COMMON HAND-TOOLS 



275 



(a) 



314. Kinds of Reamers. When not carefully sharpened, 

 all forms of reamers have a tendency to produce a rough hole. 

 Too much clearance reduces the support of the reamer in 

 the hole and tends to make it work unsteadily. 



Reamers are made from tool steel and then hardened and 

 tempered to a straw color; they may be straight or tapered, 

 and may have a square end or tapered shanks. The square- 

 end reamer is generally operated by hand. Reamers may 

 be solid or may be made with inserted, adjustable blades. 

 The solid reamer has the 

 disadvantage of becom- 

 ing undersized as soon as 

 worn, but the adjustable 

 reamers are considerably 

 more expensive. 



Figure 138a shows a 

 straight-fluted reamer 

 with a square end, the 

 type most commonly 

 used. Figure 138b shows 

 a spiral straight reamer, 



(a) Straight-Fluted Reamer 

 (6) Spiral Straight Reamer 



(c) Straight-Fluted Shell Reamer 



(d) Rose Reamer 



FIG. 138. Reamers. 



which is used when a slow feed is required. The spiral is 

 made left-handed, while the reamer, in cutting, turns right- 

 handed ; this construction tends to prevent the reamer from 

 drawing into the hole and sticking. Figure 138c is a straight- 

 fluted shell reamer, so called because it is made hollow in the 

 center in order that it may be used with a mandrel. Figure 

 138d shows a rose reamer. There are a great many other 

 kinds of special reamers made for different classes of work, 

 but space will not permit their being described here. 



Reamers are rarely given less than 6 flutes, and usually 

 have from to %0, the number depending upon the size of 



