Hello fellow woodworkers!
I’m in the beginning stages of building a small sideboard for my home and am trying to figure out how to cut some of the joinery. Without getting in to too much detail, there is a shiplapping element to the piece that has me pretty hung up. I am a huge fan of what I like to call “building in a vacuum”, in other words following processes that inherently yield uniform results (i.e. running rabbets for shiplapping on a shaper with the cut depth and height set, rotating the board and flipping it in between passes, producing one coplanar surface and consistent seams on both faces when assembled).
In this application the show face will have a double angle profile so the adjoining rabbets must be coplanar. For example, say I have a 2″ wide x 1″ thick piece of material, on the backside of the bottom of the material there needs to be a 0.25″ x 0.25″ rabbet and on the topside the mating rabbet from the front 0.25″ x 0.75″ rabbet creating a 0.25″ x 0.25″ tongue.
I’m looking for a way to machine these joints without having to fuss with my setup, or creep up to a perfect fit, similarly to how I mentioned machining a standard shiplap joint is done.
Oh, and to make things a little more interesting each mating row is decreasing both in width and in thickness.
I’ve attached a .pdf without the double angle profile to illustrate the joint I’m looking to achieve.
Replies
Using a dado stack:
You can set up for the thickest part and make spacers to run the rest on the same setup with the dado set buried in a fence, tongue formed outboard of the dado stack.
You can also set up a dado stack wide enough for your thickest part with a 1/4" space between the fence and the blade, tongue formed inboard of the dado stack. I think I'd go this way.
Makes sense, but I do feel either option would require a bit of creeping up to nail the fit. What I love about cutting a traditional shiplap is that you get a perfect fit independent of you height and depth settings, in other words you don't have to be so meticulous with your initial setup, flipping and rotating the stock inherently creates a perfect negative.
I know this process is most likely going to require spacers, but let's say I get my fence at what appears to be a 3/4" pass, leaving a 1/4" tongue on a piece of 1" stock and then stick a 1/2" spacer in to create a 1/4" rabbet. If my initial setup was anything other than 3/4" in either direction, using a 1/2" spacer to take the next pass will result in an inconsistent tongue to rabbet width.
I'm confident that I could nail that initial setup and get a satisfactory result, but I'm trying to see if there is a more "water tight" way to achieve the same result.
Thanks for the input!
Exaggerated example posted below
With a PhD in abstract geometry, and over 40 years of experience in woodworking, I don't understand how cutting a shiplap to fit properly is independent of both the cutter height above the table and the protrusion from the fence. If you have the board flat on the table for each cut, the protrusion depth will match up on both edges, but getting the other cut depths to be co-planer requires fine tuning of the height above the table, to get it exactly half the thickness of the board.
For your set-up, you should do what I did to shiplap the siding for my house, which was rough cut sassafras (of different thicknesses.) First cut the rabbet on the back side of the pieces, using a standard shaper cutter set up set to your .25"x.25" dimensions. Unlike the standard set-up, run the boards vertically against the fence. To cut the other rabbet, you need to have the cutter at the same height, but move the fence so that the space between the fence and the cutter leaves a tongue of the correct dimension to fit the first rabbet. Again run the boards vertically against the fence. The cutter will cut away more on the thicker boards and less on the thinner ones, but leave the same tongue.
For the first rabbet, any movement away from the table or fence will leave extra wood behind that can be removed with another run thru, or by hand. For the second rabbet, any movement away from the fence will take away too much wood; hold downs (or hold-sideways, really) will be helpful.
Anywhere chip-out will show (the front for sure, and maybe the back), you will minimize it by taking a first cut that is extremely shallow (1/32"-1/16") as the exit angle of the cutter edge is almost parallel to the board edge. The deeper the first cut, the greater exit angle, and the stronger the tendency to pull wood fibers out of the surface of the wood.
My apologies, you are right about needing to center the height of the cut to the stock in order to create a coplanar surface in the end. I'm not quite sure what I was thinking, but thanks for clearing that up for me. As far as your method goes, I'm not quite sure I follow how the cutting of the second rabbet produces a tongue of the same thickness independent of material thickness referencing off the front face.
I feel like the constant of that second cut isn't the cut depth it's the material that remains. If you have three boards 1", 2" and 3" and you set your fence to take a 3/4" pass you'll end up with a 1/4", 1-1/4", and 2/-1/4" tongue respectively.
Please explain.
Sorry for the unclarity. And for the delay in answering. I missed your question/response.
First rabbet: Shaper cutter protrudes 1/4" from table, 1/4" from inside the fence. Board is run with back against the fence.
Second rabbet: Shaper cutter still protrudes 1/4" from table (setting is unchanged.) Shaper cutter is all outside the fence, and its cutting circle is 1/4" from fence (have to fine tune setting to match the 1/4" distance from protruding from inside the fence in rabbet #1). Board is run with back against the fence. Cut removes rabbet leaving tongue at back of board that is the thickness equal to the distance between the cutter and the fence.
This method is independent of the widths of the boards, as well as the thicknesses (as long as your cutter will handle the varying thicknesses comfortably.)
You can use several different types of cutters for this: shaper, dado blades, moulding head on a table saw (which is what I used for my sassafras siding, as it cut quickly, and I wasn't concerned with cut quality.)
More questions, just ask. I'll try to be paying attention.
Harvey
I believe if we set cut height aside to be dealt with after we can use let's say a 3/4" skid of plywood with our stock to be cut on edge and the shaper cutter overhead set to let's say 1/2" with the fence inset 1/4" beyond the cutter we can run all of the inside rabbets and get a consistent 1/2" x 1/4" rabbet. Now lets say before we ran our first rabbet we had the fence set for the same depth but had the cutter at a height set to cut a 5/8" rabbet on the frontside of our plywood skid. Now with the first rabbet cut we flip the material and mate it with the opposing rabbet on the skid, creating a 1/2" offset and two perfectly mating rabbets independent of material thickness.
As for the length of the tongues, those can just be cut back at a later point in time referencing off the shoulder of each rabbet to create consistent length tongues.
Long winded thought, but please correct me if I'm wrong.
It's a small sideboard with a little bit of shiplap. You will have to "creep up" on your setup no matter what. Even if you ran it on a CNC you'd make a test cut.
Cut upside down with an overhang bit
The issue is you want to use the same reference face (front) for determining the location of both the rabbit and what I will call the tongue (back side rabbit).
you can do this with using a slot cutter in a router table with a fence.. use the slot cutter first as a "rabbiting" bit, cut the rabbit. Raise up the slot cutter to make the tongue. if the slot cutter kerf is not thick enough to make the full rabbit on the back side.. you can flip the board over, referencing off the back now, lower the slot cutter and finish out the back rabbit.
White side sells a slot cutter with different kerfs, largest is 5/16" and max depth based on the available bearings of 5/8".
https://www.whitesiderouterbits.com/products/6715A
White side also sells a arbor 1/2" shank with a 4" OAL would should give you plenty of range.
https://www.whitesiderouterbits.com/products/A220B
If you need a rabbit deeper the 5/16". you can set the top of slot cutter to the depth of the rabbit say 3/8", run the board, giving you a slot, put a piece of 1/4" mdf on the router table, raising up the work piece, to finish out the rabbit.
you can also put 1/8 mdf or hardboard (multiple if needed) on the fence to limit the depth of cut, if a full cut is to aggressive.
If you get any tear out or worried about tear out you can help eliminated tear out by using a wheel cutting gauge.
If you want to do this with one router bit height and fence setting, you would need a series of shims on the table to adjust the work piece in relation to the cutter.. one of those shim would be the thickness of the kerf of the slot cutter. the other shims would be needed if the rabbit or the rabbit on the back side was greater than the kerf of the slot cutter.
This forum post is now archived. Commenting has been disabled