Caldwell Model M Locking Type Structural Shape Lifting Clamp

Renfroe Model M Locking Type Structural Shape Lifting Clamp — Multipurpose Horizontal Lift Clamp for Structural Steel

The Renfroe Model M is a multipurpose locking lifting clamp engineered for the positioning, sorting, erection, and handling of prefabricated structural sections. Designed for contractors and trades professionals working with structural steel, the Model M's split lower jaw makes it especially effective when gripping structural shapes such as I-beams and H-beams in both orientations. At 0.5-ton capacity, this model handles lighter structural members with precision and control. It is manufactured by The Caldwell Group, Inc. in Rockford, IL under the trusted RENFROE brand, which has been the preferred choice of international lifting clamp users for more than 50 years.

What sets the Model M apart is its integrated "Lock Closed" feature, which secures the clamp to the member before the lift begins — a critical safety advantage over clamps without positive locking. The split lower jaw design further distinguishes it from flat-plate clamps by enabling a secure grip on the complex profiles of structural shapes, not just flat stock.

Key Features & Benefits

Lock Closed Feature

The Model M incorporates a "Lock Closed" mechanism that allows the operator to positively secure the clamp to the member before initiating the lift. This reduces the risk of accidental disengagement during attachment and throughout the lifting operation, giving crews greater confidence when working with structural components overhead.

Split Lower Jaw for Structural Shape Handling

The split lower jaw design is specifically intended for gripping structural shapes, making the Model M particularly useful when handling I-beams and H-beams. This jaw geometry accommodates the flanges and webs of structural profiles that a standard flat-jaw clamp cannot grip reliably.

Versatile Horizontal Lift Capability

The Model M is rated for horizontal lifts of an I-beam in both the I and H positions, giving contractors flexibility when orienting members during erection or placement. This dual-orientation capability reduces the need for re-rigging when structural members must be repositioned.

Multipurpose Utility Across Job Phases

Designed for positioning, sorting, erection, and handling of prefabricated sections, the Model M supports multiple phases of a structural steel project with a single clamp model. Contractors can use the same tool for receiving yard sorting, staging, and final erection, reducing the number of specialty tools required on site.

Compact, Lightweight Design

At 7 lbs. with an overall clamp height of 8.88 in. and a clamp width of 2.62 in., the Model M is manageable for ironworkers and rigging crews working in tight structural bays. Its compact footprint minimizes interference with adjacent members during close-tolerance placement work.

Common Applications

Structural Steel Erection

The Model M is used during the erection of prefabricated structural sections, providing a secure horizontal lift point on I-beams and H-beams as they are set into position by crane.

Sorting and Staging in the Yard

Fabricators and contractors use the Model M to sort and position structural shapes in the staging yard before delivery or erection, enabling efficient material handling without damaging the steel profile.

Handling of Prefabricated Sections

The clamp is suited for moving prefabricated structural assemblies from fabrication to installation, accommodating the variable flange thicknesses found across different member sizes within its jaw opening range of 0–1 in.

Horizontal Transport of Structural Members

When used in pairs, sets of pairs, or in a tripod arrangement, the Model M enables safe horizontal transport of structural members, distributing the load across multiple attachment points for balanced lifts.

Compatible Materials

• Structural steel I-beams (lifted in I or H position)
• Structural steel H-beams (lifted in I or H position)
• Prefabricated structural sections and assemblies
• Structural shapes with flange or web thickness from 0 to 1 in. (jaw opening range)

Product Documents

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

Application Instructions

Before the Lift

1. Read and understand the Operator's Manual before using the clamp.
2. Inspect the clamp before each lift following the inspection and maintenance instructions in the Operator's Manual.
3. Confirm the load does not exceed the clamp's rated capacity of 0.5 tons.
4. Select the correct clamp model for the jaw opening required (0–1 in. for Model M-00.50-A).
5. Secure the load before attaching the clamp.
6. Attach the clamp to the structural member and engage the Lock Closed feature to positively secure the clamp prior to lifting.
7. Use a flexible connection between the crane hook and the clamp shackle; do not attach the clamp directly to the crane hook.

Rigging and Lift Execution

1. Use clamps in pairs, sets of pairs, or in a tripod arrangement — never use a single clamp alone for horizontal lifts.
2. Ensure the load is balanced across all clamps before initiating the lift.
3. Do not lift over workers, safety areas, or personnel.
4. Do not side-load a straight shackle clamp.
5. Do not lift more than one structural member at a time.
6. Do not rush the lift operation.

After the Lift

1. Inspect the clamp after use and follow maintenance instructions in the Operator's Manual.
2. Use only genuine RENFROE replacement parts to ensure proper operation.
3. Do not alter, grind, weld, or modify the clamp in any manner.

Technical Specifications

Safety Data Summary

Safe Handling

• Always lock the clamp closed before lifting; never lift with the lock in the open position.
• Never lift over workers, safety areas, or personnel.
• Do not attach the clamp directly to the crane hook; always use a flexible connection between the crane hook and clamp shackle.
• Use the correct clamp for the job; do not use large-capacity clamps to lift light loads.
• Always use clamps within their rated capacity; do not overload.
• Use enough clamps to balance the load; do not lift loads that are not balanced.
• Do not misuse the clamp (e.g., do not lift a structural member from the bottom of a stack).
• Do not alter the clamp; do not grind, weld, or modify it in any manner.
• Do not use a connection that may release the clamp during the lift.
• Use only RENFROE replacement parts to ensure proper operation.
• Consult the Operator's Manual or RENFROE when in doubt about any application.

Frequently Asked Questions

Q: Can the Model M-00.50-A be used as a single clamp for horizontal lifts?
A: No. The Model M must be used in pairs, sets of pairs, or in a tripod arrangement when transporting structural members horizontally. Single-clamp use is not permitted.

Q: What structural orientations can the Model M handle for I-beam lifts?
A: The Model M is designed for horizontal lifts of an I-beam in both the I position and the H position, providing versatility during erection and placement operations.

Q: Is a handle available on the 0.5-ton Model M?
A: No. A handle is available on the 8-ton Model M clamp only.

Q: What is the purpose of the Lock Closed feature?
A: The Lock Closed feature allows the operator to positively secure the clamp to the structural member before initiating the lift. This facilitates safe attachment and helps prevent accidental disengagement during the lifting operation.

Q: What jaw opening range does the M-00.50-A accommodate?
A: The M-00.50-A accommodates a jaw opening range of 0 to 1 in. For structural members with a plate or flange thickness of 3/4 in. to 1-1/2 in., the M-00.50-B model should be selected instead.

Q: Can RENFROE Model M clamps be modified or repaired with third-party parts?
A: No. The clamp must not be altered, ground, welded, or modified in any manner. Only genuine RENFROE replacement parts should be used to ensure proper operation and maintain safety.