High Strength
Wedge Grips for Universal Testing Machines
Wedge Grips for Tensile Testing
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Wedge Grip Capacity Guide
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5 kN (1,124 lbf): narrow jaws for thin, non-flexible samples.
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10 kN (2,248 lbf): lower-strength plastics such as ASTM D638 specimens; a handle pre-tightens the jaws.
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20 kN (4,496 lbf): general plastics and light metals; about 25 lb (11 kg) per grip.
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50 kN (11,240 lbf): 1-1/4 in adapter with 1/2 in pin; lap shear, metals and reinforced plastics. A crank version pre-grips hard plastics and aluminum. For adhesive bonds, see our guide to lap shear vs block shear testing.
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100 kN (22,480 lbf): lateral door locked with a key; nickel-alloy version for furnace testing.
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150 kN (33,720 lbf): hardened steel body with a locking door for long service life.
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300 kN (67,440 lbf): 11° wedge angle, 60 mm female coupling, 40 mm pin, about 80 kg per grip.
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Above 300 kN: hydraulic wedge grips with a hydraulic power unit.
Overview:
Tensile testing wedge grips are essential fixtures for securely holding specimens during high-strength tensile testing on a universal testing machine (UTM). These mechanical wedge grips are self-tightening, meaning the clamping force automatically increases as the tensile load is applied, ensuring the sample remains securely in place throughout the test.
Each wedge grip includes interchangeable grip jaw faces designed for different specimen geometries. Flat samples typically use serrated grip faces for maximum friction, while round or wire specimens require Vee inserts for proper alignment and secure gripping. Higher-capacity wedge grips may feature a locking lateral door to maintain the position of the fixed wedge under extreme forces, enhancing safety and test reliability. High powered pneumatic and hydraulic wedge grips are also available, including all pumps, hoses, valves and switches. Universal Grip has the full solution for any brand of universal testing machine.
Universal Grip offers compact, side-lever wedge grips specifically designed to avoid interference with the UTM’s crosshead and columns. While the jaw openings are optimized for thinner samples, thicker specimens can be accommodated with resized wedges or custom inserts.
Common ASTM standards using wedge grips include:
By using wedge grips, laboratories can accurately measure ultimate tensile strength, yield strength, and elongation without risk of sample slippage. These grips are an industry-standard solution for tensile testing of metals, plastics, adhesives, and composite materials.
Testing plastics? Our guide to ASTM D638 specimen types I–V lists dumbbell dimensions, test speeds and the grips that suit each type.
Jaw Inserts:
Wedge grip jaw inserts can be interchanged for samples with different geometries. The most common jaws are serrated and are used for testing flat samples like dogbones. Vee inserts are used for round or cylindrical samples such as pipes. There are a few different options for the jaws including reversible jaws. The reversible jaws can be flipped around when the serrated file pattern starts to wear out. This essentially gives the jaws double the lifetime.
Running wedge grips on an Instron, MTS, Shimadzu, Zwick or Tinius Olsen frame? Our Tensile Grip & Fixture Selection Guide explains how to match the connection, and our grip adapters fit most frames.
Reinforcing Door for High Capacity (100kN+)
Tensile testing at high capacity (over 100 kN or about 22,500 lbf) requires a well-designed wedge grip. Universal Grip offers a high quality and long-lasting wedge grip with a reinforcing door. Once the door is locked, it increases the structural integrity which prevents any sample slippages. The door is easily opened and closed with a key crank which is included. These grips are over-engineered in order to last for many years without fail. Invest in lab equipment that will last decades instead of years.
Wedge Grips get Heavy! use a Downsize Adapter.
A downsize adapter can help when tensile testing at smaller scales. Special insert plates are used to convert the end of the wedge grip into a standard clevis pin style adapter. Platens can be added for compression testing too. Load Cells can also be attached in this manner for low capacity testing.
1K lbs. - Wedge Grips - 5 kN
The 1,000 lb. wedge grip is quite narrow and is designed to pinch the sample with an increasing amount of force. This solution is great for thin, non-flexible samples.
2K lbs. - Wedge Grips - 10 kN
This grip is great for lower strength plastics and is used commonly in plastics tensile tests such as ASTM D638. The handle is used to tighten the sliding grip jaws onto the sample before the test starts.
4.5K lbs. - Wedge Grips - 20 kN
4,500 lb. grips start to become heavy. These grips weigh about 25 lbs. each. Check out the literature page for a 3D schematic of the working principle.
11.2K lbs. - Wedge Grips - 50kN
The 50kN tensile wedge grips use a 1 1/4" adapter with a 1/2" pin. These grips are commonly used for lap shear strength testing and other tests involving metal and reinforced plastics.
50kN Wedge Grips with Crank
The 50kN Wedge Grips use a crank to force the jaws onto the sample and create a pre-grip, prior to starting the tensile test. These grips are great for hard plastics and soft metals like aluminum
22.5K lbs. - Wedge Grips - 100kN
100kN wedge grips utilize a door which is closed and locked with a key. This particular picture shows a Nickel alloy grip which has better thermal stability for use in furnaces.
100kN+ High Capacity
100kN+ Wedge grips are available upon request. They use a similar door locking mechanism as the 22,500 lbs grips.
150kN or 33K lbs. Wedge Grips
The 150kN wedge grip design is overengineered with hardened steel in order to hold up to high strength tensile testing over several decades. A special door mechanism is used to keep grip strain to a minimum. Test with confidence by using a high quality wedge grip.
300kN or 67K lbs. Wedge Grips
The 300kN wedge grip is designed with a small wedge angle of 11 degrees to allow for high capacity testing. This grip has a 60mm female coupling and uses a 40mm locking pin. Each grip weighs about 80kg.
Hydraulic Wedge Grip 300kN+
Hydraulic Wedge Grips are necessary when testing above 300kN of force. Many tensile pulls on metal bars will require hydraulic wedge grips. UGC also supplies HPUs, however if the UTM already has a hydraulic unit, the grips may be able to piggyback off of the existing HPU.
Wedge Grips FAQ
How do wedge grips work?
The jaw faces ride on a fixed wedge. As tensile load rises, the jaws slide down the wedge and squeeze the specimen harder, so grip force increases with the load.
Should I use flat or V-groove jaw faces?
Use flat serrated faces for flat specimens such as sheet, strip and lap shear coupons. Use V-groove faces for round bars, rods and wire so the specimen stays centered.
Why do specimens slip in wedge grips?
The usual causes are worn or clogged serrations, a specimen thickness outside the jaw range, or too little pre-grip before the test starts. Clean or replace the faces, pick inserts sized to the specimen, and pre-tighten with the handle or crank.
When do I need hydraulic wedge grips?
Above about 300 kN, and for many metal bar and rebar tests, hydraulic wedge grips give the clamping force and repeatability that manual wedges cannot.
Need a wedge grip for your machine? Contact us for a quote.
Screw Wedge Grips
Screw Wedge Grips close the wedge jaws with a hand-tightened screw, giving a firm initial clamp on smooth or hard specimens before the wedge action takes over under load.
Non-Shift Wedge Grips
Non-Shift Wedge Grips keep the specimen centerline fixed as the jaws close, so thin or short specimens stay aligned with the load axis and the gauge length does not move during clamping.