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DewMan

Torque Wrench 101

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DewMan

In a thread earlier today the subject of torque wrenches came up and I figured I’d do a write up of basic information for those new to the subject.

Disclaimer: I am by no means an expert on tools but I have been using mechanic’s tools since I was old enough to sit on the fender with my feet in the wheel wells helping my dad change spark plugs & oil on the family vehicles. I also spent a couple years back in the ‘80s learning motorcycle mechanics at the local Vo-Tech school as well as working for a time in a local motorcycle shop.

If you notice any missing, incomplete or incorrect information below please let me know and I’ll update accordingly.

                                                                                                              Torque wrench 101

This will cover the selection, care, use & feeding of torque wrenches.

Purpose of a torque wrench:

The purpose of a torque wrench is to ensure that fasteners are tightened to a proper level to help ensure that they will hold securely and not vibrate loose. They also ensuring that fasteners are not too tight to prevent damage to mating surfaces or strip threads from over tightening.

 

Selecting the proper Torque Wrench:

Torque wrenches come in many sizes, shapes, styles, price and torque ranges.

There are 3 main types of torque wrench styles, beam, click, and digital. There are pros and cons of all three styles. I’ll try to cover the basics of each below:

Defection/Beam Style:

1869376798_beamtype.jpg.57bdc0fe6e6ca02a84cfef8f39b1047d.jpg

This style is normally the more economical and uses a mechanical pointer to indicate the amount of torque being applied that is read on a plate with a predetermined set of marks that needs to be read while applying pressure to the fastener.  Variants can use a dial gauge instead of a pointer arm.

dial.jpg.a0de4bc33c3d5307360e2822a428f62d.jpg

Pros:

This style is normally more economical at least for the basic beam style. The ones with dials are normally more expensive.

Simplest design. Fewer things that can go wrong.

No batteries required

Cons:

Requires more room to use due to the amount of space needed for the tool itself as well needing to view gauge while using.

Not for low light situations due to requirement to view gauge while using.

Harder to be accurate due to viewing needing to be at the correct angle.

Non-ratcheting meaning slower to use in most cases due to having to reposition the wrench as you tighten.

 

Click Style:

click_type.jpg.a404e6016befde86bb0da114629a2806.jpg

A Click style torque wrench uses a preset of the wanted torque limit that gives an audible and physically felt “click” when the dialed-up limit is reached. Most come with both ft-lbs & Nm indicators. Most come in a shape very much like thick handled ratchet. The requested torque value is set by twisting the lockable handle to either raise or lower the setting.

Alternately There are click style torque screwdrivers shaped more like a ratcheting screwdriver but still function the same as the ratchet style. They are normally used for quite small torque values. I have one that measures from 10-50 In-lbs. These are used for screws more often than bolts. They are popular in hobbies requiring smaller torque values such as in gunsmithing.

torque_driver.jpg.f54ad3c6faab9a27fd9837e3a5a7b82e.jpg

Pros:

Generally more accurate than a beam style since a specific torque value can be set.

More compact allowing it to get into tighter locations.

Easier low/no light settings use.

No batteries required.

Ratcheting action speeds repositioning unlike the beam style.

Physically felt “break/click” when set torque value is reached so works well in a loud environment.

Cons:

More mechanically complex than a beam style making it somewhat less durable than a beam style.

Requires infrequent recalibration by professionals for best long-term accuracy which will cost money and loss of use of the tool while waiting for the recalibration to be completed. That said, for home use a click style torque wrench can go many years between recalibrations depending on the amount of use it gets.

Generally more expensive than a comparable beam style.

Digital Style:

digital.jpg.874dd551a8217c4982b86766ff8b2dd3.jpg

 

Alternatively there are cube shaped Digital torque adapters that can be used on your existing ratchet/breaker bar if so desired.

digital_adapter.jpg.8bff566deb9b72242087233f667e6704.jpg

 

A digital style torque wrench works in a similar fashion and has the same general physical layout as the Click style. The requested torque value and scale used is set on an LCD screen via buttons. When the specified torque value is reached it will use an audible alert to let you know. They are generally more accurate and faster to set the torque value but are generally more expensive than either of the other styles. Older generations of digital torque wrenches were not always robust or as accurate as the digital torque wrenches of today.

Pros:

Ratcheting Function

Quickly set preferred scale and torque value.

Audible tone when set value is reached.

Memory functions.

Models available with backlit displays are easier to read making it good for low light environments.

Can be generally recalibrated at home following instructions included with the wrench.

Cons:

No felt break when the preset value is reached like a “click” style so not as useful in a noisy environment.

Requires batteries.

Generally, more expensive than click and beam styles but getting more economical as time passes.

Common to all styles:

All styles come in a wide array of price points. In general you get what you pay for. A quality torque wrench should last you a lifetime and hold its accuracy longer. So, consider spending a little more if you can. A higher price will generally get you finer teeth on the ratchet mechanisms, and more robust internals that will be more accurate and hold calibration longer as well as smoother operation in general when setting the torque value.

The extreme ends of a wrench’s stated working range is where a wrench will be the least accurate. So choose one where the most frequently needed torque values are more towards the center of the working range for maximum accuracy. As an example, I have three torque wrenches that have the following ranges to handle my needs:

A 1/4in hex drive click style torque bit driver with a range of 10-50in-lbs (0-6Nm)

A 3/8in drive click style with a range of 5-75ft-lbs (7-101Nm)

A 1/2in drive click style with a range of 20-150ft-lbs (27-203Nm)

General usage information:

Note that the actual amount of torque applied, for a given setting, will vary depending on whether the threads are lubricated or dry. If using a vehicle manual’s specified torque setting note whether the torque value is for a wet or dry fastener.

Never use a torque wrench to loosen a fastener. That’s the job of your standard ratchet/wrench/breaker bar. The torque wrenches with reversible ratchets are for tightening fasteners with reverse threads. Using a torque wrench to loosen a fastener adds unwarranted stress, wear and tear.

Always remember that the torque wrench is a precision tool. Handle it with care. Store it in the case it came with when applicable. Protect it from the elements.

General guidelines to torque wrench use:

Basic steps for use:

1) After selecting a torque wrench of the required range, either note on the beam scale or dial in/ adjust to the correct torque setting needed following the tool manual’s instructions.

2) Choose the proper sized socket for the fastener.  Preferably use a six-side socket instead of a twelve-sided socket to lessen the likelihood of rounding the corners of the bolt/nut under high torque settings. If an extension is needed use the shortest one that will do the job. This will lessen the likelihood of the socket slipping off the bolt/nut.

3) Use one hand to stabilize the head of the wrench while using the other hand to apply slow steady pressure to the handle of the wrench until the requested torque value is reached.

4) Release the pressure applied to the wrench. And then repeat step 3 above. This step is optional. There is never-ending debate on the usefulness of it.

5) In the case of a Click style torque wrench, dial the torque value back down to its lowest setting after use to remove strain from the internal mechanisms. This will prepare the wrench for storage.

 

If you're still reading, Thanks for taking the time. It's appreciated. If you have any questions we'll try to help if we can.

Again if you see anything that needs corrected, updated or added please don't be shy.

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DewMan
 
Just shut up and ride.

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Zephyr
Posted (edited)

Only thing that I would change is to use a breaker bar to loosen, never a ratchet or wrench whenever possible.  They are cheap and will save you from busting up your mechanical tools and likely your knuckles as well.  Otherwise the write-up and usage are spot on from my experience.  The one point you make that I would highlight to the novice is to make sure to set the "click style" back to the lowest marked setting (ie: 5lbs for a 5-75lb range wrench) when done using. 👍

Edited by Zephyr
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Beemer

Nice write up, I think it deserves one of these bad boys next to your name …. DewMan 💫

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Beemer

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bornagainbiker
40 minutes ago, Beemer said:

Nice write up, I think it deserves one of these bad boys next to your name …. DewMan 💫

I agree:

 

1113730.gif.033a1d12e69a15ff7f815a45db93683c.gif

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sansnombre

Just an add on the "beam style" type: how you hold the wrench is very important.

As you state, you must support the head of the unit as you twist, pushing with the same force that you pull with on your other hand, in the exact opposite direction. Sounds more complicated than it is, but you're cancelling out the net forces and just having a clean torque at the head to measure with - a pure rotation.

But, more importantly, this handle floats and pivots in the center - make sure you keep the handle floating throughout the the pull. It should not touch the beam at either end of the floating handle, so you might have to rotate it slightly to keep it floating on it's pivot. What you're doing is standardizing and maintaining the moment arm length. You can shorten or lengthen it by a few inches by allowing the ends to touch.

Torque wrench anecdote: I occasionally work in a bike/ski shop as well, and we have a very long torque wrench that is used to test-release bindings. I remember a gal who worked in the shop, who was actually quite capable, but she commented about always getting under torque on her settings, and having to increase the release settings. I thought that odd and asked her to show me her style. Sure enough, she was grasping the handle mid-way with her second hand, shortening the effective moment arm and screwing up the reading. The torque wrench was at the end of the arm, so she was pulling on its handle and also on the shaft that was the moment arm.

Anyway, good write-up. Thanks.

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timjh

You should maybe add some bold typeface in Basic Steps #3 about slow steady pressure.  I don't know how many times I've seen folks jerk the clicker.

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shinyribs
3 hours ago, sansnombre said:

Just an add on the "beam style" type: how you hold the wrench is very important.

As you state, you must support the head of the unit as you twist, pushing with the same force that you pull with on your other hand, in the exact opposite direction. Sounds more complicated than it is, but you're cancelling out the net forces and just having a clean torque at the head to measure with - a pure rotation.

But, more importantly, this handle floats and pivots in the center - make sure you keep the handle floating throughout the the pull. It should not touch the beam at either end of the floating handle, so you might have to rotate it slightly to keep it floating on it's pivot. What you're doing is standardizing and maintaining the moment arm length. You can shorten or lengthen it by a few inches by allowing the ends to touch.

 

Very important and often overlooked point!

The beauty of a beam wrench is that your accuracy is based on a known quantity ( the flex of the beam ), so there's no worry of clicker springs corroding/losing tension, solidified internal grease, or pressure sensors going wonky. For production lines, clickers and electronic torque wrenches are far easier to use accurately and quickly when building things day in and day out in a factory. Assembly lines will occasionally have their tools calibrated and life is good.

For the home mechanic this production speed isn't needed.  I've owned all three types (gave my electronic to a buddy) and always grab my beam wrench. I'm old school and I trust it lol.

 

Personal preference aside, great post, @DewMan 

 

 

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mt7fan

Have the click ones, two for different ranges. When I used them for the first time was expecting click-click-click 😂

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Beemer
On ‎4‎/‎3‎/‎2019 at 9:16 AM, bornagainbiker said:

I agree:

 

1113730.gif.033a1d12e69a15ff7f815a45db93683c.gif

Why stop at that? 

ba-awesome-colorful-fireworks-animated-g Ok, so that's a bit much, hee-hee!


Beemer

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bornagainbiker
3 hours ago, Beemer said:

Why stop at that? 

ba-awesome-colorful-fireworks-animated-g Ok, so that's a bit much, hee-hee!

I like it--it's subtle LOL.

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Give Respect To Get Respect

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