Section 13. qxd

Expansion reamers
permit a slight expansion by a wedge so that the
reamer may be resharpened to its normal size or for job shop use; they pro-
vide slight variations in size. 
Adjustable reamers
have means of adjusting
inserted blades so that a definite size can be maintained through numerous
grindings and fully worn blades can be replaced with new ones. 
Shell ream-
ers
constitute the cutting portion of the tool which fits interchangeably on
arbors to make many sizes available or to make replacement of worn-out
shells less costly. Reamers float in their holding fixtures to ensure align-
ment, or they should be piloted in guide bushings above and below the
work. They may also be held rigidly, such as in the tailstock of a lathe.
The 
speed
of high-speed steel reamers should be two-thirds to three-
quarters and 
feeds
usually are two or three times that of the correspond-
ing drill size. The most common tool materials for reamers are M1, M2,
and M7 high-speed steels and C2 carbide.
Fig. 13.4.14
(
a
) Various types of drills and drilling and reaming operations; 
(
b
) spade drill; (
c
) trepanning tool with four cutting-tool inserts.
(b)
Cutting 
tool 
inserts
Shank
(c)
Table 13.4.7
General Recommendations for Drilling
Feed, mm/r (in/r)
Workpiece
Surface speed
Drill diameter
r/min
material
m/min
ft/min
1.5 mm (0.060 in)
12.5 mm (0.5 in)
1.5 mm
12.5 mm
Aluminum alloys
30–120
100–400
0.025 (0.001)
0.30 (0.012)
6,400–25,000
800–3,000
Magnesium alloys
45–120
150–400
0.025 (0.001)
0.30 (0.012)
9,600–25,000
1,100–3,000
Copper alloys
15–60
50–200
0.025 (0.001)
0.25 (0.010)
3,200–12,000
400–1,500
Steels
20–30
60–100
0.025 (0.001)
0.30 (0.012)
4,300–6,400
500–800
Stainless steels
10–20
40–60
0.025 (0.001)
0.18 (0.007)
2,100–4,300
250–500
Titanium alloys
6–20
20–60
0.010 (0.0004)
0.15 (0.006)
1,300–4,300
150–500
Cast irons
20–60
60–200
0.025 (0.001)
0.30 (0.012)
4,300–12,000
500–1,500
Thermoplastics
30–60
100–200
0.025 (0.001)
0.13 (0.005)
6,400–12,000
800–1,500
Thermosets
20–60
60–200
0.025 (0.001)
0.10 (0.004)
4,300–12,000
500–1,500
N
OTE
: As hole depth increases, speeds and feeds should be reduced. Selection of speeds and feeds also depends on the specific surface finish required.
removed to chips; the