Boring machine

A boring machine has two spindle driven boring bars mounted on a common slide and supported by separate quills, each of which is movable relative to the slide. A stop on each quill locates its respective boring bar relative to a locating surface on the workpiece so that a cutting tool on each boring bar can be fed radially to machine the face of a counterbore at the desired depth relative to the locating surface on the workpiece. The machine includes a compensating mechanism for adjusting the cutting tools on each boring bar to compensate for tool wear.

This invention relates to a boring machine for boring holes with multiple 
diameters, and, more particularly, holes where one of the diameters is a 
counterbore whose precise depth dimension is measured from a reference 
plane on the workpiece, the precise location of which is unknown. 
It is common in the metal machining industry to be required to machine a 
workpiece and maintain a dimension given from a reference surface other 
than the surface that the workpiece is supported on during machining. The 
problem is compounded by the fact that the dimensional tolerance between 
the workpiece support surface and the workpiece reference surface is 
frequently greater than the required tolerance of the dimension to be 
machined. This makes it mandatory to locate the dimension holding portion 
of the machine tool against the surface from which the machining dimension 
is given. 
Another situation that can further compound this problem is where the 
surface from which it is necessary to locate the dimension is not a true 
plane. This can be caused by several factors, but mainly by the distortion 
of the workpiece resulting from the clamping of the workpiece on the 
machining fixture and/or by the forces generated by the machining cutter 
on portions of the workpiece that are not adequately supported. This 
non-planar surface will serve as a much better reference location if it is 
contacted by a stop on the machine that consists of several locating 
buttons that are gimbaled in such a way as to average the error of the 
plane. 
A typical workpiece which presents the above problems is a cylinder block 
for an internal combustion engine, particularly a diesel engine block 
where liners are to be incorporated to define the piston bore. These 
liners have an enlarged flange at their upper end that is received by a 
counterbore in the top face of the block in such a way that the flange of 
the liner extends slightly above the top surface of the block casting. 
When the cylinder head is assembled to the engine block, the flange at the 
upper end of the liner will be pinched between the bottom of the 
counterbore and the underside of the head to form a metal seal which is 
both gas and liquid tight. This sealing requirement dictates that the 
cylinder head and the flanged end of the liner both be flat and the latter 
square with the bore. This in itself is not a difficult manufacturing 
problem; the portions of the arrangement requiring new techniques are the 
critical depth, squareness, and finish of the bottom of the counterbore. A 
single cylinder head extends over and seals several liner ends. This 
requires that all of the individual liner ends extend nearly the same 
amount above the top face of the cylinder block. This is controlled by the 
thickness of the liner flange and the depth of the counterbore. The bottom 
face of the liner flange has a critical seal requirement when it seats 
against the bottom of the counterbore and it is desirable that this bottom 
face of the counterbore be generated with a single point tool feeding 
radially at it rotates to produce a surface with spiral tool marks 
thereon. It is found that this surface must be flat and square with the 
axis of the bore, and, if not, it should have a slight conical taper which 
makes the counterbore slightly deeper as the diameter increases. Any taper 
in the opposite direction cannot be tolerated, and, to insure that this 
does not happen, the surface is preferably purposely generated with the 
desired taper. 
With the machine of this invention, to maintain the critical depth of the 
counterbore the depth is gaged immediately after it is finish machined to 
determine if tool wear or other factors are tending to make it approach 
one of its tolerance limits. If required, the tool is automatically 
compensated in the proper direction to insure that the following 
workpieces are the proper size. 
Considering that a cylinder block has many bores and the time required to 
machine a single bore, it is desirable to machine a plurality of bores 
simultaneously by utilizing a plurality of machine spindles on a single 
slide station of a transfer machine. As pointed out above, the depth of 
each of these counterbores must be individually controlled from the top 
surface of the cylinder block. Therefore the stop to perform this function 
cannot be on the slide that carries the multiple machine spindles, but 
must be on the individual spindles. In the present machine this is 
accomplished by utilizing a slideable quill in each spindle that carries 
the stop that individually controls the depth of each boring bar. 
It is an object of the invention to provide a boring spindle and machine 
slide arrangement to precision bore with the same boring bar a hole of 
several diameters, one of which is a counterbore. 
It is another object of the invention to machine the face of the 
counterbore with a single point tool that can generate a slight conical 
angle on the face. 
It is a further object to provide a mechanism for compensating the single 
point facing tool for size change, while at the same time compensating the 
boring tools with a separate mechanism. 
It is a further object to locate the depth of the counterbore from the 
surface from which it is dimensioned, utilizing a three point, gimbaled 
stop member, to average the errors in flatness of the surface. 
It is still another object of the invention to simultaneously machine 
duplicate bores in the same workpiece, with the spindles mounted on the 
same slide but separately controlled for depth of the counterbore.

FIGS. 1 and 2 are views of a machine embodying the invention showing the 
overall arrangement in a generally diagrammatic manner without structural 
details. In addition, the tool compensating mechanism shown in FIG. 4 is 
broken away and not shown in FIGS. 1 and 2. However, these views show 
sufficient structure to illustrate the general operation of the machine. 
Referring to FIGS. 1 and 2, the machine includes a base 10 on which is 
slideably arranged for vertical movement a slide 12 powered by a cylinder 
14 through a rod 16. FIG. 2 shows two separate spindle assemblies 18 
mounted on a single slide 12. Each spindle assembly is rotated by its own 
motor 20 through pulleys 22,24 and belt 25. Each spindle assembly 18 
includes a boring bar, generally designated 26, journalled within a quill 
28 arranged for vertical sliding movement in a housing 30. Each housing 30 
is fixed to slide 12. A stop assembly 32 is secured to the lower end of 
each quill 28 and is adapted to engage the top face S of the workpiece W 
around the hole to the machined. Each boring bar has mounted thereon 
cutting tools 34,36 for machining the straight vertical bores 38,40 in the 
workpiece. A third cutting tool 42 on each boring bar is adapted to 
machine the diameter of the counterbore 44 and a fourth cutting tool 46 is 
arranged to machine the face of counterbore 44 at the desired depth 
dimension measured from the top face S of the workpiece. Tool 46 is 
mounted on a tool slide, hereinafter described, but not shown in FIGS. 1 
and 2, which is shiftable transversely of the boring bar in response to 
vertical reciprocation of a rod 48 of a hydraulic cylinder 50. 
In the arrangement thus far described, at the beginning of a machining 
cycle slide 12 is fully retracted upwardly where it had been stopped at 
the end of the previous cycle by the tripping of switch 51 on base 10 by 
dog 52 on slide 12. Thus, each spindle assembly 18 is initially in a 
raised position and the two boring bars 26 are disposed above the 
workpiece W to allow its removal and replacement with another workpiece to 
be machined. When the cycle is initiated cylinder 14 will advance slide 12 
downwardly at a rapid rate until switch 54 is tripped by dog 56. At this 
point the boring bar 26 is vertically positioned to start boring the 
diameters of bores 38,40. The workpiece has had these bores rough machined 
previously so that bore 40 is at least slightly larger than bore 38 to 
allow cutting tool 34 to pass through rough machined bore 40 during rapid 
advance of the slide. When switch 54 is tripped by dog 52 cylinder 14 
advances slide 12 and the two spindle assemblies, together with their 
boring bars, at the desired feed rate to finish machine bores 38,40. While 
the slide 12 is advancing at the feed rate, tools 42 finish machine the 
diameters of counterbores 44 to the semi-finished depth. When the 
semi-finished depth of each counterbore 44 has been reached, the 
respective stop assemblies 32 will contact the top face of the workpiece 
around each of the holes being machined. Since quills 28 are slideable 
axially in housings 30, after stop assemblies 32 contact the top face of 
the workpiece slide 12 is permitted to further advance downwardly a small 
amount before it contacts the fixed stop 58 on base 10. If the top surface 
S of the workpiece is not a true plane, the above-described arrangement 
will allow each spindle assembly and its boring bar to be individually 
located by the annular surface portion of the top face of the workpiece 
that immediately surrounds the hole that it is machining. 
When slide 12 engages stop 58 switch 60 is tripped by dog 62 which 
initiates the downward stroke of rod 48 and advances cutting tool 46 in a 
radially outward direction to finish machine the face of counterbore 44 at 
the desired depth. After tool 46 has traversed the face of the counterbore 
44 to the desired extent, a collar 64 on rod 48 actuates a switch 
mechanism 66 to radially retract tool 46. When both switch assemblies are 
tripped (being wired in series), cylinder 14 is actuated to return the 
slide to its retracted starting position where the tools clear the 
workpiece. The workpiece can then be advanced one increment of its bore 
pitch or advanced to the next identical machining station to machine the 
remaining bores. 
The switches and dogs on the base 10 and slide 12 are shown 
diagrammatically and in practice are so arranged by offsetting or by swing 
dogs so that only the proper switch in the correct direction is engaged as 
described in this disclosure. The designs of particular electric and 
hydraulic circuits of the machine controls can vary widely. Since the 
design and arrangement of such controls are well known in the art of 
machine tools, they are not shown and specifically described. 
FIG. 3 is an extension of the upper end of FIG. 4. Taken together, FIGS. 3 
and 4 represent a vertical sectional view showing structural details of 
the machine. As shown in FIG. 3, pulley 22 is keyed to a hollow spindle 
shaft 70 which is supported for rotation within quill 28 by bearing 72,74. 
The upper end of quill 28 is fixedly connected to a plate 76 by screws 78. 
Plate 76 is in turn fixedly secured to the lower ends of upright support 
plates 80,82. A tool compensator assembly 84 (shown in FIG. 4 but broken 
away in FIGS. 1 and 2) is located above pulley 22 and is fixedly secured 
to a support plate 86. Plate 86 is spaced above plate 76 and extends 
between and is secured to upright support plates 80,82 by screws 87. End 
caps 88,90 are secured to the upper and lower ends of housing 30 by screws 
92 and are in sealed sliding engagement with the reduced diameter ends of 
quill 28. Quill 28 has a close sliding fit within housing 30 and forms a 
piston which is adapted to be shifted vertically within housing 30 when 
fluid under pressure is introduced through either ports 94 or 96 formed in 
end caps 88,90, respectively. 
Within the driven spindle shaft 70 there is slideably arranged a pair of 
concentric tubes 98,100 and within the inner tube 100 there is slideably 
arranged a drawbar 102. These tubes and the drawbar control the operation 
of the turning tools on boring bar 26 by means of the compensator assembly 
shown in FIG. 4. 
Referring to FIG. 4, there is illustrated a cylinder 106 in which a piston 
108 is slideably arranged. The upper end of piston 108 has attached 
thereto an adaptor plate 110 which carries two switch dogs 112 arranged to 
actuate switches 114,116. Two compensators 118, 120 are supported in 
tandem on adaptor plate 110. Compensator 120 controls the axial position 
of tube 98a and compensator 118 controls the actuation of tube 100a. A 
detailed description of the construction and operation of these 
compensators will be described hereinafter. Briefly stated, the function 
of these compensators is to make a small adjustment in the location of the 
cutting tools to compensate for tool wear. However, when port 124 on 
cylinder 106 is connected with fluid under pressure, piston 108 and both 
compensators 118,120 together with the tubes 98a and 100a will be shifted 
upwardly until switch 116 is actuated. When port 126 is connected to fluid 
under pressure, piston 108 and the components supported thereon will be 
shifted downwardly until switch 114 is actuated. These two movements will 
occur during each cycle of the machine. Piston 108 is shifted upwardly at 
the beginning of each machining cycle to position the cutting tools in the 
desired positions to machine the bores and counterbores. After the tools 
have finished their machining operations and tool 46 has been retracted 
radially, piston 108 is shifted downwardly and in the down position of 
piston 108 the cutting tools on the arbor for machining the bore diameters 
are retracted radially inwardly from the surface they have machined so 
that they will not generate an unwanted tool mark when the entire assembly 
is retracted vertically upwardly. 
As shown in FIG. 4, cylinder 50 is mounted on a support plate 128 that is 
secured to the upright plate 80. The rod 48 of cylinder 50 is connected to 
the upper drawbar section 102a through a housing 130 and bearings 131. The 
previously referred to collar 64 is fixedly secured to housing 130 and the 
previously referred to switch assembly 66 comprises two switches 132,134. 
Vertical movement of drawbar 102 is controlled by interengagement of 
collar 64 with switches 132,134. When cylinder 50 shifts the drawbar 
downwardly its position is monitored by switch 134. Switch 134 is in turn 
located on plate 128 so as to be actuated by collar 64 when the piston in 
cylinder 50 engages an internal stop within the cylinder. When the drawbar 
is in its up position, switch 132 is actuated and this position is 
controlled by adjustable stop nuts 136 (FIG. 3) threaded on the lower end 
of the drawbar. 
Referring now to FIG. 3, the previously referred to stop assembly 32 
comprises three vertically stacked rings 138,140,142. Ring 138 is rigidly 
attached to the lower end of quill 28 by screws 144. Ring 140 is secured 
to the underside of ring 138 by screws 146 and the bottom ring 142 is 
secured to the intermediate ring 140 by screws 148. The detailed structure 
which forms the interconnection between these three rings will be 
described hereinafter. 
In FIG. 3 and 5 the boring bar proper is designated 150 and has secured to 
the upper end thereof, as by screws 152, an adaptor 154. Adaptor 154 is 
fixedly mounted on the lower of spindle shaft 70 by means of screws 156. A 
tool slide 158 is slideably mounted in a slot 160 extending transversely 
at the upper end of boring bar 150. Within a boss 162 on one end of tool 
slide 158 there is slideably arranged a tool holder 164. Tool holder 164 
has a rectangular head 166 at its upper end which has a close sliding fit 
with a vertically extending rectangular bore 168 in tool slide 158. The 
cutting tool 46 is fixedly mounted in tool holder 164 by a set screw 170. 
As shown in FIG. 6, at the central portion thereof tool slide 158 is 
formed with a cross bore 172 in which is supported a cylindrical plug 174. 
Plug 174 is retained in bore 172 by a screw and washer 176. At its inner 
end plug 174 is formed with a rectangular key 178 which is engaged in a 
slot 180 formed in a cutaway flat portion of drawbar 102. As shown in FIG. 
5, slot 180 is inclined to the axis of the drawbar so that the axial 
movement of the drawbar produces radial movement of tool slide 158. 
Referring to FIG. 5, adaptor 154 is formed with a radial bore 182 in which 
is disposed a lever 184. At one end lever 184 is pivotally supported by a 
cross pin 186 in adaptor 154. At its opposite end lever 184 extends into a 
slot in the lower end of outer tube 98 and engages a pin 188 on tube 98. 
Intermediate its ends, lever 184 is pivotally mounted as at 190 on a 
follower pin 192 which is slideable axially on adaptor 154. The lower end 
of pin 192 engages the top angled face 194 of a hardened pad 196 secured 
to the head 166 of tool holder 164. With this arrangement it will be 
appreciated that any axial movement of tube 98 relative to boring bar 150 
is translated into axial adjustment of cutting tool 46 relative to stop 
assembly 32. This enables precise control of the depth of counterbore 44. 
A plurality of springs 198 urges pad 196 against the lower end of follower 
pin 192 and, thus, eliminates all of the lash of the linkage assembly. 
While tools 34,36,42 are machining the diameters of the bores, drawbar 102 
is in the down position and tool 46 is in its radially retracted position. 
When stop assembly 32 contacts the top face of the workpiece, pressure 
fluid is admitted to cylinder 50 to raise the drawbar and displace tool 46 
radially outwardly at the desired feed rate. Thus, the single point tool 
46 will generate a spiral cut across the face of the counterbore at the 
angle to the bore axis corresponding to the face angle on pad 196. 
As is apparent from FIG. 4, the upper section 98a of tube 98 extends 
upwardly into compensator 120 where it is rotatably attached to gear 200 
by bearings 202. Gear 200 is threaded into the compensator housing at its 
lower end and meshes with a worm gear 204 keyed to a shaft 206 (FIG. 9). 
Shaft 206 is journalled in the compensator housing by bearings 208 and is 
driven through a slot and tang coupling 210 by a geared motor 212. Motor 
212 is of the type to produce a precise increment of output shaft rotation 
in response to a signal received from the control sytem which is initiated 
by automatic gaging or a manual push button. Motor 212 is of the 
reversible type therefore adapted to rotate gear 200 in either direction. 
Thus, through bearings 202 it is adapted to raise or lower tube 98 and 
thereby change the axial location of cutting tool 46. As pointed out 
previously, this will determine the precise depth of counterbore 44. A 
knurled and graduated dial 214 attached to the end of shaft 206 is 
provided to enable the initial adjustment of the machine or to manually 
change the depth of counterbore 44. 
The compensator 118 is constructed identically with the compensator 120 and 
is adapted to effect vertical adjustment of the inner tube 100. In FIGS. 5 
and 6 it will be noted that the tube 100 is cut away to the axial center 
line thereof to clear over the notched portion of tool slide 158. Below 
this notched portion tube 100 extends downwardly into boring bar 150. The 
lower end portion of tube 100 has wedges 216 thereon which are engaged by 
the inner ends of pins 218 slideable radially within the boring bar 150. 
The radially outer ends of pins 218 engage the shanks of cutting tools 
34,36 and 42. When tube 100 is shifted upwardly from the position shown in 
FIG. 5, the shanks of these cutting tools are flexed radially outwardly. 
In order to reduce the amount of force required to flex these cutting 
tools outwardly, each of their shanks are partially bifurcated as at 219. 
Thus, as tube 100 is shifted vertically by compensator 118 each of the 
tools 34,36,42 are displaced radially. When all the tools have finished 
their cutting operation and cylinder 50 has retracted tool 46 radially 
inwardly, fluid under pressure is introduced into a port 126 of cylinder 
106 (FIG. 4). This moves the two compensator assemblies downwardly and 
carries with them both tubes 98,100, thus retracting the cutting edges of 
all three tools so that the boring bar can be raised out of the workpiece 
without leaving tool marks on the finished surfaces. 
FIG. 10 shows the three rings 138,140,142 forming the main elements of stop 
assembly 32 in an exploded perspective view. As pointed out previously, 
ring 138 is rigidly attached to quill 28 by screws 144. On its lower face 
ring 138 has formed a pair of diametrically opposite semi-cylindrical 
protrusions 220. For the purpose of illustration these protrusions are 
shown in FIG. 10 highly exaggerated. The protrusions 220 are engaged by 
the upper face of ring 140. The screws 146 which secure ring 140 to ring 
138 are so located that they intersect the axis of the cylindrical 
protrusions 220 and thus permit a slight rocking movement of ring 140 on 
ring 138. Ring 140 has a pair of identical protrusions 222 formed on the 
lower face thereof which are disposed at right angles to the protrusions 
220. Protrusions 222 are engaged by the upper face of ring 142 and screws 
148 are located so that they will intersect the axis of the cylindrical 
protrusions 222. This will permit a slight rocking movement of ring 142 
relative to ring 140. The assembly of these three rings provides a gimbal 
with at least a slight freedom of movement in any direction. 
FIG. 11 shows the three rings 138,140,142 in assembled relation. The lower 
ring 142 has three rest buttons 224 on the lower face thereof for 
contacting the top face S of workpiece W. A conduit 226 extends through 
each of the rest buttons 224 and the lower ring 142 for connection with a 
source of air under pressure at port 228. At the time of rest buttons are 
approaching the workpiece, air is introduced into this conduit to blow 
away any dirt or chips and to insure that the contacting surfaces are 
clean. Elastomer rings 230 are arranged at the interfaces of the three 
gimbaled rings so that they will be held in an oriented relationship but 
will be free to flex enough to accommodate for any slight irregularities 
in the top surface of the workpiece. Each of the quills on the machine is 
provided with a stop assembly of this type at the lower end thereof. 
Therefore, each quill with be located by an average of the probably 
slightly non-planar surfaces of the workpiece adjacent to the hole to be 
bored. If the weight of the entire assembly is not sufficient to hold the 
stop assembly 32 firmly against the workpiece while facing of the 
counterbore is taking place, or if the reaction of the boring tools tend 
to shift the quill upwardly, fluid pressure may be introduced at port 96 
(FIG. 3). This will be effective on the quill to urge the entire assembly 
downwardly. On the other hand, if the weight of the quill and all of the 
components carried by the quill is of a magnitude sufficient to distort 
the workpiece, fluid pressure may be introduced at port 94 to 
counterbalance a portion of this weight.