Caterpillarwork toolquick coupler

Caterpillar HEX-WEDGE

Maintenance schedule, common problems & OEM parts breakdown

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The Hex Wedge is Caterpillar's dedicated wedge-lock quick coupler: a work tool that mounts between the excavator stick and a bucket or attachment, not a standalone piece of equipment. A hydraulically actuated wedge, powered off the host excavator's own hydraulic circuit through a dedicated coupler control valve, drives a hardened wedge plate against the work tool's mounting pin and pulls the tool tight into the coupler's hook (jaw) plate, removing play between tool and coupler. A mechanical spring plus a hydraulic check valve hold the lock even if hydraulic pressure is lost. The coupler group and identification plate are sized to carrier and stick-linkage type, with documented fitment across Cat's B-series/C-series hydraulic excavators, from smaller 311B, 312B/312C, and 314 machines through 315B/315C, 317B, 320B/322B, 325B, and up to 330B. Fitted to one of these carriers, it lets the operator swap buckets, grapples, hammers, and thumbs from the cab without a technician pulling pins on the ground.

Cat's coupler lineup has since moved toward pin-grabber geometry and, on many current models, an electro-hydraulic locking system that adds an electronic position sensor and in-cab lock-status feedback on top of the mechanical lock. Those newer designs trade a small amount of breakout force for broader third-party attachment compatibility and a positive electronic lock confirmation the Hex Wedge's purely mechanical/hydraulic lock doesn't provide. That doesn't make an excavator carrying a Hex Wedge coupler a lesser machine in the used-equipment and parts market. The wedge-lock design keeps the work tool tight against the stick pin without adding offset, so breakout force is preserved, and the wedge plate, hook plate, pins, bushings, and lock cylinder remain serviceable parts long after the host machine's original production run has ended.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.

Caterpillar HEX-WEDGE specifications

Performance

Locking mechanismDedicated wedge-lock quick coupler. A hydraulically actuated wedge clamps the work tool's mounting pins into the coupler jaws. Buckets and other work tools must be fitted with a mating hook plate to engage the coupler.
Actuation sourceLock/unlock cylinder is powered from the host excavator's own hydraulic circuit through a dedicated coupler control valve; the coupler has no independent hydraulic pump or reservoir.
Carrier compatibilitySized and matched to Cat B-series/C-series hydraulic excavators, including 311B, 312B/312C, 314, 315B/315C, 317B, 320B and 322B (B or S linkage), 325B (C linkage), and 330B (D linkage); a larger coupler group also fits 345B/350 (F or T linkage). Coupler group is specific to excavator model and stick linkage type; confirm fitment by machine model and linkage with your dealer.

Values vary by configuration, region, and serial range — confirm against your machine before planning transport or lifts.

HEX-WEDGE fluids & capacities

SystemCapacityRecommended fluid
Wedge/lock pin grease points (primary greasing block on the coupler body)No fill volume published. Lubricate at the grease fitting every 10 service hours or daily, whichever comes first, until fresh grease is visible at the pin joint.Cat MPGM (multipurpose grease). In sub-zero climates the Cat OMM directs use of a lower-temperature Cat grease grade for easier gun feed; varies by region/dealer stock.
Wedge/hook pivot and bushing grease points (coupler-to-stick and coupler-to-linkage pivots)No fill volume published. Same daily/10-hour interval as the primary lock-pin points; grease until it purges from the bushing clearance.Cat MPGM (multipurpose grease), applied with a manual or pneumatic grease gun.
Coupler actuation circuit (lock/unlock cylinder, run off the host excavator's auxiliary hydraulic circuit)No separate reservoir or fill capacity — the coupler has no hydraulic tank of its own; it draws from the host machine's hydraulic system through a dedicated coupler control valve/solenoid.Host excavator's specified hydraulic oil (typically Cat HYDO Advanced 10 or the machine-specific Cat HYDO/TDTO-type oil called out in that excavator's own OMM). Grade varies by host machine and ambient-temperature range — verify against the carrier machine's OMM, not the coupler's.

Capacities are refill values from factory literature — always fill to the dipstick/sight gauge, not the number.

Caterpillar HEX-WEDGE maintenance schedule

Service intervalTasks
Every 10 h
  • Grease the wedge-lock pin fitting on the coupler body until fresh grease purges at the joint.
  • Grease the coupler-to-stick and coupler-to-linkage pivot and bushing points on the same daily cycle.
  • Wipe fittings clean before greasing so grit isn't driven into the pin joints.
  • Cycle the coupler through a full lock/unlock stroke after greasing to work grease across the wedge face.
  • Visually confirm the wedge is fully seated with no gap at the hook plate before resuming digging.
Every 250 h
  • Inspect the wedge plate and hook (jaw) plate for visible wear, scoring, or flat spots.
  • Curl and dump an attached work tool through a full cycle and check for play or rocking against the coupler body.
  • Check the lock cylinder rod and housing for scoring or a bent condition.
  • Inspect pins and bushings at the coupler-to-stick and coupler-to-tool joints for excess clearance.
  • Confirm the wedge locks fully and promptly, with no hesitation or partial engagement.
  • Compare wear against the prior inspection so an accelerating trend gets caught early, not after a failure.
Every 500 h
  • Inspect the lock cylinder seals and feed hoses for weeping, chafing, or bulging.
  • Check the hydraulic check valve that holds the wedge locked under load for correct function.
  • Measure pin and bushing wear at the coupler-to-stick and coupler-to-tool joints against service-limit clearance.
  • Inspect the mechanical backup spring on the wedge lock for full travel and tension.
  • Replace worn pins, bushings, or lock-cylinder seals before clearance becomes excessive rather than waiting for a lock failure.

Servicing the HEX-WEDGE beyond the schedule

Predictive maintenance & fluid analysis

There's no engine oil or coolant to sample on this coupler; the only fluid discipline that matters is grease. Hold the 10-hour/daily wedge-lock pin and pivot greasing interval and don't stretch it in dusty, wet, or abrasive ground conditions. Track wedge and hook plate wear at each inspection instead of waiting for a failure: a small, steady increase in play is normal wear-in, but a sudden jump points to grease starvation, a bent wedge, or a lock cylinder losing holding pressure. Log findings so a trend, not a single reading, drives replacement timing.

Corrective & common repairs

Most repairs trace to wear at the wedge plate and the hook (jaw) plate the wedge pulls against. Both wear fastest on machines that cycle attachments often or dig abrasive material, showing up as looseness between tool and coupler under load. Lock-cylinder seal and hose leaks are the other common repair, seen as slow bleed-down of the lock or fluid weeping at the fittings. Restoring lock tightness means replacing the worn wedge or hook plate, or reseating the cylinder seals, rather than trying to shim up a worn fit.

Overhaul & rebuild points

A full rebuild centers on the wedge plate, the hook (jaw) plate, the pins and bushings at the coupler-to-stick and coupler-to-tool joints, and the lock cylinder. Wedge and hook plates get replaced once wear pushes play past what regreasing and adjustment can take up. Pins and bushings are measured against service-limit clearance and replaced as a set to keep the joint tight rather than one at a time. The lock cylinder is stripped for seal replacement, or replaced outright if the rod or bore is scored beyond honing.

Seasonal & environment servicing

Cold weather calls for a lower-temperature Cat grease grade at the wedge-lock and pivot points so the gun feeds properly and the wedge doesn't stiffen on a sub-zero start; check with your dealer for the region-specific grade. In wet, muddy, or frozen ground conditions, clear packed mud and debris from the wedge, hook plate, and cylinder area before cycling the lock, since packed material can block full wedge engagement and mask a partial lock. Wash the coupler down regularly in these conditions and confirm full, solid engagement before resuming digging.

HEX-WEDGE attachments & work tools

Carrier / excavator weight class

This dedicated wedge-lock coupler is built for Cat’s B-series/C-series hydraulic excavator line, spanning roughly an 11-tonne (12-ton) 311B/312B-C-class machine up through a 33-tonne (36-ton) 330B, with distinct coupler groups for the 315B/315C-317B, 320B/322B, 325B, and 345B/350 size steps in between. Exact carrier fitment and linkage type is tied to a specific coupler group and identification-plate code, so confirm the pairing before ordering.

Work tools swapped

Lets the excavator pick up and drop general-purpose and digging buckets, grapples, hydraulic hammers, and thumbs from the cab without a technician pulling pins. Tool size and pin spacing must match the host excavator class the coupler is built for.

Pin / lock mounting standard

Uses a wedge-style lock, not a pin-grabber hook. A hydraulic cylinder drives a hardened wedge plate against the work tool rear pin/bracket, pulling the tool tight against the front pin and removing play between coupler and tool.

Safety and guarding features

A hydraulic check valve holds the locking cylinder in position, and a mechanical spring keeps the wedge in the locked position even if hydraulic pressure is lost. Cat's wedge-lock coupler family also monitors wedge position so the operator gets a lock-status read; confirm with a dealer whether this specific version includes in-cab visual/audible lock confirmation, since that feature set varies across the wedge-lock coupler lineup.

All HEX-WEDGE assemblies by section

Every catalogued assembly group for the Caterpillar HEX-WEDGE. Open an assembly to preview the parts inside — full OEM part numbers are available in Heavy Parts AI.

Hydraulic System
183-9371 Lines Gp-Coupler
08***70Sleeve1
10***50Loom; (29-cm)0
11***83Connector1
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250-1917 Lines Gp-Coupler
12***50Valve-Check; (Quick Coupler Solenoid)1
12***11Coupling-Permanent1
12***13Coupling-Permanent1
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191-8725 Lines Gp-Coupler
12***50Valve-Check; (Quick Coupler Solenoid)1
12***41Coupling-Permanent1
12***58Coupling-Permanent1
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250-1916 Manifold Gp-Control
10***02Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness)1
16***03Valve Group-Solenoid1
17***93Wire As1
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192-7657 Valve & Mtg Gp-Solenoid
16***40Plate-Bracket1
17***93Wire As1
18***04Valve Group-Solenoid1
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185-3656 Valve Gp-Control
10***02Kit-Receptacle; (2-Pin)(Engine Sensor Wiring Harness)1
16***03Valve Group-Solenoid1
16***40Plate-Bracket1
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Work Tool Arrangement
198-7902 Conversion Ar-Quick Coupler
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
12***34Bolt; (M24x3x340-mm)2
15***75Spring As2
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160-8301 Conversion Ar-Quick Coupler
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
14***48Bolt-Hex Head; (M24x3x350mm)2
15***75Spring As2
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Work Tools
172-8480 Coupler Gp-Quick
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
12***77Pin2
14***48Bolt-Hex Head; (M24x3x350mm)2
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198-4430 Coupler Gp-Quick
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
12***34Bolt; (M24x3x340-mm)2
15***75Spring As2
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198-7903 Coupler Gp-Quick
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
12***34Bolt; (M24x3x340-mm)2
15***75Spring As2
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160-8296 Coupler Gp-Quick
12***77Pin2
15***51Coupler As1
15***61Pin2
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172-8408 Coupler Gp-Quick
12***77Pin2
14***92Clamp-Collar2
15***36Film-Warning; (Read Operation Manual)1
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160-8297 Coupler Gp-Quick
12***77Pin2
15***61Pin2
15***36Film-Warning; (Read Operation Manual)1
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172-8479 Coupler Gp-Quick
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
12***77Pin2
14***48Bolt-Hex Head; (M24x3x350mm)2
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198-7900 Coupler Gp-Quick
10***45Bearing-Sleeve2
15***36Film-Warning; (Read Operation Manual)1
16***02Washer-Spring8
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172-8481 Coupler Gp-Quick
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
12***77Pin2
14***48Bolt-Hex Head; (M24x3x350mm)2
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198-7904 Coupler Gp-Quick
15***36Film-Warning; (Read Operation Manual)1
16***02Washer-Spring8
17***82Collar2
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224-9643 Coupler Gp-Quick
12***77Pin2
15***61Pin1
15***55Pin1
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224-9650 Coupler Gp-Quick
06***05. Ring; Slide, Washer; (26x63.5x6-mm Thk)2
12***77Pin2
13***34Plate-Identification; (Work Tool)1
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160-8298 Coupler Gp-Quick
12***77Pin2
15***61Pin1
15***55Pin1
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172-8409 Coupler Gp-Quick
12***77Pin2
12***34Bolt; (M24x3x340-mm)2
15***64Plate1
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172-8492 Kit-Quick Coupler
12***34Bolt; (M24x3x340-mm)2
15***64Plate1
17***34Wedge As1
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HEX-WEDGE serial number reference

The identification plate is riveted to the coupler frame near the wedge-lock cylinder or mounting ears. It shows the Cat trademark, the coupler group (parts-book) number for that size/configuration variant, and an assembly identification code rather than a machine-style PIN. Match the plate's group number and code to the parts catalog to confirm carrier class and linkage type. This coupler family is built for Cat B/C-series excavator carriers (315 through 350 class); it does not fit later D/E/F-series or compact/mini carriers, which use a different dedicated wedge-lock coupler line under separate model names.

PrefixIdentifies
BBH1-UP320B and 322B carrier, "B"/"S" linkage
BBT1-UP325B carrier, "C" linkage
BCH1-UP330B carrier, "D" linkage
CBE1-UP345B and 350 carrier, "F"/"T" linkage
FDM1-UP315B/315C or 317B carrier, standard linkage

Frequently asked questions

What excavators is the Hex Wedge coupler compatible with?

The Hex Wedge coupler group is built for Cat's B-series/C-series hydraulic excavator line, with documented fitment spanning 311B, 312B/312C, and 314 on the smaller end, up through 315B/315C, 317B, 320B/322B, 325B, and 330B. Each coupler group and identification-plate code is matched to a specific carrier size and stick-linkage type, so fitment isn't universal across the whole range. Confirm the exact carrier model and linkage type with your dealer before ordering or moving one over to a different machine.

Does the Hex Wedge coupler have its own hydraulic system?

No. The lock/unlock cylinder runs off the host excavator's own hydraulic circuit through a dedicated coupler control valve, and the coupler has no independent pump, reservoir, or hydraulic tank of its own. A mechanical spring and a hydraulic check valve keep the wedge locked even if the host machine's hydraulic pressure drops or is shut down. Because of this, any hydraulic supply problem reaching the coupler shows up as a fault on the host excavator's own hydraulic system, never as a code from the coupler itself.

What replaced the wedge-lock coupler design?

Cat's current excavator coupler lineup has moved mainly to pin-grabber geometry, and on many current models to an electro-hydraulic locking system that adds an electronic position sensor and in-cab lock-status confirmation on top of the mechanical lock. Exactly which current coupler line supersedes a given Hex Wedge fitment varies by carrier model, dealer region, and available retrofit kit, so check current options and availability with your Cat dealer for your specific excavator.

What HEX-WEDGE owners discuss

How much play is normal in a wedge-lock coupler over time, and when does it cross into a problem?
Some play develops as the wedge face and hook plate wear in, so a small amount of movement on a used unit is expected. It becomes a problem once the work tool rocks or shifts visibly under load, since that looseness accelerates further wear on the wedge and hook and can eventually undermine how solidly the lock holds. Check for play with the tool raised and cycled through curl and dump, not just resting on the ground.
How do operators verify the coupler is fully locked before starting to dig?
Common practice is to curl the bucket back hard against the coupler, then rock or shake it by hand and walk around to visually confirm the wedge and hook have fully engaged with no gap showing. Many operators also raise the tool a short distance off the ground and cycle the linkage once before loading it. Because this is a purely mechanical or hydraulic lock with no onboard lock-status warning, have your dealer verify correct engagement if there is any doubt.
What are the most common failure points on this style of coupler?
Wear concentrates at the wedge plate itself and at the hook (jaw) plate that engages the work tool pin, both of which show up first as increasing looseness between the tool and the coupler body. On hydraulically actuated units the lock cylinder's seals and feed hoses are the other weak point, showing up as slow bleed-down of the lock over time or visible weeping at the fittings.
Can a wedge-lock coupler be retrofitted with a pin-grabber style coupler instead?
Some owners do swap over to a pin-grabber unit to gain compatibility with a broader range of third-party attachments and to reverse a bucket for work against a wall or under a pipe. The tradeoff is a small loss of breakout force, since a pin-grabber design sits the work tool slightly further from the stick pin than a wedge-lock does. Pin spacing and hydraulic circuit fitment on the replacement coupler have to match the carrier's linkage, so this is not a drop-in swap across all excavators. Confirm dimensions and fitment with your dealer before ordering.
Does a wedge-lock coupler cost digging force compared to other coupler styles?
No. A wedge-lock design keeps the work tool tight against the stick pin, so it doesn't add the extra offset that some pin-grabber designs introduce between the pin and the bucket lip, and breakout force is preserved. The tradeoff is less attachment flexibility, since the wedge and hook geometry is matched to a specific pin and hook fit rather than grabbing a universal range of pin spacings.
Is it safe to use a wedge-lock coupler for pulling or prying, not just straight digging?
These couplers are built for digging loads in the normal direction of travel. Using the tool to pull, pry, or break out material back toward the cab puts abnormal load on the lock cylinder and hook, and this kind of off-axis use is a frequent cause of premature wear or failure at the jaw and cylinder. Keep loads in the digging direction and don't use the coupler lock itself as a prying point.
What should a buyer inspect on a used excavator fitted with this coupler?
With a bucket attached, cycle the tool through curl and dump and watch for any movement between the bucket and the coupler body — wedge and hook wear shows up as visible slop under load. Check around the lock cylinder for weeping hydraulic fluid or chafed hoses, and confirm the lock engages solidly and promptly when cycled, with no hesitation or partial engagement. Also check the pins and bushings at the coupler-to-stick and coupler-to-tool joints, since wear there compounds any looseness already in the wedge. If lock condition is at all uncertain, have your dealer verify it before completing the purchase.

Compiled from owner and technician discussions across the industry — experiences vary by serial range and machine history.

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