Will the edge guide be enough for cutting short slots with the plunger?


Willin

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I have a batch of tops in 13/16" cherry to machine with slotted countersunk holes, and have an MCLS bit coming soon by mail.  See the pic.

Will use my Porter Cable 1.75 hp plunge router with the PC edge guide, and hope that is enough control for this.

I watched a YouTube video of a guy showing this bit in use, freehanding through some 3/4" pine and making the slots maybe 1/4" long.  It looks as if the guide will work, but I still wonder.

What is your experience with something like this?

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You might even consider making a jig to clamp the work piece to. It would have a slot, sized to fit a guide bushing large enough to plunge the bit through. Center the cut out over where your slot needs to be, plunge and push, you are done. This effectively gives you an edge guide on both sides and both ends, so there is no chance for the router to wander. Check out Matt Cremona's recent youtube video on how guide bushings work:

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Set it up and practice on scrap ! The biggest thing you need is practice. Sounds like you are pointed in the right direction but which direction to go, how well you have the workpiece clamped down and so many little details will become crystal clear with practice. Once you achieve 2 or 3 clean slots in scrap then you tackle the actual tops .

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Rub the underside of the screw head with parrafin wax..Tighten  the screw and then loosen the screw 1/4 to 1/2 of a turn. Put the screw in the middle of the slot. A 12" wide red oak top will move about 1/8 over the year. I try to be a bit more generous with my slots. After you have to rebuild a top that cracks out of your own pocket a longer slot seems like cheap insurance.

A wood top is going to expand and contract across its width not its length which makes the example in the photo wrong.

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If the grain runs along the 23" edge then the slots on all sides should run cross grain . If you want all the movement to go to the rear then the front screws can be stationary and the slots on the other 3 sides run cross grain. The board can shrink or expand and the front edge would stay fixed.

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Yeah, the grain runs along the 23" dimension.  The front edge is glued and screwed, no slots necessary, the rest of the top can move as the wood expands and contracts.

I'll cut down a guide bushing so it will work with 6mm baltic birch, make a template, and step-plunge these cuts.  Others have said this MCLS bit is fragile and may snap otherwise.  And the bit is not very long overall, thus the need for the thin template.

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Seems a bit of overkill. Your only 16" wide and the wood is kiln dried right? It's not going to move that much to be concerned about. Unless I'm missing something. 

I would just drill and countersink. Then run a drill bit through the hole with a larger bit to give you wiggle room. You could even run a forstner bit down first and then drill and cut some plugs and fill the screw hole with the wood plugs for a finished look?

 

-Ace-

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  • 7 months later...

If you go with an edge guide (which should work fine for you) make certain that your edge guide of choice doesn't have a notch or space in the middle of it. If it does, attach a piece of wood to the edge guide so you have a long smooth edge to slide along your work. 

You are showing a few slots that are going to require very long edge guide rods to reach, so a different plan may be needed. Clamping a straight edge strip of wood (fence) to your work for your router to ride against that is spaced correctly away for the distance from the router bit to the edge of the router base will likely work better for you. Cut the slot in the direction that the leading side of the router bit is moving away from the fence (for instance, fence on left, move router away from you, fence on right, move router toward you). This will help hold the router against the fence as you cut the slot. Otherwise it will be difficult to cut the slot straight.

Charley

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