Domino problem

[cvn72]

Recently bought a domino and SCG-10 and having an issue with L type butt joint.  Mortising wood parallel to cutter is pretty easy but mortising wood perpendicular to the cutter is causing me some problems.  If I'm using narrow stock wood, the circular rubber anti slip pad acts like a fulcrum and causes the wood to rotate a little.  How do you guys deal with that.  Thought about putting some duct tape to act as a shim but figured you guys might have a more elegant solution.

Also, the domino manual recommends 8mm dominos for 3/4" stock.  Does that hold true for 3/4" pine, poplar, oak, hardwood stock and birch plywood and mdf?

 

[Rick Christopherson]

Congratulations on your new tools. I trust that you're not having any problems with your SCG-10 guide.

Are you saying that the thickness of the anti-slip pad on the face of the Domino is enough to skew the mortise from being perpendicular to the face? That pad is so thin that I am not totally sure that is the problem. The ribbed edges of the Domino tenons should permit that small of a skew to be overcome during clamping.

Especially when you are working with small pieces, it is important to firmly clamp the workpiece. Not doing so is one of the leading causes for improper joint alignment.

As for the size of the tenons, for softer materials such as you described, smaller tenons will be stronger because they will leave more of the substrate intact. The workpiece material is weaker than the tenons, so you want to maximize it. This is specifically mentioned in my manual, so I'm wondering if you have downloaded it yet. You can download it here.

 

[semenza]

Welcome to the FOG!

8mm is pretty thick for 3/4" stock, especially plywood.  Go with 6mm.  There is a general rule of thumb of usig a Domino aprox. 1/3 the stock thickness.

Seth

 

[Rick Christopherson]

Welcome to the FOG!

8mm is pretty thick for 3/4" stock, especially plywood.  Go with 6mm.  There is a general rule of thumb of usig a Domino aprox. 1/3 the stock thickness.

Seth

Unfortunately, the confusion is because the manual is poorly written.....hahahaha.....mea culpa. Festool copied my manual's text when they reissued the factory manual, so the same thing exists in their manual too. "It is acceptable to use a tenon that is slightly thicker than 1/3 when the width of the Domino tenon is relatively narrow compared to the width of the joint. This is why 8mm Domino tenons are the most common for joining ¾-inch lumber."

That bullet point can be misleading if you don't read it carefully. In the same group of bullets, I also discuss the general 1/3-rule and also when it should be varied depending on the type of material being joined.

 

[Wonderwino]

I have found that is is important to take my time and be sure that the DF500 is properly seated against the work.  I usually hang it off the edge of my MFT/3, well clamped to the top.  I have an older pin model and have occasionaly "misfired" when rushing and a pin hangs above the stock.  If it has not blown out a face of the stock, you can just glue in a domino, cut it flush and try again.

 

[RONWEN]

Welcome to the FOG!

8mm is pretty thick for 3/4" stock, especially plywood.  Go with 6mm.  There is a general rule of thumb of usig a Domino aprox. 1/3 the stock thickness.

Seth

Unfortunately, the confusion is because the manual is poorly written.....hahahaha.....mea culpa. Festool copied my manual's text when they reissued the factory manual, so the same thing exists in their manual too. "It is acceptable to use a tenon that is slightly thicker than 1/3 when the width of the Domino tenon is relatively narrow compared to the width of the joint. This is why 8mm Domino tenons are the most common for joining ¾-inch lumber."

That bullet point can be misleading if you don't read it carefully. In the same group of bullets, I also discuss the general 1/3-rule and also when it should be varied depending on the type of material being joined.

Rick, To be clear, I'm not sure if it's a Festool mistake, Rick's mistake or if it is a mistake -- I'm very surprised that 8mm is common in any 3/4" joinery -- I would have thought 6mm was far & away more commonly used for 3/4" stock and ply with 5mm used more often in cheaper ply.  Please clarify.

 

[Nick C]

I agree--6mm is the right size for 3/4". That might help with the mis-drilling issue as well, since the 6mm mortises require less force.