New to this machine. I has taken some learning. I need a looser than Domino- tenon tenon so I am drum sanding custom tenons to fit the need. One end of tenon will go into end grain maple and the other end into long grain cherry.
I have observed that the end grain maple mortise is consistently larger than the long grain cherry mortise. Note that two variables have changed- wood and grain orientation. The actual observation is that the tenon is looser in the end grain maple than the long grain cherry. A tenon that can be easily adjusted for position is difficult to move in the mating cherry part. I would estimate the difference to be less than 0.005" Anything I am doing wrong or is this variance to be expected?
Try plunging very slowly. I find that if I plunge too fast there is a bit of vibration that enlarges the mortise. Vibration is worse with harder woods.
Even with slow plunging, I've also noticed differences in mortise tolerance with different woods.
I have limited experience with a 500 model Domino. Short stubby bits cut more accurately and consistently than longer ones. I think the longer thinner bits may whip a little. Plunging slowly helps with consistency as does anchoring the machine firmly. If you leave the Dominoes exposed to open air they may acquire a bit of moisture and swell slightly. I have had sand some slightly to get them into the mortises.
As an aside, I have hundreds of maple sticks that are 3/8 by 7/8" and rounded on the edges, 16" long. They fit loosely into the 10mm mortises. Probably would be excellent tenons if you used thickened epoxy. I dressed some of them to 8mm and they are excellent. The width is correct as is. I use them for dry run assembly in place of "real" Dominoes in 10mm mortises. If they would be of use to you I would be happy to mail you some.
It's been my experience that the fit into endgrain is always a little looser than into side grain. That's been true of both plunge-routed floating tenons and Domino-cut floating tenons. I don't consider it a problem. The glue adhesion in the (looser) endgrain cut will be much better anyway because of grain orientation.
Using the Domino machine I've always found that any problems with fit have been that they are too tight rather than too loose. The tenons are fluted so that glue at the bottom of the mortise will flow up into the joint when the tenon is tapped into place. The problem is with alignment, where a little looseness will allow the pieces to be pulled into place if they are slightly off but a very tight fit will not.
A tight fit can also make assembly difficult if a glue is being used that has fast tack characteristics. For complex assemblies I like slow-setting epoxy because it acts like a lubricant in the joint until it sets.
When I'm told that Domino machines "deskill" the work I reply that effective use requires different skills. As with a table saw it takes some experience to use a Domino to its full potential.
I agree with the above comments that a slow plunge is helpful (let the tool do the work..), that endgrain joints tend to be a little looser, and that the additional looseness in endgrain is not a problem for the quality of the joint.
A few other thoughts... the angle at which the machine is held is crucial, so be sure that the fence is tight against the workpiece and the machine is parallel to the workpiece (press down firmly on the handle in the front and exert forward pressure from the back of the machine). Be sure the bottom of the machine is above your bench. Just like when I start to dovetail, I run a few domino mortises to get in the groove before doing the real thing.
BTW, there are some excellent resources on the internet. Festool manuals that come with the machines are minimal at best. Festool USA invests in more detailed (auxiliary is their term) manuals that are available at festoolusa.com. The domino manual is quite good. Another good resource is festoolownersgroup.com, with a vast collection of threads on just about any topic.
A sample of absurdly unpublicized facts: there are scribe lines on the fence and the foot of the domino that mark the center of the cut and on the side, a mark that shows the vertical center of the cut.
No idea why euro manuals are so skimpy, maybe its the apprentice/guild system.
Some of your wisdom I discovered while practicing. Ah, the "P" word. I used to think, buy a tool and the tool will ensure success. The flaws in that strategy were revealed when I bought a belt sander! So before I do anything new, or even revisit the old like dovetails, I practice.
When I have a lot of domino mortises to cut I am often tempted to see just how fast I can go. The machine does it work so quickly that speed can easily become addictive.
I usually find the limitation when I start making errors. Slow learner here.
I've not used a domino, or any other festool product. I find it curious that the manual is described as minimal. Didn't the Germans write the book on writing thorough books?
The manual provided with my Leigh dovetail jig is incredibly thorough, by comparison.