Exploring Diamond & PCD (Polycrystalline Diamond) Tools in Woodworking for Beginners

History of PCD (Polycrystalline Diamond

Diamond as a super-hard tool material used in cutting processing has a history of hundreds of years. In the course of tool development, from the end of the nineteenth century to the middle of the twentieth century, the Diamond cutting tool material is mainly represented by high-speed steel;

In 1927, Germany firstly developed cemented carbide tool material and gained wide application;

In the 1950s, Sweden and the United States synthesised synthetic diamond, and the cutting tool has since stepped into the period of super-hard material.

In the 1970s, people used high-pressure synthesis technology to synthesise polycrystalline diamond (PCD), which solved the problem of scarce and expensive natural diamond.

At present, the processing range of Diamond tools has been extended from the traditional metal cutting processing to stone processing, wood processing, metal-based composite materials, glass, engineering ceramics and other materials processing. In recent years, the rapid development of man-made panels has promoted the further application of PCD tools for woodworking. In particular, the development of man-made panels such as MDF, plywood, particle board and composite flooring has accelerated the demand for diamond tooling in the wood processing industry.

Performance characteristics of PCD woodworking tools

A survey conducted by a Japanese organisation on super-hard cutting tools shows that the main considerations for people to choose PCD cutter tools are based on the advantages of surface accuracy, dimensional accuracy and tool life after PCD tool machining. Diamond tools have high hardness, high compressive strength, good thermal conductivity and wear resistance, long service life and other characteristics, so that it has become a woodworking furniture enterprises to improve efficiency, reduce machine idling and cost waste of a major tool.

The main performance index of PCD cutting tools material:

1.Hardness of up to 8000HV, 80 to 120 times that of carbide tools.

2.Thermal conductivity of 700w/mk, 1.5 to 9 times that of carbide cutters, even higher than PCBN and copper, so diamond bit heat transfer is rapid.

2.The coefficient of friction is generally only 0.1~0.3 (the coefficient of friction of cemented carbide is 0.4~1), so polycrystalline diamond cutters can significantly reduce the cutting force.

4.The coefficient of thermal expansion is only 0.9×10 -6~1.18×10 -6, which is only equivalent to 1/5 of carbide tooling, so PCD tooling have small thermal deformation and high machining accuracy.

5.The affinity between the PCD diamond cutter and wood materials is very small, and the chips are not easy to be bonded to the tip of the diamond cutter tool to form chip tumour during the machining process.

In addition, the life of diamond cutting tool is 80~250 times longer than that of general alloy tools, and in the process of actual use, it is generally not necessary to change the tools and repair grinding for more than 3 months, thus greatly improving the efficiency of processing and the stability of the products. The precision of diamond processing products can reach 0.005mm, there will be no burr, ultra-tolerance phenomenon, the processed object can achieve the effect of polishing, especially suitable for density board, medium fibre board, particle board, artificial quartz stone and hard solid wood materials precision processing.

Manufacturing process of PCD cutters

The manufacturing process of PCD tooling mainly includes two stages:

1.Diamond blade manufacturing: PCD cutter blade is made of natural or synthetic diamond powder and bonding agent (which contains cobalt, nickel and other metals) sintered at high temperature (1,000 to 2,000 ℃) and high pressure (5 to 100,000 atmospheres) in a certain proportion. During the sintering process, due to the addition of the binding agent, the diamond crystals form a bonding bridge with TiC, SiC, Fe, Co, Ni, etc. as the main components, and the diamond crystals are embedded in the skeleton of the bonding bridge in the form of covalent bonds. Usually made of composite discs of a fixed diameter and thickness of the disc, but also need to be sintered into a composite piece of grinding and polishing and other corresponding physical and chemical processing.

2. PCD insert processing: diamond cutting blade processing mainly includes composite sheet cutting, blade welding, blade sharpening and other steps.

PCD inserts are connected to the toolholder in a variety of ways, including:

1.Mechanical clamping – by the standard knife body and can be made into a variety of collection angle of the interchangeable blade composition, with quick change and easy to resharpen the advantages – small and medium-sized machine tools

2.Integral welding – Compact and easy to fabricate, can be made into small-sized tools – Specialised tools or tools difficult to clamp, used in small machines.

3.Clamp welded – inserts are welded to the tool head, standard shanks can be used, easy to sharpen and adjust the position of the tool head – automatic machine tools, CNC machine tools

4.Indexable – compact structure, reliable clamping, no need for resharpening and welding, can save the auxiliary time, improve tool life – general-purpose machine tools.

Types of polycrystalline diamond cutters 

At present, diamond cutters can be classified into five types according to their composition and structure:

1.Natural Diamond(ND);

2.Artificial Polvcrystalline Diamond(PCD);

3.Chemical Vapor Deposition Diamond Coated Tools(CVD):It is a process that allows manufacturers to apply a thin coating that is bonded at the atomic level and that is deposited in a very uniform layer.

4.Thick Diamond Film(CD):Deposition of thick substrate-free pure diamond films up to 100µm thick

5.Coated Thin Diamond Film(CD): Deposition of diamond thin film coatings with a thickness of less than 30µm directly on the surface of the tool substrate

PCD diamond tool grades are categorised by the grain size of the diamond particles. According to the manufacturer’s standards, fine, medium and coarse PCD grades correspond to diamond grain sizes of roughly 2 μm, 10 μm and 25 μm respectively.Coarse PCD grades are stronger than fine PCD grades, with better abrasion resistance, and longer working life in rough machining, but it is difficult for the cutting edges of coarse diamond  PCD tools to reach the smoothness of the surface of fine PCD tooling cutters. Therefore, fine-grained diamond tool cutters can obtain a better surface finish, but the wear rate is faster.

Application of PCD cutting tools in woodworking

1.Board Cutting: PCD diamond bits (PCD end mills, diamond straight bits,PCD 2 flutes spiral bits, and TCT router bits) & PCD diamond saw blades (diamond circular saw blades, table saw blades, diamond miter saw blades, and diamond Jigsaw blades) areused for cutting various wooden boards, including particleboard, medium-density fiberboard (MDF), plywood, and laminated veneer lumber (LVL). Due to the presence of adhesives and hard components in these materials, PCD cutting tools can handle them more effectively without wearing out quickly.

2.Surface Finishing: PCD diamond spiral planer cutterhead are employed for scraping and finishing the surfaces of wooden materials to achieve smoother and more consistent surface quality. This is crucial for furniture manufacturing and decorative woodworking where high surface quality is essential.

3.Edge Trimming for Edgebanders: PCD diamond pre-miling cutters are typically used to trim the edges of boards to ensure they are flat, vertical, and precise. This is essential for making furniture, cabinets, and decorative panels.

4.Joinery: PCD tooling are used for creating joinery connections such as tenons (diamond tenon cutters)and mortises to ensure their quality and accuracy. This is often required in furniture manufacturing and woodworking.

5.Engraving and Decoration: PCD diamond router bit can be employed for woodworking engraving and decorative work. They can be used to cut intricate patterns and decorative elements, adding artistic flair to wooden products.

6.Cutting Special Materials: PCD cutters are also used for cutting special materials such as high-pressure laminate (HPL) and plastic laminates, which can be more challenging than standard wood.

Guidelines for the use of woodworking PCD cutters

1.Diamond woodworking cutter blades are easily damaged, protect the blade with a rubber or plastic cap when the blade is not working, when diamond woodworking cutters are not working on the machine tool, the diamond cutter should be placed in a separate cutter box.

2.Use optical instruments whenever possible during inspection and installation. Use a copper spacer or plastic item to place between the diamond tool and the micrometer or height gauge during inspection, this will prevent damage to the cutting edge and improve tool life.

3.Do not stop the diamond woodworking tool at a standstill while it is in contact with the workpiece and while it is cutting.

4.High speed can reduce the pressure of the diamond cutters edge; low speed is the opposite, to shorten the life of the CNC PCD tool, so it is suitable for high-speed cutting.

5.Vibration also reduces tool life, so processing should have a good working environment. That is, CNC machine tools, workpieces, fixtures and system rigidity should be good, cutting and processing in the presence of significant vibration, should be immediately stopped, improved and then cut.

6.PCD tool life is generally 5 to 300 times that of carbide tools. However, this is related to the equipment, processing methods and the hardness of the processed material, etc. At the same time, it is also necessary to use, on the basis of continuous mastery of experience, in order to achieve the longest tool life.

7.PCD woodworking cutters are both hard and brittle, any impact and collision may cause damage.

8.The coefficient of thermal expansion of PCD material is different from that of the cutter body metal, and sudden or intermittent cooling during the cutting process can cause cracks in the blade leading to scrapping.

9.Please do not attempt to sharpen super-hard material knives without specialized equipment and expertise, ordinary methods of sharpening will only cause damage to the PCD tool.

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