How to knit rebar correctly: hooks, guns and knitting wire

Recommendation points

• Why knitting, not welding
• What to use for knitting
• Hand Tools and Techniques
• Using automatic knitting guns
• Screed, floor or foundation – the subtleties of reinforcement of different concrete products

Looking at how deftly and quickly the reinforcement bars tie the reinforcing cages, one wonders: is this craft comprehensible to the layman, and how long does it take to fill his hand? What tools and wire to use and how to correctly construct reinforcing structures are discussed in detail in this material.

Why knitting, not welding

Arc welding has always been considered the traditional method of joining metal products, as the most versatile and providing maximum strength.

However, in the realities of construction work, attracting a welder for the construction of reinforcing structures is a waste of the budget. In addition, welding is not suitable for working with prestressed fittings, it is absolutely immobile and inconvenient for assembling products on site..

It would be a misconception that welding changes the physicochemical properties of the reinforcement to a critical extent. At least this is not true for most popular brands like A500C (C – weldable), it’s just that this method is not distinguished by high speed and convenience.

However, later you will make sure that it is more convenient to weld the fragments of the frames at an equipped workplace, and then collect a reinforcing structure from them. For an experienced welder, it will not be a problem to neatly grab the structural reinforcement to the working one, just as it will not be a problem to connect shoulder straps of reinforcement structures with an overlap of six diameters with double-sided and ten – with one-sided welding of a seam.

What to use for knitting

And yet knitting is the fastest and most convenient way to connect reinforcement knots. Strength requirements for such connections are purely symbolic: a bundle of distribution elements that are not involved in the work is performed to give the frame the correct shape and should only hold the rods in the right position during concrete pouring and its vibration shrinkage.

The elements of the working and anchor reinforcement are fastened together in the total mass of concrete products due to friction forces. The task of ligating these places is to provide the connected frame with the strength necessary for transportation and positioning during installation and movement of workers along the reinforcement. The second task is to keep the reinforcement lines aligned..

Hot rolled annealed wire with a low carbon content according to GOST 3282–74 is considered the most suitable for knitting. The optimum thickness for a bundle of structural reinforcement is 1.2 mm, for working and anchor reinforcement – up to 2.5 mm. Well suited for tying burned-out steel cord. You can also use carbon wire, having previously set it in the oven or on the fire for greater softness and ease of twisting..

It is easier to cut a wire of 30–35 cm with a grinder, having previously wrapped the coil with tape in 2–3 places. You can even purchase spring connectors or ready-made wire for knitting with loops at the ends, it is a pleasure to work with them..

Nylon tie-down clamps, otherwise called tie-downs, are becoming increasingly popular. They are very durable and allow you to work at a higher speed, but for a good tightening you need to use a special gun. You can also use 2mm PET tape cut from plastic bottles and then heat the assemblies with a gas lamp. When using plastic fasteners, they need to wrap the joint crosswise.

Hand Tools and Techniques

Today there are three main varieties of hand knitting tools and the first of them is homemade crochet hooks made of 6-8 mm wire. There is nothing tricky in the device, only the axis of the handle is offset from the knot knot by 70-100 mm, and the tip is conically sharpened for ease of extraction.

More advanced commercial items have a polished hook of the same shape, but the handle is fitted with a bearing. It is this tool that is considered the most useful in real construction conditions. The speed of working with it is maximum, convenience is at a height, besides, such hooks are not at all expensive. Nevertheless, try not to skimp on an already cheap tool: cheap products sin with low quality bearings, and their handles are not the most comfortable..

Both types of wire can be tied with ease. You need to work with gloves, otherwise calluses and injuries are inevitable. We fold the piece of wire in half, then bend it from above into opposite corners of the crosshair of the reinforcement. At the bottom, the wire unfolds and the ends are brought to the top through the other two corners.

The loop and two tails must be crossed with your fingers once in an arbitrary place. Then a hook is threaded into the loop, on the edge of which the tails of the wire are bent. A few turns and the loop is tightened. If you try, do not be too lazy to practice for half an hour, experimenting with tension and knitting technique. You will probably want to use a cordless screwdriver with the hook in the chuck.

It is useful to see the reinforcement knitting process once in the video in order to understand the intricacies of this process:

Separately, it should be said about the so-called semi-automatic hooks. They have a ratchet screw inside, so there is no need to twist the handle, it is enough to pull it towards you several times. These expensive “toys” are not designed to perform a large amount of work, the helical groove is eaten after three or four hundred tightened loops, and more reliable tools are very, very expensive. And yet, if you are tightly engaged in viscous reinforcement, such a thing should be kept close at hand: suddenly you forget to bandage in a hard-to-reach place.

Using automatic knitting guns

Among all kinds of power tools, there are models for knitting fittings. The principle of their operation is simple: the wire is guided along a curved groove, making two or three turns around the crosshairs of the rods. Then the collet is turned on and both tails are twisted with an adjustable force so that the knot does not break.

The tool is good, despite the overestimated wire consumption, but it has a number of disadvantages. First, the price of such a tool fluctuates around 1000 Euro per copy. Add to this that batteries have a service life of up to five years, then it will be difficult for them to find such a specific replacement..

The pistol is also not always convenient, often they cannot crawl inside the frame. Such equipment justifies itself either with large volumes of work, when up to ten tons of reinforcement are knitted per shift, or when tying thick rods with thick wire, where significant effort is needed. Can be useful for bench assembly of frame modules, but MIG-MAG welding can be used as well (inverter and wire cost about the same).

The best option would be to rent a gun for tying reinforcement, if there is a shop nearby that provides such a service. The key factor will be the speed of the work, if you need to complete everything in one day, then the rental price may be proportionate to this desire. You can get used to working with a pistol in a few minutes by practicing on separate segments of the fittings.

Screed, floor or foundation – the subtleties of reinforcement of different concrete products

Before you rush into battle, study the concept of reinforcement anchoring in detail. This science gives an idea of ​​how to correlate linear loads in reinforced concrete products of complex shapes by creating additional connections.

In addition to the shape of the intermediate elements, the length of the overlap on the joints is important; it can vary from 30 to almost 80 rod diameters, depending on the type of reinforcement, load and purpose of the product. Do not forget about protective layers – the minimum thickness of concrete between the steel reinforcement and the outer surface – these data are also strictly standardized.

For floors and slabs, at least two rows of mesh are knitted. Each intersection is connected on rows 1 and 2 along the perimeter of the frame, and inside – in a checkerboard pattern. When knitting ceilings, do not throw the torn edges of the wire into the formwork, it is from this that rusty spots appear on the ceilings.

Tape and block elements with a transverse load are reinforced with case structures, where the distribution fittings are made with rectangular clamps that encircle the rods of the working fittings from the outside.

It is more difficult with the reinforcement of columns and pillars. Most often, sleeve-threaded connections are involved in them, ensuring full alignment and high-quality transfer of the load between the working fittings.