Flattening the edges of a dovetail box

[Marty Tippin]

I'm working on a burial urn project and have made a basic through-dovetail box using my Leigh RTJ-400 dovetail jig. For whatever reason, the top and bottom edges of the box are a bit uneven at each corner - maybe I didn't get the stock in exactly the right position for every set of cuts with the jig, I don't know. But now I need to flatten the top and bottom edges of the box so that the base and top of the box will attach squarely without gaps. I've been using a hand plane to try to take off the high spots, but I seem to be chasing myself around in circles - get one side "fixed" and the opposite side is too high, and around I go.

I'm looking for tips on how I might get this done efficiently and without whittling the box to half its original height. Appreciate any suggestions!

The box is about 10" square by 6" tall.
335408

[Mike Henderson]

What most people who make boxes do is get a large sheet of sandpaper - perhaps purchase a sanding belt for one of those big belt sanders - and then glue it to a piece of MDF. Then you put the box on the sandpaper and move it around. Try to keep even pressure on the box - change the place you hold it. You will wind up with a flat surface.

You also use this when you cut the top off of a box. Most people make a box as a complete unit - sides, top and bottom, and then cut the top off when they want it. This give a perfect grain match. When you cut the top off, your cut is never perfect so you need the sandpaper to flatten the two sides of the cut.

I think I have a picture of a sanding board in this tutorial (http://www.mikes-woodwork.com/BoxTutorial.htm), second page in.

Mike

[Oh, yes, when you glue the sandpaper to the MDF, use something like 3M 99 spray adhesive. Do not use a water based glue or your MDF will no longer be flat.]

[Al Launier]

Mike beat me to it, but exactly what Mike said. If you don't happen to have MDF handy, a table saw would also provide a flat surface, but you would have to use double back taped to secure the sand paper to the TS.

[Marty Tippin]

Thanks, Mike (and Al). Not sure why I didn't think to use a belt sander (you know, like the one in the background of my photo...) - I'll try that and see if I can get close enough; if not, I'll use the sandpaper on a flat surface trick.

In this case, the box won't have a lid that opens - I'm permanently attaching the "top" to the box and the base will have screws to allow the ashes to be placed inside before sealing it. The urn (for my dad's ashes) will be buried at his funeral next week, so it's not going to be as fancy as one that might sit on a mantel for years and years. It's kind of a last-minute project; Dad died earlier this week after a month or so in hospice and I wasn't planning to make an urn until I saw how much the funeral home wants for one... :rolleyes:

[Roy Harding]

Mike and Al have given you the best advice. I'd only add that I've found melamine is also a great substrate to glue your sandpaper to - and you can use water based adhesive if that's what you have in the shop.

[Bob Vavricka]

You have good advice already, but your comment on trying the belt sander worries me. Generally using a belt sand has just enabled me to screw it up faster :-) than I could with a plane.

[Mike Henderson]

You have good advice already, but your comment on trying the belt sander worries me. Generally using a belt sand has just enabled me to screw it up faster :-) than I could with a plane.

This ^^^^ A belt sander will only allow you to sand one side at a time. It's very likely you won't get a flat surface.

Mike

[Jim Tobias]

+1 on what Mike said originally about using sandpaper on MDF. I put down several strips(4" wide) of the Klingspor self adhesive sandpaper very tightly fitted together to form whatever size surface I need. Make it oversized as you will need additional space as you move the box around to sand the sides.

Typically I use 180 grit so as not to create rough sanding lines that will show up.

Jim

[Mike Henderson]

If you do make your own sanding surface, consider making one side coarse, maybe 100 grit, and the other side a bit finer, maybe 180 as Jim suggested. Sometimes you have a lot to take off and just using the 180 can take a while.

If you have scratches after the 180, take some 220 sandpaper and lightly sand the scratches out by hand.

Mike

[Marty Tippin]

Thanks all for the advice. I ended up using some 3M 77 spray adhesive and stuck a couple pieces of 150 grit sandpaper to the table saw top. Worked like a charm, flattened both sides in just a few minutes. The bet sander would have made a mess of things for sure. Acetone took the residue off the table saw easily.

[Art Mann]

Using a stationary belt sander or edge sander is a method that works well for me but it has not always been that way. It takes a certain level of practice and and technique to do it without damaging something.

[Charles Lent]

Using a belt sander is NOT the way to do this. A piece of a wide sanding belt attached to a flat surface is the right way, but you could, and I did, use sheets of good quality sandpaper with the edges of the sheets fitted tightly together as they are glued on.

To use mine, I just set the uneven box edge down on the sandpaper surface and slide it around a bit for a perfectly flat box edge. An even downward pressure is important. Change your hand positions often to keep the sanding as even as possible. Inspect the edges often because this doesn't take long.

My sanding board is about 2X the size of the largest box that I usually make, so it's about 36" square. It is made with 180 grit heavy backed sandpaper, glued to a piece of 3/4 MDF. I put several coats of poly on both sides and all edges of the MDF to keep moisture out of it before I glued the sheets of sandpaper on. I've now had this sanding board in my shop for about 10 years, and it's still flat. I store it on edge in the gap between two of my workbenches. After the original sheets of sandpaper wore out I applied new sheets to the back side of the MDF and now use this side. The old sandpaper on the first side now helps keep the board from sliding around on my workbench as I use it. I used contact cement to glue the sandpaper sheets down, so the next time that I need new sandpaper I'm just going to make a new sanding board.

Charley