Choosing a gun drill

To make through and blind holes of great depth, so-called gun and gun drills are used. The holes made with this type of cutting tool are used in various types of parts, the length of which is quite large. For example, it can be a crankshaft for a particular purpose or a spindle. A conventional drill is not suitable for such tasks, therefore gun and gun drills are in demand in a certain segment of industrial production. Let us consider in more detail the features of a gun drill, cannon and other types, GOST and selection criteria.

If the length of the hole to be drilled is equal to five diameters of the cutting tool, then such a hole can be considered deep. Making deep and precise holes is a complex procedure that is characterized by high labor intensity and high professionalism of the operator. In the process of drilling, the cutting tool is cooled with a special liquid supplied to the working area of ​​the drill under pressure.

Gun drill for precise deep hole drilling it is important to position it correctly, relative to the working surface. To facilitate this process, a so-called jig bushing is used, it does not allow the cutting tool to deviate during operation. If there is no such sleeve, you can get out of the situation by first drilling a hole with a smaller diameter, and then expanding it with a different drill number to the required dimensions.

Gun boring tools make made of high strength steel alloy... It is noteworthy that such a cutting tool has a rotational speed 10 times faster than the speed of a conventional drill used for drilling shallow holes. The cutting tool is used to make holes in pumping units, in the nozzle body or connecting rod.

When working with a long tool, difficulties often arise associated with the removal of chips spent during the drilling process, therefore There is always a risk that the drill will run off the specified drilling path. Another feature of this tool is that it cannot be rotated at maximum speed, if the cutting tool is not immersed in the cavity of the workpiece being processed. Such an oversight leads to the fact that the working part of the cutting tool is displaced from the predetermined path necessary for accurate drilling.

There are the following types of cutting tools that are used to make deep and very precise holes:

• cannon - there is a V-shaped groove on the working part of the tool; it is necessary in order to remove waste metal chips from the hole;
• ejector - this tool is used for machines in which the cutting element is located in the horizontal direction;
• rifle - a variant that is equipped with carbide steel inserts, which are located on the intermediate and main cutting inserts;
• rifle - with cutting parts and surfaces made of steel and hard alloys;
• rifle - in which carbide cutting inserts are fixed to the body by soldering;
• spiral - having a shank, which is presented in the form of a cylindrical structure.

During operation, the drill heats up, you can cool it by supplying cutting fluid to a special space located inside the working part of the drill. Gun and gun drills with carbide cutting inserts have a cone-shaped working shank. This shape guides the cutting tool more precisely into the drilling area.

Dimensional parameters and technical characteristics of rifle and cannon drilling tools regulated by GOST standards, according to which these drills belong to the long series. The use of the drill is possible only on a special machine designed for deep drilling. When choosing a drill design, you need to take into account the required hole parameters - its diameter and length. For the high-quality performance of the task, the feed rate of the drill, as well as the type of its tail, are of great importance.

The main recommendations to consider when choosing a drilling tool are as follows:

• when making a hole, the length of which will be more than 400 mm, it is recommended to use 2 drills with different dimensions; first you need to use a tool whose size is 9.95 by 800 mm, and then the hole is expanded with a drill, the size of which is slightly larger and is 10 by 400 mm;
• if the metal produces a long type of chip during drilling, you need to choose a cutting tool that has long and polished grooves for its retraction;
• if it is required to process soft metal alloys, for example, aluminum, then a cutting tool should be used, the design of which provides for one cutting blade sharpened at an angle of 180 °;
• the content of the lubricant in the coolant must be at the level at least 10% of the total volume of this composition;
• if soft material is processed, then it is necessary to reach the maximum speed of the drill in stages and this must be done in 3 steps; in addition, the hole is also made in stages - first, a pilot drilling is made with a tool of a smaller diameter, and then the hole is expanded with a drill of the required size;
• when changing one drill diameter to another size, the rotation of the tool can be stopped by switching on for 1–2 seconds the high-pressure feed of the lubricant-cooling compound; after the hole is made according to the specified parameters, the drill is turned off, ceasing to supply a cooling compound to its hole.

You need to start work at the minimum rotational speeds of the drill, while it is important to ensure the supply of cutting fluid for it from the very beginning.

How to drill deep holes with HAMMOND gun drills, see below.