Reamer: Characteristics And Selection

The general working mode of reaming is that the workpiece does not move, and the reamer rotates and feeds axially into the hole.

When reaming on the lathe, the workpiece rotates and the reamer is fed axially.

The size and geometric accuracy of reamed holes are directly determined by reamers.

The reamer is composed of a working part, a neck and a shank.

The working part consists of a cutting part and a calibration part, in which the cutting part is conical and undertakes the main cutting work.

The calibration part is used to calibrate the hole diameter, smooth the hole wall and guide.

In order to reduce the friction between the calibration part and the machined hole wall, and to prevent the hole diameter from expanding, the rear end of the calibration part shall be machined into an inverted cone shape with an inverted cone amount of (0.005 ~ 0.006) /100.

The shank of the reamer is the part that clamps and transmits torque, usually a taper shank.

(1) Types of reamers

Machine reamers can be divided into machine reamers with shanks (straight shanks with a diameter of φ1 ~ φ20mm and taper shanks with a diameter of φ10 ~ φ32mm) and sleeve machine reamers (φ25 ~ φ80mm in diameter);

According to the number of cutter teeth, it can be divided into single tooth reamer and multi tooth reamer;

According to the shape of tooth groove, there are two kinds of reamers: straight groove reamer and spiral groove reamer.

Among them, spiral groove reamer is divided into left-hand spiral groove reamer and right-hand spiral groove reamer;

There are other reamers, such as adjustable reamers, modular reamers, taper reamers, guide bar reamers, etc.

Machine reamers are generally made of high-speed steel, but also hard alloy, cermet, PCBN and PCD.

Fig. 5-69 shows several commonly used reamers.

types of reamers

Fig. 5-69 types of reamers

a) Straight groove reamer

b) Spiral groove reamer

c) Single blade adjustable reamer

(2) Characteristics of reamer

The reamer has one or more cutter teeth, which are used to ream the drilled (or reamed) holes on the workpiece, mainly to improve the machining accuracy of the hole and reduce its surface roughness value.

It is a tool for finishing and semi finishing the hole, and the machining allowance is generally very small.

Because the reamer has the existence of the blunt radius of the cutting edge, a polishing edge, and a 0.03 ~ 0.05mm edge band on the back face, it has a large squeezing effect. Therefore, the reaming process is actually the result of cutting and scraping.

1. Single blade reamer

High geometric accuracy and low surface roughness can be obtained by machining holes.

When the single edge reamer is processed, it can use the machined hole to guide itself to increase the rigidity of the tool, so it can obtain high geometric accuracy in one process, ensure the roundness and cylindricity of the hole, and it is easy to operate and master.

2. Spiral groove reamer

Cutting is light, stable, chip removal is good, tool life is high, and reaming quality is good.

It is often used to ream deep holes or holes with intermittent surfaces (such as axial grooves). Spiral groove reamers are divided into right-hand and left-hand reamers.

Right rotation: the chips are discharged to the handle, which is suitable for machining blind holes.

However, when reaming, the axial component and the feed direction component are the same, which may lead to automatic feed and affect the processing quality, or make the reamer come out of the machine tool spindle and get stuck in the workpiece. Therefore, the cutting amount should be small.

Left rotation: the chip is exported along the feeding direction, which is suitable for reaming through holes.

The axial component force is pressed to the spindle of the machine tool, and the reamer clamping is more reliable.

3. Adjustable reamer

As shown in fig. 5-69c, the blade diameter of the adjustable reamer can be slightly adjusted for several times, which can be expanded for reuse, thus greatly reducing the loss of the reamer and the processing cost.

(3) Selection of reamer

1. Single blade reamer

It is suitable for finishing various materials on CNC machine tools, machining centers and turning, boring, drilling and other machine tools with certain rigidity and precision.

2. Adjustable reamer

As the reamer is a finishing tool, it has very high requirements for the hole size accuracy of the reamer.

The small loss of the reamer will affect the dimensional tolerance of the workpiece, especially in the field where reamers such as automobile engines are widely used, when the reamer edge has small loss, it can no longer be used.

Therefore, the consumption of the reamer is very large. In order to solve this contradiction, adjustable reamers can be used.

3. Selection of reamer geometric angle

(1) The recommended range of front and rear corners is shown in table 5-16.

Table 5-16 selection of front and rear angle of reamer

Processing Materials

Reamer cutting some materials

 

high-speed steel

carbide

high-speed steel

carbide

 

Front angle y0(°)

Rear corner a0(°)

Unhardened steel

0~4

0~-5

6~12

6~8

medium hard steel

5~10

-5~-10

6~12

6

Stainless steel, heat-resistant steel

8~12

5~8

aldary

0~5

-10~12

magnesium alloy

5~8

10~12

Aluminium and aluminium alloys

5~10

10~12

cast iron

0

5

6~8

8~10

(2) Selection of cutting cone angle.

Cutting cone angle 2φ mainly affects the size of feed resistance, tool life, hole machining accuracy and surface roughness.

When the cutting cone angle is small, the feed force is small, and the reamer has good guidance when cutting.

However, large deformation is caused by too small cutting thickness, and it is difficult for chip curling and chip removal due to the increase of cutting width, and the cutting in and cutting out time becomes longer.

Therefore, in order to reduce the labor intensity and feed force, a larger a value can be selected to reduce the cutting length and maneuvering time.

When processing steel, φ is 30 °, when processing brittle materials such as cast iron, φ is 6 ° ~ 10 °, and when processing blind holes, φ is 90 °.

(3) Selection of blade inclination.

As shown in Fig. 5-70, the cutting edge of the cutting part of the high speed steel straight groove reamer is generally 15 ° ~ 20 °.

In order to facilitate the manufacture of carbide reamers, λs=0 ° is generally taken.

When reaming blind holes, the reamer with blade inclination angle is still used, but a countersunk hole is opened at the end of the reamer to contain the chips.

blade inclination of reamer

Fig. 5-70 blade inclination of reamer

4. Recommended cutting parameters

Refer to table 5-17 and table 5-18 for cutting parameters of high speed steel and cemented carbide reamers respectively.

Table 5-17 cutting parameters of high speed steel reamer

Cutter diameter d/mm

low-carbon steel

low-alloy steel

high-alloy steel

cast-iron

oxidation-resisting steel

titanium alloy

120~200HBW

200~300HBW

175~230HBW

175~230HBW

f

Vc

f

Vc

f

Vc

f

Vc

f

Vc

f

vc

f/(mm/r)  vc/(m/min)

6

0.13

23

0.10

18

0.10

7.5

0.15

21

0.05

7.5

0.15

9

9

0.18

23

0.18

18

0.15

7.5

0.20

21

0.10

7.5

0.20

9

12

0.20

27

0.20

21

0.18

9

0.25

24

0.15

9

0.25

12

15

0.25

27

0.25

21

0.20

9

0.30

24

0.20

9

0.25

12

19

0.30

27

0.30

21

0.25

9

0.36

24

0.25

11

0.30

12

22

0.33

27

0.33

21

0.25

9

0.41

24

0.30

12

0.38

18

25

0.51

27

0.38

21

0.30

9

0.41

24

0.36

14

0.51

18

Table 5-18 cutting parameters of carbide reamer

Processing Materials

Cutter diameter d/mm

Back cutting depth d/mm

Feed rate f/(mm/r)

Cutting speed vc/(m/min)

steel

Rm/MPa

≤1000

<10

10~20

20~40

0.08~0.12

0.12~0.15

0.15~0.20

0.15~0.25

0.20~0.35

0.35~0.50

6~12

>1000

<10

10~20

20~40

0.08~0.12

0.12~0.15

0.15~0.20

0.15~0.25

0.20~0.35

0.35~0.50

4~10

Cast-ironRm≤100MPa)

<10

10~20

20~40

0.08~0.12

0.12~0.15

0.15~0.20

0.15~0.25

0.20~0.35

0.35~0.50

6~10

grey cast iron

Rm/MPa

<200

≤200

10~20

20~40

0.08~0.12

0.12~0.15

0.15~0.20

0.15~0.25

0.20~0.35

0.35~0.50

8~15

>200

<10

10~20

20~40

0.08~0.12

0.12~0.15

0.15~0.20

0.15~0.25

0.20~0.35

0.35~0.50

5~10

Note: reaming (Ra=3.2 ~ 1.6 μ m)

For steel and gray cast iron, the cutting speed can also be 60 ~ 80m/min.

The back feed rate is 0.15 ~ 0.35mm, and the feed rate is 0.4 ~ 0.6mm/r.

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