Consistent Domino Problem. Help!

[Bryan Hall]

I've been using my domino for a few years now and have got to admit, I think I'm absolutely terrible at using it. It's gotten to the point where I typically dread pulling it out and do everything I can to avoid it, and I'd like that to stop.

My issue is one thing and one thing only. I can never get consistent depth on the mortise location. Left to right alignment is always perfect. Everything assembles without issue. Nothing, however, ever ends up flush on the face.

Example: I was making a screen door today and I dry assembled everything prior to marking out for dominos. The stiles and rails met perfectly flush on the front and back of the door. As you'd expect since it was all planed to the same thickness. With everything clamped up I go through, mark out all of the domino locations, then disassemble.

Next I clamp all of the rails, make their cuts, set them off to the side. Then, clamp the stiles, make their cuts, set to side. Grab dominos, dry assembly. Every single rail sits proud the exact same amount on both sides, probably 2mm. Disassemble, reclamp the rails, sure enough the cutter now will not insert into the previous mortise and wants to cut higher.

So the question I'm dumfounded by is this: Is the fence somehow slipping 1/2 way through the process? If it's slipping, it would be slipping down, towards the cutter, not up (otherwise the rails would sit recessed, not proud) which doesn't seem right, I'd expect the fence to slide up due to the way the machine sits. Or, am I somehow consistently recreating a repeatedly accurate mistake on a large scale? 16 in a row that are off by 2mm and then 16 in a row that are dead on...

This is essentially the same experience I have every time I use the domino, and it's been that way since the day I got it. Occasionally things come together flush, but more often than not I end up double drilling and wondering what the point was in the first place.

I would really appreciate any advice on what I'm doing wrong here.

[Jim Becker]

Some possibilities include the material being just thin enough that the machine is bottoming out on the work surface rather than on the material and not referencing the same face on both rails and stiles, usually the "show face"; front of a door for example. I've occasionally had the first issue with my DF700 and the solution has been to block the workpiece up off the bench so that the Domino machine is always "off" the bench for sure and only supported by the material being pierced.

[Steve Jenkins]

The domino probably doesn’t cut the mortise in the exact center of the edge so you need to mark all the faces so you are indexing from the same face. Same goes for a biscuit joiner.
Jim types faster than me.

[Prashun Patel]

How thick are your pieces? Can you take some photos? It should not be consistently off like this. And 2mm is way too much. Mine are sometimes off but less than 1mm. It’s usually because there is dust on the surface or I am not using dust collection.

When cutting the side grain mortise, there is little real estate to keep the fence from tipping forward. Are you sure your fence is set for 90 degrees exactly?

[Andrew Hughes]

I also experienced the uneven depth with dominos when I first started using mine. I asked a Festool rep about the problem. He suggested holding the tool at end around the cord and pushing from there. It’s worked for me.
much better alignment. With my fingers I can still feel a slight difference but I can feel a few thousand difference with my fingers tips. God given precision instruments.
Good Luck

[Paul F Franklin]

It doesn't sound like a fence slippage problem, even though many users have had to adjust the fence position lock so it locks more securely. If that were the problem you would expect a gradually growing error, not a consistent step change, and as you say, it would likely be in the other direction. But I am at a loss to explain such a consistent source of error. The only thing that may hint at the problem is that the error occurs between the rails and stile. So it could be related to end grain vs. side grain, or it could be a technique issue with positioning the machine on the rails vs the stiles.

You could try doing a bunch of side grain to side grain joints and a bunch of end grain to end grain joints and see if/where the problem shows up.

Or, you could do as I almost always do, and reference off the bottom of the machine rather than using the fence, adding spacers under the stock or the machine as necessary to get the mortise positioned as you desire. I just find this a much less "fussy" way to position things without trying to balance the fence on a narrow piece of stock.

But don't get me wrong...with care and good technique,you should be able to achieve good results doing it the way you describe.

One last thought...is there any chance when you are clamping either the stiles or the rails that you are doing it in a way that the bottom of the machine is hitting something, preventing the fence from registering properly? The edge of the bench or ?

[Bryan Hall]

For referencing:
I have every piece marked "up" and run the domino from the same side for every piece, so it's not a flip flop error (I learned that first thing when I got it).

For clamping interference:
I actually clamp every piece off the edge of my assembly table so there is nothing below the domino to interfere with.

The stiles and rails are all about 1.25" thick and 3" wide.

Wood, in this circumstance, is sapele.

Andrew: I'll give the hand position switch a try.

Prashun: I'll double check the 90 on the fence as well.

Paul: This was also on my mind, the side vs end grain situation. I'll try to set that up this week with some scraps and see what happens. I'll have to look at setting the machine flat on the table. That sounds more difficult in my mind, but maybe hands on would be easier?

I'll try to pull together some photos, but this door is already in glue up so it will have to come from the next wave of trials.

[Jacques Gagnon]

Bryan,

You have already received great advice.

I have good success with the Domino. I use a jig made out of MDF or plywood when working with my 500. Pieces sit on the jig and cuts are made using the jig's surface as the reference plane, with the fence adjusted to sit on top of the wood piece being worked on. A couple of blocks spaced a few inches apart are used as "stops", as well as support for vertical hold downs. This allows me to easily position pieces requiring mortises in end grain when assembling mitered corners.

My understanding of your post is that the problem resides with the "height" of the mortise and not the "depth", correct?

Regards,

Jacques

[Greg Quenneville]

When I had a similar result my error was as Jim described it…the bottom of the machine resting on the bench instead of the fence resting on the stile, which makes that slot too high. Then, since its easy to clamp the rails well clear of the bench, those slots are cut correctly.

Since we aim to get the slot cut roughly in the middle of the workpiece, any such error results in being off by about two frustrating millimetres.

[Michelle Rich]

Veritas/lee valley just came out with a neat jig for the domino. Way cheaper than the Woodpecker 700.00 one. Might help keep your domino level at the attack, and remember to cut with the same side up .

[Malcolm McLeod]

For referencing:
I have every piece marked "up" and run the domino from the same side for every piece, so it's not a flip flop error (I learned that first thing when I got it).
...

This flip flop is the only thing that has bitten me. Please let us know how your testing goes.

[Robert Engel]

Bryan, I had the same issue, checking fence, hand position at end of motor, I still could never get consistently flush joints. I always figured it was operator error, but I could never figure out what I was doing wrong. So I sold it and went back to biscuits. I rarely ever used it for tenons anyway.

I got the best results by clamping the board down and registering off the base, IOW not using the fence.

I figure that's the reason Seneca made the Domiplate to bypass the fence?

[Jeff Roltgen]

+1 on what Jim and Greg said. 2mm is not merely something slipping. It's surprisingly easy for the domino machine base plate to rest on work surface vs. registering the top plate on the workpiece, yet you don't notice it.
No special jigs to buy, simply be sure the workpiece is always hanging off the edge of your workbench.
Dead-level joints is why I grab the Domino machine, and almost never reach for a biscuit anymore.

jeff

[Randy Heinemann]

Given the experience I've had with my Domino, there is only 2 possible reasons for the problem; either user error (and I've had a few) or, if the problem has existed since Day 1 of your ownership, it's possible there is something that was a defect to begin with. Did you have the tool checked out by Festool? I really don't know what the defect could be, but anything which existed from the start of ownership certainly is suspect.

Have you tried having someone watch you while you work on test pieces? They might be able to pick up something you're doing that needs to be changed.

[Dan Friedrichs]

Hold the fence handle firmly. Other hand on the cord, pushing straight forward. Work sticking off edge of bench so that the baseplate doesn't bottom out early. Multiple in-out passes without causing the machine to strain (which may cause it to shift position). Sharp cutter.

I had some poor alignment at first, but with careful following of the above rules, it is now my go-to for getting anything perfectly aligned and dead-flat. It seem to help to regard it as a "precision" machine that benefits from careful, consistent use (vs a "close your eyes and swing it in the direction of the workpiece" tool)