Adjustable boring bar

An adjustable cartridge to be mounted in a boring bar, the cartridge including an anvil rotatably affixed to said boring bar, said anvil including a pocket into which a lay-down indexable insert is affixed. The anvil is secured in an axially oriented slot which includes an arcuate seating face. Rotation of the anvil within the slot effects radial adjustment of the insert.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the filed of machining tools such as 
boring bars and more particularly to improved boring bars with adjustable 
cartridges. The boring bar includes a slotted area with an arcuate bottom 
face on which a correspondingly shaped surface of an anvil is seated. The 
boring bar also includes means for causing the anvil to slide upon a 
radiused surface of the boring bar and to rotate the anvil and cutting 
insert affixed thereto against a tension leaf spring relative to the 
boring bar. Set screws are thereby eliminated as the anvil is held in 
place by tension generated against the leaf spring. 
2. Description of the Related Art 
Pataky, U.S. Pat. No. 3,885,282 describes a machining tool including a 
holder and insert to which a cutting tool can be attached. The insert is 
rotatably mounted in a recess in the holder and fixed in a desired 
position relative to the holder by a locking screw. Rotatable adjustment 
of the insert allows for the altering of the tip working angle. 
Jester et al., U.S. Pat. No. 4,631,994 describe a linearly and angularly 
adjustable holder for a cutting tool. Such tool permits pivotal adjustment 
by means of an adjustment screw having a threaded portion seated in a 
basic element and a head which engages a recess in a rotatably mounted 
receptacle element which holds a cutting tool insert. Rotation of the 
adjustment screw causes rotation of the receptacle element. 
However, the structures described in the above mentioned patents are not 
directed to alleviating the problem of "stacked" tolerances. In addition, 
high speed boring bars cannot meet the precision cutting parameters 
required today with traditional cartridges mounted to the periphery of the 
boring bar due to the chatter created. Although creating a recess large 
enough to seat the cartridge within the bar may stabilize the bar, radial 
adjustment where the adjustment force is directed against the bar would 
still induce bowing of the bar in narrow diameter boring bars. 
Noggle, U.S. Pat. No. 4,927,301, which is incorporated by reference as if 
fully set forth herein, is directed to an improved boring bar which meets 
the shortcomings of bowing and stacked tolerances. The bar is equipped 
with a an anvil shaped cartridge which fits into a radiused bottom shaped 
groove in the bar. The anvil is adjusted by means of loosening a set 
screw, adjusting the anvil by means of an arcuate headed screw which 
forced the anvil against a spring washer retained by another screw at the 
opposite end of the anvil, and then, when the desired position is reached, 
the set screw is again rotated to lock the assembly in place. 
The present invention is an improvement over U.S. Pat. No. 4,927,301. The 
lock screw is eliminated, as are the spring washers. The method of 
operation is thereby simplified to a one step adjustment, thereby 
resulting in ease of operation, elimination of the set screws, and 
substantial labor savings. 
It is therefore an object of the present invention to provide an adjustable 
insert cartridge recessed within a boring bar where the force required for 
radial adjustment of the inserts is insufficient to induce bowing a boring 
bars, 
It is a further object to provide an adjustable cartridge which is properly 
balanced in high speed applications. 
Finally, it is a further object of this invention to provide an adjustable 
cartridge which is easily adjusted and holds the cartridge in place 
without the need for lock screw. 
SUMMARY OF THE INVENTION 
The present invention is directed to an adjustable cartridge in a rotatable 
boring bar which is easily adjusted by rotation of a single screw. The 
boring bar has a longitudinally oriented slot or recess with planar 
parallel walls which are spaced by the width of an arcuate seating 
surface. It is important that the cartridge seat have full contact, or at 
least two point contact, on the seating surface. It had been a 
disadvantage of the prior art that the cartridge sometimes did not seat 
along the seating surface in at least two points, thereby contributing to 
the chatter observed when using such boring bars. The seating surface 
intersects with the walls and opens radially to the periphery of the 
boring bar, The cartridge includes an anvil with a top face and a radiused 
bottom face. The top face includes a recessed pocket for receipt of an 
indexable insert, positioned between forward and rear portions. The 
radiused face of the anvil extends between the forward and rear portions 
and when seated within the slot, abuts against the corresponding radiused 
face. The forward and rear portions are recessed for receipt of means for 
preloading the anvil in said arcuate seat, respectively. 
The insert is positioned on the anvil and is axially spaced from the 
rotational center of the anvil such that fine adjustment may be 
accomplished and such that loading resulting from cutting operation is 
principally transferred to the bar. Inwardly directed cutting reaction 
forces on the cutting edges thus tend to load the anvil and the adjustment 
means rather that the preloading means. An advantage of the present 
invention is that the resilient preloading means is removed from the 
loading action, allowing for precision adjustment while minimizing 
chatter. Another advantage is that an indexable insert and adjustable 
cartridge is provided in a boring bar without removal of a large portion 
of bar stock, thereby maintaining tool strength. A further advantage is 
that the rotation of the anvil in the bottom of the bar eliminates the 
need for adjustment means which load the boring bar to the extent of 
inducing bowing in small diameter bars. A final improvement is that the 
cartridge may be adjusted in the arcuate sot and held in place without 
resort to lock screws passing through the bar and abutting the adjusting 
screw for the anvil or other means to retain the anvil against the side 
wall of the recess to retain the anvil in place.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the figures, wherein like numerals depict like structures, a 
boring bar 10 is provided for rotation about a longitudinally disposed 
axis 12. Boring bar 10 as is known in the art is of cylindrical form 
having a periphery 14. Disposed about the periphery is at least one, and, 
if desired, a plurality of axially dimensioned slots or recesses 16. Each 
recess includes parallel walls 18 joined at an arcuate seating surface 20 
which opens radially toward the periphery. 
The cartridge 22 comprises an anvil 24 which is generally an elongated 
piece of hardened tool steel having a uniform width and an axial dimension 
corresponding to the particular recess 16 selected. The cartridge 22 
further includes a radiused lower surface 26 which corresponds to the 
arcuate surface 27 to allow for axial rotation in the clockwise direction, 
or counter clockwise direction, depending upon the manner in which it is 
desired to adjust the cartridge. 
Anvil 24 further includes a top face 28 radially spaced from lower surface 
26 and at least one pocket 30 for receipt of lay down indexable insert 32. 
The pocket has at least two abutment walls 34 which intersect with a 
seating face 36. Seating face 36 includes an aperture 38 tapped to provide 
secure retention for an insert retaining screw 40. Although other securing 
means are available to those of ordinary skill in the art and are readily 
useable in the present invention with the appropriate modifications, a 
standard "iso" screw is preferred due to pace and weight considerations 
near the work piece. 
Referring to FIGS. 5 and 6, top face 28 includes axially spaced forward 42 
and rear portions 44 separated by insert 32. Arcuate lower surface extends 
from the forward 42 to rear portion 44. The rear portion 44 includes a 
first recessed area 46 which communicates motion from means for adjusting 
the cartridge and inducing counterclockwise rotation for radially 
adjustment of the insert 32. Although the range of adjustment is at least 
as much as the total "stacked" manufacturing tolerances of cartridge 22 
and bar 10, a range of adjustment through adjustment means 48 of as much 
as 0.020 inches is preferred. 
In particular, adjustment means 48 comprises an arcuate headed screw 50 
threaded in the boring bar and abutting a conical face 47 of the first 
recessed area 46 to provide camming force to the anvil 24. In order to 
eliminate slippage, a right hand screw is desired with a fine pitch and in 
particular with 32 threads per inch. There is no need for a securing screw 
to lock screw 50 in place as was the case in the prior art, particularly 
U.S. Pat. No. 4,927,301. This is a distinct advantage as the operator may 
easily adjust the anvil and be confident that it will remain in place 
without the added step of locking the screw in place with a locking set 
screw. The elimination of this lock screw results in substantial savings 
both in cost of manufacture because there is no need to drill apertures 
into the side of the bar transverse to the axis of rotation for receipt of 
the set screw, thereby contributing to the increased strength of the bar, 
and labor costs are reduced because the adjustment process has been 
simplified. 
The forward portion 42 includes a second recess area 52 and may include a 
dowel 54 which traverses an optional spring pocket 56 in area 52 of anvil 
24. Means for preloading the anvil 24 in recess 16 during adjustment is 
provided in the present invention as illustrated in FIGS. 5 and 6. Screw 
58 retains leaf spring 60 against second recessed area 52 and threads into 
the body 10 at floor 62 of recess 17. The recess is adapted to receive the 
aprinbg and includes sidewalls substantiall parallel to each other and 
parallel to the axis of rotation. The spring is held against the anvil at 
recess 52 to provide resilient preloading force. Dowel 54 is optionally 
present as a rolling surface to the spring. Should dowel 54 not be 
present, the spring locates against the surface of recess 54. 
Lay down inserts 32 comprise generally a wafer of hardened material such 
that tungsten carbide, ceramics or sialons to name a few. The desired 
material is dependent on the type of application and the boring 
parameters. For example, an a 21/8 inch boring bar about 32 inches in 
length and employing five adjustment cartridges as claimed and disclosed 
herein, 3/8 wide by 0.460 inch parallelogram shaped inserts available from 
GTE Valenite Corporation using tungsten carbide grade VC-2 are employed 
for soft abrasive materials such as cast iron. For boring applications in 
carbon steel, carbide grade VC-5 is available. In addition, various 
positive radial and negative axial rakes are contemplated depending on the 
application. When boring in carbon steel, it is preferable to employ 
parallelogram shaped inserts using a positive radial and axial rakes. In 
cutting materials such as cast iron, negative axial and radial rakes are 
employed. It will be recognized by those of skill in the art that the 
range of axial and radial rake angles will depend on a range of variables 
including the part specifications. 
The position of insert 32 and insert pocket 30 on top face 28 is important 
to obtaining the above disclosed range if adjustment. When anvil 24 is 
rotated within recess 16, it rotates about anvil central axis 64 when 
unrestricted by preloading means or adjustment means. Positioning pocket 
30 and insert 32 axially from cental axis 64 toward forward portion 42 
results in a decreasing range of adjustment the closer the pocket is 
placed to central axis 64. Although the exact position of insert 62 in 
anvil 24 depends in part on the size of the insert and anvil, it is 
generally known to those of ordinary skill in the art that loading during 
operation is absorbed by the boring bar rather than preloading means or 
adjusting means the closer the pocket 30 is placed to central axis 64. 
This results in reduced cartridge chatter and wear on the adjustment 
means. 
The present invention eliminates the need of a plurality of tapped 
apertures which would traverse the boring bar 10 in a direction generally 
normal to the recess walls and which open to the boring bar periphery 14 
to provide access to an operator. The apertures allow the insertion of 
screws to force the anvil to abut one wall of recess 16, thereby holding 
it in place. The elimination of these screws results in a substantial 
savings in operation and machining costs. 
In operation, rapid adjustment of the radial position of the insets 32 is 
accomplished by adjusting screw 50, thereby forcing arcuate screw head 51 
against conical surface 47 of the first recess 46 of rear portion 44 of 
anvil 24. The camming force developed between screw head 51 and the first 
recess 46 drives anvil 24 along arcuate seat surface 20, rotating anvil 24 
in the desired direction. Insert 32, spaced axially from the rotational 
central axis 64 of the anvil is generated radially a distance "d" to a new 
distance "dl". At the desired point of adjustment, rotation of screw 50 is 
halted and the preloading means, depicted as leaf spring, holds the anvil 
in place without the need for set screws or the need for means to force 
the anvil to abut one of the side walls of recess 16. 
Those skilled in the art recognize that various modifications may be made 
to the structures described herein without departing from the scope and 
spirit of the invention.