Micro-adjustable boring bar

A micro-adjustable boring bar with an interchangeable head and cartridge utilizing a micro-adjustable key and a stationary key with an adjustment screw mounted independently on a boring bar, and a replaceable and interchangeable head having a recess for the adjustable key and a slot for the stationary key, the slots in both the boring bar and the head being open ended for easy machining.

BACKGROUND OF INVENTION 
Adjustable boring bars are common in the art with radial adjustments being 
possible in various ways. With the advent of tape controlled machines and 
automation equipment, it has become extremely important to be able to 
change tooling rapidly without changing the intended dimension. Many tools 
are single purpose tools in a single location in a machine. Thus, when a 
tool point wears or breaks, it must be replaced quickly to avoid a long 
shut down of the machine. 
Thus, it is an object to provide a boring bar and head which is simple in 
construction with a minimum of parts which can be readily disassembled and 
replaced with accurate relocation. The present invention is intended to be 
an improvement on the disclosure in the U.S. patents to Kelm U.S. Pat. 
Nos. 3,486,40l (1969) and Heuser 3,516,134 (1970) in the reduction of the 
parts required, the ease of machining, the interchangeability of the 
boring heads, and the locking means for the head. 
In addition, the present invention provides a construction with open ended 
slots readily machined and ground for accuracy, eliminating the need for 
complex machining operations in either the boring bar or the head. 
Other objects and features of the invention will be apparent in the 
following description and claims in which the principles of the invention 
are set forth together with details of construction directed to tool 
makers skilled in the art to enable them to make and use the invention, 
all in connection with the best modes presently contemplated for the 
practice of the invention.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS 
In FIGS. 1 to 4, a first embodiment of the boring bar and boring head is 
shown. A boring bar shaft 20 has milled in the outer end a diametrical 
slot 22 with side walls in parallel planes which in turn are parallel to 
the axis of the bar. The slot 22 is deepened at one end to provide a side 
recess 24 with a semi-circular wall connecting flat side walls. A locator 
adjustment key block 30 has a rounded end to seat in the recess 24 with a 
portion fitted in slot 22 and a portion extending beyond the boring bar at 
32. The locator key has an L-shape so that a corner portion of the L 
interfits with the junction corner of slots 22 and 24 (FIG. 3). A socket 
head screw 34 threaded into the boring bar secures the key block 30 
rigidly in the boring bar. 
A micro-adjustment screw 36 with a graduated head 38 is fitted into a 
counterbored recess 40 and retained by a cross pin 42 acting in a groove 
in the head 38. The shaft of screw 36 threads into a square base of an 
adjustable key 50 slidably movable in slot 22. Thus, rotation of screw 36 
causes transverse movement of the key 50. Extending outwardly from key 50 
and from slot 22 is a pin 52. 
An adjustable boring head 60 has a circular base with a diameter comparable 
to the boring bar 20 with a flat bottom surface provided with a 
diameterical slot 62 with parallel walls to receive the projecting portion 
of the key 30 in a sliding relationship and relatively close fit. The slot 
62 terminates at 64. A hole 66, parallel to the axis of rotation of the 
assembly and centered with respect to the slot 62, receives pin 52 in a 
snug fit. 
A portion of the boring head 60 is cut away to provide an exposed flat 
surface 68. An elongate slot 70 is provided through the head at this point 
to accommodate a headed bolt 72 which will clamp the head against the 
boring bar. 
Thus, when the bolt 72 is tightened, the boring head is secured by the key 
block 30, the pin 52, and the bolt. By releasing the bolt 72, the screw 36 
can be rotated to adjust the transverse key 50 and the position of the 
boring head. 
A suitable pocket 80 is provided on the boring head to receive an anvil 
insert 82, a cutting insert 84, and a chip breaker 86, all held in place 
by a clamp 88 locked by a screw 90. 
In FIGS. 5 to 8, a modified boring head is shown with identical adjustment 
connections to the boring bar 20. The head in this embodiment is provided 
with an angled slot 100 with a second narrower slot 102 in the base of 
slot 100 to receive a cartridge block 104 carrying a suitable cutting 
insert 106 held by a clamp 107. An elongate slot 108 in the cartridge 
receives a bolt 110. Thus, the axial and radial reach of the cutting 
insert can be adjusted by moving the cartridge after release of bolt 110 
while radial adjustment can be accomplished by the action of micro-screw 
38. 
In FIGS. 9 to 17, additional embodiments of the invention are illustrated. 
In some cases, it is desirable to have fixed adjustment boring bars which 
operate at a fixed radius at all times. The present invention lends itself 
to either a fixed adjustment or a variable adjustment condition. This 
reduces the inventory needed for the flexibility desired and allows a 
single boring bar drive to be used for either condition. 
To accomplish the above objective, a boring bar 20 is shown in FIGS. 9 and 
14 having the same configuration as that illustrated in FIGS. 1 to 6. 
The diametrical slot 22 with the deepened portion 24 is identical in all of 
the boring bars. However, the locator block in these embodiments of FIGS. 
9 to 17 extends diametrically across the entire boring bar filling the 
slots 22 and 24. In FIGS. 11, 12 and 13, this stationary block 130 is 
illustrated having a portion 132 to fit the recess 24 and a main body 134 
to extend across the entire bar with rounded ends 136 and 138 to conform 
the contour of the bar 20. A counterbored hole 140 receives the holding 
screw 34. A portion 142 extends out of the boring bar slot 22 to serve as 
a locator for a boring head and a dowel pin 144 projects upwardly from 
surface to engage a boring head. 
The boring head 150 has an elongate recess 152 to receive extension 142 of 
block 130 and a hole 154 to receive pin 144. See sectional view in FIG. 
10. A fastening headed screw 72 functions to clamp the boring head 150 
securely in the fixed position in FIGS. 9 to 13 as was shown in the 
embodiment of FIGS. 1 to 4. The boring head otherwise is the same as in 
FIG. 1 with a cutting insert 84 and a clamp 156. 
In FIGS. 14 to 17, another boring head 170 for use in a fixed position is 
illustrated. This boring head 170 affixes to the boring bar 20 in the same 
manner as that shown and described in connection with FIGS. 9 to 13. This 
boring head 170 has an angled surface 172 as shown in FIG. 14 with a 
milled slot 174 to receive a rib 176 formed on the bottom of an insert 
cartridge 180 carrying a replaceable and indexable cutting insert 182. A 
headed bolt 184 is threaded into a tapped hole in the boring head. This 
bolt passes through a counterbored slot 184 in the cartridge 80 so that, 
when loosened, the cartridge can be moved longitudinally. A back-up screw 
186 seats against a back-up abutment 188 on the boring head to position 
the cartridge longitudinally. 
The effect of the L-shaped key block in conjunction with the pins 
extending, respectively, either from the adjustable index block or the 
stationary key block, rigidly associates the boring head and the boring 
bar making it possible to utilize not only the replaceable inserts but 
also the angled cartridge elements to provide additional flexibility for 
the tool owner. The same boring bar can be used for adjustable or 
non-adjustable boring heads and with the single clamped insert or the 
cartridge type tool.