Dominio Boards Misaligned ..

[Hotwheels]

I'm experiencing some misalignment of boards I am gluing up to make some Wood Duck nest boxes. I'm joining the boards to get enough width to cut them to size. The boards are ~3/4" pine that I took off the walls in my living room. Many of the boards have bows in them. Maybe I am missing something, when I measure the distance from the reference face to the top of the mortise, there is enough difference that the boards are misaligned enough to be noticeable. I can plane them flat, but the issue is more why is this happening?

I use the pins (2007 or so vintage domino) to cut tight mortises on each end and pencil marks to cut the other mortises loose.  For board 1 and 2 here are the left to right measurements taken using Mitutoyo  calipers.

Board 1   Board 2
7.1mm.  5.7mm.  tight
6.9mm.  5.5mm.  loose
7.5mm.  6.7mm.  loose
7.4mm.  6.2mm.  loose
7.3mm.  6.1mm.  tight

I have noticed and measured this misalignment with other boards.  I thought maybe it is a difference in the pressure to hold the domino flush to the reference surface or maybe there is some issue with the bit. I have made sure the fence plate -- the part with the handle -- is tight, but otherwise I  am not sure of the source of the difference in the placement of the mortise. 

Any ideas?

 

[ChuckM]

"Many of the boards have bows in them"

The reference face wasn't flat across, hence the discrepancies.

 

[Hotwheels]

"Many of the boards have bows in them"

The reference face wasn't flat across, hence the discrepancies.

Bear with me here, this is something I'm not be grasping ... even if the reference face is not flat, I would expect that the distance from the reference face to the top of the mortise  -- or any location the can be consistently measured -- would be the same. What am I missing?

 

[tsmi243]

He's saying if the dips are bad enough, that even the short width of the fence (5" or so) would bridge across the high spots, putting the cutter closer to the surface than it should be

Basically, there's air between the fence and the wood, right in the center. 

When you move down the row, your next one may fall on a high spot- so the center of the fence will be in contact, and THOSE slots will be the correct distance from the surface. 

 

[ChuckM]

Further to tsmi's comment, the registration faces affect both the distance and angle of the entry of the cutter. Unless the boards are flat (or at least very close to being flat), the alignment can be off a hair here and there. The bows might not be uniform and consistent among all the boards, and the fact that there were bows, it could mean the boards might have other irregularities not obvious to the naked eyes (such as twist).

To be sure it isn't a machine-related problem, or the fence moved during cuts, you can try your cuts on plywood.

 

[Birdhunter]

Can you clamp the bowed boards to a flat reference surface while you drill the mortises?

 

[RobS888]

Are you using the fence only for height? I mean not having the Domino sit on the MFT top? Also are you plunging slowly?

I had trouble with alignment along the edge of a board until I saw how Sedge puts an "x" and an  "->" on the faces the Domino fence sits on and the arrow to show the way to advance from the reference end. That has really helped me. So with that in mind I think you should only use the pins on one end.

 

[ChuckM]

Snip.
So with that in mind I think you should only use the pins on one end.

It seems he was already doing that:

"I use the pins (2007 or so vintage domino) to cut tight mortises on each end and pencil marks to cut the other mortises loose."

 

[tsmi243]

If you have some good plywood on hand, do some test cuts on it.  That will help determine if it's user error or just wonky material. 

If you're brand new at the domino, then be sure to watch the Sedge/PeterParfitt vids, remember to "overhang" the workpiece, push from the plug-it to avoid tilting, etc etc.  Lots of noob info available. 

 

[Hotwheels]

Thanks for the comments and observations.  I have used the domino for various projects since I acquired it some years ago, a bed, tables, etc....  Some of these required critical alignment of the pieces and it all worked fine.  It is not a machine I use all the time and when I begin using it again there is some repeat learning curve, mostly using it for panels, shelves where I have to remind myself about the reference face when joining 90 degrees.  I have learned the hard way about ensuring that the domino reference plate (fence) is on the workpiece reference face and off the MFT surface. I have watched the Sedge videos about using the domino and the most useful part of those for me are his comments about using the "precision of the machine" rather than relying on pencil marks to make mortises.

I used a piece of melamine to recheck the distance from the workpiece reference face to the top of the mortise. I made two on the tight setting and two on the loose setting.  I cut right to left with the first cut being tight then I switched the machine to loose and cut the next two and then switched back to tight for the last one.

Three first three mortises are within .1mm of each other and the fourth was within .25-.3 mm or sp.  I think this is close enough and indicates to me that Chuck is right about the uneven surface of the pine boards being the cause of the prior measurement differences. There is still this issue about the last mortise being enough difference to bother me and I plan to do some more cuts and measurements after my Wood Duck box is finished.

 

[Packard]

I don't have a Dominio, but I do have a biscuit cutter.  I know when I bank off the worktable surface I get better registration than when I use the adjustable fence (is that what it is called?). 

Whenever possible I rest the cutter base on the worktable surface.  In most cases, I am able to do so.

 

[Birdhunter]

I find using the adjustable height fence, I can accommodate variations in the wood thickness. Placing the Domino's or biscuit cutter's base on a surface (not using the adjustable height fence) works for me only if the wood is perfectly flat and has extremely consistent thickness. I find biscuit allow for a looser fit.

 

[Hotwheels]

I find using the adjustable height fence, I can accommodate variations in the wood thickness. Placing the Domino's or biscuit cutter's base on a surface (not using the adjustable height fence) works for me only if the wood is perfectly flat and has extremely consistent thickness. I find biscuit allow for a looser fit.

In the past I have mostly used the domino to joint hardwoods or plywoods that have been through the jointing/planning/squaring process and the results were satisfactory. Th pine I am using now, while not rough, has irregularities and it has not been planed flat mostly because I don't yet have an operational dust collector in my new residence. So, old mindset different material that I thought was close enough to to be ok for the projects I have on the list, so lesson learned for me: what looks flat may not be flat enough!

 

[Packard]

I find using the adjustable height fence, I can accommodate variations in the wood thickness. Placing the Domino's or biscuit cutter's base on a surface (not using the adjustable height fence) works for me only if the wood is perfectly flat and has extremely consistent thickness. I find biscuit allow for a looser fit.

Biscuits are made from highly compressed wood (birch? beech?) and it swells when it absorbs water.  That is why they are often sold in jars--to keep out the moisture.  And so while the biscuits are indeed loose when doing the assembly, they are quite tight once they absorb the water from the glue.

I agree that uniform thickness is required if you are not assembling the boards as oriented on the work table.  But if you assemble all the boards in the orientation you used for making the slots, then the thickness variation will not show up on the "good side" but only on the side that was not used to bank the slotter.

It is similar to using a self-centering dowel jig.  You can assemble regardless of orientation.  But if the thickness is off from board to board then the variation will show up on both sides of the boards. 

But if you use a dowel jig similar to the Rockler jig, then one side will be flat and the other side will have all of the deviations in thickness.