Thread: How to flatten box and lid

This has been a bugbear of mine for a while

I'm about to cut 3 tops off boxes tomorrow, I'm going to try some different techniques this time after some of the guys talked about it here :

Corner being rounded over when trying to sand flat

I think the outer corners sand off more when you change direction

Hodgo

The best way to mate lids with boxes is with a low angle block plane. Veritas have recently released this little beauty with a 90 x 30 sole and they also now have a honing guide for it.
CB4FCD86-8ED5-4A62-B375-9A00D449D820.jpg C5174DB2-1D40-43C6-9472-38C23FD9CD3B.jpg

Set your buzzer to a real fine cut/depth and run em across the it.

Hand plane it . A Bigger plane is better though I reckon . An 8 , 7 or 6 . The box has to be fixed down held in a vice or between bench dogs . Or nail some cleats down to hold it to a work surface . The plane sole resting on the opposite side helps guide and keep it level .
You sweep it around over the high spots with a fine set blade resting the rear of the long sole opposite to where you are planing.

Nearest I get to boxes is Cigar box guitars and like others have said I plane them flat.
Pencil lines are too thick so use a marking gauge. The other issue is likely the non slip mat and the box rocks on it. Clamp the box secure when flattening. To avoid splitting out the corners go from corners towards the middle of the box sides. On your size box a No3 or 4 plane would be my pick. Can be done with a block but I find the handles give a bit more control. If sanding is the only option then stick the paper down to a hard flat surface and slide the box over it.
Regards
John

PS reread your bit on the glass so it may be putting to much weight on the corners as you move the box around. The glass itself may still move on the rubber mat. Only thing like that I have done is lapping plane soles and that is just sliding strait back and forwards taking care to keep even pressure. Doing that I used a strip of sandpaper about twice the length of the plane stuck to the top of the tablesaw. Hard and flatish.

Originally Posted by Dengue

Usually this process works well for me, such that you cannot see the cut line when looking at the lid sitting on the box, but this time the surface is convex, as shown in the drawing, so that the lid rocks back and forth sideways along its length.

There are a couple of reasons this occurs,

1. how you hold the box
2. the motion of the box
3. build up of sanding dust
4. worn sandpaper

As the short sides are apparently unaffected that indicates its a combination of all four.

When sanding on a flat pad not all areas of the surface being sanded are being sanded "equally." The sides (long side) are being sanded with the grain, and the ends (short side) are effectively sanded across the grain.

The ends travel across "fresh" grit or at least grit that has done less "work" and hence has less dust trapped between the sandpaper grains and matrix, and less wear on the abrasive grains.

The sides and particularly the middle of the sides are always traveling across "used" surface with correspondingly more wear and more sanding dust reducing the exposure of the surface to the abrasive grain.

The figure of eight motion reduces those issues somewhat but does not eliminate it. As others have stated, holding the box by the middle of the sides will also assist in reducing the "over sanding" of the ends.

My guess is that whilst your sandpaper was fresh, the issue did not seem apparent but has now appeared because you have to do more "work" to achieve the same result. However, the more "orbits" you perform in the figure of eight motion only increases the wear differential between the mid sides and ends.

Joe,

I had the same problem a while back and i was instructed to 1. use a plane, but as i am not that handy with a plane i chose the sanding approach. But i had to master the separation part first.- i was shown never to cut through fully, i always left 0.5 mm gap then used a stanley knife or Flush saw to separate last the 0.5mm. then after cleaning up those edges with a chisel, came the sanding. Hold the box by the walls/top applying an even pressure across the 4 corners/walls. Then just push the box across the sanding board in 1 direction only, no rotating or criss-crossing, or no bringing it back, and no figure 8. Once you get to the other side, carefully lift off then repeat, and do it a few times til your happy with the result. works for me every time.

oh and by the way, i owe you a box insert cut out for that plane. my most sincerest apologies for not following through. long story but better in the PM than to broadcast one woes.

I also forgot to mention the box should be pushed across the board on a 45degree angle

like so

75E372B0-CD6A-4595-88F2-1A1CAF0C818D.jpg
The 45 degree angle allows the box to flow freely and is not having 2 of the walls being pushed at perpendicular to the direction of the push.

Joe,

Two additional ways I’ve seen this done:

1. In one of Andrew Crawford’s books he shows sanding the join using a piece of MDF about 150mm x 350 (I’m guessing) with sandpaper glued on at at one end covering about 30% of the board. Holding the board abrasive-side down the sandpaper is touching one side while the ‘tail’ of the board rests on the other side of the box keeping the whole thing flat.

2. I’m fairly sure that one of Ian Hawthorne’s Youtube videos shows him cutting the top off then running the box on it’s side across the router table. If I remember correctly he ran it through BETWEEN the fence and the router bit i.e. with the base of the box against the fence. My brown corduroys are at the cleaners so I haven’t tried this. I’m exceedingly nervous about anything being between the fence and the router bit.

Personally I use wide sandpaper with double-sided tape on a piece of kitchen melamine benchtop.
I never hold the box at the corners (too prone to round over), vacuum the sanding board every minute or so, and use very light pressure.

Best regards,

Brian

Hi Joe,

Found the Ian Hawthorne video:

How to make a Keepsake Box - Part 6 - YouTube


Trimming the box on the router table starts at about 38mins.

Brian

And here is Andrew Crawford’s ‘Blind End Sanding Board’:

B8A6623C-4261-4805-8EDD-6D87061239D0.jpeg

Originally Posted by Fumbler

I also forgot to mention the box should be pushed across the board on a 45degree angle

like so

75E372B0-CD6A-4595-88F2-1A1CAF0C818D.jpg
The 45 degree angle allows the box to flow freely and is not having 2 of the walls being pushed at perpendicular to the direction of the push.

I think you are on the money with that, I've just beheaded 3 boxes and sanded them in that manner, at 45 deg rotating after about 5 forward strokes
so far I dont have convex corners and they are all about done

I think the corners were getting rounded off with weight transfer in changing direction particularly in sanding them parallel

there was a lot less work to do using the DW 7491 as opposed to the triton TS which may have had a bit of end float in both the makita and triton saws

Originally Posted by homey

Personally I use wide sandpaper with double-sided tape on a piece of kitchen melamine benchtop.
I never hold the box at the corners (too prone to round over), vacuum the sanding board every minute or so, and use very light pressure.

Brian, I notice Ian uses talcum powder on the sandpaper. Is that to make the box slide easier so you're not fighting against it and consequently put pressure on the wrong spots.

Hi Dallas,

I’m not sure. I thought it was to stop the sandpaper from clogging

Anyone have the definitive answer?

Regards,

Brian