Profile Restoration for EMD and
GE Bull Gears





Why Grind Gears?


Reduce frictional forces, heat generation which keeps lubrication cooler.


Increase tooth strength.


Lessen noise


Reduce vibration at higher speeds


Lower heat treatment distortion in hardened gears.

Penn Machine specializes in restoring the profiles of EMD and GE bull gears. Our CBN grinding procedure re-establishes the true involute tooth form for proper gear contact.

Minimal stock is removed to restore the profile. Typically, we grind in increments of .015 inches or approximately 3% of the tooth thickness. The reprofiled surface will have sufficient hardness and case depth to provide additional gear life. A maximum radius is provided below the bottom of the gear mesh to reduced stress concentration.


When to Reprofile Gears

It is very important to recycle used gears by grinding worn areas and to re-establish a true involute profile form. Penn Machine recommends reprofiling gear teeth to industry standards when wear exceeds 0.010 inch of tooth profile (0.020 inch of tooth thickness at the pitch line). Gears should then be ground just enough to restore the profile.



When shipping gears to Penn Machine for reprofiling, gears should be free of any grease, grime or crater compound. All gears are visually inspected upon arrival for cracks in the teeth and bore. If a visible crack is found, we will notify you and ask for disposition. If there are no visible cracks and if specified, we will do a magnetic particle inspection for microscopic cracks. If cracks are found, we will determine if they can be removed by grinding. When cracks are too deep, we will notify you and request disposition.

Penn Machine has the capability to remove pitting from gear teeth, depending on the severity. When three or more individual pits on the same tooth are greater than 1/8 inch in diameter or 1/16 inch in depth, we will recommend that the gear be scrapped and request disposition. If there are three pits together that form a pit longer than ľ inch or greater than 1/16 inch in depth, we will also recommend the gear be replaced.


Restoring Gears to Specifications

If the bore size is out of tolerance, we will shrink the bore back to OEM or railroad specification to obtain required interference. If this is not possible because of the gear design, we will notify you and recommend that the gear be scrapped. Bores will be honed to bring the finish back to your specifications.

The hub face and ring diameter will be reground and burnished to restore tolerance and proper finish.



Recycled Gears

Penn Machine will verify that the gear tooth profile is correct, record tooth size and check for tooth spacing. For traceability purposes, all gears will be stamped with reworking information including an ID number for the year of reprofiling, machine ID that gear was ground on, gearís serialized number, grind number classification and hub machining verification. A detailed inspection report will be supplied with all returned reprofiled gears and this report will be maintained for a minimum of five years. Prior to shipment, gears will be coated with a rust preventative that protects the gears for a minimum of six months when stored under cover in a conditioned environment.


Download Dimensional Chart for Reprofiled and Recycled Gears

  See Penn Machine Reprofiled Gear Warranty
  Download Penn Machine Involute Profile Gauges

 © 2010