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View RichNew's profile

The strongest way to make plywood drawers?

by RichNew
posted 08-11-2016 12:59 PM


26 replies so far

View jmartel's profile

jmartel

8467 posts in 2545 days


#1 posted 08-11-2016 02:11 PM

Pocket screws would not be the correct application here. I would do rabbets going into dados. Additionally, 1.2m is a long span. Even with a 200mm deep drawer, I would still expect some sagging over time with that much weight. If you can, break that up into 2 drawers.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View RichNew's profile

RichNew

3 posts in 1050 days


#2 posted 08-11-2016 02:19 PM

So you’re suggesting the below method? I assume i would then glue and screw the joints? I see some people saying the base should be left floating in the dado’s though, which doesn’t sound as strong to me?

———- The photo isn’t resizing for some reason, but my right clicking and opening in a new tab you can see it all———-

I would, but with the drawer slides costing £120 per slide, i’d rather not add a 3rd drawer.

Not sure i have got my dimensional terms right either, so going by the photo below, the dimensions are;

Depth – 1200mm
Width – 750mm
Height – 200mm

Thanks for the help
Rich

View Redoak49's profile

Redoak49

4007 posts in 2384 days


#3 posted 08-11-2016 03:04 PM

That is one huge drawer!! I would use 18 mm Baltic Birch plywood with rabbet corner joints. I also would reinforce the corners with blocks on the inside and 18 mm plywood for the bottom I would glue and screw it in place.

Good luck with it.

View woodbutcherbynight's profile

woodbutcherbynight

5966 posts in 2804 days


#4 posted 08-11-2016 03:07 PM

The drawer you wish to make is HUGE, the weight you expect it to handle is on the high side. Pocket screws alone are not going to bear the weight load you wish to achieve. Most mechanics toolbox drawers made by the likes of Snap-ON and MAC can handle 45-65kg of weight. These are made of metal. But your measurements are much bigger than the average toolbox drawer. My suggestion would be to make a wood / aluminum hybrid drawer. Use hardwood for the drawer frame and a piece of aluminum minimum 3mm thick for the bottom. Put a brace in the middle to help with stability and weight distribution. Attach from the bottom with 50mm screws spaced 100mm apart. Or have a custom aluminum or steel drawer built to your specifications and go from that point forward.

A second approach might be to break down this into a series of 2 or 3 smaller drawers bringing the weight per drawer down to allow for drawers that can easily handle 45-65kg. The advantage would be more organized drawers with less chance of a blow out of the bottoms. The disadvantage is more drawers equals more space used for drawer slides and support which also means less available storage space.

-- Live to tell the stories, they sound better that way.

View 000's profile

000

2859 posts in 1294 days


#5 posted 08-11-2016 03:47 PM

I wouldn’t over think it.
I would use 3/4 plywood for the sides and the bottom.
Butt joints, use glue and screws.
Slap a bottom on with glue and screws.
Maybe even adding a divider or 2 to would help with strength.

View RichNew's profile

RichNew

3 posts in 1050 days


#6 posted 08-12-2016 07:42 AM

Interesting, so varying opinions then!

Yep, putting in dividers i a good idea as surely that has to add a lot of strength?

Will just screwing a base to the bottom be strong enough?!

Thanks again
Rich

View woodbutcherbynight's profile

woodbutcherbynight

5966 posts in 2804 days


#7 posted 08-12-2016 01:32 PM

Two lines of thought on attachment of the base.

1.Yes you can screw it to the bottom and any additional support you put in the middle. Advantage is that if something happens you can take it back apart and repair with relative ease.

2.Screw and Glue it for the maximum amount of strength possible. Downside, you will not be taking this apart with any kind of ease and most likely will damage it badly.

Hope this was helpful.

-- Live to tell the stories, they sound better that way.

View Dabcan's profile

Dabcan

255 posts in 3066 days


#8 posted 08-12-2016 01:47 PM

Few thoughts from me:

- that drawer alone is going to weigh at least 20kg, maybe more.

- adding dividers will strengthen it significantly, especially if you screw up from the bottom into them, will eliminate sag over time. Also, it will stop some tool from rolling all the way to the back of the drawer when you are trying to find it, so much better organization.

- 12mm is plenty for the bottom, especially if there are dividers, the rest can be 18mm

-if the slides are bottom mount, this will increase the strength as well

- lastly, since you have some metal work ability, why not glue and screw the drawer using butt joints, then take some aluminum angle iron and reinforce the corners? This would add a ton of strength and some durability as well.

Sounds like a fun project, do post some pics along the way!

-- @craftcollectif , http://www.craftcollective.ca, https://www.etsy.com/shop/craftcollective?

View jdh122's profile

jdh122

1073 posts in 3213 days


#9 posted 08-12-2016 01:57 PM

Plywood bottoms screwed and glued are plenty strong. Check out Mathias Wandel’s testing video on the subject: https://www.youtube.com/watch?v=co3EH8WZsX8

Like Dabcan just mentioned, if you get slides that are bottom mount then there is very little stress on the side to bottom joint anyway.

-- Jeremy, in the Acadian forests

View TheFridge's profile

TheFridge

10858 posts in 1881 days


#10 posted 08-12-2016 02:05 PM

Box joints

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View gargey's profile

gargey

1013 posts in 1171 days


#11 posted 08-12-2016 02:11 PM

Dip it in molten steel

View MrRon's profile

MrRon

5501 posts in 3639 days


#12 posted 08-12-2016 05:09 PM

I’m guessing you are located in Africa. Obviously you will be obtaining your materials locally. Like others, I would recommend Baltic Birch plywood, but I don’t know if it would be available where you are. Here is an idea that costs less than drawer slides. http://images1.mcmaster.com/mvA/contents/gfx/large/1714a1p1-h02d-digitall.png?ver=1452150666

View woodbutcherbynight's profile

woodbutcherbynight

5966 posts in 2804 days


#13 posted 08-13-2016 03:51 AM



Dip it in molten steel

- gargey

ROFLMAO

-- Live to tell the stories, they sound better that way.

View TheFridge's profile

TheFridge

10858 posts in 1881 days


#14 posted 08-13-2016 03:55 AM


Dip it in molten steel

- gargey

ROFLMAO

- woodbutcherbynight

Most of the time I don’t like him, but that was pretty good.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View JIMMIEM's profile

JIMMIEM

43 posts in 1237 days


#15 posted 08-13-2016 12:22 PM

Corner joints glued and screwed will be good. With good ball bearing slides there won’t be that much strain on them. I’d do a fully captured drawer bottom i.e. insert into grooves and dados on front, back, and both sides. I would increase the thickness of the drawer bottom.

View skatefriday's profile

skatefriday

452 posts in 1878 days


#16 posted 08-13-2016 03:28 PM

I’m in the make it two drawers camp. Blind rabbet joints and a dado for the drawer bottom. 12mm baltic birch for the sides. 5mm mdf for drawer bottom. Pocket screws would be a mistake I think.

View clin's profile

clin

1035 posts in 1391 days


#17 posted 08-13-2016 10:58 PM

Strongest, or strong enough?

As mentioned, simply gluing the bottom on is known to be strong enough. It’s probably a lot stronger than a typical drawer where the bottom is slid into a dado, but not glued.

I think you can make the one big drawer, but absolutely would add the dividers for additional structure and support. However, unless I really had a need for a drawer that big, I’d also go for two. You have to be able to pull the drawer open. Might be hard to pull one big, wide, and heavy drawer open with one hand.

I would also glue the bottom on and would not rely on just screws. In fact, when gluing, I’d just use brad nails. Once the glue dries, it’s the glue doing the work. Also, with screws only, keep in mind that screws are also very weak going into the edge of plywood.

You could consider using the pocket screws on the corners. But, while fanciers corner joints take a bit more time, they also tend to be self aligning making assembly easier. Butt joints (pocket screws or not), always seem to want move around once you get glue on them.

Another vote for Baltic birch plywood.

-- Clin

View marshallmosby56's profile

marshallmosby56

18 posts in 1075 days


#18 posted 08-20-2016 06:04 PM

Maybe dovetails would help you make it nice and strong at the same time. Consider if you are flexible with ideas

-- :)

View Loren's profile

Loren

10477 posts in 4043 days


#19 posted 08-20-2016 06:12 PM

Dovetails are generally overkill for strength but in this
application you might consider them.

Another good way to do it if appearance isn’t critical
is rabbeting the corners and drilling holes from
the outside and putting pegs in after the glue for
the rabbet has set.

In terms of the drawer bottom, I would probably just
glue and nail/screw on a 1/2” bottom for this application
as a floating bottom is not required and there’s no
aesthetic reason to make the drawer appear like
it’s made in the traditional way… also in kitchen
drawers a 1/4” floating plywood bottom is light
weight and cheap in terms of materials cost.

Sometimes in carpenter-built solid wood drawers
in old houses you’ll find a bottom nailed on but
never have I seen it glued… in any case, those
guys did it that way because they didn’t have
cabinetmaking tools on hand and perhaps were
even working with mostly hand tools, depending
on the age of the house.

View marshallmosby56's profile

marshallmosby56

18 posts in 1075 days


#20 posted 08-31-2016 06:39 PM

Dado joints are going to make this a whole lot stronger, In my view you should really consider grooving the horizontal and vertical planks together using this dado/groove joints.

-- :)

View gargey's profile

gargey

1013 posts in 1171 days


#21 posted 08-31-2016 06:46 PM

Glue a stack of sheets of plywood together, then use a router to dig the drawer cavity.

View 000's profile

000

2859 posts in 1294 days


#22 posted 08-31-2016 06:48 PM



Glue a stack of sheets of plywood together, then use a router to dig the drawer cavity.

- gargey

How wide of an edge do you recommend leaving, and should he run some all thread all around the edges as well?

View 49er's profile

49er

174 posts in 2000 days


#23 posted 08-31-2016 08:58 PM


Box joints

- TheFridge

I agree, box joints. They are nice and strong. However, ya do need a table saw and a jig.

View JoeinGa's profile

JoeinGa

7741 posts in 2402 days


#24 posted 08-31-2016 09:54 PM

Wooden Drawers? Hmmm, sounds VERY UNcomfortable !
.
.
.

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View TheFridge's profile

TheFridge

10858 posts in 1881 days


#25 posted 08-31-2016 11:37 PM


Box joints

- TheFridge

I agree, box joints. They are nice and strong. However, ya do need a table saw and a jig.

- 49er

Or a router table

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Mike_D_S's profile

Mike_D_S

595 posts in 2610 days


#26 posted 09-01-2016 04:16 AM

This post is full of opinion and redneck pseudo science, you have been warned!

I’d second Loren’s suggestion. Drill 1/4 holes through the side into the end of the front/back panel after the basic joinery glue up dries. Then add some glue and drive in oak or other hardwood dowels. I’d have to do a test, but I’m guessing that three 1/4 inch oak dowels every two inches (50 mm) over 200 mm would probably have an effective shear strength without glue of well over 200 lbs even in plywood.

If you do the math, the shear strength of red oak is approx 1390 psi and a 1/4” dowel being approx .2 sq in area, so on paper the shear is 272 lbs. Given the dowels probably won’t be loaded perfectly equally, derating them to 33% of theoretical still gives 90 lbs per dowel, so 270 lbs for the three, not taking into account any glue, etc.

Still a long way from 250 kg, but if you figure the weight will be distributed, then you might actually be able to pull it off.

But in reality the box joints won’t carry any of the weight. The drawer bottom transfers the weight to the sides which in turn transfer to the slides. The front and back joinery is just for show in terms of the static load. It only matters when you brake hard and all that gear goes crashing into the back of the drawer.

So my vote would be 3/4” ply in a 3/8” dado 1/2” from the bottom of the side. I use this basic joint for my rolling tool carts and have on occasion kneeled or sat on the tops of a few of them which are essentially 3/4” ply 27” wide by 20” deep and supported by the rabbit on the sides only. If it’ll hold my 110 kilo frame without much flex, then I think you can pull it off.

You’re only saying 750mm wide (+-27 ish inches), so I think you’ll be ok, but for the long term trying to glue and screw the bottom to the sides may not work out. With the drawers loaded and driving down the road, I’d be concerned that the glue joint would eventually fail just from the fatigue and the little bit of deflection on the bottom putting the top of the glue joint for the ply bottom in tension all the time while its flexing as you move on down the road.

I think the dado joint is mechanically strong enough as long as the sides don’t flex and this you could control with a few crossbars of 1/2” hardwood maybe 3” wide with a big single dovetail on each and and the matching receiver in the sides. A couple of screws to keep that locked in and I think you’ll be almost bombproof for the bottom.

I’ve made a few SUV storage boxes for gun and ammo storage (similar to Truck Vaults) and they have big drawers. I basically use the same ply/dado construction with 1/2” ply bottom and 3/4 ply sides (no crossbar though) with a few brads nailed up from the bottom to lock the ply bottom in. I’ve loaded them with a few shotguns and 6 flats of shotgun shells which ought to be in the 200 lbs range and they seem to take it fine.

Here’s a pic, it’s not the best but only one i have handy.

Post pics when you’re done!
Mike

-- No honey, that's not new, I've had that forever......

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