An essential fixing tool, the lag screw, whose mission is to support a load, is a variant of a screw. It is renowned for its strength and reliability and is mainly used in the installation of heavy structures.
A lag screw, what is it? Definition
Screws are characterized by a number of elements including the shape of the head, the diameter, the type of thread, the material or its length. If, at first glance, they all look the same, the screws come in several types. Lag screws are among the most used. Also called hexagonal head screws because of their shape, they are distinguished by their threaded body, a thread that does not touch the part located under the head. This tapered point will allow it to sink more easily with a few hammer blows and to grip the wood fibers more effectively.
In general, lag bolts are used to anchor wood or metal to wood. They replace straight screw nuts in certain hard-to-reach areas. Namely, the deeper the lag bolts are inserted into the wood, the more their resistance increases. In terms of dimensions, their diameter varies from 5 to 2 mm and their length from 25 to 400 mm.
Historically, the lag screw is not a new tool in itself. The writings tell that he was made famous in the United States at the time of the construction of the railroads by the First transcontinental rail road in the 19th century.
Now, it has become a must in DIY and construction work and is mainly used for fixing wooden rails or carpentry.
The good quality of lag screw
The quality of the lag screw plays a crucial role in the solidity of your structure. Entry-level lag bolts can damage your bracket and you will need to drill to remove it.
In this sense, you must pay attention to certain criteria before making your choice. Note that a good quality lag screw is usually made of stainless steel or zinc. The advantage of zinc-plated screws is that they resist corrosion well. Those in stainless steel are also very resistant and as their name suggests, are stainless.
When choosing your lag bolts, you should also pay extra attention to the treatment received by the screws. Those called “phosphated VBA” are not recommended, because they can flake during use and above all, can cause corrosion. The screw head is another factor of choice. To be able to tighten strongly without them being altered, it is advisable to privilege the heads comprising very solid imprints.
How to use the lag screw
The mode of use of the lag screw is a little particular. The wooden support on which it will be fixed must be pre-drilled beforehand. It is important to ensure that the diameter of the hole is equal to the diameter of the lag screw. The part to be fixed must not be thicker than the length of the smooth part of the screw. This smooth segment contributes to the flexibility of the binding and provides better compression during assembly. In case you are working on a hard and dense support, it is better to apply a little grease to the screw before fixing it, to avoid possible problems of deformation or overheating. Finally, choose a pipe wrench or a spanner to make the fixing.