Choosing Festool Domino sizes (Plywood, Hardwood, SPF)

[Wood_Slice]

Happy Holidays FOG, just recently got my first Festool product (MFT3) and since then its been downhill in $$$ rolling out. I have just purchased the Domino DF 500 as well as the Domino assortment set with the cutters. I have read the booklet that came with the machine and just wanted to get some more info. Is the cutter selected based on 1/3 of thickness of material in general or does it change with softwoods, hardwood, plywood, etc. I ask because the domino loose tenons are stronger than the softwoods and most plywoods so a thinner domino might be used as I have read in the booklet. Please consider that I have the Domino DF 500 not the XL.

PLYWOOD (birch)- what cutter size to use based on thickness of material

• 3/4 inch thick material---- 4mm, 5mm, 6mm, 8mm, 10mm?
• 5/8 inch thick material---- 4mm, 5mm, 6mm, 8mm, 10mm?
• 1/2 inch thick material---- 4mm, 5mm, 6mm, 8mm, 10mm?

SOFTWOOD- is the cutter selected 1/3 the thickness of material, more or less?

• >1 inch thick material- using multiple dominos?
• 1 inch thick material-
• 3/4 inch thick material-
• 1/2 inch thick material-

HARDWOOD- is the cutter selected 1/3 the thickness of material, more or less?

• >1 inch thick material- using multiple dominos?
• 1 inch thick material-
• 3/4 inch thick material-
• 1/2 inch thick material-

I ask all this so I can make a table and list this info for myself on the wall as reference on which to use based on material being used.

 

[ChuckM]

• PLYWOOD (birch)- what cutter size to use based on thickness of material

  • 3/4 inch thick material----  5mm
  • 5/8 inch thick material---- 4mm or 5mm
  • 1/2 inch thick material---- 4mm

  
  SOFTWOOD- is the cutter selected 1/3 the thickness of material, more or less?
  

  • >1 inch thick material- using multiple dominos (see comment on hardwood)

  1/3 of the thickness of the board
  
  HARDWOOD- is the cutter selected 1/3 the thickness of material, more or less?
  

  • >1 inch thick material- 5 or 8, or 10 depending on how the space between mortises (1/3 rule) will work out.
  • 1 inch thick material-10mm
  • 3/4 inch thick material- 8mm 
  • 1/2 inch thick material- 5mm

  
  I ask all this so I can make a table and list this info for myself on the wall as reference on which to use based on material being used.

The configuration (four 8mm dominoes instead of two 10mm dominoes) shown on the right was used for the project.

I sometimes deviate from the above guidelines if I run out of the needed size of dominoes. I am not going to hold the project until I get the replenishment, and will go ahead and use whatever that's close enough. 1mm difference won't be a critical factor.

 

[Crazyraceguy]

For 3/4" material I use 6mm Dominos, not really paying attention to what kind of sheet goods it may be. I think it's mostly because a lot of the time I am mixing solid wood with ply or MDF, either for shelf edges or faceframes.
Other times I am attaching panels edge to edge on walls where strength is not a huge issue, but alignment and unit integrity matter. Often they are combined with Lamello Tenso  clips to pull them together.
Many people recommend using 5mm Dominos for corner joints with 3/4" material because they are only 30mm long and you can set the depth of cut at 15mm and forget it. The 6mm Dominos are 40mm long, so you have to offset them with 15mm into one side and 25mm in the other.  This has the potential for forgetting and cutting thru the face.
For thinner stock like 1/2", I use 5mm just to keep from getting to close to the surface.
The 4mm are so tiny that I have only ever used them for holding miters on small mouldings where nothing else will work.
Bigger pieces like chunky table legs/stretchers get the 10mm and I use multiple rows of them if there is space. One of the very first jobs I did with it was some thick A shaped table legs. I'll see if I can find a pic of them.

 

[Wood_Slice]

Many people recommend using 5mm Dominos for corner joints with 3/4" material because they are only 30mm long and you can set the depth of cut at 15mm and forget it. The 6mm Dominos are 40mm long, so you have to offset them with 15mm into one side and 25mm in the other.  This has the potential for forgetting and cutting thru the face.

Now thats a tip i can get behind. Resetting depth on the different piece although very easy and very quick it is way too easy to forget and blow right tru. Thank Youuuuuu

 

[bertv]

When choosing a domino size for plywood make sure that you leave at least one FULL layer of ply on each side. Try to stay within the gluelines, bc otherwise glue WILL escape to the surface.

 

[jeffinsgf]

Just to reinforce some of the comments thus far, Forgetting to change the depth is one issue. Another is that the actual mortise is a bit deeper than the stated depth, particularly at the center. 25mm depth will blow through 1" thick stock right at the center of the mortise. It would actually be easier to fix if it was blown completely through. The splintery little remains are harder to patch than a clean hole. 

 

[ChuckM]

I make it a standard practice to finish the first batch of mortises at their smallest width and depth settings, before resetting the machine for the next batch that requires wider/deeper cuts. I can remortise anything that's too narrow or too shallow, if necessary. Blowouts can be fixed skillfully with veneer-topped dominoes, but I try to prevent mistakes to start with.

 

[Birdhunter]

My rule of thumb is to use the largest and longest tenon that is within the 1/3 rule. I always extend the cutter across the board to verify that I won’t blow through. As long as I have 1/4” left behind the mortise, I’m good.

I don’t trust measuring all that much.

As long as you are rolling out the $$$, look at the Mafell DDF40 dowel machine. Like. The Domino, it is a game changer.

 

[Crazyraceguy]

I make it a standard practice to finish the first batch of mortises at their smallest width and depth settings, before resetting the machine for the next batch that requires wider/deeper cuts. I can remortise anything that's too narrow or too shallow, if necessary.

Chuck, I do the same. I have only forgotten one time, very early on after getting the machine. It is exactly why I adopted this method. It's like a right of passage, you have to do it  [embarassed]