Page 671 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

2 Chapter 23 Machining Processes: Turning and Hole Making

23.6 Reaming and Reamers

Reaming is an operation used to (a) mal<e an existing hole dimensionally more accu-
rate than can be achieved by drilling alone, and (b) improve its surface finish. The
most accurate holes in vvorkpieces generally are produced by the following sequence
of operations:
l. Centering;
2. Drilling;
3. Boring;
4. Reaming.

For even better accuracy and surface finish, holes may be burnished or internally
ground and honed (Sections 26.4 and 26.7).
A reamer (Fig. 23.26a) is a multiple-cutting-edge tool with straight or helically
fluted edges that remove very little material. For soft metals, a reamer typically
removes a minimum of 0.2 mm on the diameter of a drilled hole; for harder metals,
about 0.13 mm is removed. Attempts to remove smaller layers can be detrimental,
as the reamer may be damaged or the hole surface may become burnished (see also
Fig. 21.22 as an analogy). In this case, honing would be preferred. In general, ream-
er speeds are one-half those of the same-size drill and three times the feed rate.
Hand reamers are straight or have a tapered end in the first third of their
length. Various machine reamers (also called c/ouc/Qing reamers, because they are
mounted in a chuck and operated by a machine) are available in two types: (1) Rose
reamers have cutting edges with Wide margins and no relief (Fig. 23.26a). They

remove considerable material and true up a hole for flute reaming. (2) Fluted ream-
ers have small margins and relief, with a rake angle of about 5°. They usually are
used for light cuts of about 0.1 mm on the hole diameter.

asia ....., angle, _

Radial rake
Chamfer length
/\)\
Chamfer angle Chamfer relief Margin
_.,. /K- Land Width

.1 a, gm
relief angle R-

(H)

BI d A J! “V Body
mg
Looknut 7 __
G
a e “ li
Setscrew
Adjusting nut
(D)

FIGURE 23.26 (a) Terminology for a helical reamer. (b) Inserted-blade adjustable reamer.