SAE Flanges | Tips From the Industry Experts | Centre Point Hydraulic

SAE Flanges | Tips From the Industry Experts

Although they come in different configurations, many SAE flanges, 4-bolt hydraulic flanges look quite similar to each other. Nonetheless, SAE Code 61, SAE Code 62, and Caterpillar 4-bolt flanges, in particular, exhibit small dimensional and physical differences that you can not ignore.

SAE Flanges and different types

The consequences of improperly identifying a particular flange type describes Rory McLaren, Director of the Fluid Power Safety Institute. He explains that a diesel mechanic with no formal training in hydraulics installed a new hydraulic motor on a machine. When he reconnected the hydraulic hoses to the motor, he found that the bolt holes on the 4-bolt, split flanges did not line up with the holes in the motor housing.

Thinking the holes had simply was not drilled  in the correct position on the motor, the mechanic began filing the holes. In no time at all, he though he fixed the problem.

With nothing more than on-the-job training, the mechanic did not realize that he was modifying an SAE Code 62 4-bolt flange to fit an SAE Code 61 motor. The new motor he installed on the machine was incorrect for the application.

The mechanic removed the only indication protecting him from making the error of installing a 3,000-psi component into a 6,000-psi system. It was the the bolt-hole dimensions.

Dimensional Differences

In addition to the bolt-hole’s center-to-center dimensions, other physical differences exist between the SAE Code 61 and the SAE Code 62 4-bolt flanges. Using a 1-in. flange as an example, the accompanying illustration superimposes a Code 61 flange over a Code 62 flange, revealing how dimensionally similar they are to each other.

The distance between hole centers for a 1-in. Code 61 and Code 62 flange differs by a meager 0.064 in. for dimension A and only 0.188 in. for dimension B. But that’s only part of the problem.

RN®  apparently makes a nearly identical version of the SAE Code 62 4-bolt flange. However, the Cat version differs from the standard SAE Code 62 flange head in one aspect. The SAE Code 62 thickness (dimension C in the illustration) ranges from 0.305 in. on the ½-in. flange to 0.495 in. on the 2-in. flange, but RN® makes has a flange head dimension of 0.560 in. for all 4-bolt flanges.

Accordingly, if you are working in a situation where you have SAE Code 61, SAE Code 62, and RN®  4-bolt flanges, you must be careful not to make errors in determining what fits where. The potentially catastrophic consequences of incorrect flange identification mandate training in fluid-power connectors.


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