Code 61 vs Code 62 Flange Dimensions: Complete SAE & CAT Chart

Per SAE J518 (interchangeable with ISO 6162, DIN 20066 and JIS B 8363 except bolt sizes). Code 61 sizes -08 to -64, Code 62 and CAT sizes up to -32. Flange caps and Gates half-set part numbers are listed further down, according to the Gates catalog.

How to Measure a Flange in 3 Steps

You need a caliper. Eaton and Danfoss also sell an identification kit (FT1341) with a caliper, seat angle gauge and thread pitch gauge.

Dash sizes: the number is sixteenths of an inch: -12 = 12/16 = 3/4″, -16 = 1″, -32 = 2″. They are nominal, so use them for ordering, not as exact dimensions.

Female port with no flange fitted? Measure the port hole diameter first, then the longest bolt-hole spacing.

Quick Lookup: Match Your Head Diameter

If it says “Code 62 or CAT,” measure thickness: 0.560″ = CAT. Sizes -56 and -64 are listed in the Gates section below.

Master Dimension Chart: Code 61 vs Code 62 vs CAT

Inches, with millimeters in parentheses for diameter and thickness. Values are nominal, so verify against your part.

* The Gates catalog lists bolt spacing A for Code 62 -08 as 1.55″. The SAE J518 figure of 1.594″ is shown above. Verify against your part.
** Bolt spacing A for -56 and -64 is taken from the Gates catalog, which lists 4.75″ for both sizes. Other dimensions for these sizes are in the Gates section below where available. Verify against your part before ordering.

Pressure: Code 62 is 6,000 psi in every size. Code 61 is commonly listed at 3,000 psi, though some manufacturers rate small sizes higher (up to 5,000 psi). Use your fitting manufacturer’s rating. Code 62 is not made above -32.

Split Flange Kits, Bolt Torque & O-Rings

O-rings are AS568 dash sizes with a 0.139″ cross-section. Buna-N 90A (-40°F to +250°F) is standard. EPDM and Viton are available for other fluids and temperatures. Follow your equipment maker’s torque spec if it differs.

What’s in a flange half set? According to Gates, each set contains 2 flange halves, 1 O-ring and 4 bolts (Grade 8) with lock washers.

Gates Flange Half Sets & Flange Caps (Code 61, Code 62 & Caterpillar-Style)

The tables below follow the Gates hydraulic catalog (Flange Fittings section). In the Gates tables, A is the bolt-hole spacing (center to center) and B is the bolt hole diameter, per the Gates drawings. Every item is sold with a standard pack of 1. These are Gates dimensions and may differ slightly from the SAE chart above, so verify against your part.

According to Gates, each Code 61, Code 62 and Caterpillar-style half set contains 2 flange halves, 1 O-ring and 4 bolts (Grade 8) with lock washers.

Flange Caps (Code 61 and Code 62)

Gates lists flange caps for Code 61 and Code 62 in sizes -12 to -32 (3/4″ to 2″).

CAT (Caterpillar) Flanges

2-Wire vs 4-Wire vs 6-Wire Hose: Match the Fitting to Your Hose

The flange style (Code 61, Code 62, CAT) tells you the port end. The wire count tells you what the hose end has to fit. They are two separate choices, and you need both right.

Illustration of the wire layers you would see on a cut hose end. Not to scale.

• Pressure goes up with the wire count. For example, in the Eaton catalog GH506 four-spiral hose is rated 4,350 psi in -24, while GH466 six-spiral is rated 6,100 psi in -24.
• Fittings are not interchangeable across wire counts. Eaton lists separate flange fittings for 4-wire (1E) and 6-wire (1Z) construction, and Aeroquip uses different prefixes (4S vs 6S). Order the fitting made for your hose.
• Your assembly is only as strong as its weakest part. A Code 62 flange is rated 6,000 psi, but a 2-wire hose is not. Check the hose rating too.
• Not sure what hose you have? Read the layline printed on the cover (for example 4SH, R12 or 6SP), or cut a short sample and count the wire layers.

5 Mistakes to Avoid

1. Judging by thickness alone. Measure diameter first.
2. Mixing Code 61 and 62 parts. The bolt holes look close but don’t line up (at -16 they differ by 0.063″ and 0.188″). Never enlarge holes to force a fit.
3. Standard bolts on a CAT flange. They can’t seat or torque on the thicker head.
4. Reusing an O-ring. Replace it every time and match the material to the fluid.
5. Ordering the flange style but not the hose wire count. A fitting made for 4-wire hose is not the same as one for 6-wire hose. See the wire count section above.

Part Numbers & Interchangeability

In Aeroquip part numbers, FL = Code 61, FH = Code 62, CT = CAT flange, KS = Komatsu split flange. Elbow letters: A = 45°, B = 90°, D = 22.5°, E = 67.5°, G = 60°. Codes vary by brand, so confirm in the catalog or the Danfoss cross-reference tool. Gates uses its own part numbers (see the Gates section above). SAE J518, ISO 6162, DIN 20066 and JIS B 8363 flanges are interchangeable except for bolt sizes (inch and metric bolts are both used). See our guide to hydraulic fittings worldwide.

Frequently Asked Questions

What’s the difference between Code 61 and Code 62 flanges?

Code 61 is the standard series, commonly 3,000 psi. Code 62 is 6,000 psi, with a larger head, wider bolt spacing, thicker head and larger bolts in bigger sizes.

What is a Code 62 fitting?

An SAE J518 four-bolt flange rated 6,000 psi in every size. It seals with an O-ring and is clamped by two split flange halves.

What does “CAT Code 62” mean?

A Caterpillar-style flange rated 6,000 psi. It matches Code 62 in diameter and bolt pattern but has a 0.560″ thick head.

What is the difference between Code 62 and Caterpillar flanges?

Head thickness. CAT is a flat 0.560″ in every size, while Code 62 runs 0.305″ to 0.495″. CAT needs longer bolts, CAT halves and a D-ring.

How do I tell them apart without a spec sheet?

Measure head diameter with a caliper and match it to the lookup table or identifier above. If it fits Code 62 and CAT, measure thickness: 0.560″ is CAT.

Can I use Code 61 parts on Code 62?

No. Bolt spacing, bolt size, thickness and pressure rating all differ.

Why is my Code 62 flange loose on a Caterpillar machine?

A Code 62 flange was likely installed where a CAT flange is needed. It’s thinner, so standard bolts and halves won’t clamp fully and the joint can leak.

What is the difference between 2-wire, 4-wire and 6-wire hose fittings?

It is the number of steel wire layers in the hose. 2-wire is braided, while 4-wire and 6-wire are spiral, with pressure rating rising as wire layers are added. Each needs its own fitting series (for example Aeroquip 4S for 4-wire and 6S for 6-wire), so tell us your hose type when you order.

What size hose works with a -20 flange?

-20 is 1-1/4″ nominal hose. Match the hose series to your pressure. A -20 CAT fitting such as 4S20CT20 needs the FF90319-20 D-ring.

What comes in a flange half set?

According to Gates, each set contains 2 flange halves, 1 O-ring and 4 bolts (Grade 8) with lock washers.

Are flange caps for Code 61 and Code 62 available, and can I use them under pressure?

Yes. Gates lists Code 61 and Code 62 flange caps in sizes -12 to -32 (3/4″ to 2″). According to Gates, they are for maintenance use only and are not to be used under pressure.

What Code 61 sizes go above -48?

Gates lists Code 61 flange half sets in -56 (3-1/2″) and -64 (4″) as well, with part numbers G60899-0056 and G60899-0064. Code 62 is not made above -32.

Sources: Eaton Aeroquip Hose Assembly Master Catalog (A-HOOV-MC001-E3); Aeroquip by Danfoss Rubber Hydraulic Hose & Fitting Catalog; Gates hydraulic catalog, Flange Fittings section (Code 61 and Code 62 flange caps and half sets, Caterpillar-style half sets); SAE J518.
Reviewed by: James Westervelt, Hydraulic Hoses Near Me LLC / J&N Equipment Repair — Fluid Power Association Certified
Last updated: October 24, 2026