The selection of main geometric parameters for the grinding of twist drill bit

The main geometric parameters of twist drill include the choice of cutting lip angle, the choice of land angle of cutting edge and lip clearance angle of cutting edge, the analysis of the influence of helix angle on the life of drill bit and the treatment of cutting edge.


Cutting lip angle determines chip width and bit front angle. When the diameter and feed of the bit remain unchanged, increasing the top angle will narrow the iron filings and reduce the load per unit cutting lip. Cutting lip angle has a great influence on the land angle. Increasing cutting lip angle correspondingly can improve the cutting conditions at the core. Cutting lip angle affects the direction of chip outflow. According to the relevant tool design data and the characteristics of low hardness but high viscidity of the processed product, the cutting lip angle of the bit is selected to be 140°.


The land angle of a twist drill is determined by other geometric parameters of the drill. In high-speed cutting, the rake angle has little influence on cutting deformation and cutting force, and the strength of tool tip can be enhanced with a smaller land angle. When the land angle is determined, the bigger the lip clearance angle is, the sharper the edge is, but the wedge angle will decrease correspondingly, which will affect the strength and heat dissipation area of the tool. For this purpose, the lip clearance angle of the drill bit is selected as a smaller one, which is 8°.

If you choose our drill grinding machine, you can easily finish the drill grinding work. You can achieve the desired results by choosing the right chuck according to your drill bit. Our drill bit grinding machine makes complex drill grinding easy. If you are interested in our products, please contact us. We are a manufacturer of drill bit grinding machines. The price is relatively favorable. We welcome agents to negotiate business.

What are the advantages of CVD diamond coated tool?

Chemical Vapor Deposition is called CVD. Diamond coating has many excellent properties such as high hardness, high thermal conductivity, low friction and low expansion coefficient.

In the processing of brittle materials such as graphite and carbon fiber composite materials, it has become the surface coating of cutting tools and has shown excellent performance in improving tool life and processing quality.

The selection of diamond coating thickness is not “the thicker the better”.

How many types of milling cutter according to purpose?

With the improvement in wear resistance, the quality of diamond coating is more important than that of thickness.

After continuous testing and verification of various tool materials, the service life of CVD diamond coated tool is 8 ~ 10 times of that of cemented carbide tool. The allowable cutting speed of CVD diamond coated tool is 2 ~ 3 times higher than that of hard alloy tool.

CVD diamond coated tool has sharp cutting edge and good consistency, low friction factor, and can realize high speed and precision machining of thin-walled graphite mould under high speed and low feed. Meanwhile, the service life of CVD diamond coated tool is longer among many tool materials.

The selection and application of diamond coated tools are mainly based on the properties of workpiece materials and the requirements of machining quality.

Note: When the coated bit is repaired by drill bit grinding machines, the worn coating is irreparable.

What kind of material is suitable for what kind of tool?

Determine the material of the tool according to the machining type and workpiece material. It is a common knowledge in the whole machining industry to match tool materials with workpiece materials. But not everyone knows how many conditions this so-called match will satisfy. Next, we will introduce ‘how tool materials and workpiece materials can match mechanical, physical and chemical properties’.

How do the mechanical properties of tool materials and workpieces match?

The mechanical properties are mainly designed for the strength, toughness and hardness of the tool and workpiece. All kinds of tool materials are arranged in order of bending strength from strong to weak: high-speed steel, hard alloy, ceramic tool, diamond and cubic boron nitride tool. In order of toughness from high to low: high speed steel, hard alloy, cubic boron nitride, diamond and ceramic tool; In order of hardness from high to low: diamond tool, cubic boron nitride tool, ceramic tool, hard alloy and high speed steel.

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The drill bit grinding machines produced by PURROS are sold all over the world.

With many years of experience in the industry, PURROS has successfully surpassed the industry and reached the heights of success. Our company ensures that the selection of suppliers is based on various parameters, such as batch order, customization, latest technology and high quality raw materials.
We ensure that the drill bit grinders are strictly tested on various parameters to ensure the products reach the perfect range of customers.
Our highly effective professional team has conducted intense market analysis to ensure the quality of products has been strictly inspected. Moreover, we have successfully provided the perfect product line for customers all over the world.

The drill bit grinding machines produced by PURROS are sold all over the world.

We have professional sales staff to communicate with you to confirm the products. Welcome to contact us to learn more about the products.

Why to buy sharpening machines for drill bit?

Bench grinders are so incredibly cheap that every home workshop should have one. As we covered in using bench grinders, there’s a host of uses for a bench grinder, including grinding welds and shaping metal. But perhaps the greatest real-world use is sharpening drill bits.


Our re-sharpening tool machines not only provide drill bit repair, drill bit sharpening, drill bit tipping, and chisel sharpening of our own carbide tipped drill bits, but those made by other manufacturers as well at a fraction of the cost of new ones!  So don’t throw away those expensive carbide tipped drill bits,  use PURROS drill bit sharpening machines to repair them.


Good quality drill bits are expensive – very expensive in large sizes. But once you can competently sharpen drill bits with a bench grinder, you can buy lots of your drills secondhand, massively dropping the purchase prices.

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Buy sharpening machines for drill bits, please click here.

PURROS provides the drill bit grinding machines that can repair various materials and types of drills. Reconditioning maintains the exact geometry and coating of the original tool. Tool reconditioning is a reasonably priced alternative to buying new tools while still maintaining the same performance. To this end, by the time a tool is reconditioned for the third time, tools costs are reduced by 50 percent.

Tips to Sharpen Drill Bits

Drill bits can be sharpened in several ways, and it might be handy to learn if you personally do the installation of your home’s hardwired security system. Even if you don’t hit any nails while drilling holes for your home alarm and other security devices, your bits will still get dull.

Drill Bits are very expensive, especially the long ones used for the wiring of home security system. Rather than replacing them, you should sharpen the bits to save you money and also make drilling easier and faster, since you will have in your possession freshly sharpened bits.

A drill bit grinder is available for purchase and it brings a dull bit back to its original form. It is advisable not to purchase a special tool that only has one function. Especially when an almost good drill bit grinding machines is already sitting on your workbench.

Using a drill bit grinder attachment on a bench, which can be found in various home workshops, you can easily sharpen your bits. They might not be as perfect as the original bit, but they will get you back in action as fast as possible and crazily drill holes

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Solutions Summary of Common Drilling Problems (Relationship with the Good or Bad Grinding Drill Bit)

In the actual production, PURROS Machinery has collected mass customers’ problems about grinding drill bits by hand (manual grinding drill bits), now, list the summary of the problems and how to solve as bellow for your reference and study. In the actual production, PURROS Machinery has collected mass customers’ problems about grinding drill bits by hand (manual grinding drill bits), now, list the summary of the problems and how to solve as bellow for your reference and study.

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The Check of Standard Twist Drill Bit after Grinding

Step 1: Checking the point angle (cutting lip angle) of standard twist drill bit is correct or not, and whether it is symmetric with the axis of the standard twist drill bit? (The correct point angle of standard twist drill bit is ±118°, if it be used to drill harder materials that the point angle can be extended to 120°;  if there are the softer materials, the point angle should smaller than before, but keep mind, do not smaller than 90°.)

Step 2: To check the length and height of two major cutting lip (major cutting edge) are consistent. Because the quality of the machined holes are affected by whether the length is the same.
The check method for step 1 and step 2 is that: Place the cutting part of twist drill bit keeps in a vertical position, keep eyesight at the horizontal level, and then repeatedly rotate 180°, where is the center axis of standard twist drill bit, to observe whether the length of two major cutting lips are same in rotation. It is an assumption that to observe the length of two major cutting lips at the center of axis; If the lengths of two major cutting lips are different, that the shorter side should be grinded.Continue reading