Sanding to achieve an invisible mating surface

[DLJeffs]

My neighbor and I were talking about boxes and he asked me a question I didn't have a good answer for. He has been experimenting with Rob Cosman style boxes and hinges, which recommend making a solid box and then cutting the lid loose. My neighbor uses a large flat piece of marble to which he secures full size pages of sand paper. He then rubs the lid and the box body on this surface to clean up the surface where he cut them apart. But he said he often gets a very minute gap especially at the corners. Is this the result of too much pressure applied to the lid/box? He said he is very careful to keep the lid/box flat and in complete contact with the paper. Thoughts?

 

[Ray D]

I make my humidors using that same method although I have no idea who Rob Cosman is. I’ve done the sanding using a granite plate and sheets of sand paper with good results but I occasionally have to set up my router table and take a hair off each mating surface. As you probably already know, adding a slight bevel to the outside edge of each mating surface will make slight imperfections disappear.

 

[duncsuss]

Maybe it's a bit like sharpening plane irons and chisels - I was told to work in one direction only, not to push and pull.

 

[daniscool]

Maybe it's a bit like sharpening plane irons and chisels - I was told to work in one direction only, not to push and pull.

This. As uneven pressure is applied (and as sandpaper slightly deforms under pressure) the edges will be convexed. Use polymerbacked sandpaper and only pull/push. That's it.

 

[JonathanH]

I've seen a lot of box videos where the maker runs a small hand plane over the top of the box.

Is a hand plane dressing an option?

 

[Mr. Peet]

My neighbor and I were talking about boxes and he asked me a question I didn't have a good answer for. He has been experimenting with Rob Cosman style boxes and hinges, which recommend making a solid box and then cutting the lid loose. My neighbor uses a large flat piece of marble to which he secures full size pages of sand paper. He then rubs the lid and the box body on this surface to clean up the surface where he cut them apart. But he said he often gets a very minute gap especially at the corners. Is this the result of too much pressure applied to the lid/box? He said he is very careful to keep the lid/box flat and in complete contact with the paper. Thoughts?

I used to use card scrapers first, then touch up with sand paper. I found using really high class blades to cut the lid free was a big plus as they had very little saw marks left behind. I only had the blade set just high enough to breach the wood thickness, in case I did poor holding the box while cutting. I did not do fancy grain boxes, just plain jane, so sand paper scratches often blended well with the straight grain wood.

 

[daniscool]

I've seen a lot of box videos where the maker runs a small hand plane over the top of the box.

Is a hand plane dressing an option?

Yes, but it requires a lot of setup and the blade is not allowed to have any significant camber (makes it harder to use) also, getting a wider plane for it is very useful. All in all not very practical. You will notice that antique finely made boxes always have decorated mating surfaces which make it very hard to notice any gap.

 

[Mike1950]

never used the cut lid method, but I find lid to be most important part of box and mine are never that simple. I cannot remember a lid without joinery, except sliding lid.

 

[Webb]

I glue, sand the outside, then cut the lid off. On my table saw, I completely cut through the front and back sides and then lower the blade so you almost cut through but not quite on the ends. That way the top won't move and get stray cuts. Then use a razor knife to finish the separating the top from bottom.

If you completely cut through the sides when splitting the box, you can get cut marks and uglies since the top can move when passing the box through the saw. I also recommend application of painters tape to the cut line to reduce potential of tear out. A fine tooth high quality sharp blade goes without saying.

 

[DLJeffs]

I make my humidors using that same method although I have no idea who Rob Cosman is. I’ve done the sanding using a granite plate and sheets of sand paper with good results but I occasionally have to set up my router table and take a hair off each mating surface. As you probably already know, adding a slight bevel to the outside edge of each mating surface will make slight imperfections disappear.

Thanks for chiming in Ray. I use that bevel technique a lot to hide my mistakes. But my neighbor is trying to make the mated edges and the hinge completely disappear so he's trying to get ultra - precise. That's why the sanding question. This is what he's playing around with:

 

[Ray D]

Thanks for chiming in Ray. I use that bevel technique a lot to hide my mistakes. But my neighbor is trying to make the mated edges and the hinge completely disappear so he's trying to get ultra - precise. That's why the sanding question. This is what he's playing around with:

Thanks for the link. I’ll definitely watch it.

 

[daniscool]

Thanks for chiming in Ray. I use that bevel technique a lot to hide my mistakes. But my neighbor is trying to make the mated edges and the hinge completely disappear so he's trying to get ultra - precise. That's why the sanding question. This is what he's playing around with:

They are so cool. They have been on my to do list forever.

 

[DLJeffs]

Cosman's a pretty talented woodworker and has some cool ideas. His shop looks pretty awesome too. He sells a bunch of videos and some specialty tools, such as a jig to perfectly center a pin hole in a round dowel for those hinges. Which makes me wonder if the free YouTube stuff leaves some of the important details out.