How to Test Torque on Impact Tools

Inertia Torque Impact Torque Tester L-1000

One of the greatest challenges we’ve come across when testing tools is knowing how to reliably measure and test torque on impact wrenches and impact drivers. Having done some form of torque testing or another for over 15 years, Pro Tool Reviews finally settled on the use of an inertia torque tester. In particular, our shop uses the Inertia Torque L-1000.

While this helps Pro Tool Reviews in our head-to-head comparative testing, manufacturers and other businesses can benefit from knowing exactly how much torque their impact tools generate. I’ll walk you through the Inertia Torque Impact Torque Tester (L-1000) to show you how it can help provide more consistent testing and give you greater confidence when measuring impact wrenches and impact drivers.

There are other ways to test torque on impact tools, but having done them all, I can tell you this is the best.

Setting Up the L-1000 to Test Torque

Before you get started testing impact torque, you need a spot to install the L-1000 and it needs to be solid. I recommend adding the steel mount to give you perfect mounting holes and a stable foundation, especially if you need to install it on a wood bench as I did.

Inertia Torque Impact Tool Torque Tester Mounting Plate

You can choose one of three square drive adapters to go with your unit: 3/8, 1/2, or 3/4-inch. Pick up additional sizes or spares for $125 each as needed. Installing them is simple. Use a hex key to work the set screw that holds them in place. The set screw on my L-1000 operated a little tighter than expected, but it was very obvious when it seated the adapter correctly.

Inertia Torque Impact Tool Torque Tester Drive Adapters

What I love about the adapter-based design is that it eliminates the need for test bolts. That’s one less variable!

I chose the model that comes with a digital gauge and highly recommend spending the extra to get it. It’s much easier to see exact numbers and the backlight helps if you have less light. A USB-rechargeable battery powers the gauge.

Digital Gauge

How to Test Torque on Impact Wrench and Driver Tools

Since the Inertia Torque impact tool torque tester arrived, I’ve run quite a few tests to determine how repeatable it is along with the best test methods. The torque measures in real-time, so it’s easy to adjust if your needs are different than mine.

That said, hitting the trigger for four 5-second bursts with 3 seconds of rest between each one gave me stable top-end torque values. It’s a tough test and some motors get pretty warm. Be sure to give the tool plenty of cool-down time if you’re running multiple tests.

Metabo HPT 36V 1/2-Inch MultiVolt Mid-Torque Impact Wrench Review

For the models I’ve tested so far, the top-end torque values have run between 65% and 85% of what the manufacturer’s specifications state for each impact wrench. Impact drivers are further away because of how much force the square adapters absorb.

Inertia Torque Impact Tool Torque Tester

What’s exciting is that when I or anyone on my crew runs multiple tests, the results are within the 1% accuracy rating Inertia Torque claims. Plus, I’m able to get values in every mode, including any assist modes. Even better, the unit measures torque accurately in both forward and reverse!

One thing to keep an eye on is the upper torque limit of 1000 ft-lbs. There are high-torque impact wrenches that can easily exceed that limit.


The L-1000 does require maintenance, but it’s pretty simple. Just send it in once a year for calibration and they’ll check the grease levels and other maintenance concerns at the same time. The only downside is the unit is heavy, so shipping back and forth is going to ding your wallet a bit.

The calibration cost is $100 and you can expect the turnaround to be 2 – 3 days.

Applications for Testing Torque in Impact Tools

My main purpose in using the L-1000 is to give you the best possible information when you compare or consider impact tools. That’s not most people, though. Here are some reasons you might want to order one:

  • Track torque degradation and determine when to take a tool out of service for maintenance or replacement
  • Know how much force each mode on an impact tool delivers and avoid over-torquing fasteners
  • Implement testing protocols that inspire confidence in the tools you shop or company uses
  • Save time and money by testing tools in-house

Inertia Torque Impact Tool Torque Tester Price

You can order the L-1000 with a digital gauge and adapter size of your choice directly from Inertia Torque for $1500. It’s also available with a standard gauge for $1250. Additional adapters are $125 each and the steel mount is $200. A set of four mounting plate screws is $20.

If you want it all, you can get it. With the standard gauge, mounting plate, and all three adapter sizes, the kit is $1825. You can swap out for the digital gauge and it’s $2075.

Is Inertia Torque a Good Brand?

Never heard of Inertia Torque? You’re not alone! They’re a company attached to Skidmore-Wilhelm. That’s the company responsible for other power tool torque testing instruments. They know what they’re doing and I have the highest confidence in their team.

The Bottom Line

The Inertia Torque impact torque tester has completely transformed the way I and the team here at Pro Tool Reviews test impact drivers and impact wrenches. I get accurate, repeatable readings of how much torque each setting produces, giving me much more confidence when working with delicate materials or determining when to take a tool out of service. If having that data is critical to your operations, the L-1000 is well worth the price.


  • Model: Inertia Torque L-1000
  • Available Drive Adapters: 3/8, 1/2, and 3/4-inch
  • Max Torque: 1000 ft-lbs
  • Accuracy: ±1%

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