Have you encountered any of these problems: How are drill bits made? What problems will be encountered in drill processing? About the drill material and its characteristics? What kind of measures will you take after the bit fails...

1 craft

1.1 Process

❶According to the design of the diameter and total length of the drill bit, you can choose an alloy bar cutting machine or use a wire cutting device for fixed-length processing.

❷For the bar material cut to fixed length, flat head on both ends, which can be realized on a manual tool grinder.

❸Chamfer or perforate the polished end surface of the alloy bar to prepare for grinding the outer diameter and shank of the drill, depending on whether the cylindrical grinding fixture is a male center or a female center.

❹Machining the outer diameter of the drill bit, the avoidance part and the outer diameter of the shank on the high-precision cylindrical grinder, to ensure the design requirements of outer diameter cylindricity, circle runout, surface finish and other design requirements.

❺In order to improve the processing efficiency on the CNC grinder, the drill tip can be chamfered before the alloy bar is placed on the CNC grinder, such as a 140° drill tip angle, which can be roughly ground to 142° when chamfering.

❻After cleaning the chamfered alloy bar, it is transferred to the CNC grinder process, and all parts of the drill are processed on the five-axis CNC grinder.

❼If you need to improve the chip flute and outer surface finish of the drill, you can also use the wool wheel and abrasive to grind and polish it before or after the fifth step. Of course, if this is the case, the drill needs to be processed in more steps.

❽For drills that have been processed and qualified, laser marking is performed on them, and the content or information such as the company's brand LOGO and drill specifications and dimensions.

❾Pack the marked drill bit and ship it to a professional tool coating company for coating

Note:

1. If the drill bit chip flute, or spiral or straight flute shape, this step also includes the negative chamfer of the peripheral edge; then the drill tip cutting edge is processed, including the drill tip tooth gap part and the drill tip back corner part; then proceed The back part of the peripheral edge of the drill is processed to grind a certain amount of drop to ensure that the contact surface between the outer diameter of the peripheral edge of the drill and the hole wall of the workpiece is controlled in a certain proportion.

2. For the processing of the negative chamfer of the drill tip, it is divided into CNC grinder processing or manual manual processing, which differs depending on the process of each factory.

1.2 Processing issues

❶When processing the outer circle part of the drill bit on the cylindrical grinder, pay attention to whether the fixture fails and fully cool the alloy bar during processing to maintain a good habit of measuring the outer diameter of the drill tip.

❷The drill bit is processed on a CNC grinder. When programming, try to divide the rough and finishing steps into two steps to avoid the existence of potential hot cracks due to too much grinding, which affects the service life of the tool.

❸Use a reasonably designed material tray for tool handling to avoid damage to the cutting edge caused by mutual collision between the tools.

❹For the blackened diamond grinding wheel, use oilstone for sharpening in time.

Note: According to the processed materials/equipment/working conditions, the processing technology is different. The above process arrangement only represents the author’s personal opinions and is only for technical exchanges

2. Drill bit material

2.1 High-speed steel

High-speed steel (HSS) is a tool steel with high hardness, high wear resistance and high heat resistance, also known as high-speed tool steel or front steel, commonly known as white steel.

High-speed steel tools are tougher and easier to cut than ordinary tools. High-speed steel has better toughness, strength and heat resistance than carbon tool steel. It requires UG programming, free basic video data, etc. plus Q group 45867470 cutting The speed is much higher than that of carbon tool steel (iron-carbon alloy), hence the name high-speed steel; and the performance of cemented carbide is better than high-speed steel, and the cutting speed can be increased by 2-3 times.

Features

The red hardness of high-speed steel can reach 650 degrees.

High-speed steel has good strength and toughness. After sharpening, the cutting edge is sharp and the quality is stable. It is generally used to manufacture small, complex-shaped tools.

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2.2 Cemented carbide

The main components of cemented carbide drill bits are tungsten carbide and cobalt, which account for 99% of all components, and 1% is other metals, so it is called tungsten steel (hard alloy). Tungsten steel is composed of at least one metal carbide Sintered composite material. Tungsten carbide, cobalt carbide, niobium carbide, titanium carbide, and tantalum carbide are common components of tungsten steel. The grain size of the carbide component (or phase) is usually between 0.2-10 microns, and the carbide grains are bonded together using a metal binder. The bonding metal is generally iron group metal, and cobalt and nickel are commonly used. So there are tungsten-cobalt alloys, tungsten-nickel alloys and tungsten-titanium-cobalt alloys. Tungsten steel drill bit material sintering molding is to press the powder into a blank, then heat it into a sintering furnace to a certain temperature (sintering temperature), keep it for a certain time (holding time), and then cool it down to obtain the tungsten steel material with the required performance.

Features:

The red hardness of cemented carbide can reach 800-1000 degrees.

The cutting speed of cemented carbide is 4-7 times higher than that of high-speed steel. High cutting efficiency.

The disadvantages are low bending strength, poor impact toughness, high brittleness, low impact resistance and low vibration resistance.

3 Application issues/measures

3.1 Drill tip wear

the reason:

1. The workpiece will move down under the action of the drill bit's penetration force, and the drill will bounce back after drilling through.

2.The rigidity of the machine tool is insufficient.

3. The drill material is not strong enough.

4. The drill bit jumps too much.

5. The clamping rigidity is not enough and the drill bit slips.

Measures:

1.Reduce the cutting speed.

2. Increase the feed

3. Adjust the cooling direction (internal cooling)

4. Add a chamfer

5.Check and adjust the coaxiality of the drill bit.

6.Check whether the rear angle is reasonable.

3.2 Ligament collapse

the reason:

1. The workpiece will move down under the action of the drill bit's penetration force, and the drill will bounce back after drilling through.

2.The rigidity of the machine tool is insufficient.

3. The drill material is not strong enough.

4. The drill bit jumps too much.

5. The clamping rigidity is not enough and the drill bit slips.

Measures:

1.Choose a drill with a larger back cone.

2. Check the beating range of the spindle drill bit (＜0.02mm)

3. Use a pre-center drill to make the top hole.

4. Use a more rigid drill bit, a hydraulic chuck with a neck sleeve or a heat shrink kit.

3.3 Accumulative tumor

the reason:

1. It is caused by the chemical reaction between the cutting material and the workpiece material (low carbon steel with higher carbon content)

Measures:

1. Improve lubricant, increase oil or additive content.

2. Increase the cutting speed, reduce the feed rate and reduce the contact time.

3. If you are drilling aluminum, you can use a polished and uncoated drill bit.

3.4 Broken knife

the reason:

1. The spiral groove of the drill is blocked by cutting, and the cutting is not discharged in time.

2. When the hole is fast drilling, the feed amount is not reduced or the maneuvering is changed to manual feed.

3. When drilling soft metals such as brass, the back angle of the drill bit is too large, and the front angle is not trimmed, so that the bit is automatically screwed in.

4. The sharpening of the drill blade is too sharp, resulting in a chipping phenomenon, and the blade cannot be withdrawn quickly.

Measures:

1. Shorten the cycle of changing tools.

2. Improve the installation and fixation, such as increasing the supporting area and increasing the clamping force.

3.Check the spindle bearing and sliding groove.

4. Use high-precision tool holders, such as hydraulic tool holders.

5. Use tougher materials