Thread: New box rocks on base - why?

A slight unevenness when you're clamping up can cause it, or is it possible that the ends of the sides aren't exactly perpendicular to the bottoms?
I wouldn't touch it with a belt sander. Better off turning the box upside down & planing towards the corners that need to lose a little bit. Start with short strokes near the high corners and take longer ones until they are all level. You won't be able to do that with the top, but probably no one will notice.

In boxes with really light sides it can be caused by the top and/or bottom warping and pulling the sides with them, but I don't think that would be the case here.

Thanks for your helpful insights , Alex, very much appreciated.

I examined the base with a flat surface, and decided to plane the corners on the diagonal about which the base rocked. Unfortunately, either the plane blade was not sharp enough or the timber was too difficult to work with( see pics below) , but I took a big chunk off the base on one of the edges first go. Shouldn't be too bad, as it is under the box, and recess off the sides and under a shadow line. As long as the new owner doesn't lift it all the time looking for defects, but I don't think she will, but her father might, being a boat builder

I then borrowed one of those little triangular Ozito sanders, and did each corner a bit at a time, starting with 80 grit, and slowly but surely the box base came flat....WHEW!!

Next trick is to cut the box lid away on the table saw. Should be interesting, not having ever done this before. It is 10.5mm thick sides, so will cut initially to a 10mm depth, then finish off by hand


base_02.jpg base_01.jpg

Your plan for parting the lids seems sound. Just remember to take it easy cutting through that remaining 0.5mm. If tackled to aggressively one can blow out the cut on the inside surface of the box.



Paul

As Homesy says, take it easy - I'd actually leave a little more, maybe 1mm or so. Take care that you don't stray from the thin bit - try to cut as straight as possible down the centre. Good luck.

PS, you can probably tidy up the bottom with a card scraper.

thanks to Alex S and Homesy, I followed your advice.

Prior to glueing up I had covered the cut line for the lid with masking tape inside the box, then prior to cutting, I covered the outside cut line with tape too. I then cut right through the long sides with the table saw ( there was no chipping or tearout), and left 1mm on the short sides to hold the box together.

Still made a mistake cutting the last 1mm by hand - my saw was too flexible, so cut into one side of the carcase. Ended up rubbing the box carcase cut surface along a couple of sheets of 120grit SIA sandpaper glued to a large piece of MDF to flatten the box. The end result was a neat cut line you can hardly see

The bad news is, I cut through the wrong pin, after all the trouble of making the 2nd pin 4 mm wider than the rest In lining up the box on the table saw, I aligned the wrong pin somehow. I had even gone around to the other side of the saw to check that the blade would cut exactly down the centre of the pin and still didn't pick up the mistake. So the first pin on the carcase below the cut line is 4mm larger than the rest

Talk about silly mistakes made, and lessons learnt !!!! Most mistakes happened with hurrying. There were times when I wanted to cut this box up and start again. That still might happen if I don't get these SmarHinges properly aligned and the groove perfect, and the screws in properly!!

As they say we all learn by our mistakes. Hope you can get the rest done without any further mishaps take it easy and measure twice when fitting the hinges. Good luck with the rest of the build.

thanks for your words of encouragement, DD, much appreciated.

The bad news is that the beautifully fitted box lid has just warped in the past 2 hours, and there is a 3mm gap on one corner of you hold the other 3 corners down. Happened when the temp reached 40degC , and the humidity dropped from 70% to 50%.

In addition to the lifting, the longer 300mm box sides have bowed inwards. It is the box itself that is bowed, not the lid, which is still flat.

Had been quite stable since the final leveling of the lid and box edges earlier this morning.

I would welcome any suggestions on how to fix this latest problem

This box is really a comedy of errors. I must list them as lessons to others, although most won't believe it

I've had bowed box sides before due to excessive clamping pressure along the long sides. That bowing introduced the warping you mention once the lid was separated. Were your clamps on too tight?

Paul

Hi Paul, yes, I clamped this very tight to pull the box together. It is only 10mm thick timber, so easily bent. This sounds like the real problem. Thanks for this information, another lesson learnt the hard way

Should have realized something was wrong when a couple of the dovetails didn't align, and had to be pulled in with clamps in a dry assembly, and the gaps in the corners closed up with glue and tight clamping.

The situation got worse overnight, this time with the lid warping, after being quite flat before. It is a 12mm piece of jarrah, 300x200, and the lid now has a 3mm gap on one corner when the other 3 corners are on a flat surface. Just like the base was the other day.

I think it is time to abandon this project and re-do it properly.

I reckon it could be the thick lid panel moving & pulling the rest of the lid with it. Generally try to keep lid panels fairly thin.

Thanks Alex. If I can get the box right ! Then I can put another lid on it, probably a frame with a 7mm jarrah panel. But the box has a 12mm jarrah base too, which is probably distorting and pulling the box, compounding the over-tension in the sides which are bowing inwards.

Probably best to start again, and use the lessons learnt

I'd encourage you to persist with this box. You can always use some cheaper hardware to finish it off. Then it will be your "practice" box on which to fit the hinges (and lock). But try to fit the hardware as if it were a perfect box. If you're not fitting hardware I guess you had planned to line and lip the box to hold the lid? If so, glue the lining/lip pieces to the bowed side(s) using some thick blocks as splints inside and outside the box to force out the bowing under clamping pressure. Cover the thick blocks in tape/plastic to stop them adhering the the box. I use cereal box liners. The splinting block on the outside of the box can be your bench top. Let the glue dry for 24 hours otherwise the bowing cold force off the lining inside of the box if the glue is not quite dry.

Like you, I've had tear-out when I've used a plane against the grain or used it too heavily set. Instead, I have a piece of 900x300mm 120G sandpaper I use if the base or lid rocks around a bit. Secure the sandpaper along one of the 300mm edges to a flat surface such as your bench top. Push the lid or base along the length of the paper applying more force on the high corners. Repeat until the piece doesn't rock anymore. Once the lid and base fit fairly closely together a little hand sanding just at the high spots will bring the pieces together.

If you secure the other 300mm side you could sand with a back and forth motion. I generally place a block of wood on the loose end to stop the paper rolling up on the bench and just push to sand.

Paul

Thanks for your help and encouragement, Paul, I really appreciate it. I have had the box and lid in an airconditioned bedroom room today and overnight to see if that impacts on it, then will see what tomorrow brings.

This is only my 2nd box I have made, the first has been finished in oil and trad Wax, and has remained quite stable in this heat and humidity. The dovetail joints were a breeze to fit together, no excess clamping required.

I particularly like the idea of using it as a practice box, especially to practice fitting the smartHinges.

Pretty hard to keep timber straight here in Townsville. For example at 6am this morning, it was 28.0 degC and 96% humidity, 3 hours later it is 35.0 degC and 30% humidity. Lots of changes going on in freshly dressed timber. If it rains during the day we will get high humidity and high temps