twist drill
1 Overview
Twist drill is a tool for processing holes from solid materials, and it is also the most widely used tool in hole processing tools. The twist drill is composed of three parts: working part-the working part is divided into cutting part and guide part. The cutting part is responsible for the main cutting work; the role of the guiding part is to play a guiding role when the cutting part is cut into the working hole, and it is also the preparation part of the cutting part. In order to improve the rigidity and strength of the drill bit, the core diameter of the working part increases toward the shank, and the increment of the core diameter per 100mm length is 1.4-2mm.
Shank-the clamping part of the bit, and used to transmit torque. There are two types of shank: straight shank and tapered shank, the former is used for small diameter drill bit, and the latter is used for large diameter drill bit.
Neck-The neck is located between the working part and the shank. It is used to retract the grinding wheel when grinding the shank. It is also where the drill bit is marked.
Twist drills have implemented an export product quality licensing system, and products that have not obtained an export quality license are not allowed to be exported.
2. Inspection standards
Twist drill products adopt national standards and international standards equivalently, see Table 6-10-56.
Table 6-10—56 Twist drill inspection standards
product name
National standard
Equivalent international standard
Scope of application (diameter)
Thick straight shank twist drill
GB/T6135.1-1996
—
0.10-0.35mm
Straight shank short twist drill
GB/T6135.2-1996
ISO235-1980
0.50-40.00mm
Straight shank twist drill
GB/T6135.3-1996
ISO235-1980
0.20-20.00mm
Straight long twist drill
GB/T6135.4-1996
ISO494-1975
1.00-31.50mm
Straight shank super long twist drill
GB/T6135.5-1996
ISO/DIS3292
2.0-14.0mm
Morse taper shank twist drill
GB/T1438.1-1996
ISO235-1980
3.00-100.00mm
Morse taper shank long twist drill
GB/T1438.2-1996
—
5.00-50.00mm
Morse taper shank twist drill
GB/T1438.3-1996
—
6.00-30.00mm
Morse taper shank super long twist drill
GB/T1438.4-1996
ISO/DIS3291-93
6.00-50.00mm
3. Inspection items and technical requirements:
(1) Appearance: cracks, chipping, burns, blunt cutting edges and other defects that affect the performance are not allowed.
(2) The surface roughness of the twist drill is shown in Table 6-10-57.
Table 6-10-57 Surface Roughness
Type
Rz behind the cutting edge
Blade Rz
Groove Rz
Handle surface Ra
Ordinary twist drill
6.3
6.3
12.5
1.25
Precision twist drill
6.3
6.3
6.3
1.25
(3) The dimensional deviation of the working part is in accordance with national standards.
(4) The position tolerance of ordinary grade twist drills shall be as specified in Table 6-10-58, and the position tolerance of precision grade twist drills shall be as specified in Table 6-10-59.
Table 6-10-58 Ordinary grade twist drill position tolerance mm
project
d≤3
d＞3～6
d＞6～10
d＞10～18
d＞18
Radial circular runout of the working part to the axis of the shank
0.08
Symmetry of the drill core to the axis of the working part
0.16
0.20
0.24
0.30
0.36
The bevel of the cutting edge to the axis of the working part
0.10
0.15
0.18
Table 6-10—59 Precision pole twist drill position tolerance mm
project
d≤3
d＞3～6
d＞6～10
d＞10～18
d＞18
Radial circular runout of the working part to the axis of the shank
0.06
Symmetry of the drill core to the axis of the working part
0.08
0.10
0.12
0.14
0.18
The bevel of the cutting edge to the axis of the working part
0.06
0.08
0.10
0.12
0.15
Blade ditch aliquot
0.06
0.08
0.12
0.15
0.18
(5) Diameter inverse taper of working part of twist drill: 0.03～0.10mm per 100mm length.
(6) Drilling core increment of working part of twist drill: 1.4～2.0mm per 100mm length.
(7) Material: Twist drills are made of W6Mo5CR4V2 or other brands of high-speed steel of equivalent performance; welded twist drill shanks are made of 45, 60 steel or alloy steel of equal or higher performance.
(8) Hardness: Hardening range, hardness and flat tail hardness of the working part of the twist drill. Hardening range: the overall twist drill is at a length of 4/5 of the edge groove from the drill tip; the welding twist drill is at a length of 3/4 of the edge groove from the drill tip.
Hardness: not less than 63HRC
Flat tail hardness: 30-45HRC.
(9) Ordinary grade twist drills should be subjected to steam surface treatment or other surface strengthening treatment.
(Twist drills with a diameter of d<3mm are not allowed to undergo steam surface treatment or other surface strengthening treatment.)
(10) Performance test: The cutting performance test should be carried out in accordance with the provisions of this standard before leaving the factory. After the test, the twist drill must not have chipping and significant wear, and maintain its proper performance.
① The performance test of the twist drill should be carried out on the drilling machine that meets the accuracy standard according to the provisions of Table 6-10-60.
Table 6-10-60 performance test of twist drill
Diameter dmm
Cutting speed m/min
Feed amount mm/r
Drilling depth mm
Number of holes
~2.0
30
Manual
6
40
＞2.0～2.5
7
＞2.5～3.0
9
＞3.0～3.5
10
＞3.5～4.0
12
＞4.0～4.5
28
0.12
14
30
＞4.5～5.0
0.15
16
＞5.0～6.0
0.17
20
＞6.0～8.0
0.20
25
＞8.0～10.0
0.25
＞10.0～12.0
0.28
30
20
＞12.0～14.0
0.32
＞14.0～16.0
0.36
＞16.0～18.0
0.40
35
＞18.0～20.028
0.43
40
Note: When the speed or feed of the machine tool does not meet the standard, the feed per minute should not be lower than the value calculated according to the standard.
②The test material is No. 45 or No. 50 steel annealed or normalized, and its hardness is 170～200HB. The side for drilling should be pre-machined and should be perpendicular to the centerline of the machine tool spindle.
③ The cooling liquid is an emulsified oil solution.
④ Drilling does not pass through holes.
(11) Marking and packaging:
①The mark should be on the twist drill (the twist drill with diameter d<3mm may not be marked):
a. Trademark of the manufacturer;
b. Twist drill diameter;
c. Material Code (HSS).
② The packaging box should be marked:
a. Name and trademark of the manufacturer;
b. The mark specified in this standard;
c. Material brand or code;
d. number of pieces;
e. Year and month of manufacture.
③Packaging: Twist drill should be treated with anti-rust before packaging. The packaging must be firm and can prevent damage during transportation.
