Super precision miniature ball bearings offer high reliability in surgical hand tools

The latest handheld surgical cutting and drilling tools are now more sophisticated, as well as more compact and ergonomic in their design. To ensure these tools meet performance standards and expected life, super precision ball bearings are required to support the drill or cutting tool during harsh operating conditions, including high temperatures and loads. Typically, bearings are located at the end of the cutting tool, often working inside the patient's body, so resistance to acids and corrosive media is also critical. This means the power tool manufacturer requires bearings compact enough to fit the tool's slender design, but also able to cope with high loads and operating speeds [up to 80,000rpm]. As surgical tools require regular sterilisation in autoclaves, the bearings must also be designed to withstand temperatures up to 140 deg C. The harsh operating environment means protection is required against fine skin and bone particles that may penetrate contact regions between balls and bearing raceways, which would then lead to high stress concentrations and possibly failure of the bearing. To counter this, Barden provides integral shields designed to help retain lubricant, whilst preventing contaminant ingress. This improved sealing design reduces the critical gap between the integral shield and the bearing inner ring to 60% of that when compared to conventional shield and circlip designs, resulting in reduced operating noise, greater lubricant retention and improved protection from contaminants. For surgical applications, cleanliness is essential. Barden's Plymouth plant has over 1700sqm of cleanrooms for assembly, testing and packing operations. For a recent surgical sawing tool project, Barden provided custom engineered angular contact ball bearings with an outside diameter of 4.76mm and balls just 0.79mm in diameter, the smallest diameter Barden has provided for this sort of application. Here, cleanroom facilities were essential. The bearings were a double row cartridge design with a single inner ring and two outer rings. This one-piece, pre-loaded custom designed bearing solution made assembly much easier for the customer, who simply had to 'drop' the bearing into position within the overall tool drive assembly.