Replies

1. 
   DWRead | Dec 19, 2002 03:10am | #1

   Also, the thin edges keep fracturing.

   Janet

2. 
   johnhardy | Dec 19, 2002 03:24am | #2

   You don't describe your joinery or whether this box has a back ... and if so, how the back would be joined to the box itself.

   From your description, it sounds like you're trying to use screws to put the box together. I'd use glue and then put in the screws after the glued dried, if screws were needed.

   The simplest treatment for the corners would be to cut a rabbet on both ends of the left side and both ends of the right side. The rabbet should be wide enough for the top to drop in so that it is flush with the side. Let's take a theoretical box made of 3/4 ply. (I'll use a full 3/4 for this exercise, not 23/32, since it'll be easier on the math.)

   On each side, cut a rabbet at the top and the bottom, running from back to front, that is 3/4 wide and 3/8 deep.

   To put the box together, glue the rabbets and insert the top and bottom. I'd have the front of the cabinet facing the ceiling, so that the glue joints were vertical. Use clamps to get the joints tight (but not overtight), and use a rule to make sure the box is square ... opposing diagonals need to be exactly the same length.

   If the box is to have a back, I'd cut a rabbet on all four sides of the back so that the back slips inside the box, with the 3/8 edge treatment flush with the top, each side, and the bottom. If this is cut accurately, you could put the box together, including the back, and it should be square straightaway.

   If you feel you need screws, I'd install them after the glue dries.

   To find out if the sides are square, see 9441.2 (under General, topic "Can anyone find square").

   John

   
   

   ---

   Edited 12/18/2002 7:43:43 PM ET by johnhardy

3. 
   fredsmart48 | Dec 19, 2002 09:24am | #3

   First you need a square back that will hold the top and sides square.

   rabbit and dado joints give you stronger joints.

   Dry fit the box first to make sure the box is square before gluing.

   Now to check to see if you are square you measure diagonal from corner to corner both measurement should be the same.

   For that check to work both sides need to be length, both top and bottom needs to be the same width.

   When using screws you should predrill the holes it helps keep the wood from splitting.

1. 
   HONewbie | Dec 19, 2002 04:27pm | #4

   Okay, here's a related question.  I am building some simple boxes, approximately 14" square by 5" tall, with mitered corners.  The top and bottom are 1/2" and 1/4" plywood (respectively) set into grooves (not rabbets).  I spent a fair amount of time tuning my miter saw, but I'm sure it's not quite perfect.

   Anyway, what's the best way to clamp this?  I tried using blocks at the corners with 90 degree wedges cut out to fit around the corner, but that didn't seem to work at all.  The joints just seemed to squirm around.  Strap clamps around the box worked, but there were several instances where the strap was as tight as I could get it, but there would still be a gap at the joint that I could squeeze together by hand.

   I made it work, but I'm not satisfied that I made it work in the best way.  Any ideas?

   Bart

1. 
   Marcello | Dec 19, 2002 06:47pm | #5

   Bart,

   If you have the strap clamp on in the bottom, and a gap is on top, you can use regular clamps on top by slowly tightening them in two directions to close the gap.  A big factor in getting the mitter joints to work is the trueness of the table to the angle of the blade.  A jig for this is always better if you don't have a machinist square or angle to set the blade right.  A hand plane will also tune the mitered piece to fit if it is off slightly.

   Marcello

2. 
   fredsmart48 | Dec 20, 2002 02:45am | #9

   To make a clamping jig:

   you can cut a 2x4 to 3 1/2 long and make sure at least one end and one side is square. Now clamp the square side to the side and the top of box to the 2 x4 in the corner that will hold it in place. You can make two of the blocks front and back use 4 clamps that will keep it in place while you drill the holes.

    

   BUT ply wood splits easy when you put screws parallel to the face of the ply. A full dado will help keep the ply wood from splitting, use a small diameter screw also.

   Also in your case you may want to get some aluminum angle iron and put that in all the corners and use machine screws to fasten the top and the sides together

4. 
   DWRead | Dec 19, 2002 09:53pm | #6

   John, the back of the holder is hardboard, 11"w X 13-1/8"h X 1/8"thick. The instructions say to cut a groove 1/4" away from the back edge of the top, bottom, and each side piece, to hold the hardbaord.

   Fred, I don't have any problem squaring things up for the dry fit, but as soon as I start to drill the pilot holes, everything moves! Short of making a form that is the exact size of the inside space, and clamping the sides to the form, how do you hold everything steady?

   Janet

1. 
   johnhardy | Dec 19, 2002 10:13pm | #7

   There's still not much here in terms of description of the joinery. I do know from your last post that the back slips into a 1/4 inch dado.

   If we assume that you're using rabbet joints for the top, bottom, and sides, I'd still make sure it went together well with a dry fit, and then put it together with glue. I'd wait and do the drilling and screwing until the glue were dry, The box won't shift at that point.

   If you're bound and determined to screw this together first, I'd get two pieces of plywood which had a square corner. Drill out holes in the plywood so a small bar clamp or a C-clamp can be used. Take two sides, put them together, and use the two pieces of plywood to brace the inside of the corner, using clamps to pull it all together. It should be as close to square as you'd need, and be stable. Now you should be able to drill and screw this one corner. Next, take this subassembly and attach the third side to it in the same manner. After that's done, slide the back into the dados and attach the fourth side using the same method. It should work out just fine. But to me this is much more laborious than simply gluing up the box as one unit (while checking for square), and drilling/screwing later on.

   John

   Edited 12/19/2002 2:52:42 PM ET by johnhardy

1. 
   DWRead | Dec 20, 2002 02:01am | #8

   John, the instructions basically said "assemble as shown...use screws and glue as appropriate."

   I'm using screws but no glue so I can undo my work. Once it's glued, it will have its shape forever. I figure that it will hold together well enough with just screws.

   Janet

   
1. 
   johnhardy | Dec 20, 2002 02:56am | #10

   The joinery on this box is crude, to be blunt. These are just butt joints which have no strength except for the screws. Glue would do almost no good here.

   I'd suggest changing the joints from butt joints to rabbet joints. A rabbet is a groove at the edge of a board. Using 3/4 plywood for an example, the rabbet would be 3/4 inches wide and 3/8 inches deep. I'd glue the pieces together and if I felt it needed something extra I'd put in some finish nails in the corners ... going both directions. The rabbet gives you overlap so the nails can go in each direction. Or, you could try to use screws. Up to you.

   I also think this box would be stronger and would be more likely to stay square if you made the back as big as the outside dimension of the back side of the box, and had a 3/4 wide by 3/8 deep rabbet which ran around all four sides. This way the back would slip inside of the box, making a fairly tight fit, and it could be glued (and nailed/screwed) for additional support. Of course the back would be 3/4 ply instead of 1/4 hardwood, but it'd be much more rigid.

   John

2. 
   crt2cu2 | Dec 20, 2002 10:05am | #12

   DW,

   Several suggestions: biscuits or splines for the joints forget screws but consider a brad nailer (pinner) for ease and quickness of alignment.  Then (assuming cuts are square) everything should self reference when clamped.  But be sure to use the cross tape (diagonal) measure method.  Also, when clamping boxes try to offset your clamps.  That means put the head of one clamp one one side, apply gentle pressure then put the head of another clamp on the opposite side with gentle pressure.  Then, when all is square, snug up the clamps but not too tightly lest you distort the box squareness.

   sawick

2. 
   GeeSeaWhy | Dec 20, 2002 09:22pm | #14

   "as soon as I start to drill the pilot holes, everything moves! Short of making a form that is the exact size of the inside space, and clamping the sides to the form, how do you hold everything steady?"

   OK, so I'll guess you're trying to get the screw holes lined up by putting the top and sides together and drilling through the top into the side? If so, it won't work - you can't hold the pieces together steadily enough. Drill the holes through the top first. Now balance the top on the sides, put nails through the holes in the top and hit them with a hammer. Remove the nails and the top and make sure you can see where the nails marked the top edge of the side. That's where you drill the holes into the side and your only problem now is keeping the drill square so you don't come out the side of the side.

   HTH,

   Graeme

5. 
   JeffKurtz | Dec 20, 2002 07:01am | #11

   I've found a rather simple method for keeping things square.  On one corner of my assembly bench I have two pieces of 2x2 hardwood set perfectly square and screwed down to the bench.  I just push the pieces to be assembled/clamped tightly into the corner, and all comes out nice and square.

   Jeff

6. 
   DWRead | Dec 20, 2002 07:34pm | #13

   Now I remember having encountered this problem before, trying (unassisted) to assemble the sides of a gingerbread house. The butt joints were fastened with the culinary equivalent of brads and glue, i.e., toothpicks and white icing. Every time I used a toothpick, the joint moved out of square, the icing smeared, and the walls came a tumblin' down. What a mess.

   Those subconscious memories are probably the real reason that I haven't used glue on this current project (nor have I ever been tempted to make another gingerbread house).

   These drawers are handy and colorful, so I will be buying more. Next time, however, I will follow your suggestions for better joints and squaring jigs. Thank you!

   Janet