Heavy Duty, Mobile Shop Cart From a Sheet of Plywood

This is an instructible about building simple, but VERY strong mobile shop carts from a single sheet of plywood.

These will, easily, support 300 pounds. The one in the picture with a cabinet on top held nearly 500 pounds without so much as a creak or a groan.

One of the things that make this cart unique is, cutting the profile of the support legs out of the corners of the bottom of the cart and adding 5" x 5" blocks under the cut out profiles (the blocks lined up flush with the bottom corner edges, so the corners are square again).

This allows you to rest the supports directly on the caster mounting blocks, gives you more glue area for the supports, and helps keep the legs vertical during construction.

From start to finish, and depending on which options you incorporated into your build, building one of these will consume about a day. If you are building more than one, the time required for constructing each cart will be reduced, significantly.

I have nine of these carts in my shop. Each is sized according to the use to which it was put. For example, a cart in the pictures measure about 24" wide by 48" long by 34" tall, the height of my table saw top. When not acting as a horizontal catch all surface, the cart supports full sheets of flat stock being cut on my table saw. Another cart houses serves as my router table and houses my Porter Cable 3-1/4 horse router, BadDog lift and Freud fence. Yet another, shorter version holds my planer. Then there is my 1" belt sander, my oscillating sander, my four wheel grinder, over-arm pin router and so on.

The cart can be made as simple or elaborate as you desire. For example:

* You can add a back and sides to cart by cutting pieces of, for example, beadboard cut to just fit inside the cart (easiest done before the top and bottom are framed).

* You can cut pieces of solid wood banding to the same thickness as the plywood and edge band all visible edges not covered by the framed top and bottom pieces.

* You can use CDX (very rough) plywood, AC plywood (smooth on one side with holes filled with birds eye patches), or even oak or other high end plywood.

* You can cover the top in laminate, like Formica ( http://www.formica.com/en/ca/products/formica-lam... ). Of course, you can even cover the vertical supports and the bottom, if desired, for a more professional end appearance.

* You can adjust the size (width, length and height) of your cart to accommodate your needs.

* You can add drawers to your cart and make it into a rolling chest for storing sandpaper, tools or whatever you desire.

* If you needed even more strength (limited, primarily by the wheels you use), you could go with solid sides and back, versus the four corner supports. As well, you could extend the stiffners (horizontal trim to add strength to the top), or reduce it some, if you didn't need as much strength.

To build your own cart, you'll need the following tools and materials:

[TOOLS]

1) Table saw, or circular saw and guide system.

NOTE: You can make your own circular saw guide system using plywood by cutting a pieces just a little longer than the piece to be cut and wide enough for the saw to ride on, then adding a second piece on top and flush with the edge of the first. Of course, both pieces have to be straight. Running the saw down the guide, pressed against the second piece you added to the first, will trim it to the perfect width. From that point on, you only have to lay the guide on a line on the wood being cut to get a table saw quality cut.

2) Miter saw.

NOTE: This can be a hand saw and miter box guide system or an electric - your call.

3) Hand held saw. This can be an electric scroll saw or a good, old fashioned hand saw.

4) Hammer, or nail gun.

5) Air compressor [for the nail gun and if applicable].

[MATERIALS]

1) A single sheet of 3/4" plywood.

NOTES:

-The quality of the plywood is dependent, entirely, on how nice you need or want the cart to look, when finished.

- When writing this ible, I was making a 20" x 40" cart for my FlatMaster sander. Enough material was left over, after cutting the top, bottom and supports, I could have made a second cart nearly the same size.

To be sure I had enough material for a second cart, I would have cut the supports/legs first and used what was left for the top and bottom of the cart.

2) 1x3 or wider (e.g., 1x4) boards for the trim (think picture frame).

3) Glue

4) Nails (about 1-5/8")

NOTE: These can be finishing nails you hammer in by hand or brad nails for a nail gun. Either way, they need to be able to secure two 3/4" pieces of ply, so should be about 1-1/2" long.

5) Casters/Wheels

NOTE: I recommend at least four or even five inch wheels. The larger the wheels, the better they can tolerate rough floors. Too, larger wheels, generally, can hold more weight. For example, I built a box storage system to hold several hundred pounds of Acrylic and Plexi and used the only wheels I had handy at the time, 2-1/2" ones from Harbor Freight. One of the wheels has given up the ghost after just a little use. On the other hand, 4" casters on a cart which carried five hundred pounds are still doing great.

6) Screws to secure the casters/wheels (four for each wheel). These need only be about 5/8" long, which should be more than enough to secure the wheels. Because you have two layers of plywood on which to mount the wheels, longer screws that do not go through the two layers of ply would be fine too.

NOTE: If the screw heads would pull through the screw holes of the casters, you can use flat washers on the screws. Alternatively, you can install each screw at the extreme outer edge of each screw hole, so each screw is pushing out from the center of the wheel/caster.

Decide how you are going to use your cart to determine its finished height, width and length.

[MOBILE CART HEIGHT]

If you are going to use it to support wide flat stock being ran through a table saw, the top of the finished mobile cart, needs to be the same height from the floor as the top of your table saw. If you are going to be using the cart as a work table, you need to choose a comfortable working height for you.

When figuring the height of your cart, start with the height you've decided fits your specific use. Let's use 40" for this example.

From the 40" of our example, subtract the height of the wheels. Let's say they are 4-1/2" tall, that would leave us an an actual cart height of 35-1/2".

Now we have to determine the length of the four legs/supports, which, simply, requires you subtract the thickness of the top and the plate on which the wheels/casters will mount. If you were using 3/4" plywood, that would be 1-1/2". That would leave you a leg/support height of 34".

[MOBILE CART WIDTH]

Then there is the matter of the width of the cart. Your planer may require no more than a 20" width, for example. If making a hobby work table, you may want the cart to be a full 24" wide. Again, your call.

TIP:

The width of the finished cart will include the trim you used to hide the edge of the plywood. As such, if you use 3/4" thick stock to frame the top and bottom horizontal surfaces, the trim will add 1-1/2" (the sum of the two sides) to the width of the cart. As such and if the width is critical (e.g., the cart must fit in a tight space), you will need to subtract the thickness of the two trim pieces from the width of the plywood, when determining how wide to cut the plywood.

Of course, if the added trim thickness will not create an issue, you can just go with your original width measurements for the top and bottom of the cart.

[MOBILE CART LENGTH]

Like with establishing the width, you need to determine how long the cart needs to be. If you have limited shop space, you may want to limit the cart to the minimum needed. For example, I had my planer sitting on a 24"x48" cart, but wanted more room for other tools and equipment, so I dropped down to the minimum of what was required for the planer, which was about half as long as the original cart.

Again, as with the width, keep in mind the trim will add to the width, if that would cause an issue.

[SUPPORT LENGTHS]

To determine the length of the four supports (made from eight pieces, subtract from the total finished height the following:

- The height of the casters/wheels

- The thickness of the top (e.g., 23/32" or 3/4")

- The thickness of the bottom plate, which attaches to the bottom and on which the supports rest.

NOTE, the thickness of the bottom has no effect on the height of the cart, since the supports go past it, to the bottom plates.

[BOTTOM LEG/SUPPORT BLOCKS & WHEEL/CASTER MOUNTING BLOCKS]

These do not have to be a specific size, but I make mine at least 5" by 5" from scraps or a piece from what was left over after cutting the other parts.

Regardless of where your blocks come from, use at least 3/4" stock for strength.

1) Using the width and length dimensions you arrived at in the previous step, cut two pieces, one for your top and one for your bottom.

When cutting from a full sheet of plywood (48"x96"), you may want to made the length cut first (e.g., 48" wide, for a full sized cart). If you cut the 24" pieces first, then have to cut them in half, and presuming you are not using a sled on you saw, there would be more chance of binding the wood and getting a kick back. On the other hand, cutting a 48" wide piece to 24" widths poses far less risk of binding and a kickback.

2) From the remainder of the sheet, cut the four legs. They can be as wide as you wish, but should not be shorter than 3", for strength.

If the combined length of both sides of a support will be less than the width or length of the remaining pieces, you can cut long pieces, then cut them to length on the miter saw.

When done, you should have eight pieces of equal of the length determined in the previous step.

NOTE: I cut all eight pieces of the supports with a 45 on one side, to allow me to join them at a 90 and avoid a visible plywood edge at the joint.

As an alternative to using 45's for your joints, you could just butt the two pieces and, though it may not have as nice an appearance as the 45'd pieces, the supports will still get the same job done.


If taking this approach, you could reduce the width of one of the pieces of each support by the thickness of the pieces, so both sides would have the same width, when joined by butting the edge of the shorter piece against the wider piece. Otherwise, one side will be wider than its opposing side.

3) Use scraps or cut a piece from what was left over after cutting the pieces for your cart to make the four wheel-support/leg mounting blocks. As mentioned, make them at least 5" x 5".

Using your preferred glue, join the to pieces and nail them sufficiently to hold the pieces while the glue hardens.

Pin one end, then check for a good joint and work your way down. You should be able to press the ply to align it, BUT be mindful of keeping your fingers out of harms way. Nails often double back, when shot from a nail gun.

If need be, use a clamp to pull the 45 together, then pin the joint.

1) Consecutively number each support/leg "1" through "4."

2) Set one leg on each corner with the outer edge of the support/leg flush with the outer edge of the bottom.

3) Mark the number written on each leg onto the bottom to allow you to identify which leg goes on which corner.

4) Trace around each support/leg onto the bottom.

5) Using a hand held saw (e.g., electric scroll or jig saw), cut out the area of the bottom.


NOTE: Using a beefy blade, rather than a fine scrolling blade, is less likely to result in deflection of the blade, giving you better ninety degree cut angles.

Apply glue to each of the glue blocks and nail them to the underside of the bottom. The installed support blocks will look like the one in the picture (their edges flush with the corners.

For the best end appearance and to ease installation of trim or stiffners, you may find it helpful to use an L-square, to insure the blocks line up well (flush) with the bottom corner edges.

Install the wheels/casters to the plates you just installed.

Make sure you set the wheels back far enough that, when spun, they will not catch on trim, stiffners or banding covering the edges of the plywood.

Because you should have significant glue squeeze out from installing the support blocks, do not delay too long installing the wheels before going to the next step.

Add glue to the the support block, as shown in the picture.

Insert a leg with a number corresponding to the number written on the bottom and secure it with about three nails.

Repeat the process for the remaining three supports/legs.

Apply glue to the tops of each of the supports/legs.

Lay the top on the supports, aligning it with the edges as well as, reasonably, possible.

Pull or push the one of the supports or the top so that the edges of the top align flush with the support and nail the top to the support.

Work your way around repeating the process for the remaining three supports.

Installing trim over the edges of the plywood top and bottom will greatly increase their strength. The wider and thicker the trim, the more strength you will gain.

Using 3/4" x 2-1/2" material for your edging cut four pieces for the top and four for the bottom. Each piece should be the length of the side plus two times the thickness of your trim material whether you are using forty-five degree angles or butting the pieces.

Glue the pieces on for maximum strength. As with previous glue ups, secure the pieces with nails until the glue hardens.

For the best fit, start with one side and work your way around.

You can use a piece of scrap trim to check that the frame inside is positioned properly at each corner.