Patent Application
20090020937
The present invention relates generally to a device for positioning a work piece in a vise and more specifically to a device for selectively positioning a work piece relative to a hard jaw of a machine vise.
In some machining operations, a rotating cutting tool selectively removes material from a work piece held on a table on a machine tool. The work piece may be held on the table by a holding means such as a clamp, a vise, a purpose-built fixture, or other positioning or restraining devices. Some examples of a machine tool having a table on which a work piece is held are horizontal mills, vertical mills, grinders, drill presses, and computer numerical control (CNC) mills. The holding means aids safe and accurate machining by limiting work piece slippage while the work piece and cutting tool are in contact with each other. For CNC mills, which are well adapted for repetitive machining operations as may occur in high volume production, the holding means may also facilitate rapid and accurate replacement of one work piece with another.
Configuring a holding means for a machining task may involve substantial labor time and material expense and may contribute to a significant fraction of the finished cost of a machined product. In some cases, a purpose-built fixture may provide the best accuracy and fastest work piece setup, but design, fabrication, validation, and storage costs are usually higher for a purpose-built fixture than for other holding means. Furthermore, a purpose-built fixture may require extensive modification or may even be scrapped entirely should a change be made to the machined product.
Holding means comprising toggle clamps, modular clamps, V-blocks, and other multi-purpose holding and positioning devices are adaptable to a variety of machining projects. However, the time to set up a holding means with multi-purpose holding and positioning devices may be substantial, and removing a work piece from the holding means and replacing it with another work piece may be inconvenient or time consuming. The accuracy of such a holding means is subject to the skill of the person setting it up, and the accuracy may vary from one work piece placement to the next. Furthermore, care must be taken to ensure that the various components comprising the holding means do not interfere with a desired path of a cutting tool.
A holding means comprising a vise may provide an amount of accuracy, an economy of set up, and an ease of changing work pieces that is intermediate between a purpose-built fixture and multi-purpose holding and positioning devices. Many kinds of vises are available. A type of vise known as a machine vise comprises a fixed jaw and a floating jaw that is moved relative to the fixed jaw by a floating jaw positioning mechanism. Some machine vises have a floating jaw positioning mechanism with a manually-operated screw. Other machine vises have a floating jaw positioning mechanism that is electrically or hydraulically driven. In some machine vises, a hard jaw attached to a face of the floating jaw and another hard jaw attached to a face of the fixed jaw provide accurate surfaces and edges for locating and holding a work piece. The work piece is held firmly in place by a compression force generated between opposing faces of the hard jaws on the floating jaw and fixed jaw. The magnitude of the compression force may be changed by an adjustment of the floating jaw positioning mechanism. The fixed jaw is attached to a base which houses the floating jaw positioning mechanism. The base of the vise may be formed with apertures or flanges for attaching the vise to a table on a machine tool.
Devices for positioning a work piece relative to the jaws of a machine vise are known in the art. A vise parallel is an example of such a positioning device. A vise parallel may be a metallic rectangular solid having a first and a second planar face formed parallel to each other and perpendicular to a third planar face. A separation distance across a narrow dimension of the first or second planar face is referred to as a height of a vise parallel. Vise parallels are generally used in pairs having matching heights. A first vise parallel is placed in contact with a face of a hard jaw attached to a fixed vise jaw and a second vise parallel is placed in contact with a face of a hard jaw attached to a floating vise jaw. A work piece may optionally be placed between the fixed vise jaw and floating vise jaw with a bottom surface of the work piece in contact with a top surface of the first vise parallel and a top surface of the second vise parallel, the height of the vise parallels defining a vertical reference position for the work piece. Vise parallels are held against the hard jaws by an expansion spring placed in the space between the vise parallels, by one or more spring posts having an expansion spring and a cylindrical portion with a shoulder which engages a hole in a vise parallel and presses the vise parallel against a hard jaw, by magnetic means, or by other removable attachment means.
Vise parallels are often used to define a vertical reference position for a work piece held in a vise, but other means have generally been used to define a lateral reference position for the work piece. A convention followed herein defines a lateral direction as a direction parallel to a transverse dimension of a vise and a vertical direction as a direction perpendicular to a table surface. Reference locations from which position measurements may be made include, but are not limited to, an edge of a cutting tool, an edge of a hard jaw, a surface on a table, or another object having a surface or edge with a known or trusted position or known deviation from an ideal shape, such as deviation from a straight line or deviation from an ideal plane. Other locating devices known in the art provide a lateral reference position with an error of about 0.002 inch (0.051 millimeter) or more for repeated placement of a work piece. A repeatability error of 0.002 inch is large compared to the best accuracy available from many modern machine tools. Separate clamps are sometimes added to a machining set up using vise parallels to provide a lateral reference position, or an alignment procedure may be performed each time a new work piece is placed in the holding means. Adding more clamps increases the time to set up a holding means and increases the number of obstacles that may interfere with a preferred cutting tool path. Alignment procedures may be time consuming and are subject to the skill of the person performing them.
What is needed is a device for establishing a reference position of a work piece that attaches rapidly and securely to a machine vise, has a repeatable positioning error of 0.0002 inch (0.0051 millimeter) or less, establishes a range of vertical reference positions for a work piece with vise parallels having a range of heights, and minimizes interference with cutting tool paths.
A vise understop attaches to a hard jaw of a machine vise and establishes a selectable reference position for a work piece held in the machine vise. The vise understop comprises a flat front surface against which a vise parallel is held. A top surface of the vise parallel establishes a vertical reference position for a work piece placed in contact with the top surface. The vise understop further comprises a relocatable stop removably connected to an understop body. A lateral position of the relocatable stop may be selected from a plurality of discrete positions formed along a length of the understop body. A vertical surface on a side of the relocatable stop establishes a lateral reference position for a work piece placed in contact with the vertical surface.
The understop body comprises a back side formed with a rectangular channel having a long dimension adapted for a loose clearance fit of a hard jaw. In some embodiments, at least one locating post is attached to the back side of the understop body. The locating post has a position and a size adapted to fit inside the aperture of a socket head threaded fastener used to attach a hard jaw to a vise jaw.
In one embodiment, a shoulder on a front side of the understop body and a corresponding surface on the relocatable stop have a profile in the shape of a serpentine curve. Other embodiments have a shoulder on the understop body and a corresponding surface on the relocatable stop that is alternatively flat, crenellated, or other shapes. A face on the front side of the understop body is formed with a plurality of apertures adapted for a close sliding fit of a pin attached to the relocatable stop. Contact between a pin on the relocatable stop with a wall of an aperture in the understop body and further contact between the shoulder of the understop body and the corresponding surface on the relocatable stop cooperate to establish a stable, secure, and repeatable lateral reference position for the relocatable stop and correspondingly for a work piece placed in contact with the relocatable stop.
In some embodiments, a channel is formed in a right side of the understop body. The channel is adapted for a clearance fit of a shaft of a spring post used to press a vise parallel against a surface. Another channel may optionally be formed in a left side of the understop body. The right and left sides may also be formed with threaded apertures through which compression screws are cooperatively assembled. An adjustment of the compression screws holds the vise understop firmly in contact with a hard jaw. Tightening a compression screw against a hard jaw also causes the locating post on the back side of the understop body to firmly contact a wall of an aperture in a socket head threaded fastener used to attach a hard jaw to a vise jaw, thereby limiting an amount by which the understop body may move relative to the hard jaw and correspondingly improving the accuracy and repeatability of a positioning reference for a work piece.
This section summarizes some features of the present embodiment. These and other features, aspects, and advantages of the embodiments of the invention will become better understood with regard to the following description and upon reference to the following drawings, wherein:
Embodiments of the invention include a device intended to establish a reference position for a work piece held in a vise. Devices built in accord with the invention are particularly suited for use with a machine vise, but other kinds of vises may also be used. Some of the benefits of the embodiments of the invention include, but are not limited to, rapidity and simplicity of installation, small positioning error, good repeatability, minimal interference with preferred cutting tool paths, suitability for a variety of machine tools and work pieces, stable support for vise parallels having a range of a height dimension, and ease of adaptation to vises of various styles and sizes.
An embodiment of a vise understop adapted for attachment to a hard jaw on a machine vise is shown in
An example of a machine vise on which a vise understop 1 may be used is illustrated in
A function of the understop body 2 is to support other elements used to establish a lateral reference position and optionally a vertical reference position for a work piece held against a hard jaw in a machine vise. The understop body 2, shown in a top view in
A locating post 16 extends perpendicularly from a back surface of the understop body 2, as shown in
The understop side flange 12 is formed with a spring post channel 17 extending from a front surface of the understop side flange 12 to a back surface of the understop side flange 12. A spring post channel 17 provides clearance for an end of a spring post optionally used to hold a vise parallel against a hard jaw and against a vise understop. A shape and size of the spring post channel 17 are adapted for a clearance fit of a spring post. In the embodiment of
A depth of the relocatable stop support shoulder 13, shown from above in
A portion of a side surface of the relocatable stop 3 projects above a top surface of a vise parallel to provide a contact area between the side surface of the understop 3 and an edge of a work piece. Contact between a side of the relocatable stop 3 and an edge of the work piece is necessary to establish a lateral reference position for the work piece. In the example of
The relocatable stop support shoulder 13 and a plurality of pin apertures 14 cooperate to form a set of discrete attachment positions for the relocatable stop 3 along a length of the understop body 2. The relocatable stop support shoulder 13 and pin apertures 14 are shown from the top of the understop body 2 in
The pin apertures 14 in the understop body 2 have a size and a position adapted for a close sliding fit of a locating pin attached to a relocatable stop 3. A relocatable stop 3 is illustrated from the front in
A relocatable stop 3 is connected to an understop body 2 by slidably inserting the locating pins 19 on the relocatable stop 3 into corresponding pin apertures 14 on the understop body 2. In the embodiment illustrated in
A combination of the curved surface of the relocatable stop support shoulder 13, the corresponding curved surface forming part of the relocatable stop locating bosses 20 on the relocatable stop 3, the pin apertures 14, and the locating pins 19 are effective in reducing positioning error and improving repeatability of a position of the relocatable stop 3 relative to the understop body 2. Reduced positioning error and improved repeatability in a position of the relocatable stop 3 corresponds to an improvement in the accuracy of a machined work piece. Contacts between parts of the relocatable stop 3 and corresponding parts of the understop body 2 occur in more than one plane and more than one direction. A displacement of the relocatable stop 3 relative to the understop body 2 causes the locating pins 19 to bind in their corresponding pin apertures 14 and also causes firm contact between the relocatable stop support shoulder 13 and relocatable stop locating bosses 20, thereby limiting the displacement to a small value. In some embodiments, the contribution of relative motion between parts of the vise understop to errors in positioning and repeatability, corresponding to accuracy errors in a machined work piece, is 0.0002 inch (0.0051 millimeter) or less.
An example of a vise understop attached to a hard jaw 8 fastened to a fixed vise jaw 6 of a machine vise 5 appears in
A pair of vise parallels 22 and a two spring posts 23 are added to the example of
In the example of
An example of a work piece 21 is added to the example of
The present disclosure is to be taken as illustrative rather than as limiting the scope, nature, or spirit of the subject matter claimed below. Numerous modifications and variations will become apparent to those skilled in the art after studying the disclosure, including use of equivalent functional and/or structural substitutes for elements described herein, use of equivalent functional couplings for couplings described herein, or use of equivalent functional steps for steps described herein. Such insubstantial variations are to be considered within the scope of what is contemplated here. Moreover, if plural examples are given for specific means, or steps, and extrapolation between or beyond such given examples is obvious in view of the present disclosure, then the disclosure is to be deemed as effectively disclosing and thus covering at least such extrapolations.
Unless expressly stated otherwise herein, ordinary terms have their corresponding ordinary meanings within the respective contexts of their presentations, and ordinary terms of art have their corresponding regular meanings.
