Replies

1. 
   oldusty | Sep 20, 2006 11:47pm | #1

   R- Chris ,

                    You don't say how tall the box is or what the application is kitchen / utility or tool storage or hardware or gold bars .

          In a kitchen standard duty drawer box this example is well within the normal and adequate range. Baltic Birch  ply seems stiffer to me than standard 1/4" plywoods .

      In kitchens I usually make what I consider large stacks of drawers to accommodate pots and pans and such , even plates and bowls . These run 28 - 36"in width across the face . For these I use 1/2" bottoms and 150lb capacity slides , you could almost stand in them . I have never had a failure .

        So the rating of the drawer slides will pretty much limit the capacity of the box in general . I still place my drawer bottoms in a groove on all 4 parts and glue them in .

                            good   luck     dusty

    

1. 
   Chris2 | Sep 21, 2006 12:21am | #2

   Thanks,

    

   I'm planning on making a stack of 10 drawers on 75lb. slides.  The drawers will only be 3" deep to hold small hand tools.  Even if I have a drawer full of c-clamps I wouldn't expect the maximum wt. in a drawer to exceed 35lbs.  I've never used or made a 20"w drawer and wasn't sure if unsupported 1/4" was good enough for the bottom or if I needed a brace or 1/2" mtl. to prevent sag. 

1. 
   cadiddlehopper | Sep 21, 2006 12:56am | #4

   I'm curious as to why there are 3 and not 4 dadoes. Whether it fails or not, leaving the fourth side unsupported is a curious design feature. Even if a dado is impossible to make for some reason, some other support feature seems appropriate -- maybe a glued on cleat or even screws in tension.Cadiddlehopper

1. 
   mudman | Sep 22, 2006 05:43pm | #14

   There are two main reasons for 3 side dados on drawer bottoms. First it is a lot easier to install the bottom. And more relavant for today, the concealed undermount style slides require large notches on the under side so is is easier to rip the drawer back dado off than to  cut the notches.

    Pardon my spelling,

   Mike

   Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.

1. 
   K1500 | Sep 22, 2006 11:17pm | #17

   In addition, if the bottom ever gets damaged, you can slip it out and replace it with a new one without having to destroy the drawer.  This assumes you don't glue the bottom in the remaining 3 grooves.  Simple slip the bottom in from the back and secure it to the back of the drawer with a few screws. 

   This can be handy in shop cab's where sharp tools can cause damage and and nasty adhesives and other goops can spill and ruin a bottom.  For shop cabnets, 1/4" Masonite works fine for me with no appreciable sag, and I'm not afraid to load them up.  If you go to 1/2" you can rabbet the edges to fit in a drawer side with 1/4" grooves, thus not losing any space (as another poster already mentioned).

2. 
   JohnWW | Sep 21, 2006 12:43am | #3

   There is no appreciable creep with plywood, so that isn't a factor.  For an average load 1/4" ply would be adequate for that size drawer.  If in doubt why not make a rough test box?  As someone else posted, supporting the bottom with dados on all four sides will add to the stiffness.

   John White, Shop Manager, Fine Woodworking Magazine

3. 
   douglas2cats | Sep 21, 2006 12:57am | #5

   This site might help

   http://www.woodbin.com/calcs/sagulator.htm

    

   If you build it he will come.

4. 
   JeffHeath | Sep 21, 2006 02:19am | #6

   Chris

   The cost difference between a sheet of 1/4" and 1/2" baltic or apple ply is negligible compared to the solid benefit received from the thicker bottom.  The only time I use 1/4" is for jewelry box drawer bottoms.  I think that if you asked any pro on this site who builds custom cabinets for a living, none use 1/4" unless their running a processing center competing with home depot.  You'll be much, much happier with 1/2" bottoms.  As Nike says,  "Just Do It!".

   Jeff

5. 
   Chris2 | Sep 21, 2006 05:43am | #7

   Good info thanks.  I like the magical sagulator!  These drawers are going in my garage where there's is almost daily a large humidity change 80% rh in the a.m. and 30% rh in the p.m. so I was thinking a traditional 3 sided dado to allow movement. A 4th side dado with a 1/16" for movement is a nice option. Then in my market a 5'x5' 1/2" baltic sheet is about $7.50/sheet greater than the 1/4" sheet so that's another $28 in mtl. Not to bad. then the biggest drawback to using 1/2" in my opinion is the loss in drawer depth.  If I only have a 2.5" or 3" deep drawer I loose one drawer for every 5 high stack with 1/2" bottoms vs. 1/4"  bottoms.  That would bring my stack of 10 drawers down to 8 or for two stacks I'd loose 4 drawers.   

    I'll probably go out into the shop and weigh the contents of my existing drawers sharpen the pencil on the layout and build a test box this weekend and then make a decision.  I have enough info now. Thanks.

1. 
   BarryO | Sep 21, 2006 08:16am | #9

   You could go 3/8" (9 mm) and split the difference. ;)

2. 
   douglas2cats | Sep 21, 2006 02:59pm | #10

   You could reclaim some of that lost drawer depth by not using a full wdith dado for the drawer bottoms. Use the 1/2" BB ply and rabbet out the underside to leave a 1/4" tounge all the way around. Then put a 1/4" dado in all 4 sides, 1/4" up from the bottom. Someone on another forum recommended this method when I was making some large tool storage boxes out of 1/2" BB and it worked great. All the stiffness of a thicker bottom but it's flush with the sides at the bottom. You will need to do stopped dado cuts on 2 of the sides though or risk seeing the gap at the corners.

    

   If you build it he will come.

   Edited 9/21/2006 8:01 am ET by douglas2cats

   Edited 9/21/2006 8:02 am ET by douglas2cats

3. 
   trialnut | Sep 21, 2006 05:33pm | #11

   "If I only have a 2.5" or 3" deep drawer I loose one drawer for every 5 high stack with 1/2" bottoms vs. 1/4"  bottoms.  That would bring my stack of 10 drawers down to 8 or for two stacks I'd loose 4 drawers."

   With the differance between 1/4" bottoms and 1/2" bottoms I think you lose 1 drawer for every 10 rather than 5, or am I missing something. 1/4" differance per drawer times 10 = 2.5".

   RichThe Professional Termite

1. 
   Chris2 | Sep 22, 2006 01:22am | #12

   That's correct.  I figured that error out this a.m.  and loosing one drawer in a stack of 10 ain't that bad. That means I'll only have two unused slides instead of 4 and these won't go to waste.  I'm already thinking about putting a couple of pull out trays in the bottom of two of the neighboring cases that have cabinet shelves.  So now it's a no brainer. I'll be going with 1/2" drawer bottoms.  Once again it's proven that a little bit of thought and communication solves most issues.

   Thanks Everyone and Regards,

    Chris

1. 
   cadiddlehopper | Sep 22, 2006 04:57am | #13

   You did not mention the material used for drawer sides & ends. If it is also BB ply, douglas2cats gave you a very fine idea. Furthermore, using his design idea, you could glue up the entire drawer bottom since all parts are the same material with bidirectional grain. You would have very solid drawers. Something you said makes me think that you would glue the bottoms on one edge anyway, though I don't know why you would do that. If you are using all BB ply, what joint goes from end to side?LOL!!Cadiddlehopper

4. 
   RonT | Sep 22, 2006 08:04pm | #15

   Give it a true test.

   Put four runners on the floor forming a square, (your drawer sides), cut your 20X20X1/4 plywood, set it on the runners and stand in the middle. For sure your tools don't weigh as much as you do.

   You'll be surprised at the results.

1. 
   oldusty | Sep 22, 2006 08:49pm | #16

     RonT ,

                   Not so sure the test you mention would be applicable unless you only weighed 75lbs as that I believe is the type of slides the OP is using . He felt he would only have maybe 35 lbs in each at the most I think .

1. 
   RonT | Sep 25, 2006 05:21pm | #18

   I agree with you, the test is overkill; however, if it will support you without fracturing, and I believe it will, it will also hold 35 pounds which is nothing. I believe the concern is overstated as is the advise to go to 1/2". But, when in dought give it a tough test.

1. 
   oldusty | Sep 25, 2006 10:18pm | #20

     Hi Ron ,

                       I also agree that 1/2" is over kill for this particular  35 lb application . It won't hurt to use 1/2" but imo is not necessary . A 1/4" bottom captured on a slot and glued in should be more then adequate . He could also glue a support under the bottom to stop any sagging . Say 1/2" X 1" or so in any direction .

                                dusty

2. 
   RonT | Sep 25, 2006 11:23pm | #21

   Oldusty

   This kind of dialogue is good for future reference.

   <!----><!----> <!---->

   I build drawers sides from pine milled to 5/8” and a 3/16” deep dado in the sides for the runner. The drawers are nice and solid and carry plenty of weight; 1/4" bottom incidently.

    

6. 
   seb | Sep 21, 2006 06:02am | #8

   20" is on the edge ... as Dusty said "use 1/2" and be sure,,,
   Bud

7. 
   alfie | Sep 25, 2006 07:46pm | #19

   Over the years I have made many drawers, all dovetailed. The early ones are, and feel, thick and heavy. I gradually began to appreciate the feel of just-right drawers, in terms of weight and thickness. I use 1/4" bottoms, even for shop drawers that are loaded, and have had no problems. I also try to keep the drawer sides, as well as front and back, as light as they can be without feeling flimsy. Once all the parts of a drawer are in place, they support each other and provide rigidity and strength to the drawer.

8. 
   hammer1 | Sep 26, 2006 05:08pm | #22

   I repair or restore a lot of old furniture. I've yet to see a 1/4" bottom that wasn't bowed down, regardless of the size.

   Beat it to fit / Paint it to match