Articulated hollowing system for lathe

A manually directed lathe tool system for removal of internally disposed material and creating a void inside a lathe turned form. As shown in FIG. 1, an articulated boring bar (32) of a tubular crosssection is slidably manipulated and supported by a plane surface (140) during a cutting action. To increase offset cutting ability several different lengths of a detachable and hinged arm assembly (40) are used. Arm assembly can be fixed or moved to three different positions relative to boring bar (FIG. 2) by manipulating a hand knob (36). A moveable and replaceable cutting tool (198) is held at the end of the arm assembly. A wall thickness caliper system (44) which ends in a tip (130) of some flexible material to allow operator appraisal of the internally disposed cutting tool's position. A back restraint assembly (141) is used to prevent the downward pitch of the boring bar's cutting end during material removal and consequent upward pitch of the opposite end of the boring bar, and especially during a highly leveraged cutting action. An outrider (38) attached to the boring bar prevents rotational movement of the tool relative to its longitudinal axis, especially during a leveraged offset cutting action. The outrider is able to be attached at several different locations on the boring bar and also serves as the support for the caliper system. Platform base (34B) is mounted rigidly to the lathe bed (30) and maintains platform assembly (34A) at a proper height. A precise wall thickness that mirrors the outside form can be achieved with this system. The system can be used to hollow-out forms not possible with previous practice. A narrow and restricted mouth opening does not hinder hollowing-out large diameters and deep forms. The operator is in control during all leveraged cutting actions and experiences minimal operator fatigue.

BACKGROUND 
1. Field of Invention 
This invention relates to the tools and implements for the manual removal 
of internally disposed material in a lathe tamed form leaving an internal 
void with a predetermined wall thickness. 
2. Description of Prior Art 
The following terms and their strict definitions are introduced here as an 
aid in the understanding of this specification: 
"Hollowing-out: removal of material from the end of a lathe turned form, 
said end being perpendicular to the form's turning axis and opposite the 
form's end that is mounted to the lathe. Material removal resulting in an 
interior void of accurate and consistent wall thickness that mirrors the 
outside form." 
"Limited-access opening: the mouth diameter of the form to be hollowed-out 
is not substantially greater than the diameter of the boring bar being 
used for the hollowing-out process, allowing minimal side to side and 
angular movement of the boring bar." 
The process of removing solid material (usually wood) with a hand held 
cutting tool and hollowing out a turned form is a difficult procedure. 
Contending with restricted tool movement and a limited visibility 
condition (blind boring), the lathe operator has a challenging task. A 
well-made, thin-walled and small-mouthed vase form (small-mouthed relative 
to the outside diameter of the form) is considered the epitome of good 
craftsmanship by many wood turners due to the challenges in making. 
When hollowing-out, the lathe operator is concerned with two directional 
forces that develop with a lathe tool during a cut. The operator must 
control these forces exerted on the tool in order to produce quality work 
efficiently. These problems, along with several others are listed for 
discussion: 
1) Tool pitch: the teeter-totter motion of a hand held lathe tool that 
develops during a cutting action with the tool rest acting as a fulcrum. 
As the lathe operator extends the cutting tool over the edge of the tool 
rest, tool pitch increases. The downward movement of the cutting tip 
during a cutting action in the spinning form must be overcome by the 
operator. The resultant upward movement of the opposite end of the tool 
must be physically controlled by the operator. During a highly leveraged 
cutting action, loss of operator control is always present. Mental anxiety 
and physical fatigue result. 
With an increase in tool pitch, the skill, strength and sensitivity of the 
operator must also increase. It can take years of practice before an 
operator of these hand held tools can develop sufficient confidence and 
technique to get much depth or breadth of cut to successfully and 
consistently hollow-out turned forms. 
2) Tool Roll: rotational force that develops during a cut because a lathe 
tool's cutting tip deviates or is offset from the tool's longitudinal 
axis. 
In order to hollow-out forms that have much of a "shoulder" or curvature to 
the form (relative to the mouth), lathe tools that are bent or curved near 
their cutting tip are commonly used. If this bend or curve deviates from 
the longitudinal axis of the lathe tool, then axial rotation or tool roll 
develops during a cutting action. The operator must physically overcome 
this force when attempting to cut, resulting in operator fatigue. An 
operator can take years to learn to deal with this particular torsional 
force when attempting to hollow-out a turned form. 
3) Achieving accurate wall thickness: 
Another problem to overcome, particularly when hollowing-out a 
limited-access large diameter form, is calibrating the exact wall 
thickness. With a limited access form, the operator cannot see the cutting 
tip or easily monitor its position in relationship to the outside of the 
form. During this blind boring process, the operator can easily pierce 
through the form when hollowing-out to a thin wall. A method to keep track 
of the position of the internally disposed cutting tool relative to the 
outside form would alleviate this problem, especially during a cutting 
action. 
4) Lack of ability offered by conventional practice to hollow-out many 
types of turned forms: 
The type of form that can be hollowed-out with conventional practice is of 
a basic spheroid shape. A skilled operator of the lathe can easily create 
many types of forms that would prove impossible to hollow-out with these 
conventional practices. 
Several patents have tried to deal with some of these problems, but these 
had and still have significant problems. 
A) U.S. Pat. No. 4,924,924 to Stewart (1990) attempts to control resultant 
tool pitch exerted on a lathe tool during a cutting action by an elaborate 
handle system that ties or straps the operator's forearm to the cutting 
tool. However, this system still places physical demands on the operator. 
This invention still depends upon a high level of operator skill as the 
cutting tip is further extended from the tool rest. As this distance 
increases, so does resultant operator fatigue. The operator can experience 
anxiety if during a highly leveraged cutting action the cutting tip 
"catches" (a sudden directional change of the cutting tool during a cut 
that results in temporary loss of operator control) in the material with 
this tool handle system so securely a part of the operator's arm. 
This same tool system attempts to deal with tool roll of an offset cutting 
tool by keeping the cutting tip in line with the longitudinal axis of the 
main shaft of the tool (FIG. 11, #74 of Stewart) and having the curved 
part of the tool run off-axis behind and supporting the cutting tip. This 
design does allow control of tool roll but with a fixed and limited amount 
of offset. This inflexible solution to the problem of tool roll severely 
compromises the turned form designs that can be hollowed-out. 
There is no obvious way to monitor wall thickness during blind boring with 
the Stewart patent. The operator must stop the lathe often to measure wall 
thickness, a very time consuming process. Even with the advantages this 
tool system offers over previous practice, the process of hollowing-out 
with this method is still very laborious, fatiguing and time consuming. 
B) U.S. Pat. No. 4,615,365 to Arnall (1986) is another attempt to deal with 
some of the problems of hollowing-out turned forms. A claim of this tool 
support is "to restrain rotational movement of such chisel or tool about 
its longitudinal axis" (Arnall, 1986) or what this specification has 
defined as tool roll. The conventional practice with this tool support 
system would be to use a tool of a square or rectangular cross-section. 
Conventionally found lathe tools are to be used with it. A very heavy 
conventional tool would have dimensions of 25 mm wide and 13 mm thick. A 
conventional amount of offset to this tool would be 13 mm to 38 mm at a 45 
degree angle from the tool's shank. My articulated hollowing system uses 
an offset cutting tip up to 9 times the width of the main shank of a tool 
or 229 mm at 90 degrees for a tool of the size discussed above. The amount 
of tool roll developed by an offset of 152 mm at 90 degrees from the 
tool's shank (a commonly used amount of offset with my system) would be 
over 4 times greater than the extreme conventionally used length of 38 mm 
at 45 degrees. 
Due to the design and purpose of this tool support, this much increase in 
tool roll torque would make the sliding action of this offset tool shank 
through the "parallel sided slot" (Arnall, 1986) during a cutting action 
very difficult. The operator would be fighting "tool bind" in this 
parallel sided slot, a strain that this system was not designed to deal 
with. A square sectioned tool would bind up even more easily than a 
rectangular tool with the same amount of tool roll torque. Indeed, Arnall 
(1986) advises to use rectangular tools rather than square tools, so 
obvious is this problem. This problem is due to the small amount of 
surface area used to deal with this force. To sum up, only tools of a 
square or rectangular cross section with a very limited amount of offset 
can be used with the Arnall tool support. The design of this tool support 
system is very limiting to the type of tools and implements that can be 
used with it. 
Lathe tool shanks of a cylindrical design, especially if the cutting tip is 
offset would not work at all with the Arnall tool support. A round tool 
shank would easily rotate or spin away from the cut, unable to be held by 
the Arnall tool rest. Cylindrical tools have a greater amount of tool 
movement potential in a round hole than a square or rectangular tool of 
equal strength or rigidity. The ability to use cylindrical tools is 
important when hollowing-out where lathe tool movement is restricted by a 
limited-access opening. 
The fixed nature of the Arnall tool's space between the upper and lower 
bars ("preferably of welded construction", Arnall, 1986) demands that only 
a certain thickness of tool can be used. This is a severe limitation to 
the size and type of tools that can be used with it and the resultant 
forms that can be hollowed-out. 
Due to the design of the Arnall tool support, there is also a very 
restricted horizontal movement allowed any tool used with it. The support 
platform is very narrow and if a large mouthed form is to be hollowed-out, 
this invention would need to be moved often to keep the tool in a proper 
position for material removal. It was designed for small work or 
small-mouthed work only. Due to the very narrow platform design and small 
amount of surface area offered to hold a tool and its implements, the 
types of tools and resultant forms that can be hollowed-out are again 
severely limited. Indeed, the types of tooling that my system uses could 
not be used with the narrow Arnall support platform. 
The Arnall tool support was designed to be used in conjunction with a wood 
lathe's existing tool rest holder. The tool rest holder of a wood lathe 
was made to control the downward force that a lathe tool develops when 
cutting. The corresponding upward force on the opposite end of the tool is 
controlled by the operator. The Arnall tool support was designed to help 
control lathe tool pitch. When the Arnall tool support is in use with a 
lathe's existing tool rest holder, it will subject that tool rest holder 
to the resultant pitch force of the lathe tool in use. A wood lathe's tool 
rest holder was not made to control the teetertotter motion of tool pitch. 
A tool rest holder was made to resist the compression from the downward 
force developed by a lathe tool during a cutting action. Not the flexing 
or deflection that will develop using the Arnall tool support attached to 
it. Vibration will quickly develop during a leveraged cutting action when 
the tool rest holder starts to deflect. 
The post of a conventional tool rest for a wood lathe is of an appropriate 
diameter for the compressional force it will have to control, not the 
deflection it will have to endure with the Arnall system. By necessity, 
the Arnall tool support uses the same size diameter post as the tool rest. 
Again, vibration from the support system of the Arnall will have to be 
endured by the operator with just a low leveraged cutting action. The 
seeming stability offered by this invention will be compromised by its 
dependency on another tool system that was not designed to deal with lathe 
tool pitch or tool roll, particularly during a leveraged cutting action. 
Objects and Advantages 
Accordingly, several objects and advantages of the my articulated hollowing 
system are: 
(a) to provide a system which is much safer to use than any other 
conventional method. Any "catch" in the material being removed by the 
cutting tool is restrained and controlled by the system and not the 
operator. 
(b) to provide a system that is conducive to less operator fatigue than any 
other method. The operator experiences no physical duress from the two 
forces already discussed. This is due to the fact that all tool pitch and 
roll is totally controlled by the system. 
(c) to provide a system that is easier to learn and use than any other 
method. A beginner requires little instruction and practice to quickly and 
successfully master the techniques of this system in order to accomplish a 
previously difficult task. 
(d) to provide a system capable of greater precision and accuracy than any 
other method. An accurate and uniform wall thickness can be achieved with 
the use of the system's modular caliper assembly. 
(e) to provide a system that is able to hollow-out a turned form faster 
than other methods. This system can use very aggressive cutting tools due 
to the high degree of control the operator has over the offset boring bar. 
(f) to provide a system that is solid enough, large enough and versatile 
enough to handle more types of tools and implements than any other 
methods. Tools other than my articulated boring bar can easily be adapted 
to use with this system. Tool vibration during a leveraged cutting action 
is minimized due to the design of this system. 
(g) to provide a system that allows a greater range of design possibilities 
in the turned forms that can be hollowed-out. A long neck with a small 
diameter but with a large diameter body is an example of a type of form 
that is impossible to hollow-out with any other conventional method. This 
form can be done routinely with this system. 
(h) to provide a system that will allow the lathe operator greater 
creativity. Turned and hollowed vessel forms have been produced for a 
number of years using conventional practices. This system will allow an 
increase in creativity in this area of craft work due to all the objects 
and advantages listed above.

DESCRIPTION OF FIGS. 1 THROUGH 16 
A typical embodiment of the articulated hollowing system of the present 
invention is illustrated in FIG. 1 (perspective view). A platform mounting 
assembly 34B is securely bolted to the lathe bed ways 30 (the lathe bed 
ways are not part of the invention but are introduced here only for 
clarification). Mounting assembly 34B secures a platform assembly 34A. It 
is upon platform assembly 34A that an articulated boring bar assembly 32 
is slidably manipulated during its operation. 
FIG. 2 contains a further detailed breakdown of the various assemblies that 
make up bar assembly 32. From left to right in FIG. 2 the front of the bar 
assembly 32 has an articulating arm 40 shown in its three main positions 
or articulations. Articulating arm 40 is held by an arm holder assembly 42 
in which articulating arm 40 can move 0 degrees to 45 degrees to 90 
degrees in relationship to bar assembly 32 and its longitudinal axis. A 
caliper arm assembly 44 is attached to an outrider assembly 38. Outrider 
38 is attached to a barrel 46. A hand knob assembly 36 is threaded into 
barrel 46 and, through its action locks articulating arm 40 into one of 
its three positions. 
FIG. 3 shows a left-hand side view of bar 32 and the relationship of the 
different assemblies. From left to right in FIG. 3, a cutting tool 198 is 
held in articulating arm 40 by an arm screw 102. Articulating arm 40 is 
held in blade holder 42 at the 0 degree or straightened position by an arm 
pin 84. Caliper 44 is a plurality of caliper links 116. Outrider 38 is 
attached by an outrider screw 48 to barrel 46 by a threaded outrider 
adjustment 51. 
FIG. 4 is a front view of bar assembly 32 of FIG. 3. This view also has 
removed articulating arm 40 and caliper links 116. With articulating arm 
40 and an arm pin 84 removed from blade holder 42 an arm holder aperture 
88 is shown. Inside aperture 88 is the end of a rod 50 and a pressed 
bearing 52. Bearing 52 is fitted into the end of rod 50. With caliper 
links 116 removed the end of a caliper arm 76 is shown. Caliper arm 76 is 
held in place when a caliper arm set screw 72 is tightened. An outrider 
slot 54 and an outrider cavity 56 allows caliper arm 76 to be squeezed in 
place when screw 72 is tightened in outrider 38. 
FIG. 5 is an exploded view of an end of barrel 46 and hand knob 36. Rod 50 
goes through a barrel aperture 58 (and ends at bearing 52 in arm holder 
aperture 88). A rod stem 62 accepts a spring 64. Stem 62 and spring 64 go 
into a hand knob cavity 68 with spring 64 riding on a bearing 66 at the 
end of cavity 68. A threaded knob hole 60 in barrel 46 accepts a threaded 
knob stem 61. Hand knob 36 is machined out at one end with a hand knob 
aperture 70. 
FIG. 6 is an exploded view of outrider assembly 38. FIG. 6 shows the top 
side of outrider 38. As shown in FIG. 3 and FIG. 6 outrider screws 48 go 
through an outrider screw opening 49 and into outrider adjustments 51. 
Caliper arm 76 is held in a closed position by screw 72 which passes 
through a caliper set screw opening 73 and into a caliper set screw hole 
75. When screw 72 is tightened caliper arm 76 is held in a caliper arm 
slot 55. When screw 72 is loosened caliper arm 76 is allowed to pivot on a 
caliper hinge pin 74 which passes through a hinge pin opening 78 in 
outrider 38 and caliper arm 76. Caliper links 116 (not shown in FIG. 6) 
are attached to caliper arm 76 by seating on a caliper arm flat 82 and 
held by a screw in a caliper link screw hole 80. 
FIG. 7 is an exploded view of arm holder assembly 42. Arm pin 84 fits 
tightly in an arm pin opening 86. Arm holder aperture 88 is shown without 
rod 50 and bearing 52 as in FIG. 4 but in an exploded view. An arm holder 
clevis 90 fits the sides of articulating arm 40 (not shown) tightly. An 
arm holder stem 92 is press fit into a barrel stem orifice 94. 
FIGS. 8A through 8C show articulating arm 40 in different relative 
positions to help understand its shaping. It is constructed of a hardened 
steel milled from one piece. An arm mouth 106 in FIG. 8A is accurately 
milled to accept cutting tool 198, which is held in place when arm screw 
102 is placed in an arm screw opening 104 and tightened in a screw hole 
105. As screw 102 is tightened an arm slot 108 and an arm cavity 110 allow 
clamping pressure to be exerted on cutting tool 198. Arm pin 84 is shown 
above an arm pin aperture 114 where it fits when articulating arm 40 is 
placed in arm holder clevis 90. Also shown in FIG. 8A is a detent 112 
where bearing 52 seats (see FIG. 10). FIG. 8B shows all three detents 112 
and all three flats 113 which determine the three positions (0 degrees, 45 
degrees and 90 degrees) that articulating arm 40 can be locked into by 
bearing 52. FIG. 8C shows the underside of articulating arm 40. Arm mouth 
106, rabbet 115, flats 113 and detents 112 must all be machined to close 
tolerances to work properly. FIG. 8D shows the different lengths of blade 
40 needed for hollowing-out a limited access opening turned form. 
FIG. 9 shows rod 50 that goes through barrel aperture 58 of barrel 46. Rod 
50 must slide easily through aperture 58, or articulating arm 40 will not 
be able to move easily to its various positions. Bearing 52 and stem 62 
are shown to establish rod 50 position in aperture 58 relative to holder 
42 and hole 60. Barrel 46 can be made of some hardened thick wall metal 
tubing of accurate outside dimensions and aperture 58 not over 1/3 the 
diameter of barrel 46. Rod 50 can be made of some hardened metal rod, but 
does not have to be as high quality as barrel 46. 
FIG. 10 is a section view of arm holder assembly 42 and articulating arm 
40. Rod 50 holding bearing 52 is pushed into detent 112 when hand knob 
assembly 36 (not shown) is tightened. Articulating arm 40 is held in 
position by bearing 52 being pushed into detent 112 and arm pin 84. Upon 
relief of pressure on rod 50 bearing 52 can be released from detent 112 by 
sliding back rod 50 in barrel aperture 58. Upon this release articulating 
arm 40 can be pivotably moved to one of three positions provided by the 
three detents 112 or arm pin 84 can be removed so that another 
articulating arm 40 of different length can be fit into arm holder 42. 
FIG. 11A is a perspective view of caliper link 116 of caliper arm assembly 
44. A caliper link screw 118 seats in a link screw opening 120. A link 
rabbet 124 is then seated on another link 116 on a link register 126, 
screw 118 being threaded into a link screw hole 128. FIG. 11B is a section 
view of links 116. Various reference numerals are shown for clarification. 
The most important aspect of this view is link relief 122 which allows 
link rabbet 124 to seat fully and accurately on another link 116 on that 
link's register 126. FIG. 11C shows different lengths of link 116. This 
plurality of different length links are necessary for the operation of 
this system. FIG. 11D shows a tip link 137 which is of a slightly 
different configuration than links 116. A flexible tip 130 is of some type 
of material that is able to be bent but can retain its original position. 
Tip 130 is held to tip platform 138 by a tip screw 134 inserted through a 
tip slot 132 and threaded into a tip screw hole 136. Flexible tip 130 is 
able to be moved into different positions by loosening screw 134 and 
sliding tip 130 along slot 132. When tip 130 is in its desired position 
screw 134 is tightened. Caliper links 116 and tip link 137 are made of 
some light weight material such as aluminum, plastic, etc. for ease of 
operation. Rabbet 124, register 126 and relief 122 should be accurately 
machined to have caliper assembly 44 line up properly for use. 
FIG. 12 is a perspective view of platform assembly 34A and platform 
mounting assembly 34B. A platform 140 holds restraint assembly 141 
comprising a hinged restraint bar 142 with a restraint bar hinge assembly 
144 and a restraint bar locking assembly 146. Platform 140 is held to a 
platform post 150 by a bolt 174 (FIG. 14) threaded into a platform bolt 
hole 148. Assembly 34B holds a platform assembly 34A by a platform post 
holder 152, a post holder ring 154 and a post holder set screw 156 which 
are threaded into ring 154 and can be tightened into post 150 to hold 
assembly 34A. Post 150 slides inside post holder 152 and can hold platform 
assembly 34A in a variety of different vertical positions. Gussets 158 
help hold and stabilize post holder 152 to a base 160. A platform post 
hole 155 must be perpendicular to the bottom of base 160. 
FIG. 13 shows platform assembly 34A removed from assembly 34B. Restraint 
assembly 141 is shown in its up or open position. Locking assembly 146 has 
been released by unscrewing a wing nut 176 and allows restraint bar 142 to 
be pivotably moved on a screw 182 in hinge assembly 144. Platform 140 can 
be made of a surfaced metal plate of sufficient thickness to restrain 
vibration. 
FIG. 14 shows a view of the underside of platform assembly 34A. Post 150 is 
of a large diameter metal tubing with a post slot 170 and a post flat 172 
milled along its longitudinal axis. Post 150 is typically 51 mm in 
diameter. Slot 170 accepts the end of screw 156 and keeps platform 
assembly 34A from rotating in post hole 155 thus keeping assembly 34A 
square to assembly 34B. Flat 172 allows screw 156 to have its end 
tightened into post 150. Post 150 fits post hole 155 with close tolerances 
for stability. Post 150 is press-fit into a platform post base 168. Base 
168 is bolted by post base bolts 174 to the bottom of platform 140 into 
bolt holes 148 (see FIG. 12). A hinge post bolt opening 192 is used to 
hold and align hinge assembly 144 to platform 140. A locking post bolt 
opening 184 is used to hold and align restraint bar 142 by locking 
assembly 146 (FIG. 13). 
FIG. 15 shows base 160 held to lathe bed ways 30 by bolt 164 threaded into 
bolt hole 166. When bolt 164 is tightened into bolt hole 166, base 160 is 
secured in position by base holder 162 from the underneath of lathe bed 
30. Bolt 164 is typically 16 mm diameter. 
FIG. 16A shows a close-up view of restraint assembly 141. Restraint bar 142 
is held in position relative to platform 140 by a post 178. A wing nut 176 
secures restraint assembly 141 to platform 140 by a bolt 186 through 
opening 184 (FIG. 14). Upon removal of wing nut 176, restraint bar 142 can 
be lifted to a vertical position, pivotably moving on a hinge post screw 
182 held by a hinge post 180 (FIG. 13). Hinge assembly 144 is secured to 
platform 140 by a hinge post bolt 190. 
FIG. 16B is an exploded view of FIG. 16A, showing different component parts 
of restraint bar 142. Bolt 186 which passes through opening 184 is shown 
at the bottom of post 178. A thickness shim 194 is shown removed from 
restraint bar 142. A screw 196 holds shim 194 to restraint bar 142 when 
needed. Different thickness shims can be used depending on tooling desired 
and its diameter or thickness. Hinge assembly 144 and its component parts 
are shown with bolt 190 that passes through hole 192 (see FIG. 14) and is 
held to platform 140. Restraint bar 142 is pivotably attached to hinge 
post 180 by screw 182 which passes through a hole 181 in restraint bar 142 
and post 180. Clevis 188 allows acceptance of restraint bar 142 and also 
acts as a hinge stop to hold the restraint bar in a vertical position when 
in the open position. 
Operation--FIGS. 1, 2, 5-8, 10-12, 15-18 
The procedure of using the articulated hollowing system to hollow-out a 
turned form is of a completely different manner than previous practice. As 
shown in FIG. 17A after the outside shaping of a turned form 202 is 
finished a pilot hole 200 is drilled to a pre-determined depth. Form 202 
is mounted to a lathe head stock and is ready to begin the hollowing-out 
process. Platform 34A and 34B is placed on lathe bed ways 30 (FIG. 1 and 
12) and positioned so that the leading edge of platform 140 is 
sufficiently near a mouth 204. Platform mounting assembly 34B is bolted 
securely to lathe bed ways 30 as shown in FIG. 15. Platform assembly 34A 
is adjusted for proper height to allow suitable alignment with a lathe 
head stock. Suitable alignment will allow the center of mouth 204 and 
barrel 46 to be disposed on a horizontal plane 206 with the lathe 
headstock axis (FIG. 17B). The predetermined height of platform 140 is 
secured by tightening screws 156 to post 150. The large mounting area of 
base 160 and its method of securing to lathe bed ways 30 as described 
above and the large diameter of post 150 offer a solid basis to control 
tool pitch, roll and vibration as already discussed. 
For the initial removal of material from form 202 articulated bar 32 is set 
with the short articulating arm 40 in the 0 degree position (FIGS. 2 and 
17A). This is accomplished by tightening hand knob 36 which presses 
bearing 52 held by rod 50 into detent 112 and fixing articulating arm 40 
into this position (FIG. 10). To remove and replace articulating arm 40 as 
shorter or longer lengths are needed hand knob 36 is loosened to relieve 
pressure from articulating arm 40 by bearing 52. Arm pin 84 is then 
grasped by the operator and removed from arm holder 42 (FIG. 7). 
Articulating arm 40 is then removed from arm clevis 90. A different length 
articulating arm 40 is then placed in clevis 90 aligning aperture 114 with 
arm pin opening 86 and reinserting arm pin 84. 
Cutting tool 198 is held in a 90 degree position in arm mouth 106 of 
articulating arm 40 by tightening screw 102 when tip 198 is in position. 
Cutting tip 198 can be adjustably fixed in a variety of positions in arm 
mouth 106 depending upon the location of material to be removed inside 
form 202 as will be shown. To begin the initial hollowing-out process bar 
32 is inserted in pilot hole 200 and positioned so that material removal 
begins inside the body of long-necked form 202 as shown in FIG. 17A. With 
bar 32 inside form 202 and the lathe rotating form 202 the operator lifts 
bar 32 against restraint bar 142. The clearance between restraint bar 142 
and platform 140 is typically 0.50 mm larger than the diameter of bar 32. 
In this slightly lifted and restrained position tool pitch is 
non-existent. The downward thrust exerted on cutting tool 198 when a cut 
is taken inside spinning form 202 is held by the leading edge of platform 
140. The consequent upward thrust of the opposite end of bar 32 is held by 
restraint bar 142. As the operator removes material inside pilot hole 200 
and slidably moves bar 32 further down hole 200 towards the base of form 
202 tool pitch leverage increases but is fully contained by this system 
and the operator experiences no physical duress from this increased 
leverage. The only limitation to the depth of cut that the operator can 
take is by barrel 46 and its particular vibration periods. The diameter of 
barrel 46 and the quality and hardness of material used in its manufacture 
are the main determinants to the distance an operator can extend bar 32 
over the leading edge of platform 140 without undue vibration. Platform 
34A and 34B will not offer any detrimental vibration of its own if 
properly manufactured. 
When all the material that can be removed from the predetermined setting of 
assembly 32 (FIG. 17A) is complete, then articulating arm 40 and cutting 
tool 198 are re-positioned to reach other internal material that needs 
removal. The capability of articulated bar 32 to be moved and fixed in a 
variety of positions becomes important to successfully hollow-out form 202 
through the limited-access opening determined by its long and narrow neck. 
Long-necked form 202 is impossible to hollow out with previous practices. 
The long neck severely restricts the amount of side-to-side and angular 
movement of barrel 46 (FIG. 17B). This lack of allowed movement with bar 
32 is made up for by different length arms 40 (FIG. 8D) that can extend 
further and further from barrel 46 to reach more material for removal 
inside form 202. This will be demonstrated further in the specification. 
FIG. 17C shows bar 32 with a longer length articulating arm 40 than shown 
in FIG. 17A. A larger void has been developed in form 202. Articulating 
arm 40 is locked in the 90 degree position with cutting tool 198 locked in 
a 90 degree position relative to articulating arm 40. In FIG. 17C the 
inside top of the void of form 202 is having material removed. Caliper arm 
assembly 44 is in a predetermined position and is being used to monitor 
the final wall thickness of form 202 during a cutting action. Cutting tool 
198 and flexible tip 130 are set at a predetermined distance from each 
other. This set distance between the ends of tool 198 and tip 130 is the 
desired wall thickness. Before this final wall thickness is achieved the 
flexible tip 130 will deflect downward with the rotation of form 202 (FIG. 
17D). As excess material is removed and final wall thickness approached 
flexible tip 130 will rise until it is in a horizontal position and 
directly opposite cutting tip 198. Tip 130 will be in horizontal plane 206 
when the final wall thickness is achieved. 
It is important to keep cutting tool 198 at a perpendicular position 
relative to the outside shape of form 202 for accurate results in 
hollowing-out. The ability of tool 198 to be moveably clamped in a variety 
of positions to keep it perpendicular to the outside shape is achieved by 
the design of arm mouth 106, slot 108 and cavity 110 (FIG. 8A). It is also 
important to keep flexible tip 130 opposite and in line with cutting tool 
198. This is achieved by lengthening, shortening and curving caliper arm 
assembly 44 with a plurality of varying length articulating links 116 
adjustably fixed to each other. Tip 130 can be rotated, extended or 
shortened on tip link 137 by tip slot 132 and maintained in its desired 
position by tightening screw 134 (FIG. 11D). Keeping tip 130 opposite tool 
198 as shown in FIG. 17C, 17F and 17G is necessary to achieve an accurate 
wall thickness. Constant monitoring of the internally disposed cutting 
tool 198 is necessary to keep from piercing through a thin walled form 
during a cutting action. 
In FIG. 17C articulating arm 40 is in the 90 degree position and tool roll 
will develop during a cutting action. While cutting, a tool with an offset 
cutting tip will attempt to roll in the operator's hands. Tool roll is 
controlled with this system by outrider 38 being slidably held against 
platform 140. Platform 140 must offer a large flat and smooth surface for 
outrider 38 to be slidably manipulated on. Tool roll is negated by 
outrider 38 and the operator cannot discern any effect of it on tool 
control with this system. Outrider 38 has several adjustment holes 51. If 
during the hollowing-out process the material to be removed is deeper than 
the current position of outrider 38 on barrel 46 will allow, outrider 38 
can be repositioned by loosening and removing screws 48 (FIG. 6). Once the 
desired position is determined screws 48 are placed in screw opening 49 
and threaded and tightened in outrider adjustments 51. Outrider 38 can be 
repositioned up and down barrel 46 as needed. 
FIG. 17E shows a longer version of articulating arm 40 in the 0 degree 
position entering mouth 204 of form 202. Caliper arm assembly 44 has been 
pivoted out of the way. Caliper arm 76 pivotably moves on hinge pin 74 
(FIG. 6). When articulating arm 40 is in the 0 degree position and 
inserted in mouth 204 its position inside the void of form 202 is 
determined by the number of clicks the operator allows articulating arm 40 
to achieve. Spring 64 puts a light pressure on rod 50 (FIG. 5). Bearing 52 
is seated in one of three detents 112 and when the position of 
articulating arm 40 is being changed bearing 42 rides on flat 113 until it 
clicks into detent 112 from the pressure of spring 64 (FIG. 10). With 
articulating arm 40 in the 0 degree position the operator simply pushes 
articulating arm 40 with bar 32 into form 202 and against the bottom or 
sides of the void in form 202. With one click the operator knows that arm 
40 is in the 45 degree position and with two clicks it is in the 90 degree 
position. In the predetermined position hand knob 36 is tightened which 
secures articulating arm 40 into a fixed condition (FIG. 17E and 17F). To 
remove bar 32 from form 202 when articulating arm 40 is in an offset 
position hand knob 36 is loosened sufficiently to allow articulating arm 
40 to be straightened out and click into the 0 degree position (FIG. 17E). 
Bar assembly 32 is then withdrawn from form 202. 
FIG. 17F is the sequence of FIG. 17E and shows articulating arm 40 locked 
into the 90 degree position with caliper arm assembly 44 moved into 
position to a predetermined distance from cutting tool 198 and fixed in 
this position by tightening set screw 72 when caliper arm 76 is pivotably 
moved into caliper arm slot 55 swiveling on hinge pin 74 (FIG. 6). This 
design allows accurate re-alignment to a predetermined setting. The 
ability of this system to have various component parts moveably fixed to 
allow easy entry into a limited access form and then quickly and 
accurately re-aligned to a predetermined position allows this type of 
demanding work to be accomplished accurately. 
In FIG. 17F cutting tool 198 is in a 0 degree position relative to the axis 
of articulating arm 40. Tip 130 will be in a flexed mode disposed against 
the outside of form 202 as the operator removes material with cutting tool 
198 (FIG. 17D). With the amount of offset of articulating arm 40 and the 
amount of overhang of bar 32 from the leading edge of platform 140 tool 
pitch and roll would be impossible to control with previous practice. The 
length of articulating arm 40 in FIG. 17F is a mid-length articulating arm 
40. If a larger diameter form 202 is desired articulating arm 40 lengths 
of up to nine times the diameter of barrel 46 have been used in the same 
limited-access long-necked mouth 204. Lack of allowed movement of barrel 
46 is made up for by incremental lengths of articulating arms 40. Forms of 
large diameter and depth with a limited-access opening are normal 
operating procedure with this system. 
FIG. 17G shows bar 32 with articulating arm 40 fixed in a 45 degree 
position being used to remove material on the inside bottom of the void of 
form 202. Caliper 44 has had links 116 added to it to lengthen it. Caliper 
44 also has a slight curvature so that flexible tip 130 can be positioned 
opposite and in line with tool 198. The operator is again using the 
predetermined position of tip 130 and tool 198 to monitor the position of 
the internally disposed cutting tool during a cutting action to arrive at 
a predetermined wall thickness. Previous practice would have the operator 
stop the lathe often and attempt to get a measurement of the wall 
thickness. Then the operator would have to restart the lathe and with the 
cutting tool relocate the material that needs to be removed without 
accurate guidance. Measuring the wall thickness at the bottom of form 202 
in FIG. 17G would be extremely difficult with previous practice. With this 
system the locating of material that needs to be removed is disclosed 
while the form is turning and the material can be removed. The operator 
does not have to stop and restart the lathe to monitor wall thickness. 
FIG. 18A shows a fixed offset lathe tool 208 with its cutting tip about to 
enter form mouth 204. This lathe tool is of a larger diameter than bar 32. 
Thickness shim 194 is being removed from restraint bar 142 to accommodate 
its larger size (see FIG. 16B). Restraint assembly 141 is in a raised or 
open position to allow tool 208 to enter form 212. A simple outrider 210 
has been attached to previous practice tool 208. 
FIG. 18B shows tool 208 inside partially hollowed-out form 212. With 
thickness shim 194 removed restraint assembly 141 has been returned to its 
locked position holding tool 108. A fixed restraint assembly 141 to 
platform 140 would not allow entry of tool 208 into form 212. Tool roll 
and pitch are controlled with this slightly altered previous practice tool 
208 by the addition of outrider 210 and using it with platform assembly 
34A and 34B. 
Summary, Ramifications and Scope 
Accordingly, the reader will see that the methods of this invention with 
its boring bar and adjustably fixed articulating arms, moveably clamped 
cutting tool and adjustably fixed articulated caliper assembly can be 
easily used to hollow-out a variety of turned forms that would prove 
impossible with previous practices. The articulations of the various 
component parts of the boring bar assembly allow the lathe operator to 
quickly reach and remove internally disposed material with conditions that 
are highly restrictive to tool movement. The easily adjusted articulations 
of the caliper assembly allow the operator to achieve a high degree of 
accuracy when hollowing-out to a predetermined wall thickness. The 
operator is able to make numerous fine adjustments to the system to attain 
a precisely finished inside wall. 
The problems of tool pitch and roll are negated by the system thus 
providing the operator with safety, ease of operation and a lack of 
operator fatigue from physical stress. Persons of little or no experience 
with this type of work can learn to use this system rapidly, without the 
difficulty and anxiety of previous practice methods. However, the 
versatility offered by this system will challenge the advanced lathe 
operator with design and technical possibilities that have not been 
seriously considered. 
Furthermore the articulated hollowing system has the additional advantages 
in that 
it will permit production work of hollowed turned forms in a variety of 
materials for a variety of purposes due to its speed and ease of 
operation. 
it will allow hollowing-out to be done quickly because aggressive cutting 
tools can be used to quickly remove material and still maintain operator 
control during a cutting action. 
it can be used on most lathes with little or no adaptation necessary. 
it will permit previous practice tools with slight modification to be used 
with it. 
it will permit hollowing-out methods to be taught at learning institutions 
with shop facilities. 
Due to the safety and ease of operation, the inexperienced can use this 
system with little supervision. 
While my above description contains many specificities, these should not be 
construed as limitations on the scope of the invention, but rather as an 
exemplification of one preferred embodiment. Many other variations are 
possible. For example there are other methods and techniques for getting a 
boring bar to articulate. Besides other strictly mechanical methods, 
techniques can be used that are pneumatic, hydraulic, electrical, etc. 
There are many methods of holding the cutting tool on the articulated arm 
assembly. Other techniques could be used by an operator to ascertain the 
location of the internally disposed cutting tool inside a hollowed form 
such as x-ray, metal detectors, light, etc. There are other strictly 
mechanical or automatic systems that could be used to keep track of 
cutting tool position during a cutting action. The platform assembly could 
be done away with as the preferred way to hold the articulated boring bar. 
A system such as the saddle and cross slide on a metal lathe could be used 
to hold the articulated boring bar and move mechanically or automatically 
by computer rather than manually on the platform. With some adaptations to 
the preferred embodiment of the articulated boring bar and methods of 
controlling it, the bar could be used to hollow-out very hard materials 
such as are commonly used in the metal working industry. 
Thus, the scope of the invention should be determined by the appended 
claims and their legal equivalents, rather than by the examples given.