How to do this compound angle with Domino

[Rick Christopherson]

Well-looking at this for the second day, I can see what the problem is.  There is no way for me to mortise the long piece from the outside(where I would scribe the pencil mark) and have both the fence and the face of the Domino touching the wood.  The fence would need to be able to go to 93.5 degrees to do that.

I hadn't considered this because it didn't immediately jump out (visually) in your graphic. This does change the problem. However, considering your angle is so minor, I believe you should consider making the plunges at 90 degrees to the reference faces. If you did manage to set the fence to 93.5 degrees, it would mean that your mating plunge would have to reset the fence to 86.5. The problem with that is that you have made a set-up change in your Domino between making plunges. That will invariably lead to inaccuracies.

So my recommendation is to keep your fence at 90 degrees. The fence will sit flat on the surface of both workpieces. The front of the Domino, however, will touch the edge of the workpiece only in a line with a slight angled gap top-to-bottom.

If the angle was greater than 3.5 degrees, you would have to make your plunges deeper than normal. But in your case, there is enough extra depth built in to the plunge depth that you can ignore it.

 

[Sparktrician]

Well-looking at this for the second day, I can see what the problem is.  There is no way for me to mortise the long piece from the outside(where I would scribe the pencil mark) and have both the fence and the face of the Domino touching the wood.  The fence would need to be able to go to 93.5 degrees to do that.

I hadn't considered this because it didn't immediately jump out (visually) in your graphic. This does change the problem. However, considering your angle is so minor, I believe you should consider making the plunges at 90 degrees to the reference faces. If you did manage to set the fence to 93.5 degrees, it would mean that your mating plunge would have to reset the fence to 86.5. The problem with that is that you have made a set-up change in your Domino between making plunges. That will invariably lead to inaccuracies.

So my recommendation is to keep your fence at 90 degrees. The fence will sit flat on the surface of both workpieces. The front of the Domino, however, will touch the edge of the workpiece only in a line with a slight angled gap top-to-bottom.

If the angle was greater than 3.5 degrees, you would have to make your plunges deeper than normal. But in your case, there is enough extra depth built in to the plunge depth that you can ignore it.

Given that the end pieces are of a different dimension due to the apparent tapered nature of the product, I can see having the 93.5° setting on the end pieces closest to the viewer, but the mating mortises in the long pieces would be at 0°.  At the opposite end, the mortises in the end piece would be at 86.5° while the mating mortises in the long pieces would stay at 0°, if I'm thinking correctly.  Concur?

 

[Rick Christopherson]

No. What I wrote above is based on looking at only 1 joint at a time. You can't look at the other joints at the same time because we don't know exactly what is happening with them.

 

[tbellemare]

I would just set the fence at 86.5 degrees and mortise the end piece using the outer edge (obtuse edge) as the reference. Then, turn around and use the mating edge (acute edge) on the long piece as the reference.

The only tricky part would be keeping the face of the machine (where the bit comes out) flat on the small face of the long piece.

Tom

 

[Rick Christopherson]

Tom, this would result in a vertical placement error because the sharper pointed workpiece will fit into the gap between the Domino face and Domino fence.

 

[tbellemare]

I'll have to go get a Domino out to see what you mean, Rick. I don't have mine at the moment...

Tom

 

[tbellemare]

I just looked at one set at 12.5mm location to bit and 6.5 degrees. I don't see the gap of which you speak, Rick?

Tom

 

[Rick Christopherson]

I just looked at one set at 12.5mm location to bit and 6.5 degrees. I don't see the gap of which you speak, Rick?

The gap I'm referring to is on the machine, not the result. It's between the sight gauge and the front face of the Domino.

By the way, in your above example, did you make a 3.5 (6.5) degree miter joint? That wouldn't be the same as this. Instead, make a 3.5 degree scarf joint. Then you may understand where the difference will come from.

 

[Sparktrician]

No. What I wrote above is based on looking at only 1 joint at a time. You can't look at the other joints at the same time because we don't know exactly what is happening with them.

Rick, it's a marimba frame.  One end is longer than the other, and the long pieces slant in at 8°.  We do know what the joints are doing.  For purposes of the domino, the 8° cant is apparently irrelevant.  What does matter is that the mortises in the side pieces are at 90° while those in the end pieces are at 93.5° (long piece) and 86.5° (short piece).  Take a look at the picture of the marimba frame that I attached.  I think you'll see it. 

 

[mbira]

I think you guys are seeing the difficulty of this. 

Rick made a very good point that:
Any mortice must be plunged perpendicular to the FACE of the joint, regardless what angle may be involved between the pieces.

And the problem is that I can't do that unless I reverse the domino and then have to reference from the inside of the joint instead of the outside edges.  If I could put the fence to 93.5 then I could in fact reference the face.

Sparktrician.  Funny-that's a pic of one of my marimbas.

 

[Rick Christopherson]

Rick made a very good point that:
Any mortice must be plunged perpendicular to the FACE of the joint, regardless what angle may be involved between the pieces.

Yeah, except I backpedaled on that once I realized that your joint closely resembles a low-angle scarf joint. As such, you are better off putting your tenon parallel to the long face of your stretcher (or whatever they're called for these things).

I modeled up a quick scarf joint just to make it more clear.

[attachimg=1]

 

[mbira]

Sure-in other words maintain whatever angle you are choosing for both parts. 

I challenge you to do that though when one of those pieces in your pic is long and flat and you are trying to flush up the sides.

I think I'm giving up on this quest.  Easier to modify my design and offset the piece in.

Finding the exact center and flipping pieces is proving tough as any error is doubled.  If I'm off by .5 mm on the tiny little dial when I flip the pieces to line them up then they are off by 1mm.

 

[Sparktrician]

Sparktrician.  Funny-that's a pic of one of my marimbas.

Now, THAT's funny!!! 

[big grin]

 

[bkharman]

Any reason you can't clamp the parts together and plunge all the way through?  Do you have an XL or 500?  If you went through, you could make your own dominoes with the same wood or get some nice contrasting wood...  Your preference.

If you have the 500, it might not work out.

Cheers. Bryan.

 

[Rick Christopherson]

Finding the exact center and flipping pieces is proving tough as any error is doubled.  If I'm off by .5 mm on the tiny little dial when I flip the pieces to line them up then they are off by 1mm.

Never flip your references! That's a cardinal rule for Domino, and the reason why I stress over and over for new users to not even try to make their mortices centered in the workpiece (it makes it obvious if you accidentally do flip one.)

Sure-in other words maintain whatever angle you are choosing for both parts. 

I challenge you to do that though when one of those pieces in your pic is long and flat and you are trying to flush up the sides.

You're not choosing an angle. The fence angle is 90 degrees to keep the mortice parallel to the registration surface. Yes, there will be a 3.5 degree gap between the end of your board and the face of the Domino. As long as this angle is small, it's OK. If the angle was bigger, then you would have to increase the depth of your plunge, but it would still be OK.

Yes, the challenge is morticing your end caps. You have to register the fence face of Domino from the 3/4" thick edge of these pieces. To overcome this, you could stack several 3.5 degree pieces together to make the edge effectively wider. (You can also use one of your long pieces that already has the 3.5 degree bevel cut. It is only to support the Domino fence, not to make a mortice.)

 

[canadamike]

This is a really good thread, I've been trying to figure out how to use the Domino to replace some angled tenons on a chair design. It would be great if someone could post of a couple pics showing Rick's solution, as it reads like it is going to work. I'm way better with pics though (as many of are)...

 

[mbira]

I am currently convinced after three days of trying with scraps that this can not be done (without just drawing the marks and going from there without a reference edge.

Hopefully tomorrow I will connect with someone that has a lot more experience with this tool than I do and be proven wrong!

 

[Bohdan]

Sorry to suggest a non domino solution and I can't remember its name but a while back I saw a demo of a doweling jig that did exactly that on Youtube. It lined up two surfaces on a compound mitre join.

The jig was one of those that you can screw it to one piece and can then flip it to drill the other piece from the other side.

This makes the dowels automatically perpendicular to the join surfaces.

 

[mbira]

OK-having slept on it, I realized that I was misunderstanding something Rick (and perhaps some others) were saying. 

There's two ways to do it:
1) have the domino perpendicular to the end piece (and angled into the long piece).
2) Have the domino parallel to the long piece (and angled in to the end piece).

At first I tried the first way but then ran in to the problem of cleanly plunging in to the end piece.  I tried the second way, but that gets me into the need to not register from an edge. 

As Rick suggested, I took a piece of 8/4 stock and beveled the same angle into it and then layed the end piece on it and flushed it up and clamped it down. 

Then-keep the fence at 90 for both pieces.
Plunge into the long piece.  The face of the domino will not be flush with the face you are plunging.  the FENCE will be held flush the the long piece.
Then for the end piece, the FENCE will be held firmly to the edge of the endpiece (and the 8/4 stock).  Something I was doing to make my life more difficult was that I had that extension accessory on the domino, and that was making the gap between the face of the domino and the workpiece larger so it was harder for me to firmly keep that fence properly lined up.  Removing that accessory helped.

Thanks to everyone for helping me to learn the tool!

 

[canadamike]

Hi mbira,

Would you mind posting a pic or 2 of what you've worked out? I'd be most appreciative, Mike