What Jaw Type Should I Use for My CNC Vise? A Complete Guide To GT Vise Jaw Selection

One of the most powerful features of a precision modular vise is its interchangeable jaw system. Unlike a standard milling vise where the jaw plates are fixed and rarely changed, a modular vise is designed to accept different jaw types — each optimized for a specific workpiece geometry, material, or machining operation.

This flexibility means that a single GT vise body can be adapted to hold flat pre-machined parts, raw stock for roughing, cylindrical shafts, tall workpieces, delicate aluminum components, and complex custom profiles — simply by swapping the jaw plates. No additional fixturing, no dedicated vise for each part type, no wasted machine table space.

But this flexibility only delivers its full value when the right jaw type is selected for each application. Using the wrong jaw type leads to poor clamping contact, insufficient grip, workpiece movement during cutting, increased runout, and unnecessary wear on both the jaw and the workpiece surface.

This guide covers every jaw type available for the GT precision modular vise series, explains the engineering purpose behind each design, and provides clear, practical guidance on which jaw to select for every common CNC machining scenario.

All jaw types described in this article are available for the full GT series — GT100, GT125, GT150, GT175, GT200, and GT300 — and are interchangeable on the same vise body. View the complete interchangeable jaw range for GT precision modular vises.

Why Jaw Selection Matters

Before diving into the individual jaw types, it is worth understanding why jaw selection has such a direct impact on machining results.

A jaw's job is to transfer clamping force from the vise lead screw into the workpiece in a way that:

• Holds the workpiece securely against cutting forces without allowing movement

• Positions the workpiece accurately relative to the machine axes

• Distributes clamping pressure evenly to avoid distortion or damage

• Provides repeatable location so that every part in a batch is clamped in the same position

Different workpiece geometries and surface conditions require different jaw designs to achieve all four of these objectives simultaneously. A flat jaw that works perfectly on a pre-machined steel block will provide almost no grip on a round bar. A serrated jaw that bites firmly into raw stock will damage a finished surface. A standard jaw that holds a 20 mm thick part securely may allow a 5 mm thin plate to tip and shift under cutting forces.

Jaw selection is not a secondary consideration — it is a fundamental part of workholding design.

The GT Vise Jaw System: How It Works

All GT precision modular vises use a standardized jaw mounting interface that allows jaw plates to be exchanged on the same vise body. The jaw plates are precision-ground to maintain the 0.005 mm squareness and parallelism standard of the GT series, ensuring that changing jaw types does not compromise the accuracy of the setup.

Key specifications that apply to all GT jaw types:

• Material: 20CrMnTi alloy steel

• Hardness: HRC 58–62

• Precision: 0.005 mm squareness and parallelism

• Compatibility: GT100, GT125, GT150, GT175, GT200, GT300

• Application: CNC machining centers, milling machines, grinding machines, drilling machines

Jaw Type A: Flat Jaw

What it is:

The flat jaw is the standard, general-purpose jaw type. It features a smooth, precision-ground flat clamping face with no serrations, steps, or grooves.

How it works:

The flat face makes full, even contact with the workpiece surface across the entire jaw width. Clamping force is distributed uniformly, minimizing the risk of surface damage or localized stress concentration.

Best applications:

• Pre-machined workpieces with flat, smooth surfaces

• Finishing operations where the workpiece surface must not be marked or damaged

• Second-operation work where a previously machined face is used as the clamping reference

• Precision grinding setups where surface integrity is critical

• Inspection fixturing where the workpiece must be held without distortion

When not to use it:

• Raw, scaly, or hot-rolled stock — the smooth face provides insufficient grip on rough surfaces

• Round or cylindrical workpieces — line contact only, no secure clamping

• Very thin or flexible workpieces that need height-positioning support

Key advantage:

Zero surface damage. The flat jaw is the only jaw type that can be used safely on finished surfaces without leaving marks.

Jaw Type B: Step Jaw

What it is:

The step jaw features a series of precision-machined horizontal steps at defined depths on the clamping face. Each step provides a flat seating surface at a specific height above the vise bed.

How it works:

When a workpiece is placed against a step jaw, the bottom face of the workpiece rests on one of the steps rather than hanging in free air. This provides a positive vertical reference point, eliminating the need for separate parallel blocks to raise the workpiece to the correct height.

Step jaw dimensions (GT series):

Step width: 3 mm across all sizes.

Best applications:

• Thin plates and sheet stock that need to be raised above the vise bed for tool clearance

• Parts requiring consistent height positioning across a production batch

• Eliminating parallel blocks — reduces setup time and removes a potential source of positioning error

• Batch production where every part must be clamped at exactly the same height for consistent machining depth

When not to use it:

• Workpieces that are taller than the highest step — the step jaw provides no advantage if the workpiece already sits above the vise body

• Round or irregular workpieces that cannot seat stably on a flat step

Key advantage:

Built-in height reference eliminates parallel blocks, reduces setup time, and improves batch-to-batch repeatability.

Jaw Type C: Lattice Jaw / Serrated Jaw

What it is:

The lattice jaw features a diamond-pattern serrated surface on the clamping face. The raised points of the serration pattern bite into the workpiece surface under clamping pressure.

How it works:

The serrated points create multiple small contact areas that penetrate slightly into the workpiece surface, generating very high local friction and mechanical interlock. This dramatically increases the effective grip compared to a smooth flat jaw, particularly on rough or irregular surfaces.

Best applications:

• Raw, unfinished stock — hot-rolled bar, plate, casting, or forging where the surface is rough, scaly, or irregular

• Heavy roughing operations where cutting forces are high and maximum grip is needed

• Hard materials such as hardened steel or stainless steel where smooth jaws may slip

• Applications where surface marking is acceptable — the serration pattern will leave marks on the workpiece surface

When not to use it:

• Finished or pre-machined surfaces — the serrations will damage the surface

• Soft materials such as aluminum or brass where the serrations may dig in excessively and distort the workpiece

• Thin-walled or delicate parts where the concentrated clamping forces could cause deformation

Key advantage:

Maximum grip on rough or hard-to-hold surfaces. The lattice jaw is the correct choice whenever secure clamping of raw stock is the priority and surface marking is acceptable.

Jaw Type D: V-Groove Jaw

What it is:

The V-groove jaw features a V-shaped channel machined into the clamping face. The V-groove is oriented horizontally, so that a cylindrical workpiece placed against the jaw is supported and centered by the two faces of the V.

How it works:

When a round bar or cylindrical workpiece is placed against the V-groove jaw, the two inclined faces of the V make contact with the curved surface of the workpiece at two lines rather than at a single point. This provides stable, centered clamping that prevents the workpiece from rolling or shifting laterally.

Best applications:

• Round bar stock — the most common application

• Cylindrical workpieces such as shafts, pins, and bushings

• Tubing and pipe where the outer diameter needs to be held securely

• Drilling and milling operations on cylindrical parts where the workpiece must be held perpendicular to the machine axis

When not to use it:

• Flat workpieces — the V-groove provides no advantage and may actually reduce contact area

• Very large diameter cylinders that exceed the V-groove geometry — use the Large V-Jaw (Type E) instead

• Workpieces with irregular cross-sections that do not seat stably in the V

Key advantage:

Self-centering clamping of cylindrical workpieces. The V-groove jaw eliminates the need for V-blocks or special fixtures when machining round parts.

Jaw Type E: Large V-Jaw

What it is:

The large V-jaw is a wider, deeper V-groove profile designed for cylindrical workpieces with larger diameters than the standard V-groove jaw can accommodate effectively.

How it works:

The same principle as the standard V-groove jaw, but with a wider V-angle and deeper groove to provide stable two-line contact on larger diameter cylinders. Without the large V-jaw, a large diameter cylinder would contact only the tips of the standard V-groove, providing minimal support and poor centering.

Best applications:

• Large diameter round bar where the standard V-groove jaw does not provide adequate contact

• Large shafts and cylinders requiring secure clamping for milling, drilling, or grinding

• Thick-walled tubing with large outer diameters

When not to use it:

• Small diameter cylinders — the large V-jaw will not provide stable contact on small diameters; use the standard V-groove jaw instead

Key advantage:

Extends the cylindrical workholding capability of the GT vise to larger diameter workpieces without requiring a separate fixture.

Jaw Type F: Thread Hole Jaw

What it is:

The thread hole jaw features a grid of threaded holes on the clamping face. These holes accept bolts that secure soft jaw blanks — typically made from aluminum — directly to the jaw face.

How it works:

The operator bolts aluminum soft jaw blanks onto the thread hole jaw, then machines the soft jaw blanks to match the exact profile of the workpiece. The result is a custom jaw face that conforms perfectly to the workpiece geometry, distributing clamping force evenly across the entire contact area regardless of how complex or irregular the workpiece shape is.

Because the soft jaw material is aluminum (or sometimes mild steel for harder applications), it is softer than the workpiece and will not damage finished surfaces.

Best applications:

• Complex or irregular workpiece profiles that cannot be held securely by any standard jaw type

• Delicate or soft workpieces — aluminum, brass, plastic, or thin-walled parts — where clamping force must be distributed over the maximum possible area to avoid distortion

• Second-operation work where a previously machined profile needs to be used as the clamping reference

• High-precision finishing where the workpiece must be located with maximum accuracy and held without any surface damage

• Dedicated production fixtures for a single part number where the soft jaw is machined once and reused for the entire production run

Soft jaw machining procedure:

1. Bolt aluminum soft jaw blanks onto the thread hole jaws

2. Close the vise to the approximate clamping position

3. Machine the soft jaw face to match the workpiece profile using the CNC program

4. Open the vise, place the workpiece, and clamp — the workpiece seats perfectly in the machined profile

When not to use it:

• General-purpose work where the setup time for machining soft jaws is not justified

• Applications where the workpiece geometry changes frequently — soft jaws are most cost-effective for dedicated or repeat production

Key advantage:

Unlimited adaptability. The thread hole jaw combined with aluminum soft jaws can hold any workpiece geometry with maximum contact area, minimum clamping distortion, and zero surface damage.

Jaw Type G: Elevation Jaw / Square Jaw

What it is:

The elevation jaw is a taller jaw profile that raises the workpiece higher above the vise body than a standard jaw allows.

How it works:

By increasing the height of the jaw face, the elevation jaw positions the workpiece higher above the vise bed. This creates additional clearance between the bottom of the workpiece and the top of the vise body, allowing cutting tools to access the sides and lower portions of the workpiece without risk of collision with the vise.

Best applications:

• Tall workpieces that need to be clamped near the bottom while the upper portion is machined — the elevation jaw provides clearance for the tool to reach lower on the workpiece

• Operations requiring underside access — where the tool needs to machine close to or below the clamping plane

• 5-axis machining setups where tool approach angles are steep and clearance around the workpiece is critical

• Parts with features near the bottom face that need to be machined while the part is held from the sides

When not to use it:

• Short or compact workpieces where standard jaw height provides adequate clearance

• Applications where the increased jaw height would reduce clamping stability

Key advantage:

Maximizes tool access to the workpiece without requiring the part to be repositioned or re-fixtured for operations near the lower face.

Straight Jaw Design Vise

In addition to the interchangeable jaw types described above, Zhenghao also offers a straight jaw design variant of the GT vise. In this configuration, the jaw faces are designed to be perfectly parallel and perpendicular to the vise body axis, optimized for applications where maximum squareness of the clamping reference is the primary requirement.

This design is particularly suited to:

• Precision grinding where the workpiece must be held with absolute squareness

• Inspection and measurement setups where the vise is used as a precision reference fixture

• Applications where jaw geometry consistency is more important than adaptability

Custom Jaw Profiles

Beyond the standard jaw types, Zhenghao manufactures custom step jaws and special-profile jaws to customer specifications.

Custom jaws are appropriate when:

• A standard jaw type does not provide the optimal grip geometry for a specific workpiece

• A dedicated production fixture is needed for a high-volume single-part-number run

• The workpiece has an unusual shape that requires a purpose-designed clamping interface

• The customer wants to reduce setup time by eliminating the need to machine soft jaws for each production run

Custom jaw orders can be discussed directly with the Zhenghao technical team. Provide your workpiece drawings or jaw profile requirements, and we will manufacture jaws to your specifications.

Quick-Change Jaw System: When Jaw Changeover Speed Is the Priority

For production environments where multiple jaw types need to be used on the same vise in a single shift, Zhenghao's GT Quick-Change Jaw Vise provides a further level of efficiency.

The quick-change mechanism allows jaw plates to be swapped in seconds without removing any bolts — eliminating the time, chip contamination risk, and re-torquing requirements of conventional jaw plate changes. Each quick-change vise includes a pair of aluminum soft jaws as standard, providing immediate soft jaw capability for delicate or complex workpieces.

The quick-change jaw system is particularly valuable in:

• High-mix, low-volume production where part types change frequently throughout the day

• Job shops handling a wide variety of workpiece geometries on the same machine

• Environments where minimizing non-cutting time is a key productivity objective

Jaw Selection Decision Guide

Use this reference table to identify the correct jaw type for your application at a glance:

Practical Tips for Getting the Most from Your GT Jaw System

Keep a complete jaw set on hand

The full value of the interchangeable jaw system is only realized when all jaw types are available. Purchasing a complete jaw set for each GT vise body allows operators to select the optimal jaw for every job without compromise.

Match the jaw type to the operation, not just the workpiece

The same workpiece may require different jaw types for different operations. For example, a casting may be held with lattice jaws for roughing, then transferred to flat jaws or soft jaws for finishing. Plan the jaw selection as part of the overall process plan, not as an afterthought.

Inspect jaw faces regularly

Jaw faces wear over time, particularly serrated and V-groove jaws used in heavy production. Worn jaw faces reduce grip and increase the risk of workpiece movement. Inspect jaw faces periodically and replace them when wear is visible or clamping performance deteriorates.

Clean jaw faces and vise body before every setup

Chips, coolant residue, and debris on jaw faces or the vise body introduce positioning errors and accelerate wear. Clean all contact surfaces thoroughly before each setup, particularly when changing jaw types.

Use the correct clamping torque

Over-tightening the vise lead screw compresses the workpiece excessively and can cause distortion, particularly with soft materials or thin-walled parts. Under-tightening allows workpiece movement during cutting. Use a torque wrench where precision clamping force is required, and follow the manufacturer's recommended torque values for each vise size.

Conclusion

The interchangeable jaw system is what transforms a GT precision modular vise from a single-purpose clamping tool into a versatile workholding platform capable of handling virtually any CNC machining application. Flat jaws for finishing, step jaws for height positioning, lattice jaws for raw stock, V-groove jaws for cylinders, thread hole jaws for complex profiles, elevation jaws for tall workpieces, and custom jaws for dedicated production — each jaw type has a specific engineering purpose and a specific range of applications where it delivers optimal results.

Selecting the right jaw type for each job is one of the simplest and most effective ways to improve clamping security, reduce setup time, improve part accuracy, and extend the service life of both the jaw and the workpiece.

Zhenghao manufactures the complete range of GT vise jaw types in 20CrMnTi alloy steel, hardened to HRC 58–62, and precision-ground to 0.005 mm — ensuring that every jaw type delivers the same level of accuracy and durability as the GT vise body itself.

Explore the full GT precision modular vise jaw range, or contact us at zhjx@pyzhjx.com or +86-18660185316 to discuss jaw specifications, bulk orders, or custom jaw requirements.

FAQ

Can I use any jaw type on any GT vise size?

Yes, with minor size-dependent variations. All standard jaw types are available for GT100 through GT300. Step jaw depth options vary slightly by vise size — for example, the 18 mm, 23 mm, and 28 mm step depths are not available on GT100. All other jaw types are available across the full GT size range.

How often should I replace my vise jaw plates?

This depends on usage intensity and the jaw type. Flat jaws used on pre-machined surfaces wear slowly and may last for years. Lattice jaws used on raw stock in heavy production wear more quickly and should be inspected regularly. Replace jaw plates when visible wear is present on the clamping face or when clamping performance deteriorates.

Can I machine my own soft jaw profiles into aluminum soft jaws?

Yes. This is the intended use of the thread hole jaw system. Bolt aluminum soft jaw blanks onto the thread hole jaw plates, then machine the desired profile directly into the soft jaw face using the CNC program. The machined profile provides a custom clamping surface that conforms exactly to the workpiece geometry.

Do jaw plates need to be re-qualified after installation?

For most production applications, no. The GT jaw plates are precision-ground to 0.005 mm and mount on a precision-ground jaw interface, so they do not require re-qualification after a standard jaw change. For the highest-precision applications, a quick runout check after jaw installation is good practice.

What is the difference between the V-groove jaw and the large V-jaw?

Both provide V-shaped clamping for cylindrical workpieces, but the large V-jaw has a wider and deeper V-profile designed for larger diameter cylinders. The standard V-groove jaw is optimized for smaller to medium diameter round stock. Selecting the wrong size V-jaw for the workpiece diameter will result in poor contact and unstable clamping.

Can Zhenghao manufacture custom jaw profiles to my drawings?

Yes. Zhenghao manufactures custom step jaws and special-profile jaws to customer specifications. Provide your workpiece drawings or jaw profile requirements and our technical team will advise on the optimal jaw design and manufacturing approach.