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GearWear& Lubrication

Wear

Another factor to consider in the successful design of a gear train is tooth surface wear.It can take onmany forms but always leads to reduced accuracy and loss of smooth operation.Wear can eventuallycause enough deterioration to introduce dynamic forces that are strong enough to break or bend gearteeth.The most common types of wear are Pitting, Scuffing and Scoring: Pitting is caused by localized metal fatigue on the surface of the gear.Microscopic cracks are forcedto propagate which causes small metal chunks to break off.The best ways to avoid this are:- reduce contact stress- use hardened gears- use proper lubrication Scuffing is caused by small surface irregularities that can rub each other as gear teeth come into andout of mesh.It is caused by the plastic deformation of microscopic surface protrusion.The best waysto avoid scuffing are:- use gears that are cut to a high quality surface finish-“run in”with1/2 load for the first 10 hours- use proper lubrication at all times Scoring is caused by small particles in the lubrication that get caught in the meshing teeth.Thiscauses scratches that can extend from the roof to the tip.These can be quite deep.The best ways toavoid scoring are:- proper high quality lubrication- change the lubrication after the “run in”period- change or filter the lubrication as needed

Lubrication

Using the proper lubrication can extend the life of your gear train by a factor of 4 or more.Thelubrication will form a thin layer between the teeth in contact.This will reduce all types of tooth wearwhich will keep your gear running smoothly.This is especially important with Worm Gear Sets andHelical Gear Sets as these types of gears operate with more of a sliding motion than a rolling motion(as in spur gears).There are many lubrications that work extremely well with gear sets.The one you choose depends onyour application.For lightly loaded, low speed systems, a light coating of grease can be brushed on during assembly.The grease will not fly oil or overheat, and should be replaced regularly to ensure optimal life.For higher speed systems, an oil bath is recommended.Oil is more effective than other lubrications atdissipating heat.The gears will always be in contact with the oil, so flying off is not a problem.The oilshould be replaced after the “run in”period and regularly thereafter.Many other lubricants exist for applications in which oil and greases could present a problem.Theyvary greatly in price, durability, thickness consistency and lubricity.For low torque and low speedsystems where dry running is essential, you might make use of plastic gears against a metal pinion.Generally, this offers a low enough co-efficient of friction to ensure long life.

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