The first cylindrical drill, which became the prototype of the modern “crown”, was patented in 1874 by Benjamin Forstner and received a name in honor of its creator. After many years, the tool has been modified and improved, but its principle of operation has remained the same. A feature of such a device is that it has three cutting elements: a guide segment in the form of a central pointed drill, a sharp edge for cutting the contour of the hole of a given diameter and a pair of internal cutters (rotating planers). They are designed to take material deep into the workpiece.
Features of use
The Forstner drill was conceived specifically in order to use it to form flat-bottomed holes (not through) in wood of any hardness. With the advent of new materials based on natural wood (MDF, Fiberboard, Chipboard), the use of cylindrical fixtures has become more frequent.
Blind technological holes on workpieces are most often formed in the carpentry and furniture industry, where wood is the main material, and are connecting grooves or recesses for mounting loops, locks and any other fittings. The given depth and size of the hole, as well as its neatly defined neat contours, make it possible to install various mechanisms that require maximum accuracy.
Thanks to its special design, the Forstner drill allows you to leave the bottom of the workpiece intact up to 1-2 mm deep. The carpentry tools are constantly being upgraded, but there are still nothing to replace Forstner drills. Standard screw specimens with a pointed conical end do not provide material sampling in the plane, and the crown does not accurately and cleanly process the side surfaces. Today, the best products are presented in a wide assortment by a number of well-known brands such as PROJAHN (Proyan), Bosch, Enkor, Metabo, DeWALT, etc.
Design
As mentioned earlier, the cutting part of the Forstner drill consists of two main cutting edges and a pointed centering pin. An elective cutter is located on the jumper of the fixture, and a cutting torch is located on its edges. After deepening into the material, the cutting edge serves as a kind of limiter, which helps to hold the tool in the seat, thereby observing the diameter of the cut.
The design features of the drill provide for the discharge of chips to the top, which avoids jamming the tool, so even a person without special skills can do such work with his own hands. Cuts around the circumference of the selected edge are formed for automatic sharpening of a blunt tool, however, if necessary, it can also be corrected manually using a file with a diamond coating or a fine notch.
High-quality cylindrical tools are made of high-speed steel, which withstands moderate heating of the working edge and does not deform. Many well-known manufacturers (Bosch, DeWALT, Enkor, PROJAHN, Zubr, etc.) additionally supply Forstner drills with reinforcing pads, which are used in the manufacture of carbide material. The Fostner drill on wood with threaded devices on the edge reduces the heating of the working area and increases productivity while maintaining high quality cuts. Interchangeable knives can be operated with a drill, securing the hexagonal shank cutter in a standard chuck. For example, a tool with a diameter of 15 mm to 26 mm is equipped with a shank of 8 mm. If the diameter of the working zone of the drill is 28–60 mm, then a similar parameter of its shank increases to 10 mm.
Work rules
The location of the tool is provided with a centering tip, which must be placed at the intended point before cutting begins. Then, with a force, the drill is pressed into the workpiece until its cutting edge touches the workpiece. The Forstner drill can operate at speeds from 800 to 1800 rpm.
Each millimeter added to the diameter of the working area should lead to a decrease in sawing speed, otherwise overheating of the edges cannot be avoided, and high speeds increase the risk of drill breakdowns from a given position. The Forstner drill with limiter guarantees safe sawing and increases working comfort. This type of product will stop the process and form a recess of the required depth.
When processing thin-walled material with your own hands, in order to avoid the centering element coming out, it is better to use two tools of the same diameter. For example, these will be Forstner drills for wood 16 mm. In this case, drilling begins with a conventional sample, and ends with a drill with a sharpened tip, while it does not fall off the seat due to the lateral edges being held in the groove.
Main advantages
The Forstner drill, in contrast to joinery products of a similar purpose, has several advantageous features, among which I would especially like to note the cleanliness of processing and reliable fixation on the surface. The side walls of the workpiece are cut off qualitatively due to the fact that the fibers are filed along the contour before coming into contact with the main cutter, so the wood is not covered with chips and burrs outside the diameter being machined, and the hole is neat.
Recommendations
When purchasing a drill for a tree of this type, it is necessary to determine in advance the nature of future work (professional, household). If you need to drill one or two holes, it makes no sense to buy a whole set of expensive nozzles, and it would be more expedient to limit yourself to one cutting part of the required diameter. For example, you need a Forstner cutter of 35 mm and 30 mm, and the set contains samples of 12 mm, 19 mm, 20 mm, 22 mm and others. If you do not plan to use them in the future, then why overpay? And vice versa, if you are assembling various furniture, and cutters of all sizes will be required in the work, then it is better to purchase them with a set from one manufacturer you trust.
Drill | Size mm | Price, rub |
ENCOR 19166 | 35 | 245 |
PRACTICE 036-834 | 35 | 300 |
STAYER MASTER 29985-30 | 30x8 | 371 |
ENCOR 19172 | 15 | 245 |
ENCOR 19174 | 25 | 315 |
MATRIX 70490 | 35 | 262 |
KWB 706065 | 16 | 118 |
Bosch 2608577016 | 35 | 1 995 |
For regular use, craftsmen recommend purchasing cutting elements that have established themselves as a high-quality and reliable tool. With their help, the wood will be processed correctly.For experienced joiners, Bosch Forstner drills are especially popular. Their price is in the optimal ratio with quality. Metabo, PROJAHN and Encore drills demonstrate excellent technical and operational characteristics. They manage to drill wood material of various thicknesses and degrees of hardness without any problems. The video shows the cutting tool Encore.