A torque wrench with your own hands

Almost a torque wrench with their own hands

When tightening nuts and bolts (especially in the process of repairing suspension joints, intake manifold and other car components) it is necessary to observe strictly specified tightening torque. Detailed information on the permissible values can be easily found on the Internet.

By observing the exact tightening torque of nuts and bolts, the mating surfaces adhere more tightly and evenly to each other. It is for tightening with a certain force and uses a torque wrench, which comes in mechanical and semi-automatic.

It costs a lot, so there is no sense to buy a torque wrench just to use it a couple of times. Of course, if you have extra money, you can buy a torque wrench. However, if your main goal is to save money and make do with improvised means, in this case it is reasonable to make almost a torque wrench with your own hands.

The principle of operation of the tool

Semi-automatic torque wrenches resemble in shape and design an ordinary ratchet wrench, which is used for socket heads. The only significant difference from their “brethren” is the presence of a special ratchet mechanism that allows the built-in pinion to turn in two directions.

For example, it takes a relatively small effort to bring the tool handle back after a full turn. To tighten the nut, on the other hand, a little more force is required.

When the required value is reached, the ratchet gear simply begins to skip (a characteristic sound is heard), as a result of which the nut or bolt is no longer tightened. This eliminates the possibility that the threads will break.

Torque wrenches with a force rating scale do not have a torque limiter by default when the set point is reached. In this case, this torque must be controlled by yourself with a mechanical or electronic digital measuring scale.

A homemade near torque wrench, depending on the design, can work along the lines of the first and second options described above.

Why count Newtons and meters

Before you begin making a simple homemade torque wrench for tightening bolts and nuts, you will need to do some calculations. For example, in order to achieve a tightening torque of 10 N*m, it is necessary to apply a force equal to one kilogram of force to a lever or arm 1 meter long.

Except that in the conditions of the home workshop or garage, a one-meter lever is not the most practical and convenient option. Ideally, it is better to use a shoulder within the range of 20-50 cm. And in order to correctly calculate how much force should be applied to the lever to achieve the required tightening torque, you need to calculate the Newtons and meters.

However, it is not necessary to go into the maze of mathematical equations. The necessary values can be easily calculated in proportional ratio. That is, if you take as a basis that to get the torque of 10 N*m, you need to apply a force of 1 kg to a meter lever, it is similarly easy to calculate what force will have to be applied to the lever of a shorter length.

The shorter the lever used, the more force is required to tighten the bolt or nut – this is, so to speak, an axiom. For example, if you use a 50 cm long lever instead of a meter long one, you have to apply a force of 2 kg to get 10 N*m of torque.

If you use, for example, a lever 22 cm long, the force would be 4.5 kg. In other words, you need to divide the torque (10 N*m) by the length of the lever (in this case, 0.22 m) and multiply by 0.1. Using this simple formula, you can easily calculate the exact force required to tighten the nut.

Buy or Make?

During the process of doing maintenance works, almost every owner of a vehicle is faced with the fact that it is necessary to tighten the bolt or nut, applying a certain force, but a torque wrench is not handy. You can’t run to the store to buy an expensive tool, use it for 20-30 minutes and forget about it for a year.

Therefore the best option – to make a homemade torque wrench for tightening the nuts and bolts. And you can make a tool like a ratchet with a ratchet mechanism, as well as made by analogy with a simpler design – using regular hand scales.

Homemade torque wrench without a scale

This version of the homemade wrench does not have a scale, as on the factory torque wrench, but the torque on it can still be adjusted. This simple hand tool is used to apply the same force when tightening nuts and bolts. Thanks to a system that triggers at a certain load, it becomes clear that the right limit has been reached. About how to make a torque wrench with your own hands, read below.

This tool is very simple to make, while it can be much more reliable than the factory wrenches, and gives a lot of torque when tightening the nuts or bolts, thanks to the length of the handle. To make a homemade torque wrench without a scale yourself, you will need very simple and accessible materials:

• A piece of half-inch steel pipe;
• two 5 mm thick plates with 12 mm diameter holes;
• a long bolt with a nut of suitable diameter;
• one homemade thick-walled washer;
• a spring and a metal ball from a bearing.

To the steel half-inch tube weld “ears” made of metal plate thickness of 5 mm. Place a thick-walled washer between the plates and secure it with a steel “finger”.

Inside the tube install the pusher with the ball from the bearing (it is necessary to make a small hole equal to ½ of the ball diameter in it beforehand). After the pusher, install the spring and press it with a bolt and nut, which is welded to the end of the half-inch tube. Another recess for the ball must be made in the thickest washer itself.

In the last stage of the work to the washer will only have to weld a lever – for example, from a small piece of pipe. Note that the longer the lever, the less effort you will have to apply when tightening the nuts or bolts. A socket wrench is welded to the lever.

The force to be applied can easily be adjusted with the pressure bolt. The more the bolt is tightened, the more force will need to be applied when tightening. This is a practical homemade torque wrench without a scale that you can make with inexpensive materials.

Tightening with a hand scale

As an option, as a replacement for the factory or homemade torque wrench in the form of a ratchet, you can take an ordinary wrench or ring spanner. We attach to it a hand scale of “canter” or “changeless” type (or you can, for example, take one with a digital display), and tighten the bolt or nut. Also quite a working option at home, if there is nothing at hand at all.

To tighten the nuts or bolts with a certain force with the help of hand scales most often it will be enough the “dummy” for 20-30 kg and a piece of steel tube 50 cm long (but you can and less) with a suitable inner diameter – not less than 25-30 mm, so you can put it on the key. In the case where you need to tighten large moments, you need to pick up the appropriate scales.

What you will need for work:

1. A wrench (horn or ring spanner) on which a piece of steel pipe with a length of about 40-50 cm is put on;
2. A spring canter (hand scales) with a “limit” of about 20-30 kg. You can also use to make a dynamometer electronic scales.

Tightening process

To begin with, it is necessary to install a ring spanner or horn wrench on the bolt or nut, and for the other end we hook the hook of the hand scales. Having calculated in advance the necessary force, pull the ring of the scales, keeping 90 degrees, until the required value is reached.

Thus, even not having a torque wrench at hand in the garage or workshop, you can tighten the nut and bolt connection with the required force and the exact torque.

Self-made torque wrench: how to make your own hands

Every experienced car enthusiast or professional technician knows that many parts in the car require a special effort when tightening. Thus, if the nut will be transferred to a torque insufficient for its full tightening, it can loosen when moving, and, conversely, over tightening the fastener, it is possible to ensure deformation of the part.

That is why a torque wrench is one of the most important parts of every technician’s tool kit. However, it is quite expensive, and some craftsmen make the tool with their own hands.

Torque wrench

A torque wrench with your own hands

The torque wrench is a tool for the masters of service stations, designed primarily to ensure an even application of the load on a particular fastening element, it provides an even tightening of each bolt or nut.

The electronic or pointer scale on this product allows you to tighten parts to within tenths or even hundredths of a mm.

This is an expensive device, and if a person does not use a wrench daily, its purchase is not advisable. However, knowing thoroughly the principle of its operation, you can make it with your own hands at home.

At a closer look, the product represents an ordinary lever with a ratchet at the end, which does not allow a master to overdo the effort and simply scrolls idly, according to the pre-set parameters on the dynamometer.

The dynamometer is a simple spring mechanism that, when tensioned, causes the hand on the dial to deflect from the zero mark to the limit value set by the user.

Hidden in the tool head itself is a cogwheel that is driven when a wrench pin is hit, but when the desired torque in N*m is reached, the pinion pinion simply begins to pop off and the mechanical action on the pinion stops. This measuring tool records the value as the product of the force exerted by the user’s hand on the arm relative to the point where the wrench is attached to the jaw nut and the point where the load is applied.

At the base of the lever there is a rotating limiter, by means of which the craftsman sets the exact value of the required limit force before starting work.

Parts for the wrench with your own hands

Thus, having at hand some home appliances, as well as a little ingenuity and knowledge of elementary physics, any man can make a similar wrench without leaving home or garage, and the result will not differ much from the readings of the device purchased in the store.

Torque wrench without a scale: what to replace it with

To make a wrench easy to use and to be able to properly operate, the user needs to know a simple formula from school physics, namely that the torque of 10 N*m is the product of the weight of 1 kg, applied at a distance of one meter from the point. So, it is not difficult to guess that a lever of 0.5 m reaches this value with a force of 2 kg, 0.2 m – 5 kg, etc.

Based on these calculations, the craftsman should purchase or find the following parts to make the tool:

• The handle, which has square-shaped tips, and the length of the product should correspond to the above calculations in order to achieve a more accurate result.
• If it is not possible to cut the lever, you can always mark it with a marker or simply put on a tight clamp, which will be the starting point for applying load to the fastener.
• Instead of a dynamometer you can take the usual high-precision spring balance – a scale that shows the load in grams, depending on the strength of the tension. Experts advise to buy this instrument with a scale value of at least 100 grams and a limit of weighing up to 50 kilograms.

To make a torque wrench is enough to fix the changer on the handle at the place of the marked mark, put the nozzle on the opposite end of the lever and gently pull the scale until the scale shows the desired result, which will correspond to the achieved torque when tightening. To avoid confusion in the readings of the device, it is enough to spend 15 minutes and make a detailed table of dependence of the readings of the device, the length of the lever and the final force in N*m.

Electronic bezeman up to 50 kg

Professional tips for making a wrench

From the first time the tool may not work, and the measurement will not be correct. However, any experienced craftsman can give some detailed tips, following which every beginner will achieve the desired result.

For a more accurate measurement, it is better to buy a changer exactly with an electronic scale and a set weighing limit, because such a product will emit a sharp beep when the desired load is reached and will prevent the fastener from overtightening. This kind of changelessness has the same effect as a good indicator wrench with a pressure gauge.

If you do not have a lever or materials for one, you can use an ordinary wrench with an open-end wrench on one side and a ring spanner on the opposite side. However, the length-to-torque ratio should be calculated more carefully, as the arm size will probably be a fractional number.

For the best fixation of the changer to the lever, you should be especially careful about where you mount it. The best option is a carefully drilled through hole, exactly where the load is applied, and the instrument will never slip off the handle.

Working with a homemade torque wrench

Depending on the tension required, the craftsman may have several changers at once with different weighing limits, each of which should have its own table of load vs. arm and torque.

Since all the effort in determining the degree of tightening is applied only to the scales, it is necessary to ensure a comfortable grip on the handle, as 20-30 kg with a poor grip will not allow comfortable work with the device.

Active smartphone users can enter the above examples of calculations into the pre-downloaded application with all the results saved, and the master will always have the required force values at hand.

How to Measure Tightening

In order to correctly measure the tightening with a homemade device, a few simple rules must be followed:

• Assemble the device and put it in working condition – attach the bezmen to the handle, set it to zero, if possible – set the limit of weighing with an alarm, and at the end – put the necessary nozzle on the working body of the device or initially choose a horn wrench of suitable size.
• Put the spanner on the nut or bolt. The device will show the exact value only if the pairing with the fastener is made directly through the lever, and with the participation of one or more adapters and extensions when giving the result, an error of up to 5-8% is possible.
• Carefully pull the bezzer so that its position is strictly perpendicular to the axis of the lever and the load indicator is not distorted by decomposing into vectors.
• If normal force has been achieved, the instrument will confirm this with the measurement and the nut will not move. If, however, the tightening was not sufficient, the fastener will turn around its axis until the required torque is reached.

To prevent the bolt connection from failing, do not put an excessive load on the homemade dynamometer, and tighten only on the nominal values prescribed in the technical service manual for this or that part in the car. Otherwise, there is a risk of deformation of the factory product.

Re-tightening a bolt on a car wheel

Basic mistakes when making a wrench

Any high-precision tool can not be made completely without mistakes, since the craftsman does not have at hand any exact designs or drawings, and all this can lead to incorrect measurements and the breakdown of car parts later. However, many professionals have answers on this point as well, offering car owners a number of recommendations in order to minimize errors and inaccuracies, in particular:

• As a lever should not take a soft metal, which can easily bend when pressed, because the force applied to the changeless without observing orthogonality will not give the desired result, and the purpose of the device will be completely lost.
• You should not choose a cheap changeless scale, because the accuracy of its measurements is very questionable, and the spring quickly stretches and fails. So, as of December 2018, the cost of the scales should be around 400-500.0 rubles. This is not much compared to the price of the torque wrench itself – about 3-4 thousand rubles, and the low-quality component is better to change immediately.
• When attaching the nozzle to the nut, you need to take into account that it must be perpendicular to the axis of the lever, and otherwise the measurement will not work.
• Most of the changeless machines have only an informational function and do not limit the actions of the craftsman in any way, who can easily get distracted and overtighten the bolt without paying attention to the reading on the scale.

Thus, when using a homemade one, the foreman is much more responsible because the device may not have the automatic force-relief features of a commercial counterpart.

Service Station

A homemade device is best used to monitor bolt tension when in doubt. If it is necessary to control the tightening on any complex component part, the motorist should still go to the service station for diagnosis and repair, not to replace important components in your garage, because unauthorized intervention can be much more expensive than the money saved on the key.