| 1. | A dado shim for spacing apart a plurality of two steel dado blades mounted on an arbor, comprising: a magnetic sheet adapted to be securely attached between said steel dado blades by magnetic attraction, so as to prevent shifting. |
| 2. | The dado shim of claim 1 wherein said magnetic sheet is highly flexible for resisting damage. |
| 3. | The dado shim of claim 1 wherein said magnetic sheet has a thickness of 0.020 inch. |
| 4. | The dado shim of claim 1 wherein said magnetic sheet has a thickness of 0.012 inch. |
| 5. | The dado shim of claim 1 wherein said magnetic sheet has a thickness of 0.010 inch. |
| 6. | The dado shim of claim 1 wherein said magnetic sheet has a thickness of 0.008 inch. |
| 7. | A dado shim for spacing apart two steel dado blades mounted on an arbor, comprising: a magnetic sheet having an arbor hole adapted to be concentrically mounted on said arbor, said magnetic sheet is adapted to be securely attached between steel dado blades by magnetic attraction, so as to prevent shifting. |
| 8. | The dado shim of claim 7 wherein said magnetic sheet is highly flexible for resisting damage. |
| 9. | The dado shim of claim 7 wherein said magnetic sheet has a thickness of 0.020 inch. |
| 10. | The dado shim of claim 7 wherein said magnetic sheet has a thickness of 0.012 inch. |
| 11. | The dado shim of claim 7 wherein said magnetic sheet has a thickness of 0.010 inch. |
| 12. | The dado shim of claim 7 wherein said magnetic sheet has a thickness of 0.008 inch. |
| 13. | The dado shim of claim 7 wherein said arbor hole has a diameter of 5/8 inch. |
| 14. | The dado shim of claim 7 wherein said arbor hole has a diameter of 11/8 inch. |
| 15. | A dado shim for spacing apart two steel dado blades mounted on an arbor, comprising: a circular magnetic disc having a central arbor hole adapted to be concentrically mounted on said arbor, said circular magnetic disc is adapted to be securely attached between said steel dado blades by magnetic attraction, so as to prevent shifting. |
| 16. | The dado shim of claim 15 wherein said circular magnetic disc is highly flexible for resisting damage. |
| 17. | The dado shim of claim 15 wherein said circular magnetic disc has a thickness of 0.020 inch. |
| 18. | The dado shim of claim 15 wherein said circular magnetic disc has a thickness of 0.012 inch. |
| 19. | The dado shim of claim 15 wherein said circular magnetic disc has a thickness of 0.010 inch. |
| 20. | The dado shim of claim 15 wherein said circular magnetic disc has a thickness of 0.008 inch. |
FIELD OF THE INVENTION
This invention relates generally to dado blades used with power saws, specifically to a magnetic dado shim for spacing apart dado blades.
BACKGROUND OF THE INVENTION A dado is a groove on a board for receiving the edge of another board, such as for joining perpendicular pieces of a cabinet, drawer, etc. A dado is cut with a set of dado blades, which typically includes a pair of circular blades spaced apart by one or more two-tooth blades, or four-tooth blades. Typical dado blades have standard 5/8" or 1-1/8" arbor holes for mounting on the drive shaft or arbor of a power saw, and are tightened thereon by a nut and a washer. The blades are of a standard thickness, so that a suitable number of blades can be stacked together for cutting a dado for receiving a board of another standard thickness. E.g., two 1/8" thick circular blades can be spaced by two 1/8" thick two-tooth blades to make a 1/2" dado set for cutting a 1/2" dado for a 1/2" thick board. Although boards are available in standard thicknesses, the actual thickness of any particular board can vary somewhat from its intended size due to poor manufacturing, shrinkage, expansion, etc. Therefore a dado cut to a standard width would often be slightly too narrow or too wide for snugly receiving a board.
Various adjustable dado sets have been proposed for providing an adjustable cutting width. U.S. patent 5,368,079 to Benway (1994) shows a dado set with a special blade having a non-standard, threaded hole for receiving a threaded collar. Turning the collar adjusts the spacing of the special blade from other blades. U.S. patents 4,589,458 to McCord, Jr. (1986) and 5,309,962 to
McCord, Jr. et al. (1994) each shows an adjustable dado set with special blades having non-standard holes for receiving a pair of opposite cams. Turning the cams adjusts the spacing between the blades. However, the Benway and McCord devices both require special blades specifically designed for fitting their adjusting mechanisms, so that they cannot use conventional blades. Therefore, obtaining replacement blades for these devices is relatively difficult and expensive.
U.S. patent 5,316,061 to Lee (1994) shows plastic dado shims for positioning between and spacing apart dado blades. The shins are circular, and have an arbor hole and a radial slot for being installed on an arbor without removing the blades. The shims are provided in various thicknesses, so that one or a combination of several different shims can be used for minutely adjusting the spacing of a set of blades. Other dado shims commonly known in the carpentry
trade are simple discs each with an arbor hole sized for closely fitting on an arbor, and are made of either paper or metal. All prior art dado shims are very difficult to install, because they frequently fall into and get caught in the relatively coarse thread of the arbor, i.e., they become eccentrically positioned on the arbor. As a result, the edges of their
holes are cut or otherwise damaged when the blades are tightened together. Further, the crumpled shims cause the blades to be improperly spaced. When the shims fall into the arbor's thread, they hinder the installation as well as the removal of the blades. This problem is compounded several folds when several shims are used, because a properly placed shim would easily fall into the thread when the user is busy installing additional shims or blades. Therefore, ensuring the proper installation of any prior art dado shim is a very frustrating and time consuming exercise. Furthermore, prior art paper and metal dado shims can easily become bent or otherwise damaged in harsh shop environments. Once damaged, they cannot be adequately flattened or repaired.
Still another problem is that blades stacked with nothing therebetween, or with metal shims therebetween, are prone to metal-to-metal vibration. This causes a chattering or whistling noise, which can become very annoying when the saw is used for prolonged periods of time. Also, when a user tries to measure the total width of a set of dado blades mounted on an arbor, but before they are tightened, the blades will tend to fall to one side of the arbor's coarse thread, so that they will not sit straight or parallel to each other. Therefore, accurate measurement of the set cannot be easily made.
OBJECTS OF THE INVENTION
Accordingly, the primary object of the present invention is to provide a magnetic dado shim which stays securely in position once placed against a blade, so that it will not fall into and get caught in the thread of an arbor. Another object of the present invention is to provide a magnetic dado shim which greatly facilitates the installation and removal of dado blades.
Still another object of the present invention is to provide a magnetic dado shim which can minutely adjust the cutting width of a set of dado blades.
Still another object of the present invention is to provide a magnetic dado shim which prevents dado blades from chattering or whistling.
Yet another object of the present invention is to provide a magnetic dado shim which holds adjacent blades together and in parallel, so that their cutting width can be accurately measured before they are tightened on an arbor.
Yet another object of the present invention is to provide a magnetic dado shim which can also hold paper, plastic, or metal shims flat against a blade.
Further objects of the present invention are to provide a magnetic dado shim which fits all conventional saws, which is durable, and which is very economical to manufacture.
SUMMARY OF THE INVENTION
A magnetic dado shim is a disc cut from flexible magnetic sheeting. A central arbor hole on the shim allows it to be installed on the arbor of a power
saw. The magnetic dado shim sticks firmly against any steel saw blade, so that it will not fall into the thread of the arbor to hinder installation or removal of the dado set The magnetic dado shim dampens vibration between adjacent blades to prevent chattering or whistling. It can also be used for holding other shims that are made of paper, plastic, or metal flat against a blade.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side perspective view of a magnetic dado shim in accordance with a preferred embodiment of the invention. Figure 2 is an exploded side perspective view of a dado set with magnetic dado shims.
Drawing Reference Numerals
10-Magnetic Dado Shim 11-Circular Magnetic Disc
12-Arbor Hole
13-Circular Dado Blades
14-Two-Tooth Dado Blades
15-Arbor 16-Thread
17-Washer
18-Nut
DETAILED DESCRIPTION OF THE INVENTION
In accordance with a preferred embodiment of the invention shown in the side perspective view in Figure 1, a magnetic dado shim 10 is a circular magnetic sheet or disc 11 with a central arbor hole 12. In this example, magnetic dado shim 10 is 4" in diameter, but it can be of any other diameter. Arbor hole 12 is of an industry-standard size, such as 5/8" or 1-1/4", for closely fitting on standard arbors (not shown), or it can be of any other suitable size for fitting other types of saws. Magnetic dado shim 10 is economically manufactured by being die-cut from commonly available, inexpensive and highly flexible magnetic sheeting (not shown), which are available in a variety of thicknesses, including but not limited to 0.020", 0.012", 0.010", and 0.008", for making shims of different sizes.
Detailed Description-Figure 2.
Magnetic dado shims 10 are first positioned concentrically on a conventional, steel circular dado blade 13 and a conventional, steel two-tooth dado blade 14 before the blades are fitted onto an arbor 15 of a power saw (not shown). When magnetic dado shims 10 are thus positioned on the blades, they stick firmly thereto by magnetic attraction, and will not easily shift in position. Therefore, when dado blades 13 and 14 are being installed on arbor 15, magnetic dado shims 10 will not fall into and get caught in the thread 16 thereof. Any number of sizes of magnetic dado shims 10 can be stacked together, or alternating
between blades, for finely adjusting the total cutting width of dado blades 13 and 14.
Magnetic dado shims 10 will hold adjacent blades 13 and 14 firmly together in parallel by magnetic attraction before they are tightened, so that the total cutting width of the blades can be accurately measured and adjusted with additional or fewer shims 10, without having to repeatedly install and remove washer 17 and nut 18. Furthermore, if a paper, plastic, or metal shim (not shown) is placed between magnetic dado shim 10 and a blade, shim 10 will hold the non-magnetic shim securely in place by attracting both toward the blade. When the total cutting width of blades 13 and 14 is properly set, they are tightened on arbor 15 with washer 17 and nut 18.
When dado blades 13 and 14 are being removed from arbor 15, magnetic dado shims 10 will remain attached to their respective blades for convenient removal. As a result, magnetic dado shims 10 are much quicker and easier to install and remove than all prior art dado shims. Unlike prior art paper and metal dado shims, which are easily damaged, magnetic dado shims 10 are highly flexible, so that they can withstand a great deal of abuse without suffering any damage. Also, flexible magnetic dado shims 10 will dampen vibration between adjacent blades 13 and 14, so that they will prevent annoying chattering or whistling.
CONCLUSION, RAMIFICATIONS, AND SCOPE
Accordingly the reader will see that I have provided a magnetic dado shim which will firmly stick to conventional steel dado blades, so that they will not fall into and become caught in the thread of an arbor. It is much quicker and easier to install than all prior art dado shims, none of which is magnetic. It dampens vibration between adjacent blades to prevent chattering or whistling. It holds adjacent blades firmly together, before they are tightened, so that their cutting width can be conveniently measured and adjusted without having to repeatedly install and remove the nut. It can be used to securely hold non-magnetic shims against a blade. It can be easily and economically made in a variety of different diameters, with different arbor hole sizes for fitting different saws, and in a variety of thicknesses for finely adjusting the spacing of dado blades. It is also very durable.
Although the above descriptions are specific, they should not be considered as limitations on the scope of the invention, but only as examples of the preferred embodiment. Many other ramifications and variations are possible within the teachings of the invention. For example, the magnetic dado shims can be made in other shapes, such as square, triangular, octagonal, etc., and in other diameters and thicknesses. Therefore, the scope of the invention should not be determined by the examples given, but by the appended claims and their legal equivalents.