Peening Medias that are used are ceramic bead shot, cut wire, glass bead or fine steel.

The fillets at the root of the gear are usually the areas of high stress and should be Shot Peened. However, it has also been found that the fine indentations produced by Shot Peening on the face of the gear tooth act as tiny oil reservoirs which help to give better lubrication, reduce fretting and scoring, and reduce operating temperature. Gears which have to be held to very close tolerances may be lapped after shot peening or the gear face can be masked if desired. 

New Technology of peening by Engineered Abrasives has been tried, tested and proven on parts which after going through our special bead and shot peening process has eliminated gear-tooth pitting. ( Patents 5272897, 6238268 B1, 6612909 B2) 

NOTE: Also this special process will eliminate the need to Shot Peen in root radius 

Bead and Shot Peening Process

What is it: Shot Peening consists of bombarding a metal surface with a peening media such as ceramic beads, ceramic shot beads, aluminum beads, metal beads, etc.

What it does:  Shot Peening causes the material in the surface zone to yield. It literally shakes the metal grains into a more relaxed state. Thus, a thin layer of the surface is placed in uniform compression. This compressively-stressed "skin" counteracts tensile stresses within and effectively blocks cracks. 

Why it is needed: Machining and forming metal parts create stress concentrations internally.  Burrs, scratches, welds, etc. may cause additional defects. 

These problems may be responsible for premature fatigue failure, porosity, loss of strength and corrosion....unless something is done. 

Since fatigue cracks generally begin at surface imperfections... a compressively-stressed peened skin is highly effective in preventing crack formation and growth. 

Gears are frequently shot peened after carburizing. In recent years, increasing use has been made of steel at hardness levels above Rockwell 60RC, for fatigue and shock applications such as gears.  Such parts are always Shot Peened in all critical areas.  The figures below shows the close connection between  peened verses unpeened gears. 

Air pressure, time and shot size will determine KSI.

Engineered Abrasives machines are designed and set-up to peen critical areas of the part to meet your customer's demands.

Deburred Parts are shown in the picture to the right.