Drill a round hole in the material of any density according to the strength of each. But what if a square hole is needed? It would seem improbable to many to drill a square in soft, supple wood or in a piece of durable metal. The Watts drill copes with this difficult task.
History with geometry
Today, masters drill a round hole of the corresponding diameter to obtain a square hole and grind corners with special tools. Much faster and easier to perform this operation, you can "Watts" square drill. The basis of its construction is the Röhlo triangle - a figure formed by the intersection of three identical circles. The radii of these circles are equal to the side of the regular triangle, and its vertices are the centers of the circles.
The figure bears the name of the German scientist Franz Röhlo, as he was the first to study in detail the properties of the resulting triangle and apply them in his inventions. However, the geometry of the Ryelo triangle was used in the form of windows during the construction of the Church of Our Lady in Bruges in the 13th century. At the beginning of the 16th century, Leonardo Da Vinci depicted a “map of the world” on four Ryelo triangles. This figure is found in his manuscripts and the Madrid Code. In the XVIII century, the triangle of equal arcs of three circles was demonstrated by the famous mathematician Leonard Euler. In 1916, an English engineer working in the USA, Harry Watts, developed and patented a square hole milling cutter in a floating chuck.
Watts Drill Features
A unique invention allows to obtain holes of almost the correct shape: the corners of the square are rounded with a small radius. The raw area of the square hole does not exceed 2%. A distinctive feature of the Watts triangular drill is that, when rotated, its center describes arched ellipsoidal curves, and does not stand still like a traditional spiral drill. The vertices of the triangle in this movement draw a square with parallel perfectly even sides. The chuck for such a cutter has an original, non-obstructing movement design.
Build Drill for Square Holes
When drilling holes , chips are formed, and the cutter must have grooves for its removal. The profile of the working part of the Watts drill is a Ryelo triangle with three halves of ellipses cut from it.
This design with grooves for chip removal solves 3 problems simultaneously:
- The inertia of the drill is reduced.
- Spindle load is reduced.
- Increases the ability of the drill to cut.
Usually square holes are made on turning or milling broaching machines. The drill for square holes is fixed with a special adapter for the machine chuck. For domestic use of the square cutter, manufacturers offer overhead frames that connect to the universal joint chuck and give the cutting tool eccentric movements. The depth of the hole corresponds to the thickness of the frame.
Steel for drill
Today, high-quality drills that work quickly and for a long time are made from high-alloy steel grades. In their composition, such alloys contain more than 10% alloying additives, such as tungsten, chromium, vanadium and molybdenum. Different percentages of elements and various methods of hardening steel form alloys that differ in level of hardness, toughness, impact resistance upon impact, cost and other characteristics.
Drills for metal are the most widely used consumables for electrical equipment for several reasons:
- Metal products most often need holes for fastening: threaded connections, rivets and other types of connections.
- Drills for metal can also be used when working with softer materials, such as wood.
- The production technology of this type of product is similar to the principles for the production of drills for various applications.
In Russia and many other countries, drills made of high-speed steel grade P6M5, which includes tungsten and molybdenum, are in greatest demand. The strength and price of products significantly increases when cobalt is added to the alloy or coated with drills by cooling titanium-nitride spraying.
Types of drills for metal products
Drills for metal are used for making holes in products made of bronze, cast iron, copper, steel of various grades, cermets and other materials. High-strength products with the addition of cobalt are used for drilling viscous difficult-to-work steel. When working with twist drills, the chips are diverted along two longitudinal grooves. According to the shape of the tail, such tools are divided into three types:
The drill bit for metal with a tapered shank is inserted directly into the machine when used. For hexagonal and cylindrical shanks, a special cartridge is required.
Quality definitions by color
The quality of a drill for any material is determined primarily by its color:
- Black tools have increased wear resistance, as at the final stage of manufacture they are steamed.
- Heat-treated products do not have internal stress, are highly resistant to high temperatures and are not deformed when working with carbide steels. These drills have a slightly golden hue.
- The highest quality and durable have a bright golden color. They are coated with friction-reducing titanium nitride.
- Conventional raw gray drills have a minimum life and the lowest price.
Size range
The working dimensions of metal drills are represented by modern manufacturers in a wide range. GOST provides for the separation of such products into types in accordance with certain sizes.
Drills for metal are divided into several categories:
| Series | Short | Elongated | Long |
| diameter mm | 0.3-20 | 0.3-20 | 1-20 |
length mm | 20-131 | 19-205 | 56-254 |
GOST 4010-77, 886-77 and 10902-77 regulate the classification of drill bits by length and diameter.
How to choose a drill for glass or ceramics
Professional craftsmen in their collection have drills for every material: brick and concrete, metal and plastic, diamond drill bits for glass and ceramics. Glass is an extremely capricious material and requires the use of a high-quality and durable drill. Glass and ceramic surfaces can be machined with diamond-coated drill bits at the working end. The quality of such products is determined by the method of their manufacture. The thinnest and most inexpensive drills are made by a galvanic method. Stronger tools are made in powder form. They are distinguished by durability and stability. Relatively inexpensive high-strength drills with increased abrasiveness are produced by the modern vacuum method.
To drill a hole in a glass surface, you must have good skills. This long and painstaking process is carried out smoothly and slowly at maximum speed without pressing only with a diamond drill mounted strictly vertically. The hole must be constantly moistened with water for cooling. This action is more like scratching a hole with diamond grains.
If you have at hand the necessary tools and drills of the right size, any repairs will go quickly and efficiently.