Caldwell Model DWS Locking Lifting Clamp

Renfroe Model DWS Horizontal Locking Lifting Clamp — Lock-Closed Security for Horizontal Sheet Lifting

The Renfroe Model DWS is a horizontal locking lifting clamp engineered for the controlled, horizontal lifting of individual steel plates and sheets. Available in three capacity ratings — 1/2 Ton, 1-1/2 Ton, and 3 Ton — this clamp is built for contractors, steel fabricators, and rigging professionals who demand reliable, repeatable performance when handling flat stock horizontally. The DWS incorporates Renfroe's industry-renowned "lock-closed" feature, providing a positive mechanical lock that prevents accidental jaw release during the lift cycle. Manufactured by The Caldwell Group, Inc. in Rockford, IL, the Renfroe brand has been trusted by international lifting clamp users for more than 50 years.

Unlike standard horizontal clamps that rely solely on cam grip tension, the Model DWS adds a dedicated lock assembly that mechanically secures the jaw in the closed position before and during the lift — a critical distinction when working overhead or in high-traffic job sites. The serrated gripping cam delivers a firm, positive bite on the plate surface, eliminating slippage under load that can occur with smooth-cam alternatives.

Key Features & Benefits

Lock-Closed Mechanism

The DWS's signature lock-closed feature mechanically locks the cam jaw shut before the lift begins, preventing inadvertent opening under shock loads or vibration. For contractors lifting plate over personnel or in confined areas, this provides a critical layer of drop prevention beyond what friction-only clamps offer. The lock must be engaged prior to every lift — a simple, fast step that significantly reduces risk.

Serrated Gripping Cam

The hardened, serrated gripping cam bites into the plate surface to maintain a secure hold throughout the lift cycle. This design ensures grip integrity even on plates with mill scale, light surface rust, or minor surface irregularities common on structural steel. The cam geometry is optimized for horizontal orientation, distributing load forces appropriately across the jaw contact area.

Three Capacity Sizes

The DWS is available in 1/2 Ton (0–3/4" jaw opening), 1-1/2 Ton (0–1" jaw opening), and 3 Ton (0–1-1/4" jaw opening) to match the specific plate thickness and load weight of each job. Selecting the correct capacity size — rather than using oversized clamps on light loads — is essential to proper cam engagement and safe operation. Consult the factory for possible larger capacities beyond the standard range.

Paired / Tripod Arrangement Requirement

The Model DWS is designed to be used in pairs, sets of pairs, or in a tripod arrangement to ensure the lifted plate remains balanced and level throughout the lift. This engineered usage requirement prevents tipping, edge loading, and uneven stress distribution across the plate. Proper pairing also allows for balanced rigging geometry when using a spreader beam or crane hook assembly.

Compact, Robust Construction

At just 9 lbs. for the 1/2 Ton model, the DWS is easy to handle, transport, and position on the plate prior to lifting. The compact clamp body (4" length x 3.56" height) keeps the rigging profile tight and manageable, particularly in steel yards or fabrication shops where working space is limited. The overall clamp height with shackle of 7.38" keeps the lifting assembly low-profile relative to the load.

RENFROE-Genuine Components

Every Model DWS is assembled from factory-specified Renfroe components — including the DWS-1 gripping cam, DWS-2 lifting shackle, DWS-3 lock assembly, DWS-4 lock spring, and DWS-10 lock ring — ensuring full parts traceability and compatibility with Renfroe repair kits. Using genuine replacement parts maintains the clamp's rated capacity and ensures the lock mechanism functions as designed. Field modifications, grinding, welding, or alterations to any clamp component are strictly prohibited.

Common Applications

Horizontal Steel Plate Lifting

The DWS is purpose-built to lift individual steel plates in the horizontal (flat) position, making it the standard choice for moving structural plate in fabrication shops, steel service centers, and on-site steel erection work.

Steel Sheet Yard Handling

Steel distributors and plate processors use the DWS in pairs to pull sheets from storage racks or floor stacks and transfer them to processing equipment such as plasma tables, press brakes, or shears without tipping or marring the plate surface.

Bridge and Structural Steel Fabrication

Fabricators handling large structural plate components during bridge construction or heavy structural steel projects rely on the DWS's lock-closed feature and high cam grip for confident horizontal picks over working personnel and equipment.

Crane and Hoist Integration

The DWS integrates with standard overhead cranes, gantries, and chain hoists via the included lifting shackle, making it compatible with most existing rigging setups in fabrication and manufacturing facilities. A flexible connection between the crane hook and clamp shackle is required per the operator manual.

Steel Erection and Site Placement

On construction sites, the DWS is used to precisely position base plates, embed plates, and large flat structural members horizontally during placement operations where vertical clamps or slings are not practical or safe.

Maintenance and Equipment Rebuilds

Maintenance crews use paired DWS clamps to horizontally lift and reposition heavy machine base plates, equipment beds, or steel frame sections during machinery installation and plant rebuild projects.

Compatible Materials

• Structural steel plate (A36, A572, A514, and similar grades)
• Carbon steel sheet and plate with mill scale or light surface rust
• Flame-cut and plasma-cut steel plate
• Rolled steel flat stock
• Steel base plates and embed plates
• Heavy steel machine beds and equipment frames (horizontal orientation)

Product Documents

• Download Catalog
• Download Manual
• Lifting Clamp Survey Report
• Lifting Tool Inventory and Maintenance Form
• Minimum Recommended Clamp Inspections
• Renfroe Repair Kits Catalog

Application Instructions

Stage 1: Pre-Lift Inspection

1. Read and understand the operator manual completely before first use. Take the manual to your supervisor before putting the clamp into service.
2. Inspect the clamp before each lift per the Minimum Recommended Clamp Inspections document. Check for wear, cracks, deformation, or missing/damaged components.
3. Verify the clamp capacity rating matches or exceeds the weight of the plate to be lifted. Do not use large-capacity clamps to lift light loads.
4. Confirm the plate thickness falls within the jaw opening range for the selected clamp size (1/2 Ton: 0–3/4"; 1-1/2 Ton: 0–1"; 3 Ton: 0–1-1/4").
5. Confirm all Renfroe components — gripping cam, lock assembly, lock spring, lock ring, lifting shackle — are present and undamaged.

Stage 2: Clamp Setup and Attachment

1. Secure the load in its resting position before attaching the clamp.
2. Open the jaw to the appropriate width for the plate thickness being lifted.
3. Position the clamp on the edge of the plate in the horizontal orientation, ensuring the serrated cam contacts the plate surface squarely.
4. Engage the lock-closed mechanism to lock the jaw in the closed position around the plate. Do not proceed with the lift if the lock is in the open position.
5. Attach the clamp to the rigging using a flexible connection between the crane hook and the clamp shackle. Do not attach the clamp directly to the crane hook. Do not use a heavy flexible connection.
6. Arrange clamps in pairs, sets of pairs, or tripod arrangement to balance the load. Do not lift with a single clamp.

Stage 3: Lifting Operation

1. Verify load balance before lifting. Use enough clamps to keep the plate level and stable throughout the lift.
2. Do not lift over workers, safety areas, or personnel.
3. Lift only one plate at a time. Do not lift plate from the bottom of a plate stack.
4. Do not side-load a straight shackle clamp.
5. Do not rush the lift operation. Maintain controlled crane or hoist speeds.
6. Do not exceed the rated capacity of the clamp at any point during the lift.

Stage 4: Post-Lift Maintenance

1. Inspect the clamp after each use per the operator manual maintenance and inspection schedule.
2. Log clamp condition on the Lifting Clamp Survey Report (Good Condition / Needs Repair / Beyond Repair — Discard).
3. Use only genuine Renfroe replacement parts for any repairs to assure proper operation and maintain rated capacity.
4. Do not alter the clamp in any way — do not grind, weld, or modify any component.
5. Store clamps in a clean, dry location when not in service.

Technical Specifications

Safety Data Summary

Hazard Information

• Risk of dropped load if lock is not engaged prior to lifting
• Risk of load imbalance or tipping if clamps are not used in proper paired or tripod arrangement
• Risk of overload failure if clamp capacity is exceeded or incorrect size is selected for plate thickness
• Risk of cam slippage if clamp is used on plate thickness outside the rated jaw opening range
• Risk of clamp release if attached directly to crane hook without a flexible connection
• Risk of structural failure if clamp components are modified, welded, or ground
• Risk of injury from lifting over workers or personnel

Personal Protective Equipment

• Hard hat required when working in areas where overhead lifting is in progress
• Steel-toed safety boots required during clamp attachment and load positioning
• Heavy-duty work gloves recommended when handling clamp and steel plate edges
• High-visibility vest recommended in active crane or hoist operating areas

Safe Handling

• Read and understand the full operator manual before first use; take manual to supervisor before putting clamp in service
• Engage the lock-closed mechanism before every lift — never lift with the lock in the open position
• Always use clamps in pairs, sets of pairs, or tripod arrangement — never use a single clamp alone
• Never lift more than one plate at a time; never lift from the bottom of a plate stack
• Never side-load a straight shackle clamp
• Never attach clamp directly to the crane hook; always use a flexible connection between crane hook and clamp shackle
• Never use a heavy flexible connection with this clamp
• Never lift over workers, safety areas, or personnel
• Select the correct capacity clamp for each job; do not use oversized clamps to lift light loads
• Do not exceed rated capacity at any time
• Inspect clamp before every lift; follow all maintenance and inspection procedures per the operator manual
• Use only genuine Renfroe replacement parts for all repairs and maintenance
• Do not alter, grind, weld, or modify the clamp in any manner
• Attend a Renfroe factory training class to establish proper clamp use
• Consult the operator manual or factory when in doubt about any aspect of clamp selection or operation

Frequently Asked Questions

Q: Can the Model DWS be used as a single clamp for a horizontal lift?
A: No. The Model DWS must always be used in pairs, sets of pairs, or in a tripod arrangement to ensure the load remains balanced and level. Using a single clamp would result in an unbalanced, unsafe lift and is explicitly prohibited in the operator manual.

Q: What plate thicknesses is the 1/2 Ton DWS designed for?
A: The 1/2 Ton Model DWS accommodates plate thicknesses from 0 to 3/4" (0.75"). The 1-1/2 Ton handles 0 to 1", and the 3 Ton handles 0 to 1-1/4". Always confirm plate thickness is within the rated jaw opening range before lifting.

Q: What is the lock-closed feature and why does it matter?
A: The lock-closed feature is a mechanical lock assembly that positively secures the jaw in the closed position around the plate prior to and during the lift. Unlike clamps that rely solely on cam friction, the lock prevents the jaw from opening due to shock loads, vibration, or sudden load shifts — a critical safety advantage when lifting overhead or near personnel.

Q: Can replacement parts be sourced for the Model DWS?
A: Yes. The DWS uses fully specified Renfroe components including the DWS-1 gripping cam, DWS-2 lifting shackle, DWS-3 lock assembly, DWS-4 lock spring, DWS-5 shackle pin, DWS-6 cam pin, DWS-7 body bolt and spacer sleeve, DWS-8 spring clip, DWS-10 lock ring, and DWS-11 cam stop pin. Only genuine Renfroe replacement parts should be used to maintain rated capacity and proper lock function. Refer to the Renfroe Repair Kits Catalog for ordering information.

Q: Can the DWS be used to lift plate vertically or to turn plate from horizontal to vertical?
A: No. The Model DWS is a horizontal-only clamp. It is not rated for vertical lifting or turn/lift operations. Using a horizontal-only clamp for vertical lifts is explicitly listed as a prohibited misuse in the Renfroe operator manual. Select a Renfroe vertical lift or vertical turn/lift clamp for those applications.

Q: Are larger capacities available beyond the standard 3 Ton model?
A: Possibly. The manufacturer states to consult the factory directly for possible larger capacities beyond the standard 1/2 Ton, 1-1/2 Ton, and 3 Ton sizes. Contact The Caldwell Group at 800.628.4263 or 815.229.5667 for custom capacity inquiries.