- Reamers are normally supplied with straight flutes or
Helical Flutes for RH Cutting
- Intermediate diameters, if ordered, shall be supplied with
the same dimensions as the next larger standard size.
- Non standard or special reamers are manufactured against
specific orders.
- Morse Taper Shanks dimensions are according to IS : 1715 -
Dimensions for self holding tapers.
- Driving square according to IS 1850 - Dimensions for shank
diameters and driving squares for rotating tools.
- Other general requirements are maintained according to IS
: 5443. Technical supply conditions for high speed steel Reamers.
| Hardness : |
|
| Cutting portion |
: |
760 HV to 900 HV. |
| Shank portion |
: |
|
| Parallel Shank |
: |
240 HV to equal to Cutting portion |
| Morse Taper Shank |
: |
|
| Tang of Morse Taper Shank |
: |
300 HV to 450 HV. |
- Reamers are normally supplied with m6 tolerance on cutting
portion and are expected to produce H8 holes ; by selection will also be suitable for H7
holes.
- Runout Tolerance :
Run-out tolerances are usually maintained for standard reamer as shown in the table below
RUN OUT TOLERANCES |
Reamer diameter |
Machine Reamer |
Hand Reamer |
|
|
On
Bevel Edge |
On
Diameter |
On MT
Shank
Large End dia |
|
|
1
3
6
10
18
30
50 |
3
6
10
18
30
50
80 |
|
0.020
0.020
0.025
0.025
0.030
0.030
0.040 |
0.005
0.006
0.008
0.008
0.009
0.011
0.013 |
0.010
0.012
0.015
0.018
0.021
0.025
0.030 |
|
0.030
0.030
0.030
0.036
0.042
0.050
0.060 |
|
- Reamers shall have a back taper at the rate of 0.010 to
0.020 per 100 mm cutting edge length upto 30 mm diameter and 0.020 to 0.030 per 100 mm for
sizes above 30 mm diameter.
- Reamers according to DIN, BIS and ANS are also
manufactured against specific orders.
Method of Determining the
Special Tolerance
The maximum limit for the reamer diameter
= the maximum limit of the hole - 0.15 .
The value of 0.15 is to be rounded to next higher value of 0.001 mm.
The minimum limit of the reamer diameter
= the maximum limit of the reamer - 0.35 .
The value of 0.35 is to be rounded to next higher value of 0.001 mm.
Example :
For a 12H7 hole
Alfa - 0.018 Hole size maximum limit - 12.018
Minimum limit - 12.000
Maximum limit of reamer diameter= Maximum limit of the hole - 0.15 Alfa
= 12.018 - 0.15 x 0.018=12.018 - 0.0027
= 12.015
Minimum limit of reamer diameter = Maximum limit of reamer diameter-0.35
Alfa
= 12.015 - 0.35 x Alfa = 12.015 - 0.0063
= 12.015 - 0.007 = 12.008
Dimensions in mm
Conforming to IS : 5443 - 1984
RECOMMENDED UNDERSIZES FOR REAMING
| Material |
Range of diameter
of bore |
|
| |
From 3 Upto 5 |
Over 5
Upto 10 |
Over 10
Upto 20 |
Over 20
Upto 30 |
Over 30 |
Steel upto 70
Kg/mm2
Cast Iron
Plastics - soft |
0.1-0.2 |
0.2 |
0.2 |
0.3 |
0.4 |
Steel 70-100
Kg/mm2
Brass, bronze |
0.1-0.2 |
0.2 |
0.2 |
0.3 |
0.3 |
Copper,
Light metals |
0.1-0.2 |
0.3 |
0.3 |
0.4 |
0.5 |
| Malleable cast
iron |
0.1-0.2 |
0.2 |
0.3 |
0.4 |
0.5 |
| Plastic-hard |
0.1-0.2 |
0.3 |
0.4 |
0.4 |
0.5 |
| Steel casting |
0.1-0.2 |
0.2 |
0.2 |
0.2 |
0.3 |
Values shown in mm.
To obtain optimal surface quality when reaming hard material the above values for
allowances to be halved and preferably performed in two operations pre-finishing and
finishing. If pre-drill hole finish is obtained rough the above values may have to be
increased slightly.
REAMING SPEEDS AND FEEDS
Reaming Speeds-vary considerably depending on part of the material to be
reamed, type of machine and finish and accuracy required. Generally reaming is done at
about - 2/3 the speed used for drilling the same material.
Reaming Feeds-Feeds are usually much higher than those recommended for
drilling the same material i.e. as much as 200 to 300% of drilll feeds. Very low feed will
result in more reamer wear. Very high feed may lower the finish and accuracy of hole. It
is desirable to use high feed at the same time finish and accuracy should be achieved. |
|
|
|
