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I have seen torque adapters being used to challenge manufacturers’ torque specs, but it’s not always the best comparison to make.
To start off – what is a torque adapter?
Shown above is a Neiko digital torque adapter ($40-43 via Amazon). Basically, you place this device between your ratchet and socket, and it will measure your application torque. The selling point is that this will convert any ratchet wrench into a precision torque wrench, or an accurate calibration device for existing digital and analog torque wrenches.
You can find similar tools in different sizes, shapes, and configurations. This adapter can be thought of as the torque sensor part of a digital torque wrench.
This – and many tools like it – are said to only be suitable for hand tool use, and not electric or air-powered tools.
The device can measures the torque being exerted on whatever fastener you are tightening, and it can also function like a torque wrench and alert you when a programmed torque is achieved.
Let’s say you just bought a cordless drill, and it’s rated as delivering 100 in-lbs of maximum torque.
You whip out your torque adapter, attach some power tool accessories, and drive some screws into wood. The torque adapter shows the tool maxing out at 60 in-lbs. Whoa, this means that the 100 in-lbs torque specs are bogus, right? Not necessarily.
The Power Tool Institute
To understand where torque specs come from, let’s talk about PTI, or the Power Tool Institute. The Power Tool Institute is a trade organization with popular power tool manufacturers as its members.
PTI members include:
- Black & Decker
- Chervon North America
- Koki Holdings (Metabo HPT)
- Milwaukee Tool
- Ryobi/One World Technologies
- Stanley Black 7 Decker
- Techtronic Industries (TTI)
My understanding – or at least my assumption – is that PTI tool brands all volunteer to follow the same procedures in how they measure and advertise different tools’ max torque specs.
They have a document (PDF) that details the PTI lab test procedure for determining stated relative torque measurement for corded and cordless drills, drill/drivers, and screwdrivers. The document defines a common method for measuring a relative torque output with a claim of such values having 95% confidence.
Basically, the Power Tool Institute published a procedure for measuring torque specs, and I’m under the impression that member brands all adhere to this in how they rate their drills and drivers. Well, except for Stanley Black & Decker brands, which use UWO in North America, but you can find their torque specs in European user manuals and datasheets.
There are of course other ways to measure torque, but it seems to be suggested that PTI members use a common procedure to ensure fair competition.
PTI Torque Measurement Procedures
Here are some of PTI’s prescribed testing steps:
1) Manually energize the test sample as quickly as possible by actuating the switch to
the full on position. This action should represent normal use. Allow the joint rate
simulator to tighten until it comes to a complete stop. Record the output torque.
2) Allow the test sample to cool a minimum of three minutes before performing the
next trial. This will allow the test sample to cool prior to the next measurement, and
insure more consistent readings.
3) Repeat steps 1) and 2) for a total of five trials. For cordless tools, utilize the
same battery pack or sample for the five trials without recharging.
(PTI’s measurements require that 25 total trials be completed – 5 samples with 5 trials each.)
Do member brands still adhere to PTI test procedures and measure relative torque at the full on position to represent normal use? We don’t know. Do they use dynamometers instead of a simple torque tester? (Dynamometers measure a motor’s torque and speed, usually with a programmable brake to provide an adjustable load for the motor.) What methodologies are they using today?
One thing I try to keep in mind is that brands are absolutely buying and testing their competitors’ products. Even if YouTube testers and other reviewers aren’t replicating the exact test procedures used to determine official torque specs, it seems reasonable to assume that PTI trade organization brands are keeping each other in check. Competition is fierce, and it’s reasonable to assume that these brands are preventing each other from uneven advertising practices.
Hard Joint vs Soft Joint
If you look at how cordless drills and other such tools are advertised in Europe, there will often be two torque ratings – a soft joint torque spec and a hard joint torque spec.
(I have also seen these described as rigid and flexible joints.)
To simplify things, here are two fundamental examples.
A typical hard joint might involve a metal plate being fastened to a threaded metal substrate, or two metal plates being fastened together with a bolt and nut. To go from finger-tight to desired torque might only require a small additional rotation of the fastener, such as 1/8 rotation.
A typical soft joint will involve materials that require additional effort to achieve the desired torque, such as a wood screw attaching two pieces of softwood together. When driving a wood screw into a 2x wood stud, for instance, you might need to turn a screwdriver or wrench 1/2 turn or more to go from finger-tight to final tightness.
A soft joint requires more effort to build up torque.
Think about how it feels to fasten two steel plates together. There’s very little torque delivery until final tightening, which is done with a small fractional rotation of the fastener. Now fasten two pieces of soft or medium density wood together. As the fastener threads deeper into the wood, more and more effort is required to drive it further. For final tightening, the wood might also be compressed a little until the fastener is fully seated.
What’s the maximum weight you can lift? What’s the maximum weight you can lift slowly and with full control? The numbers are going to be different, right? The same is true for power tools.
Why is All This Important?
If you’re using a torque adapter, such as the one above, and measuring maximum torque in a soft joint type of application, but the tool’s max torque is described in terms of its maximum hard joint torque, there’s going to be a disagreement.
What does that disagreement mean? Well, if you’re comparing soft joint torque to hard joint torque, it means nothing.
The resulting torque measurements could potentially be used to compare different tools’ maximum stall torque for the same application. Meaning, if you make assumptions or fully understand the measurements, you could possibly use a torque adapter for comparing different tools’ capabilities. Torque adapters seem to be an imperfect way of doing that, but the error likely won’t be as large as improperly comparing measured soft joint specs against brands’ advertised hard joint specs.
In every example I have ever seen, tools’ maximum soft-joint torque specs are lower than hard-joint torque specs, and it makes sense why.
So, if you have a cordless drill that’s said to deliver 100 in-lbs of maximum torque, but you use a hand tool torque adapter to measure its max stall torque in wood as being 60 in-lbs, the two values should not be compared against each other.
Now, if you want to measure the maximum torque exertion of a tool, there are apparatuses for that, although they do tend to get rather pricey.
And, when testing a tool’s maximum torque delivery, you will often need a joint simulator, which is basically an adapter that behaves as if it were a hard of soft joint fastening task. A soft joint adapter, for instance, will often have a compressible spring that behaves in a similar manner as a long screw being driven into soft wood.
Just because test data might disagrees with advertised specs, that doesn’t mean anything is wrong or incorrect, it just means that the circumstances need to be carefully analyzed and understood. Sometimes test results might be off, or advertised specs could be inflated, or two sets of values simply cannot be equated due to very different test conditions.
Be Careful with Your Conclusions
Someone might watch a YouTube video, and then email me “see, brand specs are utter crap,” but it turns out that it’s simply a case of hard vs. soft joint measurements.
If a reviewer or tester measures max torque at 0 RPM, are they comparing it to a measurement taken under similar conditions, or a max torque at certain RPM under load? Are they refuting brands’ specs measurements, or simply reminding you of them?
When you start getting into data collection, things get really messy, and fast.
Data collection is actually pretty easy. Good data collection, and data that is repeatable and reliable – that’s trickier. And once you have data, understanding what it means is another challenge altogether.
As an aside, attaching two cordless drills together to see which motor burns out faster – that’s not science, that’s just done for entertainment.
The fact of that matter is that brands don’t often disclose the methodology they use in measuring tool performance or specifications. You don’t need to know this in order to validate or refute measurements such as torque specs, but it helps.
Measuring torque in the same exact way isn’t actually needed for independent comparisons, although it would be ideal, but it’s important if you want to compare your own data against brands’ specs.
I have seen some excellent qualitative comparisons, but not many where I could fully trust the quantitative data. Meaning, if an independent YouTube tester is drilling screws into wood with a torque adapter, you can compare the stall torques for different tools – under those specific conditions – but the actual numbers and test conditions usually aren’t controlled enough or tailored in the best way to be used as absolute maximum torque values.
Even if a hard joint is tested, are the fasteners perfectly clean, or are there residues that could act as lubricants, which could alter the torque profile? There are a lot of things to look out for.
Can a Torque Adapter be Used to Measure Max Torque Specs?
Maybe? Torque adapters like the one shown above are specifically designed and advertised for hand tool applications, and it’s unclear as to if or how measurement accuracy might change if used with a motorized tool. The Neiko is available in 3/8″, 1/2″, and 3/4″ drive, and there are a few 1/4″ drive models from other brands. Each size has its own torque range with different floor and ceiling measurement capabilities.
For power tool torque measurements, the CDI ETT-series testers mentioned by PTI are about as inexpensive as power tool-rated torque testing systems can go, with a ~$2000 price tag not including joint adapters. It cannot be used with impact tools, however, only hand tools or electronic drills and screwdrivers. A different brand, Imada, makes ~$2000 torque testers that can be used with impact tools.
It’s easy to see why some reviewers are using torque adapters to compare different tools’ capabilities, when proper testers cost 50X as much as the least expensive digital torque adapters.