Why can't I make square joints with my Domino?

williaty

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Joined
Dec 30, 2011
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87
OK, so I've been running through all the different things that I can calibrate on the Domino and accessories and then trying out making samples of each kind of joint. Most of it is going well. One joint is not working at all. I'm not sure exactly what to call it but it's just a basic butt joint where one mortise is into the face of the board and the other mortise is into the end grain of the second board. This joint is not coming out square no matter what I do. They're all tighter than 90*. What should I be checking to try to straighten this out?
 
Have you tried to put the 2 pcs together without the domino and see if your cut is not what's causing the problem?
 
First use a high quality machinists type square to check the board that you dominoed into the edge of.  Check that the edge is 90* to both faces in several spots.  If not, the saw cut your edge at a bevel.

Next insert dominos into the edge of that board and check to see whether they are at 90* to both faces of the board.  If not, you either have the Domino fence set off of 90* or you are tipping the machine as you line it up and/or plunge.

Lastly check the other board where the domino slots are on the face.  Insert dominos and check that they are at 90* to the face.  If not, you tipped the machine as you plunged.

You might for the heck of it want to check that the fence and base of the Domino machine is 90* to each other.  I don't think it would be an issue, but it can't hurt to eliminate that.
 
Ken,

[big grin] for not embarrassing me.  I learned the hard way that if you do the joint depicted and your boards do not have true perpendicular faces then you will introduce a bad reference point/ edge and they will not align.

As has been suggested, check your boards.

Peter
 
Boards check good. It appears the plastic extension table thing that comes with the Domino isn't square to the Domino. I put some blue tape on it to act as a shim and now I'm getting better joints. Without the blue tape, the dominos themselves stick out of the board crooked.
 
Will, You have to check your stock first with a reliable square.  I use a Starett  combination square but when in doubt, I have a 12" machinist square to make sure that I didn't damage my combination square.  Also, I buy all of my wood rough cut and make sure that my stock is straight and square before I cut joints.  I have never had problems with my Domino Joiner.
 
Like I said, the wood checks square. It's the black plastic extension support thing. It has to be shimmed with a little tape and then everything seems to work out just fine.
 
I've found issues with the plastic accessories for the Domino in the past.  Wish they weren't plastic.  Anyway, either call Festool Service and discuss the possible part replacement with them or the dealer you bought it from.

Even so, I still would recommend making sure you are resting the metal fence of the Domino flat against the work surface no matter what attachment may be on the Domino.  Trust the fence first.
 
Since the fence is only pressing against, the end-grain of the board, there's not much contact. The board is 19mm thick. Most of that is touching the face of the Domino, not the fence. Hence the need for the plastic outrigger.
 
If you are dominoing the edge of a board, your fence should look like this with most of the force applied on the top of the fence at the handle and lightly pressing the area where the pins or paddles are contacting the edge.

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If you are dominoing the face of a board, your fence should look like this.

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I'm doing the operation you show in the 2nd pic. If I fold up the fence like that, I lose my reference to where the domino should be. Since the fence (folded out flat as in the first picture) is what sets the distance of the domino down the endgrain from the reference surface, I wanted to keep the fence in that position in order to place the domino into the face of the other board in exactly the same position relative to the reference surface.

With the fence folded up as in your second picture, how you do position the Domino with the correct offset relative to the reference surface?
 
If anyone knows where to locate that video tutorial or the written tutorial, please post it while I try to explain this in another post.
 
Example:  2 pieces of plywood that will be assembled in a 'T' shape with the edge of one going into the face of the other.

Place the horizontal piece on a flat work surface.  Place and line up the vertical piece in position.

Using a pencil, mark along one edge of the vertical piece where it meets the horizontal piece.  This is a reference line.

If you marked the line on the right side of the vertical piece, lay the vertical piece of plywood down flat to the right keeping the length of that edge against the pencil line you made.  If you made your mark on the left side of the vertical piece of plywood, just lay the vertical piece down flat to the left while keeping the bottom edge against the pencil line.

Make sure that you understand that the pencil line is still in contact with the same edge of the previously vertical piece of plywood.  All you did was lay the piece of plywood flat.

Clamp the two pieces so your previous vertical piece stays on that pencil line.

Mark your domino mortise slots on both pieces of plywood where the edge of one piece meets the face of the other piece.

Fold the Domino's fence up as in the 2nd picture.  Now take the Domino and butt the bottom of the Domino against the edge of the plywood of your ORIGINAL vertical piece making the fence of the Domino flat against the face of the ORIGINAL horizontal plywood piece.

Make all of your necessary plunges with the Domino making sure the depth is set for the thickness of the plywood.  That is the ONLY adjustment you need to make.  FENCE HEIGHT DOESN'T MATTER.

Turn the Domino around.  Rest it flat on the ORIGINAL horizontal piece and plunge into the edge of the PREVIOUS vertical piece at all of the locations that line up with your plunges you did in the previous step.

Unclamp the boards, insert the domino tenons and you have it!
 
OK, here's how I'm doing it now:

First mortise is plunged like this. Endgrain flush to the face of the Domino, depth from reference face set via placing the fence on the reference face.
6945628771_2dea5e5a9c_b.jpg


Result is this:
6799516686_be7f9a06f2_b.jpg


Second mortise is plunged like this. Face of board flush against the face of the Domino and the black plastic face extension outrigger, depth from reference face (which is the endgrain in this case) set via placing the reference face against the fence.
6945628161_aa067926d6_b.jpg


Result is this:
6945627691_dc0ec581c9_b.jpg


A domino is inserted and the result is this:
6945626715_0c719dce74_b.jpg


Note that the visible step on the edges of the boards is because I made no attempt to line them up in that axis. On the reference edge, the joint is flush enough I can't feel a step, only the texture change from endgrain to long grain.
 
Ken, that method makes a lot of sense for doing a line in the middle of a board and if you're ok with the domino being placed 10mm away from the reference, well, corner in this case. With the joint needed to be at the ends of the board to make a corner like in my pictures, that method will leave very little surface (only one board's thickness) to reference the Domino to for flat/square. That's going to be a little dicey, at least for me. Also, what do you do if it won't work to place the domino 10mm from the reference?
 
In your 3rd picture, instead of trying to use the narrow edge of a single board as a bearing surface under the fence, add two or three boards for a wider surface.  Clamp those boards together so the tops remain level and they don't move while mortising.  Try that and see if it solves your problem.

I'll just add these pictures in the next post to show you the steps I was referring to previously.
 
Pictures illustrating steps from previous post.

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Ah! Stacking/clamping some boards to increase thickness makes a LOT of sense. That way I wouldn't even need the little black plastic jobby.

I'll also definitely use that method you showed for joints in the middle of sheet goods.
 
Practice on scraps and let us know how things turned out/if you need more help.

If you still have a problem, I have Kreg's (honeydokreg) phone number, so I'll call him, probably around 3am telling him he has an emergency Domino lesson with you.  [big grin]
Just make sure you have plenty of milk 'n cookies for him.
 
It's too late to fire up the tools tonight since I work in the living room, which is too near the bedroom where my wife is already asleep. Starting tomrow, I'm pulling an engine out of a car for a rebuild (I'm a mechanic) so I won't get back to this until next week.
 
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