Cutting a groove

[Dave Norris]

Good Day to Everyone,
I'm making some cabinets, and I need to cut a groove along the long edge of the sides to accept the plywood back, and then cut dados along the bottom and tops of the sides to accept the tops and the back. My plywood is 3/4" (but not really, more like 23/32 or some such). I don't have a dado blade for my TS, so I'm probably looking at using the shaper, making one pass, readjusting, and making a second pass to get the groove/dado the right width. I did this on a couple trial runs, and the result turns out ok, but it's a lot of tinkering. I seem to recall reading a thread from a while ago about making the initial setup, then simply putting a piece of the ply on the fence as a spacer, and that would give the right size dado. I think that method was for a TS though. I haven't had a chance to give it a try though. Any advice on this process?

[Steve Clardy]

A router with a rabbiting bit.

[Lance Norris]

Steve has the right idea. You can rout your rabbet after the cabinet is complete and then square the corners with a chisel. This way you dont have a hole sticking out the side or end, whichever you dont cover with the butt joint of the side or top/bottom.

That being said, my father never had a dado blade and he would just use the regular rip blade with his tablesaw. Simply make a cut where needed and bump the fence and continue to make cuts until you have the dado the width you need. Make sure you cut all the panels together so you have all the dados the same exact width.

[Michael Liechty]

Get a ply router bit that si sized to fit the undersized plywood. They are available in 1/4" 1/2" and 3/4" nominal. This and a straightedge is how I do my dado's.

Hope this helps
ML

[Roger Warford]

Do you need rabbets or grooves? You can use a 3/4" straight bit for rabbets on a router table. Adjust the fence to reduce the width of the rabbit to fit your stock, testing on scrap. Once the fence is set, you can make all of your cuts without the need for any further adjustments (though you may need to make two or three passes raising the height slightly each time).

(EDIT: using a 3/8" straight bit you could make a groove or rabbet the exact width in just two passes. Use a spacer for the first pass, remove the spacer and make the second pass. Width of spacer = Width of Ply - 3/8)

If you want grooves on a TS, you could use a crosscut sled. Set stops on each side to limit the width of the cut, then make multiple passes moving from one stop toward the other. It would take about 6 passes for each groove, assuming a full 1/8" kerf.

[Dick Bringhurst]

Dave, be sure to measure the thickness of the ply along its length. BORG Ply will vary by as much as +/- 1/16th of an inch. The plus can be aggravating and the minus sloppy. Dick B.

[Frank Drew]

Dave,

Unless there's a compelling reason to use 3/4", a 1/2" ply back would be more than adequate; even 3/8" would do, but I wouldn't go as far as 1/4".

[Ralph Barhorst]

Dave,
This is the thread about using a dog board with a table saw to make perfect dados. I have used it many times and it works great. http://www.sawmillcreek.org/showthread.php?t=77289

I would think that this technique would also work with a router bit. For instance, if the 3/4" plywood is actually 23/32", then I would make the first cut using a 3/8" diameter router bit. I would then insert a dog board that is 11/32" wide (23/32 minus 3/8) between the fence and the part and make the second cut. The dado would then be 23/32" wide.

Let me know how it works.

[Cary Swoveland]

Dave,
This is the thread about using a dog board with a table saw to make perfect dados. I have used it many times and it works great. http://www.sawmillcreek.org/showthread.php?t=77289

I would think that this technique would also work with a router bit. For instance, if the 3/4" plywood is actually 23/32", then I would make the first cut using a 3/8" diameter router bit. I would then insert a dog board that is 11/32" wide (23/32 minus 3/8) between the fence and the part and make the second cut. The dado would then be 23/32" wide.

Let me know how it works.
I would like to thank the man from Tipp for the great tip. On a router table, why not make the dog board from thin material that you would cut through with the router bit (maybe in two passes)? Maybe that's what you had in mind.

Cary

[Gene O. Carpenter]

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[Dave Norris]

Thanks to all who replied... the dog board was exactly what I was thinking of. Thanks Ralph!

[Cary Swoveland]

Thanks to all who replied... the dog board was exactly what I was thinking of. Thanks Ralph!
Does anyone know why this is called a "dog board"? Cary