dado question

[Jerome Hanby]

I'm about to build a doll house shaped book case. Really simple, all right angles except for the roof on top. There is a vertical divider, offset to one side of the middle (middle being the top to bottom line that goes through the top angle on the roof) between the top shelf and the roof. I plan on cutting dadoes for these dividers to fit. That means the one on the underside of the roof will be at an angle. Can I just tilt my dado stack on the table saw to cut this angled dado?

[John TenEyck]

Can I just tilt my dado stack on the table saw to cut this angled dado?

I don't see why not. Just be aware that the bottom of the dado will not be parallel to the board; it will be at whatever angle you set the saw at, so take that into consideration when setting the depth of cut so you don't cut through. If the bottom has to be parallel with the board then you'll have to use just your saw blade and take multiple passes to create the dado.

[Jerome Hanby]

Shouldn't be a problem (not being parallel). I'd just never heard of tilting a dado stack and wanted to see if there was any reason for not doing it.

[Peter Quinn]

Won't work. Draw this up then draw your dado stack and look at it. The sides of the dado you describe ( in the vertical plane) need to be plumb, the bottom of the dado needs to follow the pitch of the roof angle. You can certainly tilt your dado stack to the roof pitch and run the roof boards over it, but when you put them in place the sides of the dado will be ninety degrees to the roofs pitch, not plumb! You would need a chamfer cutter whose angle matches the roof pitch, and these I have never seen for a TS. You might try Laying out the cut on the board, taking out as much as you can with a 1/4" or 1/2" dado stack, then cleaning up e side walls plumb with a hand saw and or chisels and a guide block. Make sense? Remember, a dado set always makes cuts whose bottom is 90 degrees to ne sides but that is not the condition you are faced with here. You might be able to angle the top of e vertical to make it fit into the out of plumb dado too.

[Peter Quinn]

Ok, I actually drew it for myself on a knapkin, and you could make a birsdsmouth with a dado set. It might not be deep enough to hold the whole vertical partition in place, but it could give a flat to land your vertical on. But if your roof os the same thickness as your vertical it may significantly weaken your roof.

[Chris Kennedy]

You would have to bevel the top of your divider to match the angle. I can foresee another technical problem -- depending on the angle, if you take this route, make certain that your throat plate will allow you to tilt to the angle you need.

Chris

[Jerome Hanby]

I planned on beveling the top of the divider to match the dado. The "roof" is purely decoration, but it would be bad form to have it so delicate that it could be snapped off. I suppose I could pocket screw the divider to the roof. It's all 3/4" material and I bought a box of screws to handle that size connection. The bottom of the divider will be sitting in a dado, so the top just needs to keep it upright. I guess I could put together some type of jig to hold the divider so I could cut biscuit slots in the top beveled end. The slots on the underside of the roof would be easy 90 degree plunges.

I've got some scrap birch plywood pieces hanging around the shop, I may play with the tilted dado notion tomorrow and see how it looks and how much it weakens the piece.

Thanks everyone for the feedback and advise!

[Peter Quinn]

I was thinking more about that cut, and my suggestion is try it first not with a dado blade but a single regular blade. Remember to back up the cross cut to avoid chip out. A single blade, using a TS or skill saw will allow you to create a "housing" (fancy English term for dado) with sides that are plumb, and a series of cuts will yield a dado bottom with a basically flat plane that has tiny triangular ridges which can easily be cleaned up with a chisel and a sanding block beveled to match the roof pitch. Then you only need to bevel the top of your vertical to match the roof pitch and you have a strong connection. The most difficult part IMO is figuring out exactly where to put the "housing" so the vertical partitions remain plumb. Easy enough to lay out full scale with a framing square or draw on the computer.

For a bookcase the biscuits might be an easier or more expeditious method?

[Chris Fournier]

I've made angled dado cuts like the one you need to make doing just as you suggest, no problem - given the trunion limitations and the required angle of course. Set up your dado and carefully dial in the angle you require. Spin the dado stack by hand at the required height to ensure that there is no interference. For this type of cut I would always use a zero clearance mdf throat plate and clamp it down while I raised the dado stack through it. My sliding table saw actually won't allow me to tilt an dado stack off of 90 degrees. I miss my cabinet saw for this reason amongst others.

[Jerome Hanby]

Maybe I'm just on the wrong track. Here is the picture of what I was asked to copy

dollhouse_bookcase.jpg

The middle divider that connects the top shelf to the slanted roof is what I'm trying to work out a solution for. I'd like something more substantial than a butt joint. My copy is all plywood and I'm planning on using dadoes and rabbets for the rest of the joinery. That angle makes things complicated...

[Jay Allen]

There is absolutely no reason that you couldn't do that by tilting the dado. You will just have to work out the angle and location, probably by testing. You could do the same on the side walls too.

[Jerome Hanby]

Sides would make sense, would be same cut. If I'm working out the procedure to make one cut, why not do two more...

[Peter Quinn]

There is absolutely no reason that you couldn't do that by tilting the dado. You will just have to work out the angle and location, probably by testing. You could do the same on the side walls too.

It does not work with a dado. Try to draw any intersection between roof and vertical, you will quickly see the problem. Either you make a very shallow cut which creates a bird's mouth effect but does little to support the roof without further fastening, or you have to go so deep you compromise the roofs integrity at that point. At an angle one outside edge of the dado blade becomes the point of a triangle. Even at a 6 pitchwith a 1" roof and 3/4" verticals that has to go pretty deep to create a full width cut. A single saw blade with multiple passes beveled to match the roof pitch lets you run in a proper dado with sides parallel to the verticals (plumb) and a series of very little triangular ridges you can easily pare flush with a chisel.

Jerome, I find it easiest to draw this sort of thing full scale on a piece of plywood or cardboard. You don't have to do any math, just plot the lines, mark the intersections and pull your lengths from the drawing. You can actually just put your boards on the drawing later to mark the cuts. Cutting these dados is far easier than finding there locations. Try a single test cut with a single straight blade on any piece of scrap, you will immediately get the concept. Set your saw's bevel to around 26 degrees for a 6 pitch. Set a bevel square to the saws bevel angle, place it on the top face of your test piece with the metal arm facing down, and mark a pencil line. Without moving the bevel square place a piece of scrap the thickness of your verticals against the bevel square, and mark another pencil line using the other edge of the scrap as your guide. Set your blade just light of 1/4" above the table, use a miter gauge or similar to guide the wood, take out all the wood between your two pencil line. Done. Maybe 6 passes with an 1/8" blade? maybe 7? Strong, simple, visually correct, and actually very easy to do. Think of it as an 1/8" dado blade!

[Jerome Hanby]

Ok, I see what you are getting at. With the dado blade tipped at an angle, the floor of the dado wouldn't be parallel to the surface as the width of the dado would be the longest side of the triangle sloping away (becoming shallower) from the top surface of the roof. You get the same effect with each cut of the normal saw blade except that the sloping portion is much shorter and can be shaved away with a chisel.

You know, I may be making this far more difficult than it needs to be. Why not just cut a normal dado, then put my regular blade back on, tilt it to the correct angle, and make the two beveled cuts? Then just clean up the difference with a chisel. I had to do something similar to make the "french cleat" cuts in my lumber rack uprights.

It does not work with a dado. Try to draw any intersection between roof and vertical, you will quickly see the problem. Either you make a very shallow cut which creates a bird's mouth effect but does little to support the roof without further fastening, or you have to go so deep you compromise the roofs integrity at that point. At an angle one outside edge of the dado blade becomes the point of a triangle. Even at a 6 pitchwith a 1" roof and 3/4" verticals that has to go pretty deep to create a full width cut. A single saw blade with multiple passes beveled to match the roof pitch lets you run in a proper dado with sides parallel to the verticals (plumb) and a series of very little triangular ridges you can easily pare flush with a chisel.

Jerome, I find it easiest to draw this sort of thing full scale on a piece of plywood or cardboard. You don't have to do any math, just plot the lines, mark the intersections and pull your lengths from the drawing. You can actually just put your boards on the drawing later to mark the cuts. Cutting these dados is far easier than finding there locations. Try a single test cut with a single straight blade on any piece of scrap, you will immediately get the concept. Set your saw's bevel to around 26 degrees for a 6 pitch. Set a bevel square to the saws bevel angle, place it on the top face of your test piece with the metal arm facing down, and mark a pencil line. Without moving the bevel square place a piece of scrap the thickness of your verticals against the bevel square, and mark another pencil line using the other edge of the scrap as your guide. Set your blade just light of 1/4" above the table, use a miter gauge or similar to guide the wood, take out all the wood between your two pencil line. Done. Maybe 6 passes with an 1/8" blade? maybe 7? Strong, simple, visually correct, and actually very easy to do. Think of it as an 1/8" dado blade!

[Neil Brooks]

I ran into this very problem, while building a "tapered wine tower" (of my own design), for some friends of mine.

For some reason .... like you ... I got lucky, and _thought_ before I _cut_.

I was scratching my head, realizing that -- what I needed wasn't _really_ an angled dado, at all, but a beveled dado. I calculated the bevel, and went so far as to cut the sides of the shelves at that angle.

But ....

Under a bit of a deadline, I scrapped the entire "taper" idea, and built the thing using only right angles, re-cutting the shelf ends to square them up. I just couldn't figure out an easy way to do this beveled dado thing, and ... pretty much still haven't

It's one of those projects that -- when I'm visiting their house, and I see it -- I get a little frustrated.

It should have been easier than that