Category Archives: Technology

Technology page is shared the experience of technical talent in field of drill bit grinder, help you to resolve the technical difficulties, and makes you into a specialist of drill bit re-grinder.

What properties should good tool material have?

Tool material is the fundamental factor that determines the cutting performance of a tool. When carbon tool steel is used as tool material, the cutting speed is only about 10m/min. In the early 20th century, high-speed steel tool material emerged, cutting speed increased to tens of meters per minute; In the 1930s, cemented carbide appeared and the cutting speed was increased to more than 100 meters to several hundred meters per minute. At present, the appearance of ceramic cutting tools and super hard cutting tools increases the cutting speed to over one kilometer per minute. The development of processed materials has greatly promoted the development of cutter materials.

What are the properties of good cutter materials?

 

Cutting tool material with excellent performance is the basic condition to ensure efficient working of cutting tools. The cutting part of the tool works under strong friction, high pressure and high temperature and should have the following basic requirements.

 

High hardness and wear resistance

The hardness of cutter material must be higher than that of processed material to cut metal, which is the basic requirement of cutting tool material. The current tool material hardness is above 60HRC. The harder the tool material, the better its wear resistance.

 

Sufficient strength and impact toughness

Strength refers to the ability to resist the cutting force without breaking the blade or breaking the blade. It is usually indicated by bending strength. Impact toughness refers to the ability of cutter materials to ensure that the blade does not collapse under discontinuous cutting or impactful working conditions. Generally, the higher the hardness, the lower the impact toughness, the brittle materials. Hardness and toughness are a pair of contradictions and also a key to overcome the material of cutter.

 

High heat resistance

Heat resistance is the main index of tool material performance. It is a comprehensive reflection of the tool material under the high temperature to maintain hardness, wear resistance, strength, oxidation resistance, adhesion and diffusion.

 

Good workmanship and economy

In order to facilitate manufacturing, tool materials should have good technological properties, such as forging, heat treatment and grinding. Of course, economic considerations should be taken into account when manufacturing and selection. The cost of superhard materials and coated tool materials is now more expensive, but the service life is very long, and in mass production, the cost of each part is reduced. Therefore, the selection must be comprehensive consideration.

Standard of tool dressing

Whether or not you have a good set of standard is the standard to measure whether a center is professional. Standard of grinding, the general rules for different Cutting tool in Cutting different materials when the Cutting edge of technology parameters, including the blade Angle, Cutting Lip Angle, rake Angle, Lip Clearance Angle, blade, chamfering etc parameters (in the carbide drill, make the blade passivation process is called “blade”, pour the width of the blade and the Cutting material, generally between 0.03-0.25 Mm. The process of chamfering on the edge (tip) is called chamfering. Each professional company has its own years of review and repair standards.

The use and safety management of drill bit grinder grinding wheel

The use and safety management of drill bit grinder grinding wheel

Differences between HM drill and HSS drill:

HSS drill bit: Cutting Lip Angle is usually 118 degrees, sometimes greater than 130 degrees; The blade is sharp; The precision (edge elevation, symmetry, circumferential pulse) is relatively low. There are many ways to mend a chisel edge.

HM drill bit: Cutting Lip Angle generally 140 degrees; Straight slot drills are usually 130 degrees and three-edge drills are generally 150 degrees. The blade and tip (edge) are not sharp and are often passivated, or referred to as chamfering and chamfering; High demand for accuracy. The chisel edge is often cut into an s-shape for cutting.

Lip Clearance Angle:

The Lip Clearance Angle of the blade is very important for cutting tools. Lip Clearance Angle is too big, the blade is flabby and easy to tie up. Lip Clearance Angle is too small, then friction is too large, cutting disadvantage.

The Lip Clearance Angle of the cutter varies with the cutting material, type and diameter of the cutter. Generally speaking, the Lip Clearance Angle decreases as the cutter diameter increases. In addition, if the cut material is hard, the Lip Clearance Angle is smaller, otherwise, the Lip Clearance Angle is larger.

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There are nine causes of screw tap failure

  1. Poor quality of tap: main materials, cutter design, heat treatment, machining accuracy, coating quality, etc.

For example, if the dimensions at the transition point of the tap cross section are too different or there is no designed transition angle resulting under stress concentration, it is easy to break when used.

The cross section transition to the junction of the handle and blade is too close to the welding mouth, which results in the superposition of complex welding stress and the stress concentration at the cross section transition, resulting in a larger stress concentration, leading to the tap breaking in use.

For example, the heat treatment process is improper.

In the heat treatment of tap, the tap may crack if it is not preheated before quenching, overheated or over-burnt, not tempered in time and cleaned too early.

  1. Improper selection of tap:

High quality screw tap should be used for tapping parts with too high hardness, such as cobalt high speed steel tap, hard alloy tap, coating tap etc. In addition, different tap designs are used in different work situations. For example, the number of chip slots, size, Angle, and so on of the tap affected chip removal performance.

  1. No matching between tap and processed materials:

With the increase in new materials and the difficulty of processing, in order to meet the market demand, the variety of cutter materials is also increasing. This needs to select a suitable tap product before tapping.

  1. Small bore size of bottom hole:

For example, when machining M5 x 0.5 thread of black metal material, the cutting tap should be used to make the bottom hole with a 4.5mm diameter bit. If the 4.2mm diameter bit is misused to make the bottom hole, the cutting part of the tap must be increased when tapping, so that the tap will be broken. It is suggested to choosing the correct bottom hole diameter according to the type of tap and the material of tapping.

  1. Material problem of tapping parts:

The tapping material is not pure, and there are some hard points or pores, causing the tap to lose balance and break.

  1. The machine does not meet the requirements for the accuracy of tap:

Machine tool and clamping body are also very important, especially for high-quality taps, only certain precision machine tool and clamping body can give play to the performance of taps. Common is lack of concentricity. At the beginning of tapping, the tap is incorrectly positioned, that is, the spindle axis is different from the center line of the under hole, and the torque is too large during tapping, which is the main reason for the tap breaking.

  1. Cutting fluid and lubricating oil has poor quality:

The cutting fluid and lubricating oil have problems in quality. The quality of the processed product is prone to defects such as burrs, and the service life is also greatly reduced.

  1. Unreasonable cutting speed and feed amount:

When there are problems in machining, most users will reduce the cutting speed and feed amount, so that the propulsive force of the tap is reduced, and the thread precision of its production is greatly reduced. As a result, the roughness of the thread surface is increased, the thread aperture and thread precision are uncontrollable, and the problems like burrs are inevitable. However, if the feed speed is too fast, too much torque will cause the tap to break. The cutting speed of machine attacked is generally 6-15m/min. The tempered steel or hard steel material is 5-10m/min. Stainless steel is 2-7m/min; Cast iron is 8-10m/min. In the same material, the diameter of the tap is smaller and higher, while the diameter of the tap is larger and lower.

  1. The operator’s skills and skills do not meet the requirements:

Above these problems, need operation personnel to make judgment or feedback to technical personnel. For example, when processing blind hole threads, when the tap is about to contact the bottom of the hole, the operator did not realize that, still press the tapping speed when it did not reach the bottom of the hole, or if the chip removal is not smooth forced feed causes the tap to break. Operators are advised to being responsible.

It can be seen from above that there are various causes of tap fracture, including machine tool, fixture, workpiece, technology, chuck and cutter.

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When the tap wears out, we can use our PG-Y3C screw tap grinder or PG-600 universal tool grinder. But if it breaks, you can only replace it with a new one. In the use of tap, we should try to avoid the above reasons to prevent the tap fracture caused by losses.

Why are so many customers buying universal tool grinding machines now?

The universal tool grinder has been a hot seller in recent years. A large part of the reason is that more and more people have realized its importance and its advantages. Why don’t we take the worn-out tools to a professional organization for grinding and choose to buy the Universal Tool Grinder for grinding?

 

What kind of tools need grinding?

Most cutting tools require grinding and are designed with future grinding in mind.

The small-diameter taps and most of the indexable blades give up the grinding due to their low price and relatively high grinding cost.

Some of the machined cutting tools of the groove can not be sharpened because the diameter should be reduced after grinding.

 

Why do tools need sharpening?

Tool grinding is a low carbon activity to reduce production cost and resource consumption.

 

Key points of tool grinding

Sharpen the dull and worn original blade, and grind the new blade on a better matrix.

The wear of the guide part must be taken into account comprehensively for hole cutting tools.

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How to deal with tool wear?

Tools is arguably the most commonly used key component, and it’s also easy to wear out. How to reduce the tool wear is very important.

Common causes of tool wear:

All components of the cutter will be worn by milling and shaping materials. If one of the components of the cutter is damaged, such as the blade tip, steel body, gasket or snap spring, the entire cutter should be replaced to prevent damage to the relatively expensive tool holder system. Moreover, the replacement of the cutter holder system is more complicated. Therefore, how to reduce the tool wear is very important.

How to deal with tool wear with drill bit grinder

Common tool wear includes the following reasons:

  1. Incorrect installation;
  2. Use components from different manufacturers;
  3. Choose the wrong type of cutter (different type of cutter should be selected for different types of machine);
  4. Milling planer materials are bonded and continuously accumulated on the cutter, which is generally caused by incomplete cleaning;
  5. Insufficient water supply in the sprinkler system inside the casing of milling plane.

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How to reduce tool wear?

Tool wear is unavoidable, but can at least be minimized. Adequate water supply is the basic premise to ensure normal rotation of cutter. According to the material selection of milling cutter, can also optimize the use and reduce wear.

  1. Select the suitable working condition milling tool;
  2. Pay attention to daily thorough cleaning;
  3. Regularly check the cutter, and timely find and deal with the wear or damage of components;
  4. Regular maintenance and inspection of sprinkler system;

 

Only through proper maintenance can the wear of key parts be minimized, thus greatly saving cost and ensuring efficient operation of the machine. If the cutter is only slightly worn, a cutter grinder can completely repair the wear. The use of universal tool grinder can reduce the waste of many tools, saving cost and time.

The use and safety management of drill bit grinder grinding wheel

From the transportation and storage of the grinding wheel, the inspection before use for the installation, dressing of the grinding wheel, and the operation of the grinding machinery, any negligence of any link will bury a hidden danger to the drill bit grinder.

 

  1. Grinding wheel inspection

The grinding wheel with cracks and other defects is absolutely not allowed to use. The grinding wheel must undergo strict inspection before it is used.

(1) Visual inspection is to observe whether there are cracks or damages on the surface of the grinding wheel directly with the naked eye or with the aid of other instruments.

(2) Sound inspection is also known as percussion tests. The inspection method is to beat the grinding wheel with a small wooden hammer. The normal grinding wheel is crisp. If the voice is active and hoarse, it will be problematic.

 

  1. Grinding wheel device

Whether the grinding wheel matches the spindle size.

(1) Check whether the characteristics of the grinding wheel meet the requirements of use.

Do not press hard. The matching gap between the grinding wheel inner diameter and the spindle and chuck is appropriate.

(2) Assemble the grinding wheel freely to the spindle of the grinding wheel. Prevent too large or too small. The matching surface should be clean and free of debris.

(3) The chuck of the grinding wheel should be symmetrical. Abundant contact with the front of the grinding wheel and stable clamping prevented the two sides of the grinding wheel from deformation or even fragmentation due to unbalanced force.

(4) A certain thickness of flexible data lining (such as asbestos rubber board, elastic cardboard or leather) should be inserted into the chuck and the end face of the grinding wheel to make the chuck clamping force evenly distributed.

(5) The tightness of the grinding wheel should be tightened enough to make the grinding wheel do not to slide.

 

  1. Balancing test of grinding wheels

For example, the imbalance of the grinding wheel is due to the fact that the center of gravity of the grinding wheel does not coincide with the axis of rotation. The reasons are the defects of grinding wheel manufacture and installation, uneven density of grinding wheel, non-parallel end face, geometric shape or concentricity error of inner and outer holes, eccentricity of grinding wheel device and so on. When an unbalanced grinding wheel rotates around high speed, the centrifugal force which forces the grinding wheel to deviate from the axis will occur, thus causing the vibration of the grinding wheel. The results not only affect the grinding quality, but also accelerate the wear and tear of the main shaft bearing of the grinding wheel. When the centrifugal force exceeds the allowable range of the grinding wheel strength, the grinding wheel will be broken.

 

  1. Dressing of grinding wheels

To prevent passivation, blockage and distortion of grinding wheel, regular dressing can make grinding wheel adhere to good grinding performance and correct geometry. The usual dressing tool is diamond pen.

 

  1. Storage and transportation of grinding wheels

(1) It can not be subjected to strong vibration and impact. The wheels are in transportation and storage. It is not permitted to move the wheel when handling, so as to avoid cracks and surface  to damage.

(2) Signs of characteristics of wheel and safety speed must not be smeared or damaged at will.

(3) The storage time of grinding wheel should not exceed the validity period of grinding wheel. If the storage time exceeds one year, it must be qualified after the rotation test is used.

(4) Grinding wheel storage site should be kept dry. Prevent mixing with other chemicals. Prevent wheel dampness, low temperature, overheating and harmful chemicals from erosion.

(5) Grinding wheels should be based on specifications, shapes and sizes. Prevent overloading damage or cause improper grinding wheel deformation.

How to solve the problem after the bit is broken?

 

 

Cause Solution
Bending, deformation, sliding Increase the rigidity of tool and machine tool, increase the rigidity of workpiece and jig
Lip Relief Angle is too small Regrinding Lip Relief Angle
High Stock Removal To reduce Stock Removal
Bit wear Use drill bit grinder to grinding
Blocking of chips Re-select the alloy bit (chip groove, helix Angle);

Re-select machining method (adjustment of feed rate, step-step method, etc.)
Poor cutting Increase the rigidity of tools and machine tools

Increase the rigidity of workpiece and jig

Predrilling center hole

The cutting plane is first adjusted or processed into a horizontal plane with a guide sleeve

What are the difficulties in drilling stainless steel?

The difficulties of stainless steel material processing mainly include the following aspects:

  1. High cutting force and high cutting temperature

This type of material has large strength and large plastic deformation during cutting, so the cutting force is large. In addition, due to the poor thermal conductivity of the material, the cutting temperature is increased, and the high temperature is often concentrated in the narrow area near the cutting edge, which accelerates the tool wear.

 

  1. Severe work hardening

Austenite stainless steel and some high temperature alloy stainless steel are Austenite structure. These materials tend to be hardened when machined, often several times as much as plain carbon steel. The cutter is cut in the hardened area to shorten the tool life.

 

  1. Easy to stick the tool

Both Austenite stainless steel and Martensite stainless steel have the characteristics of strong and tough chip and high cutting temperature. When the strong and tough chip flow through the front surface of the cutter, the phenomenon of bonding, welding and other adhesion will occur, affecting the surface roughness of the processed parts.

 

  1. Tool wear is accelerated

The above materials generally contain high melting point elements, large plasticity and high cutting temperature, which make the tool wear faster and the tool wear and change frequently, thus affecting the production efficiency and increasing the tool use cost.

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Problems encountered during the operation of the alloy bit and its solution

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

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

 

Problem Solution
The front end of the alloy bit is broken Aimed at the bit again
Repair with a drill bit grinder
Improve stability, re-clamp parts, shorten overhang of alloy bit
Check speed/feed
The outer diameter of the alloy bit is worn Aimed at the bit again
Improve stability, re-clamp parts, shorten overhang of alloy bit
Check speed/feed
Repair with a drill bit grinding machine
Oversize/undersize holes To aim at tungsten steel drill bit
To reduce feed
Check speed/feed
The alloy bit is clogged with chips in chip removal tank Increase coolant flow, clean filter, clean bit coolant hole
To reduce feed
Improve stability, re-clamping the parts, shortening the overhang of alloy bit
Check speed/feed
Increase speed
vibration To reduce feed
Improve stability, re-clamping the parts, shortening the overhang of alloy bit
Check speed/feed
A small crack in the cutting edge Repair with a drill bit grinder
Aimed at the bit again
Check the carbide number
Increase speed
Hole asymmetry To reduce feed
Improve stability, re-clamp parts, shorten bit overhang
Check speed/feed
Alloy tool has short life Increase coolant flow, clean filter, clean bit coolant hole
Improve stability, re-clamping the parts, shortening the overhang of alloy bit
Check the carbide number
Check speed/feed

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.