Claims
- 1. A tool bit for cleaning surface material from the bottom of a dado channel cut in a workpiece comprising:
- a shank having a first end and a second end, said first end for securing to a power tool to provide high speed rotation of said shank about a given rotation axis, said second end having a cutting member for contact with said floor of said dado channel, said cutting member having a solid cylindrical body member and a cutting edge along only a bottom of said body member, said cutting edge further comprising a plurality of cutting teeth formed along the bottom of said body member, said teeth having cutting surfaces spaced equidistant from each other, each of said cutting surfaces having an inner edge circumferentially close to said axis of rotation and extending to an outer edge aligned with the outer circumferential surface of said cutting member, said teeth and said body member cooperating to dissipate the heat generated by high speed rotation of said bit during cleaning of said surface material from said cut, the entire surface of said outer circumferential surface of said cutting member presenting no cutting edge for engagement with side walls of said channel in said workpiece during said cleaning.
- 2. The tool bit of claim 1 wherein said cutting teeth further comprise a slight cant in the range of 82.degree. to 92.degree. from said inner edge to said outer edge of each of said teeth to impart a shearing force to said surface material during said cleaning.
- 3. The tool bit of claim 1 wherein at least 75% of the surface area of each of said teeth is in heat transferring contact with said body member to dissipate said generated heat during continuous operation of said bit.
- 4. The tool bit of claim 2 wherein the perpendicular distance from the midpoint of said inner edge of each of said teeth is less than 1/8" from said rotation axis.
- 5. The tool bit of claim 4 wherein said cutting teeth further comprise an approximate cutting angle of 7.degree..
- 6. The tool bit of claim 4 wherein the diameter of said body member is approximately 1/2" and each of said teeth is 1/8" wide by 3/16" long by 1/2" high with approximately 1/8" of said height extending below a bottom of said body and 3/8" of said height in heat transferring connection to corresponding notches in said body member.
BACKGROUND OF THE INVENTION
This is a continuation-in-part of U.S. patent application Ser. No. 07/728,660 filed Jul. 11, 1991.
The present invention relates to a tool bit, and more particularly to a specialized bit for cleaning uneven surface material from the bottom of a dado channel cut in a workpiece.
The dado cut is used in the production of furniture to provide a means for perpendicularly adjoining two separate members. It is a well known joint cut in the furniture construction industry. Typically the cut is accomplished by means of a dado cutting blade set, known as a "Dado Stack", mounted in a table saw or on a radial-arm saw. The workpiece is moved against the fence and the blade of the radial-arm saw is drawn across the workpiece. This "Dado Stack" cuts a channel or slot in the workpiece. In the radial-arm saw the distance the blade can be drawn across the workpiece is very limited.
The table saw method of dado cutting is generally employed as the mainstay of all cabinet and furniture production because of the length of the dado channel cut which may be obtained.
With the table saw method complications result as the workpiece is pushed or fed against the fence and over the dado set. The forward motion of the workpiece creates a resistance between the surface of the workpiece and the dado blade set. This resistance results in the workpiece lifting at intervals along the dado channel being cut. This lifting or rising action is created by the bombarding of the blades of the dado set against the surface of the workpiece. This creates a serpentine floor elevation in the dado channel.
The router was adopted as an alternative for creating an accurate cut. This accuracy is due to the high revolutions per minute (rpm) developed by the router. The use of high rpm in excess of 10,000 rpm is the only known way of removing the amount of material necessary to produce the dado joint with a cutter blade the width of the finished dado channel. However, two problems exist with this router method of producing a dado joint. The first problem is that router guides must be secured to the workpiece in a precise location to guarantee that every dado joint is cut in the anticipated location. This problem has been overcome by the invention of a device known as the "over-arm router". Such machines work accurately and can even be computer assisted. These machines are extremely expensive. Further, as a result of another problem, the "over-arm router" devices are not cost effective for dado joint manufacture.
The second problem with the router method of producing a dado joint is that the carbide blades designed to cut dado joints in a workpiece with a router, any router, dull very quickly. When they are sharpened, the parallel blades become too narrow to construct a dado wide enough to accept the pre-planned crossmember.
When the inaccuracies of the dado joint are projected throughout the assembly of a casegood item, time consuming and expensive compensations must be made to insure a saleable casegood product.
In the assembly of furniture, an uneven floor in a dado joint will result in a misalignment so significant that the side pieces joined by the dado joints are not parallel. This slows down the entire production of the casegood product The furniture industry has ignored this unevenness in the floor of a dado because it has been impractical until the development of the present invention to create an even surface economically.
The tool related industry has developed other methods to achieve even dado surfaces, but these methods, however, are not cost effective when applied in production.
Most of the methods and devices attempting to solve existing problems and effect an accurate dado joint are based on a one-step process. These one-step processes use complicated guide systems to insure accurate placement of the dado channel. Again, this creates slow production resulting in higher costs.
However, a factor which makes existing two-step methods impractical is that existing apparatuses used in the second step operate at very low rpm. Considering that a very high blade-to-material ratio must be achieved in order to remove enough material efficiently and to produce an accurate cut, existing devices operating at low rpm have been technologically impractical to date.
The only reasonable solution for the industry is to continue to produce the initial dado channel using existing manufacturing techniques and then to have an inexpensive way to even the dado floor. The present inventive bit provides the apparatus for accomplishing this step, without totally abandoning the present manufacturing practices.
U.S. Pat. No. 1,632,440 discloses a simple clean-out router bit for use in the woodworking industry which was designed to eliminate the hand labor involved in cleaning out openings cut by hollow mortising chisels. When using hollow mortising chisels in the construction of wooden furniture, the bottom of the groove remains rough and uneven and small corners hang in the openings. The router bit of U.S. Pat. No. 1,632,440 is intended to solve this problem. The router bit, however, is of conventional design and not only cleans the bottom of the groove but also cuts the side of the groove, because its cutting face or edge extends along the outer circumferential surface of the bit. As the friction collar of the bit wears, the bit begins to remove more of the side wall than necessary. This eventually leads to a loose or slopping fit of the mating parts.
Another type of cleaning bit for dado joints is illustrated in U.S. Pat. No. Des 269,348. Again, as with the 1,632,440 device, the bit has a cutting edge which is presented for engagement with the sidewalls of the dado channel.
U.S. Pat. No. 3,303,862 discloses a conventional cutting tool which presents an adjustable cutting blade that allows side contact in order to create a channel where a channel did not previously exist.
U.S. Pat. No. 4,168,730 discloses a complicated guide system working in conjunction with a bit of conventional design for the manufacture of dovetail joinery.
U.S. Pat. No. 4,412,571 discloses a one-step process using complicated guide systems to effect dado channels, mortises and grooves where no cuts previously existed. This tool claims to remove a substantial amount of material.
The cutting bit of U.S. Pat. No. 4,412,571 drives its blades off of the outer periphery of the cutting head, therefore creating a mechanical disadvantage from a standpoint of centrifugal leverage. In other words, the cutting surface is not close to the axis of rotation of the bit. The blades of this tool are only 1/16", and are claimed to be kept very sharp very easily. The tool is intended for use with a standard electric hand drill. The guide assemblies are also designed for use with an electric hand drill. All electric hand drills develop relatively low rpm, i.e., under 2500 rpm, which dictates and results in a very low blade-to-material ratio. This contrasts significantly with the present invention in which there is removal of substantial amounts of material.
The described depth guide of the tool bit of U.S. Pat. No. 4,412,571 has a larger inside diameter so as to form a ring that fits loosely around the main cutting member. This ring or depth guide is held securely in place by a set screw on one side so that the guide does not slip or move. At low rpm, any problem of imbalance due to the design of this depth ring would not be a significant factor. However, at high rpm, in excess of 4000 or 5000 rpm, any imbalance in the ring would set up oscillations in the tool which would render the tool uncontrollable.
All tool bits operating at high rpm must utilize special cutter blade materials. These materials are very difficult and somewhat costly to sharpen. Specialized equipment employing diamond grinding wheels are necessary to sharpen these various blade materials. The most commonly used material in high rpm blade technology is carbide.
A standard in the industry is to rate the cutter blade quality by carbide thickness. The professional grade blade possesses carbide which is over 1/16" in thickness. The commercial grade possesses carbide which is 5/8" in thickness. The industrial grade possesses carbide that is 3/16"+ in thickness. The cutter bodies of these blades are usually made of a material known as high speed steel with the carbide thickness then affixed to the high speed steel member.
High speed steel is also used for the entire construction of the common twist drill bit. The twist drill bit possesses no carbide because it is used generally in an electric hand drill. The common twist drill bit cannot safely exceed 3000 rpm without danger to its workpiece or its operator. Heat build-up, metal fatigue, crystallizing, and shattering of a high speed steel drill bit at high rpm is a common occurrence.
The cost of high speed steel is low since it is a moderately soft material. It is not cost effective to make low-speed, cutter blades from the more durable and expensive materials such as carbide. One of the advantages of cutter blades made of high speed steel is that they may be easily sharpened. The bit described in U.S. Pat. No. 4,412,571 is understood to be constructed of high speed steel and not carbide because it is designed with a guide system utilizing an electric hand drill. Thus the bit is not intended or designed to be used in high rpm technology.
Further, the device of U.S. Pat. No. 4,412,571 is intended to effect dado channels, mortises, and grooves where no cuts previously existed, i.e., to effect joint manufacture from start to finish in a one-step process. The present inventive bit is significantly different than the device of U.S. Pat. No. 4,412,571; they operate on very different principles.
There has been a long-standing problem with the existing devices or methods for creating perfect symmetry concerning the dimensions of the dado channel. There has been a long-felt need for a tool which would create such accuracy in perfecting the close dimensions of such a furniture joint. The present inventive tool bit solves the existing problems and obliges the demands of the industry.
The present inventive tool bit for operation in routers and laminate trimmers developing excess of 10,000 rpm provides an advanced design of a bit in which only the bottom surface of the cutting member removes material from the floor of a dado channel. However, this dado channel must have been previously cut in a workpiece. The outer circumferential surface of the cutting member utilizes the side wall of the previously cut channel as a guide for the path of the bit. The design of this bit enables this function to be possible because the cutting member presents no cutting edge for engagement with the side walls of the channel in the workpiece in any way.
In one embodiment of the present inventive tool bit, the cutting edge of the cutting member is made up of four separate cutting teeth spaced equidistant apart from each other and circumferentially close to the rotation axis of the tool bit. The teeth are set into notches in the solid, cylindrical body of the cutting member. The size of the teeth and their connection to the body member result in cooperation whereby the heat developed during operating of the bit is quickly dissipated allowing the bit to rotate at high rpm and still remove sufficient material from the floor of the channel.
While the discussion below refers to a dado channel, it should be understood that the inventive tool bit may be utilized to clean the floor of any perpendicularly adjoining surfaces.
US Referenced Citations (3)
| Number |
Name |
Date |
Kind |
| 1632440 |
Follett et al. |
Jun 1927 |
|
| 3656521 |
Czerniewicz |
Apr 1972 |
|
| 4412571 |
Czerniewicz |
Nov 1983 |
|
Continuations (1)
|
Number |
Date |
Country |
| Parent |
728660 |
Jul 1991 |
|
Patent Grant
5127774
