Fine feed adjustment for milling machines and methods relating thereto

A fine feed adjustment adapter for new milling machinery or retrofitted to existing milling machines is used in order to obtain adjustments of between 1/4 and 1/10,000th of an inch along the z-axis. The fine feed adjustment mechanism does not interfere with the preexisting coarse, vertical adjustment arm which is standard on commercial milling machines.

FIELD OF THE INVENTION 
The present invention is directed to a fine feed adjustment adapter for 
milling machinery, and more particularly, is directed to a device to 
retrofit existing milling machines in order to repeatedly obtain 
adjustments of between 1/4 (0.250) and 1/10,000th (0.001) of an inch along 
the z-axis. 
BACKGROUND OF THE INVENTION 
Milling machines, commonly used by operators for milling items, such as 
metal, plastic or wood are available in various forms and from various 
manufacturers. The majority of milling machines include a head assembly 
which includes a spindle and a quill. The spindle holds a milling tool 
used for milling a workpiece and the head assembly includes a spindle 
motor for causing the spindle to rotate within the quill. The quill and 
spindle is typically movable along a third axis of movement which is 
perpendicular to the first and second axes of movement, such third axis 
generally defined by a vertical line extending in both directions through 
the center of the spindle. Milling machines are generally operated in 
substantially three modes: manual operation; and computer controlled or 
aided two axis operation and computer controlled or aided three axis 
operation. In manual operation, a milling machine operator manually turns 
x or y cranks to desirably position the workpiece, often tracking the 
movement via position indicating dials, electronic readouts or other 
similar means. In this way, a workpiece can be manually moved relative to 
the rotating spindle within the quill to an appropriate location for 
desired machining. In two or three axes computerized numerically 
controlled or aided (CNC) milling machines, programmed positioning is 
provided along either two or three axes of motion. In two axis computer 
controlled or aided machine, a computer typically receives position 
information from an operator or from a stored program and controls the 
positioning of the machine along the axes of motion to a desired position 
based on the position information received. Movement of the quill along 
the third axis, or z-axis, is typically left to be manually operated. 
In a three axis machine computer controlled or aided, movement of the quill 
along the third axis is also automated. Dedicated three axis milling 
machines are more expensive and are not suitable for the production of one 
or a few prototype workpieces given the time and effort required to 
properly program such machines to produce a particular desired workpiece. 
In normal operation of a manual or two axis computer controlled or aided 
milling machine, a workpiece is manipulated into a desired position 
relative to a tool mounted in a spindle, for example, by an operator 
turning hand cranks so that the table holding the workpiece moves along x 
and y axes of movement to a desired position relative to the spindle or by 
computer controlled or aided. Once adequately positioned, the operator 
mills or drills the workpiece with the tool by manually rotating an 
adjustment lever about an axis of rotation adjusting the depth of cut 
causing the quill to move vertically downward along the z-axis of 
movement. The tool mounted within the spindle contacts the workpiece as 
the spindle rotates within the quill. 
In prior embodiments of 3 axis computer controlled or aided machines, servo 
motors have been used to move the quill in the z-axis, such motors 
substantially interfering with the ability of an operator to manually 
position the quill along the z-axis. 
Other prior inventors have attempted to alleviate this problem by providing 
various quill control mechanisms, for example, Welch et. al, U.S. Pat. No. 
5,330,298 teaches the positioning of controlling elements so that both 
manual positioning of the quill and automatic positioning of the quill can 
be achieved. Welch et. al fails to provide, however, a fine feed 
adjustment mechanism to enable an operator to manually adjust the quill 
along the z-axis with the precision, speed and efficiency required in 
commercial operations, for example, the production of one or a few 
prototype workpieces. Still other prior inventors have conceived of 
position indicating mechanisms. For example, Vershowske et. al, U.S. Pat. 
No. 4,909,683 describes a scale adapted to provide a highly accurate 
digital readout of the linear position of a quill. Vershowske et. al, 
however, must still rely upon the manual ability of an operator to 
properly control the existing coarse lever control on existing milling 
machines in an attempt to achieve the desired vertical movement, 
regardless of how well the vertical movement is indicated on a positioning 
mechanism. In other words, reliance upon the existing coarse vertical 
adjustment mechanisms on existing machines is insufficient to provide 
repeatable and accurate operation of a milling machine to small 
tolerances, regardless of the degree of accuracy of the readout provided. 
Still other inventors have conceived of stop assemblies for milling 
machines to provide quick and accurate adjustments of a stop assembly 
setting (see, for example, Obrecht et. al, U.S. Pat. Nos. 5,252,010; 
5,106,242; Ginter, U.S. Pat. No. 4,521,144; Kronfeld, U.S. Pat. No. 
4,574,441; Guthrie, U.S. Pat. No. 4,787,794). Others disclose adapters for 
mounting depth gauges onto milling machines (Escobedo et. al, U.S. Pat. 
No. 5,286,147). All previously existing milling machines suffer, however, 
from a particular shortcoming in that none of them provides for a way in 
which to easily provide a fine feed mechanism in the z-axis which allows 
an operator to manually gauge depth within 1/10,000th of an inch without 
the need for complicated and time consuming adjustment of 
automatic/computer operated controls and still maintain coarse adjustment 
functions. 
Thus, none of the prior art devices is suitable for the production of one 
or a few number of prototypes in a cost effective and time efficient 
manner. A long-felt but unsolved need therefore exists for a fine feed 
adjustment mechanism that is preferably retrofittable to existing 
machines, that is relatively inexpensive, easy to operate, and that does 
not interfere with the original operation of the handles provided on 
existing machines for more coarse adjustment of a quill along the z-axis. 
The present invention, as described in greater detail below, provides a 
solution to this long-felt but unsolved need. 
SUMMARY OF THE INVENTION 
One aspect of the present invention relates to an add-on accessory device 
adapted to be retrofitted to conventional milling machines for 
conveniently enhancing precision adjustments along the z-axis. Partial 
disassembly and then reassembly of an operator's original equipment is 
required to properly fit the present device to the milling machine. The 
present invention is useful on a variety of machines which require an 
adjustment of the depth of a "downfeed" spindle, including manual drill 
presses and other types of "Bridgeporttype" vertical turret milling 
machines. 
The fine feed adapter device of the present invention attaches to the 
existing hub on milling machines, such hub connected to a lever handle 
which, upon operation of the lever and rotation of the hub, vertically 
manipulates the quill up and down. A regular handle length on existing 
machines is approximately 9 inches long. The fine feed adapter device of 
the present invention thus allows an operator to finely adjust the 
vertical feed and therefore attain exact desired depths of a tool into a 
workpiece. The present device is particularly useful for machines equipped 
with a digital depth readout and can dramatically reduce the amount of 
time necessary to make precise adjustments to milling machines in order to 
produce a prototype workpiece. Moreover, all functions of the original 
handle are still available to the operator, since the present fine feed 
adapter of the present invention retrofits between the handle and the hub, 
keeping the original handle for use in more coarse vertical adjustments of 
the quill.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is particularly directed to a milling machine fine 
precision adjustment device 10 which allows an operator to control the 
z-axis vertical movement of a quill, down feed spindle, and a tool 
attached thereto so that the operator can expeditiously produce one or a 
few milled workpieces by setting the cut quickly and precisely utilizing 
either a manual or computer operated machine. This avoids the prospect of 
improperly milling a workpiece due to the inability of existing one and 
two axis machines to repeatedly produce the exact depth of cut necessary 
to produce precision constructed workpieces. The coarse adjustment lever 
12, which is standard on existing machines, simply does not permit fine 
adjustment of the milling machine in the z-axis. The present invention 
satisfies this long felt, but hitherto unsolved need without the 
expenditure of significant time using hunt-and-peck, empirical methods to 
arrive at an acceptable milled workpiece. In brief, the present invention 
provides an operator with a device that can quickly and precisely mill a 
workpiece to exacting specifications while still maintaining the ability 
to operate a coarse feed mechanism to adjust the z-axis. 
In one aspect of the present invention, a milling machine fine precision 
adjustment device 10 is provided having a first rotatable component 24 
(e.g., a large gear) capable of being attached to a milling machine at a 
point adjacent and/or beneath the standard lever handle that controls 
vertical movement of the quill. The milling machine shaft is capable of 
being manually rotated to move the shaft in a substantially vertical 
direction via a first manual quill adjuster 12 (e.g., the standard lever 
handle). A second rotatable component 26 (e.g., a small gear) has an axis 
of rotation different from that of the first rotatable component 24. The 
first and second rotatable components 24, 26 are operatively connected so 
that a full rotation of the second rotatable component 26 causes less than 
a full rotation of the first rotatable component 24. A second manual quill 
adjuster 34 (e.g., a fine adjustment knob) is operatively connected to the 
second rotatable component 26 for rotating the second rotatable component 
26. When an operator of the milling machine manually moves the first 
manual quill adjuster 12 so that the quill is moved downwardly, thereby 
providing an approximation of a desired position of the quill, the 
operator can then move the second manual quill adjuster 34 to provide a 
more precise positioning of the quill relative to the workpiece. 
As illustrated in FIG. 1 a standard lever handle 12 of a milling machine is 
connected to a circular hub 14 which rotates around a central axis 20, 
thereby vertically adjusting the quill of the milling machine relative to 
a workpiece. The device of the present invention is inserted between the 
lever handle hub 14 on existing machines and the milling machine itself to 
thereby provide a device for fine adjustments in the vertical direction of 
the quill. 
In one embodiment, the present device consists of a housing 16, 18, 
preferably consisting of two substantially equally shaped compartments 16, 
18 held together by a screw 32 which connects to a threaded nut 33 on the 
opposing housing side 18, as well as a screw 40 that connects the lever 
hub 14 to the device 10. The housing 16, 18 is preferably in an oblong or 
egg-shaped configuration with the wider portion of such configuration made 
to accommodate the lever handle hub 14 of existing machines, whereas the 
narrow portion of such configuration accommodates a fine adjustment knob 
34. The knob 34 is rotatable on a bearing 36. Inside the housing 16, 18 is 
positioned a large gear 24, such gear positioned substantially along the 
axis of rotation 20 of the lever handle hub 14. A second smaller gear 26 
is provided in the narrow most portion of the housing 16, 18 and is 
attached to the fine adjustment knob 34 and rotates about a small gear 
axis 30. A set of bearings 36, 38 may be placed under and over the small 
gear 26 to hold it in place along an axis of rotation 30 of the fine 
adjustment knob 34. The large gear 24 attaches to the connection plate 22 
via one or more pins 44 which may include an existing pin 44 from the 
lever handle assembly 14, and the existing machine hub 14 is secured with 
a large screw 40. 
With the large gear 24 fitting over an existing rotation hub 20 of a 
conventional milling machine, rotation about such hub 20 raises and lowers 
the quill/spindle by vertically adjusting the shaft of the milling 
machine. The large gear 24 is attached to the milling machine hub 20 in 
such a manner that the large gear 24 rotates with the milling machine hub 
20 whenever the lever handle 12 is manipulated. 
Connecting the large gear 24 to the small gear 26 is a toothed band 28 
which engages the gear teeth of the large gear 24 as well as the gear 
teeth of the small gear 26. Rotation of the large gear 24 thus operates to 
rotate the small gear 26 and vice versa. Rotation of either of these gears 
24, 26 will vertically adjust the quill/spindle along a vertical 
direction. Obviously, adjustment of the fine adjustment knob 34 will 
operate to vertically adjust the quill/spindle over small distance 
increments whereas movement of the large gear 24 via the standard lever 
handle 12 hub rotation 20 will vertically adjust the quill/spindle along 
larger vertical distances. Tensioning assembly rollers 48 are positioned 
within the housing 16, 18 and come into contact with the belt 28 to 
provide for tension adjustment of the belt 28 as it moves around the large 
24 and small gears 26. By adjusting the tension of the belt 28, for 
example, by screwing the tensioning devices 48, (which rotate about a pin 
axis 49) back and forth as relates to the housing 18 to which it is 
secured, an operator is able to easily release tension to remove or 
replace a toothed band 28 and once installed, the toothed band 28 can be 
appropriately adjusted so that a proper feel of the adjustment knob 34 is 
achieved. The tensioning device roller 48 thus provide a frictional 
restraint on the toothed band 28. The contact of the roller 48 mechanism, 
rotatably housed within a tensioning device housing 45, (such device 
having a threaded pin 46 and a nut 47 associated therewith) is movable 
back and forth in relation to the tensioning device housing 45. For 
example, the pin 46 can be accessible by an operator from the exterior of 
the housing 16, 18 and the rotation thereof causes the roller 48 to 
contact the band 28. 
The housing 16, 18 is designed to maintain the first 24 and second 26 
rotative components in a desired operational orientation to one another so 
that rotational movement is transferred therebetween. The housing 16, 18 
preferably includes an opening for receiving the standard hub 22 which 
attaches to the lever handle hub 14. The housing 16, 18 is then fixedly 
positioned relative to the milling machine itself with existing or 
supplied screws 43 into existing tapped holes. The housing 16, 18 
therefore has an interior compartment containing at least the first 
rotatable component 24 and the second rotatable component 26. While in 
some embodiments the first rotatable component 24 (e.g., the large gear) 
and the second rotatable component 26 (e.g., the small gear) are connected 
with a toothed band 28 as described above, any acceptable rotational 
movement transfer components can be used to transfer the rotational 
movement between the first 24 and second 26 rotatable components. Indeed, 
a gear to gear interaction whereby the teeth of a large gear interact with 
the teeth of a small gear and replace the toothed band may even be 
preferable in various instances. In other embodiments, a gear within a 
gear arrangement can be utilized wherein, for example, a large gear would 
have teeth on its inside diameter and a small gear would be positioned 
within the confines of the large gear diameter with teeth along the small 
gear's periphery. In such a manner, the rotation of the small gear would 
cause the outer periphery teeth of the small gear to interact with the 
inner periphery teeth of the large gear, causing the desired rotational 
movement and thus, desired z-axis movement of the quill. 
Still further embodiments of the present invention do not utilize gears but 
instead, rely upon frictional contact between two rotating elements. For 
example, a large rotating element can be contacted by a smaller rotating 
element, such smaller rotating element having a rubberized surface that 
contacts the larger rotating element, such that when the smaller rotating 
element is rotated, the rubberized contact with the large rotating 
component also causes such large component to rotate. The particular size 
and shape of any rotatable component may vary depending upon the 
particular uses and machinery employed. Moreover, it is also within the 
scope of the present invention that one or more rotating components are 
interconnected through means other than frictional and/or gear-toothed 
relationships, for example, electrically and/or magnetically 
interconnected to accomplish the sought-after fine-feed adjustment 
mechanism rotation. For example, a full rotation of a small rotatable 
component could cause a 1/60th of a rotation of a larger component to 
which the smaller rotatable component is connected. 
The toothed band 28, in one embodiment, comprises a flexible closed loop 28 
extending about the circumference of both the first 24 and second 26 
rotatable components. In alternative embodiments (not shown), the 
rotational movement transfer components include a rigid member that 
rotates about an axis different from both the axis of rotation for the 
first rotatable component and the axis of the second rotatable component 
(e.g., a third, fourth, etc. gear can be placed between the large and 
small gears). 
Another aspect of the present invention relates to a method for providing a 
fine precision adjustment of a milling machine quill relative to a 
workpiece comprising removing a manual quill adjustment component from a 
fully assembled milling machine, thereby providing access to a free end of 
a quill adjustment shaft whose rotation causes vertical movement of a 
quill. The quill adjustment shaft 20 is inserted through an opening in the 
housing 16, 18 to align the present adjustment assembly 10 with the quill 
adjustment shaft 20. A first rotatable component 24 (e.g., large gear) of 
the adjustment assembly 10 is then secured to a quill adjustment shaft 20 
by aligning holes 42 of the first rotatable component 24 with holes 42 in 
the connection plate 22 by means of a pin 44. A second rotatable component 
26 (e.g., small gear) is operably connected to the first rotatable 
component 24 so that when the second rotatable component 26 rotates to 
adjust the vertical direction of the quill over substantially small 
distances (e.g., between about 1/4 inch and 1/10,000th inch) the first 
rotatable component 24 is rotated slightly, thus moving the quill 
vertically by the desired small amount. Manual rotation of the manual 
quill adjustment component 12 (e.g., the lever handle) rotates the quill 
adjustment shaft and thereby provides an approximation of a desired 
position of the quill along the z-axis. Finally, manual movement of the 
second quill adjustment component 34 (e.g., the fine adjustment knob) 
allows the operator to precisely adjust the vertical movement of the quill 
due to the fact that a full rotation of the second rotatable component 34, 
26 causes less than an entire rotation of the first rotatable component 
24. In this manner, fine adjustment of vertical positioning of the quill 
relative to a workpiece is accomplished. 
While the above discussion was directed to conventional milling machines 
which have a table upon which the workpiece is secured movable in an x and 
y direction and the spindle is moved solely in a z-axis direction and not 
in an x-y axis direction, other embodiments that will be obvious to one of 
skill in the art given the guidance and direction of the present 
specification, include the use of the present invention for various other 
machines, such as routers, cutting, molding, and shaping machines, wherein 
the tool itself is movable in various directions. In brief, the present 
invention can be used with various cutting and tooling machines to provide 
a fine-feed adjustment mechanism that works in concert with the coarse 
feed adjustment mechanism available on conventional machinery. 
While various embodiments of the present invention have been described in 
detail, it is apparent that further modifications and adaptations of the 
invention will occur to those skilled in the art. However, it is to be 
expressly understood that such modifications and adaptations are within 
the spirit and scope of the present invention.