages, sensor probes, clean-room equipment, food-contact machinery, and anything where a brass cage would corrode or where grease is not allowed.
POM (acetal resin) has natural low friction against hardened steel, does not need lubrication, runs quietly, and will not rust in washdown or humid environments. It is also significantly lighter than brass — which matters in moving axis assemblies where inertia is a concern.
Where the plastic cage stops short
Be realistic about the limits. POM is softer than brass. Under heavy load, high speed, or continuous side thrust, the molded ball pockets can wear and the balls can brinell into the cage. If your application sees more than a few newtons of preload or runs at high duty cycle, a brass or machined steel cage will outlast the plastic one. The plastic cage wins on quiet, light, clean, and dry — not on load capacity.
How we make the N500 equivalent
You send us the N500 sample or a drawing. We measure the bore, outer diameter, length, ball size, pocket pattern, and end details. The POM cage is machined or molded to match the envelope, and the same precision steel balls are staked into the pockets so they retain without falling out. The result drops into the same housing and runs on the same shaft as the original.
If your N500 size is obsolete or your local distributor has it on long lead time, send the sample or drawing. We can quote an equivalent miniature POM ball cage for guided probes, small stages, and light-load linear motion.
