Abstract

In turning hardened steel, polycrystalline cubic boron nitride (cBN) compacts are widely used, due to their higher hardness and higher thermal conductivity. However, in milling hardened steel, fracture of cBN cutting tools readily occurs because they have poor fracture toughness. Therefore, coated cemented tungsten carbide tools, which have good fracture toughness and wear resistance, are generally widely used.

In this study, hardened steel (ASTM D2, JIS SKD11, 60HRC) was milled with three physical vapor deposition (PVD)-coated cemented tungsten carbide end mill cutters in order to determine effective tool materials for cutting hardened steel at high cutting speeds.

The coating films used  were (Ti,W)N/(Ti,W,Si)N and (Ti,W)N/(Ti,W,Si,Al)N coating films. (Ti,W,Si,Al)N is a new type of coating film. The inner layer of the (Ti,W)N/(Ti,W,Si)N and (Ti,W)N/(Ti,W,Si,Al)N coating system is (Ti,W)N coating film, and the outer layer is (Ti,W,Si)N and (Ti,W,Si,Al)N coating  films, respectively. Furthermore, commercial (Ti,Al)N-based coating film was also used.

(To be continued. This article is divided into several parts. Here is part 1. For part 2 please refer to http://news.chinatungsten.com/en/tungsten-information/80790-ti-10484)

In last part we know that tungsten carbide spoon bits are used to boring holes in chairmaking with a spoon like point and grooved shank. This part we talk about how it works.

When reaming a pre-bored straight-sided hole, the tungsten carbide spoon bit is inserted into the hole and rotated in a clockwise direction with a carpenters' brace until the desired taper is achieved. When boring into solid wood, the bit should be started in the vertical position; after a "dish" has been created and the bit has begun to "bite" into the wood, the angle of boring can be changed by tilting the brace a bit out of the vertical. Holes can be drilled precisely, cleanly and quickly in any wood, at any angle of incidence, with total control of direction and the ability to change that direction at will.

Parallel tungsten carbide spoon bits are used primarily for boring holes in the seat of a Windsor Chair to take the back spindles, or similar round-tenon work when assembling furniture frames in green woodworking work.

The spoon bit may be honed by using a slipstone on the inside of the cutting edge; the outside edge should never be touched.

(The end-This article is divided into 2 parts. Here is part 2. For part 1 please refer to http://news.chinatungsten.com/en/tungsten-information/80786-ti-10481)

Tungsten carbide spoon bits consist of a grooved shank with a point shaped somewhat like the bowl of a spoon, with the cutting edge on the end. The more common type is like a gouge bit that ends in a slight point. This is helpful for starting the hole, as it has a center that will not wander or walk. These bits are used by chair-makers for boring or reaming holes in the seats and arms of chairs. Their design is ancient, going back to Roman times. Spoon bits have even been found in Viking excavations. Modern spoon bits are made of tungsten carbide or carbon steel, carefully heat-treated and then hand ground to a fine edge.

Spoon bits are the traditional boring tools used with a brace. They should never be used with a power drill of any kind. Their key advantage over regular brace bits and power drill bits is that the angle of the hole can be adjusted. This is very important in chairmaking, because all the angles are usually eyeballed. Another advantage is that they do not have a lead screw, so they can be drilled successfully in a chair leg pretty much without having the lead screw peek out the other side.

(To be continued. This article is divided into 2 parts. Here is part 1. For part 2 please refer to http://news.chinatungsten.com/en/tungsten-information/80787-ti-10482)

In the process of tungsten copper, silver-tungsten, ferro tungsten mechanical parts and metal-ceramic materials, the infiltration method is one of the most major processes. Take tungsten copper electrodes for example, the infiltration process is immerse tungsten skeleton in liquid copper after high temperature sintered, so that the pores are filled with liquid copper, then by annealing and cooling to obtain a dense tungsten copper materials.

Thus, infiltration process is the preparation of tungsten-copper electrode in the most critical a process, which directly affects the overall performance of tungsten copper electrodes. However, the most of present study concentrated on the parameters of infiltration, for infiltration mechanism is quite few, and most of these studies are directed to coarse particles of tungsten powder, and rarely comes to fine particles of tungsten powder. Infiltration is the process relies on an external metal powder wetted porous body (tungsten skeleton), under the action of capillary force, the liquid metal (Cu) along the inter-particle porosity within the particle porosity flow or until completely filled up the pores.

Tungsten copper electrode production process flow sheet as follow:

1. Preparation: Firstly, put tungsten powder, induced copper powder in ball grinding mill, and add 1% of stearate and dried and sieved to thereby obtain mixed powder after a while.
2. Compacting: Hydraulic machine pressing, we should concern the weighing in case of the loss of powder loss during the compacting process,
3. Degreasing: Using H₂ as protective atmosphere when thermal degreasing, adhesive must be removed in order to avoid contamination and clean sintering furnace.
4. Sintering: Sintering in molybdenum wire furnace, H₂ as protective atmosphere.
5. Infiltration: Using H₂ as protective atmosphere and infiltrated copper at 1200-1300℃.
6.After-processing: The infiltrated tungsten copper alloy electrode after annealing treatment to improve the performance of the alloy, and then subjected to a surface treatment to remove excess copper.

In last part we know that tungsten carbide Forstner bits can only be used in a drill press, cannot remove chips automatically, are relative more expensive and difficult to sharpen. In this part we explain how to sharpen a Forstner bit.

Some woods, such as cedar, contain silicates that can gradually dull, albeit slower, the tungsten carbide Forstner bits. To sharpen a Forstner bit, we can follow the below steps:

(The End--This article is divided into several parts. Here is part 7. For part 6 please refer to   http://news.chinatungsten.com/en/tungsten-information/80739-ti-10469)

In last part we know that tungsten carbide drill bits have special cutting rims, which make them able to drill holes cleanly, more precisely, faster and better than other bits, and are multifunctional as well. In this part we explain the drawbacks and precautions to use a Forstner bit.

In most cases all tungsten carbide Forstner bits are intended for mounted drill presses rather than hand-held tools. They typically require a lot of force, which can be dangerous and sometimes even unwieldy on a smaller appliance.

So people who want to use it typically have to invest in a drill press, and even then they often have to have at least a bit of training in order to control and properly use it. The bits also tend to be somewhat difficult to sharpen, and they don’t have any way of blowing dust back out the way some bits do; what this means in practical terms is that carpenters may have to pause more often to clear the bores. These bits also tend to be a bit more expensive than their counterparts.

(To be continued. This article is divided into several parts. Here is part 6. For part 5 please refer to http://news.chinatungsten.com/en/tungsten-information/80738-ti-10466; for part 7 please refer to http://news.chinatungsten.com/en/tungsten-information/80740-ti-10470)

In last part we know that tungsten carbide Forstner bits are especially used to drill through multiple pieces of wood or precise hinge holes in furniture making. They come in varied sizes from 0.25 to over 3 inches (6 to 75 mm) to form a set. In this part we explain the benefits to use a Forstner bit.

Carpenters often praise this bit’s ability to drill precisely and cleanly through imperfections, like knots and baubles, in wood. A lot of this owes to the rim. The Forstner bit’s rim guides itself, which means that it won’t be thrown off when it hits problem areas or end-grain the way a center point-guided bit could be.

Speed and precision are also important factors. Experienced woodworkers often say that the Forstner bit is able to do work faster and better than almost any other bit, and can do a number of different tasks, too. It can drill both complete holes and partial bores; it can cut on an angle and against the grain.

(To be continued. This article is divided into several parts. Here is part 5. For part 4 please refer to http://news.chinatungsten.com/en/tungsten-information/80737-ti-10467; for part 6 please refer to http://news.chinatungsten.com/en/tungsten-information/80739-ti-10469)

In last part we know that tungsten carbide Forstner bits are guided by outside rim instead of the center spur, use cutting edges to shear wood and radial sides to smooth the hole and finally create a flat bottom hole. In this part we explain where and when to use a Forstner bit.

Today, the tungsten carbide Forstner bits are more commonly used by furniture makers and home builders. Big projects like these often require a drill that can quickly move through multiple pieces, join different types of wood, and cut through multiple surfaces. The tungsten carbide Forstner bit fits that bill for many carpenters.

They are available in a wide array of diameters, typically ranging from 0.25 to over 3 inches (6 to 75 mm), and they are often sold in sets that come with an array of sizes. Even bits with very small diameters are often able to bore through deep, thick wood at most angles. Their unique shape makes them very efficient at removing a lot of material, known as “hogging,” in a short amount of time. They’re also really useful for making precise holes for hinges and other moving parts.

(To be continued. This article is divided into several parts. Here is part 4. For part 3 please refer to http://news.chinatungsten.com/en/tungsten-information/80736-ti-10468; for part 5 please refer to http://news.chinatungsten.com/en/tungsten-information/80738-ti-10466)

In last part we know that tungsten carbide Forstner bits are characteristic of a center point, cylindrical cutting edges and radial cutting edges, and no mechanism to clear chips. In this part we explain how a Forstner bit works.

Most drills are guided through material by a central point, but Tungsten carbide Forstner bits are primarily guided by the outside rim. This means that they can be used to drill pocket holes, which are holes drilled at an angle; partially overlapping holes; and holes that are on the edge of the material. They have central spurs, but these are normally used to locate and mark a center-point rather than to serve as the actual drill guide.

When the tungsten carbide Forstner bit enters wood, it bores down by essentially spinning fragments up and out with a sawing, rotary motion. The sides of the bit often look jagged and when they first enter the wood they often shear it and leave it somewhat splintery. As the bit’s radial sides continue through the hole, though, the edges tend to smooth out. Most of the time the result is a flat-bottomed hole.

(To be continued. This article is divided into several parts. Here is part 3. For part 2 please refer to http://news.chinatungsten.com/en/tungsten-information/80701-ti-10455; for part 4 please refer to http://news.chinatungsten.com/en/tungsten-information/80737-ti-10467)