Specification for high speed steel drill bits

Drill bit Materials and Steels

  1. HSS bit is the most widely used bit in the industrial manufacturing of twist drill. We usually use high speed steel drill bits. When selecting the most suitable bit type for a particular hole processing task, the technologist needs to calculate the length-diameter ratio of the bit. What is the length-diameter ratio of the drill bit? Length-diameter ratio is the ratio of the depth of the hole processed to the diameter of the drill bit. For example, the drill bit diameter is 12.7mm and the hole depth to be processed is 38.1mm, so its length-diameter ratio is 3:1. When the length-diameter ratio is about 4:1 or less, the chip grooves of most standard high speed steel bits can discharge the chip removed from the cutting edge of the bit more smoothly.


  1. When the length-diameter ratio exceeds the above range, a specially designed deep-hole drill is needed to achieve effective machining. The standard products of HSS drill bits are in accordance with international standards. Once the aspect ratio of the machined hole is greater than 4:1, it is difficult for the HSS bit to push the chip tip out of the cutting area. The chip will soon block the bit’s chip drain. At this point, we need to stop drilling, withdraw the bit from the hole, remove the chip in the chip removal groove, and then drill down again to continue cutting. The above operation needs to be repeated many times to produce the required hole depth. This drilling method is often called “pecking”.


  1. The use of “peck” method to process deep holes will shorten the tool life, reduce the efficiency of machining, and affect the quality of the processed holes. Each time the drill bit is pulled out of the hole, and then the chip is removed and re-inserted into the hole, it is possible to deviate from the center line of the hole and make the hole diameter larger than the specified dimensional tolerance range. In order to solve the problem of deep hole machining, in recent years, drill bit manufacturers have developed two new types of deep hole machining bits — ordinary parabola bit and wide edge parabola bit.

The sizes of the metric drill bits

Are you looking for the size of the metric drill bit?
Here is a detailed introduction. We hope we can help you. If you have a problem with the drill bit, you can also use our drill bit grinder to repair it. The size of various drills can be repaired by corresponding drill bit grinding machines.

Are you looking for the size of the standard bit? Here is a detailed introduction. We hope we can help you. If you have a problem with the drill bit, you can also use our drill bit grinder to repair it. The size of various drills can be repaired by corresponding drill bit grinding machines.

Metric drill bit sizes define the diameter of the bit in terms of standard metric lengths. Standards organizations define sets of sizes that are conventionally manufactured and stocked. For example, British Standard BS 328 defines sizes from 0.2 mm to 25.0 mm.Continue reading

Wood drill bits: Lip and spur drill bits

Lip and spur drill bits are generally readily available in sizes from 3-16 mm (0.12– 0.63 in).

Conventional twist drill bits have the tendency to roam when offered to a level workpiece. For metalwork, this is responded to by piercing a pilot opening with a spotting drill bit. In timber, the lip and also stimulate drill bit is one more remedy: The centre of the drill bit is provided not the straight carve of the twist drill bit, however a spur with a sharp factor and also 4 sharp edges to reduce the timber. The sharp factor of the spur merely presses right into the soft timber to maintain the drill bit in line.Continue reading

Metal drill bits are used in spotting hole centers

Metal drill bits are used in spotting hole centers buy cheap drill bit grinder

Many contemporary solid-carbide bits need to not be made use of together with a spot drill bit or a facility drill bit, as solid-carbide bits are especially developed to begin their very own opening. Generally, area exploration will certainly create early failing of the solid-carbide little bit as well as a specific loss of opening top quality. If it is regarded essential to chamfer an opening with a place or facility drill little bit when a solid-carbide drill bit is utilized, it is finest technique to do so after the opening is pierced. When the solid-carbide bit which has the coating is ground by bit grinding machine, its coating film will be gone.

While the above is a typical use center drill bits, it is a practically inaccurate method and also ought to not be thought about for manufacturing usage. The proper device to begin a generally pierced opening (an opening pierced by a high-speed steel (HSS) spin drill bit) is a spotting drill bit (or a spot drill bit, as they are referenced in the United States). The consisted of angle of the spotting drill bit need to coincide as, or higher than, the standard drill bit to ensure that the drill bit will certainly after that begin without unnecessary anxiety on the little bit’s edges, which would certainly trigger early failing of the little bit and also a loss of opening high quality.

Standard spin drill bits might have the tendency to stray when begun on a not really prepared surface area. As soon as a little bit stray program it is challenging to bring it back on facility. A facility drill little bit regularly gives an affordable beginning factor as it is brief as well as consequently has actually a lowered propensity to stray when boring is begun.

When piercing with a hand-held drill the versatility of the bit is not the main resource of inaccuracy-it is the customer’s hands. Consequently, for such procedures, a facility strike is typically made use of to identify the opening facility before piercing a pilot opening.

Cutter Sharpening and Re-Grinding of Twist drill

The dimension precision and surface roughness of drilling, and drilling efficiency are directly related to the quality of cutter sharpening and re-grinding of twist drill.

In short, to avoid the cases as figure (b), (c), (d) during twist drill grinding that not only improve the drilling quality, but also will improve the drilling conditions, and come to prolong the service life of the twist drill.

Figure1: The impact of bit grinding on machining

(a) Grinding Correctly
(b) Point angle asymmetry
(c) Different Length of Cutter Grinding
(d) Point angle and Cutter Grinding are asymmetric

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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

Cutting performances and Advantages of Ni Zhifu Ordinary Twist Drill Bit

Definition of Ni Zhifu Ordinary Twist Drill Bit: Based on standard twist drill that the cutting part is grinded onto a special shaped drill bit. The standard twist drill consist of two major cutting lips (major cutting edges) and a chisel edge. The most fatal weakness is that the negative front angle of chisel edge and dead center are larger, led to the cutting conditions are unfavorable. Ni Zhifu Ordinary Twist Drill Bit is that grinding two symmetrical crescent grooves based on standard twist drill, forming arc blade, and then sharpening two inner straight edges on the chisel edge and dead center. After that, with the chisel edge and original two straight edges, making the standard twist drill into “Three knife-points and seven knife-edges” that is the Ni Zhifu Ordinary Twist Drill Bit.Continue reading