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Dado Accessory Joinery
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Tip #14
Dado Set

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version of Tip - Pg 1-4, Pg 5-8

Dado Accessory Joinery

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Figure 3-18. The dado accessory consists of two outside blades and an assortment of chippers. The paper washers are for slight adjustments to compensate for variations in material thicknesses.

In joinery and some other special applications, it is often necessary to make a cut considerably wider than the saw kerf. For this type of work, a dado accessory is usually used.

A dado accessory (Figure 3-18) consists of two outside blades, four 1/8" and one 1/16" chippers that are used between the blades. Width of cut, which can range from 1/8" to 13/16", is controlled by the number of components that you mount. A single outside blade will cut a 1/8" kerf; if you mount the two blades, the cut will increase to 1/4". You must add chippers to go beyond 1/4". For example, for a 1/2" cut, use both outside blades and two 1/8" chippers. To increase the kerf to 9/16" wide, add the 1/16" chipper. Since there can be some minute variation in nominal wood and even plywood thicknesses, paper washers are supplied for mounting on the arbor between the components; thus you can make slight adjustments in width of cut.

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Figure 3-19. The dado accessory mounts on the 5/8" molder/dado arbor which is then locked to the Mark V's main spindle.

The dado accessory is mounted on a 5/8" molder/dado arbor which locks on the Mark V's main spindle (Figure 3-19). Warning: Be sure the tongue washer is used under the hex nut and the threaded shaft of the arbor is flush or ex-tends past the end of the hex nut. Never use chippers alone or mount chippers with only one outside blade, because a kick-back hazard is created. Arrange chippers so they are evenly distributed and so their swaged cutting edges align in the gullets of the outside blades (Figure 3-20).

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Figure 3-20. Chippers are always used between outside blades. Situate the chippers so the swaged cutting edges are in the gullets of the outside blades.


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Figure 3-21. Use the special dado table insert with the dado accessory. The Model 500 insert is shown.

Because the dado accessory makes extra-wide cuts, you must use a special table insert that accommodates it (Figure 3-21). Warning: Be sure that the dado accessory has clearance in the slot. Rotate it by hand, using the auxiliary spindle, before turning on the power.

The projection of the dado ac-cessory is always less than the thickness of the stock. You can set projection by using a measuring scale or a step gauge (Figure 3-22).

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Figure 3-22. The projection of the dado accessory can be set by using a step gauge.


You work with a dado accessory in much the same way as you do a saw blade, but since the tool will be removing much more material, the pass should be made very slowly to give the blades a chance to work without clogging. Form extra-deep cuts by making more than one pass. For example, if you need a cut that is 1-1/4" deep, make one pass with the cutter's projection at about 5/8". Make a second pass after adjusting the saw table for the full 1-1/4" deep cut. This procedure is especially applicable if you are working with a hardwood like oak or maple. Warning: The dado accessory is used without the upper saw guard in place. Whenever you remove the upper guard, keep the lower guard in place and make sure the lock knob is secured. Use a push stick, push blocks and safety devices. Work with extreme caution.

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Figure 3-23. Because the dado accessory is designed for wide cuts, the metal lower saw guard must be modified by using a spacer between the main part of the guard and its cover. Click on image for larger view.

Guard Spacer (Mark V with Metal Lower Saw Guard Only)- Because the dado accessory can be used for extra-wide cuts, you must place a spacer (offered free through Customer Service) between the two halves of the lower saw guard. If you want to make a spacer, remove the cover from the guard and trace its contour on a piece of 1-1/4" stock that measures 3-1/2" wide by 10" long. Mark the location of the bolt holes and then draw another line parallel to the first one but about 1/4" smaller. Cut the stock on a bandsaw or scroll saw, and drill 9/32" holes for the attachment bolts. When you are finished, the spacer should look like the one shown in Figure 3-23. Secure the spacer between the two halves of the lower saw guard with 1/4"-20 x 1-3/4" bolts.

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