When discussing ring and pinion gear sets, you may have heard the following terms thrown around: two-cut, five-cut, face-hobbed and face-milled gears. If you're new to aftermarket driveline upgrades, you're almost certainly wondering what these terms mean. In this guide, the experts at Revolution Gear & Axle explain the differences between the various cut gear sets, how to identify them and which you should use for an off-road ring and pinion installation.
Types of Ring and Pinion Face Gears Remove "Face Gears" pluralize Ring and Pinion(s)
The terms we're going over refer to the machining process for how ring and pinion gears are made. While there are a few methods to produce ring and pinions, the two most popular are:
- Face milling, or five-cut, followed by lapping
- Face hobbing, or two-cut, followed by lapping
You can also grind face-milled gears instead of lapping. However, although this is growing in popularity, it is not yet a common method used on OE or aftermarket gears.
How Do I Know Which Gear is Which?
It is easy to identify a face-milled (two-cut) versus a face-hobbed (five-cut) gear by reviewing the ring gear tooth depth.
Face Milled (5-Cut) Ring Gear: The Heel (Outside) of the Gear is taller than the Toe (Inside).
Face Hobbed (2-Cut) Ring Gear: The ring gear has constant depth from heel to toe. Two-cut gears also have a natural "bias" condition - that is, the pattern shows up slanted when the pattern is rolled with a gear marking compound.
So how do gear manufacturers choose which method to use? Two-cut or face hobbing is a relatively new technology compared to the classic five-cut face milled method. Thus it requires expensive modern gear-cutting machines. Both methods can produce high quality ring and pinions, however, two-cut gear cutting machines can process gears at a much faster rate. Both the ring gear and pinion gear require only 1 cutting pass to complete the gear, hence the name two-cut versus 5 total cutting passes required on face milled, five-cut ring and pinions. Due to faster processing speeds, OE manufacturers predominantly use the two-cut method.
Most aftermarket suppliers only offer face-milled gears. At Revolution Gear & Axle, we offer both. The majority of our gears are five-cut, but we also offer two-cut gears on our Chrysler 9.25" and GM 8.5" ratios and will be launching our newest two-cut gears for 2018 and newer Wranglers and Gladiators and 2021 and newer Broncos in 4th quarter 2023.