Dominos showing through on sheet goods.

[Mountain-man]

Anyone established a minimum distance dominos should be from top of sheets. 1/8 inch, more. Was staining and sanding sheet goods put together with dominos. ANd I could see every domino they installed when I stained boards. I don’t know if they slightly raised boards or something else. So they joined two sheets plywood, 3/4 thick with dominos every 12 inch or so.

 

[ChuckM]

For 3/4" (19mm) sheets, you should be using 6mm dominoes. That means the mortises are about 9mm (1/4"), not 1/8" from the top based on the 1/3 rule. Did you use much larger dominoes, or were the mortises cut much off-center?

 

[Wood_Slice]

With tenons or mortises the common rule is 1/3. Meaning if the thickness is 3/4" then the tenon/mortise should be around 1/4". For example for a 3/4" baltic birch plywood (18mm) the domino you would want to use is 6mm. I have heard people using smaller and larger dominos as well. Many use the 5mm domino (5x30) and on a 3/4" (18mm) plywood you can set the depth of cut to 15mm and use it on both pieces without having to reset the depth of mortise on but joints.

 

[Crazyraceguy]

If you are seeing them, they are either too close to the surface because of fence adjustment or they are just too big.
I use 6mm on 3/4" sheet goods and have never had one show through.

I have heard of the 5mm reasoning for 90 degree but joints and it does make sense, but I don't do it....living on the edge.
I do sometimes switch over to 5mm on mitered corners.
Another thing I do that might help someone involving miters is cutting the mortices parallel to one of the sides. rather than perpendicular to the miter itself. This can make assembly much less of a struggle, depending upon how the pieces fit, how thick they are, etc

 

[ChuckM]

Snip.

I have heard of the 5mm reasoning for 90 degree but joints and it does make sense, but I don't do it....living on the edge.

I don't do it either. If I can use just one size of dominoes (and hence one bit, instead of changing bits between 5mm and 6mm) for the whole project, that's a plus for me.

After making my share of mistakes (including blow through) over the years, I now am accustomed to a comfortable system of almost error-free domino operation. Like using a dovetail jig with a router, if you use it enough, you'll be a pro on that machine. I use my DF500 on average 8 - 10 times a year; only the table saw and other standard machines outdo it in terms of usage.

Whether it's bevels or butt joints, I always do a dry cut (by plunging the bit without turning it on) before milling the FIRST mortise. This one single habit, combined with the use of marking, will prevent countess no. of blunders including, for example, incorrect fence setting in addition to any wrong depth or angle setting.

 

[Michael Kellough]

If you are seeing them, they are either too close to the surface because of fence adjustment or they are just too big.
I use 6mm on 3/4" sheet goods and have never had one show through.

I have heard of the 5mm reasoning for 90 degree but joints and it does make sense, but I don't do it....living on the edge.
I do sometimes switch over to 5mm on mitered corners.
Another thing I do that might help someone involving miters is cutting the mortices parallel to one of the sides. rather than perpendicular to the miter itself. This can make assembly much less of a struggle, depending upon how the pieces fit, how thick they are, etc

Yes, makes the assembly as easy as a lock miter joint and usually only need to clamp parallel to the mortiser rather than across the miter joint.

 

[RobS888]

There was a problem with biscuits; if you sanded them too soon after glue up the glue had swelled a bit causing a slight bump over the biscuit. sometime later after sanding the swelling goes down and the area has a slight depression. Biscuits are thinner than dominos so I think the same could happen.

Is the area the domino is showing through elevated or depressed below the surface?