Intro: CrossFit Style Plyo Box (Table Saw)
This was a project I embarked on because I thought it would be quick and easy. I wanted something I thought I could finish in a single trip to TechShop. With a little more planning I could have done this but it would have been a long day so it ended up taking me 2 days or roughly 8 hours. I ran into a few problems with my design and available tools but it wasn't a big deal.
1 sheet of 3/4 in plywood (4'X8') I chose birch
Screws (I had 2.5 in outdoor screws lying around that I used)
Drill - bits and countersink
Jig Saw/Scroll Saw
Optional - Clamps
Step 1: Modifying the Design
I searched for a few designs out there and found a few good starts. Ultimately, I wanted something I liked.
I found a site has a step by step for their plyo box but there were a few things I didn't like. I used their original layout found in the PDF and modified it for my use based on other designs I saw.
The Rogue Box pictured in this step is what I modified the above plans to match. I like the interlocking pieces and am familiar with them from my own crossfit work outs, I was also curious why they cost $150 to buy!
To modify the design, each piece extends to the full extent of the box dimensions.
So: Two 20" X 30" pieces, Two 20" X 24" pieces, Two 24" X 30" pieces
I chose to make the pockets for each piece a different size. For a 30" long side, the pocket was 10". For a 24" side the grove was 8". For the 20" side, I decided a 6" pocket with two 7" sides was easiest to track, measure and cut.
The sketch is my poor mock up to track the pieces and how this was all laid out.
Step 2: Acquiring the Materials, First Cuts
I don't have a big car so I was curious how I would get a sheet of plywood to TechShop. Home Depot will do two cuts for free on their panel saw so based on my measurements I needed two 30" long cuts across the 48" width. I went to Home Depot and had them cut to 31" twice to give myself some room for error. These pieces fit in my car great!
So I went to TechShop with three pieces at 48" wide, and different lengths over 30" but under 33" that could be trimmed down to the sizes listed before.
On the table saw I cut one piece straight down the middle of the 48" to get two 24" pieces. These were then trimmed to 30" on the other dimension. The plywood was 48 1/8th across so the table saw took off the perfect amount.
The other pieces were easier to trim to their respective 20X30 and 20X24 in. sizes. Follow the rough outline on the pdf for a guide.
Table Saw tips: remember to use a safe blade height with the wood and stand to the side. You shouldn't need anything to push the wood through the table saw but keep your hands away from the blade to be safe.
Step 3: Cutting the Joints
I moved over to the band saw to cut the joints on the pieces. This is better than the table saw or a miter saw because you get the perpendicular cut through the material rather than a graded cut from a circular blade.
I first used a T square to draw out the joint cuts on each piece. These joints are 3/4" deep and varying widths based on which side of which piece you were cutting. I marked each piece I was cutting and disposing vs. the ones I was keeping.
Note: not every piece of plywood is the same thickness. Measure and get your thickness to determine the depth of your grooves. 3/4" should be close enough though.
On the band saw I cut the pieces that would have the discarded wood on the outside first. I cut into the groove to the line at a few intervals (on a band saw you don't want to be too deep into a cut so you cut into it every 5 inches or so) and then cut along the line to get rid of the pieces.
Step 4: Problem With the Joints
The inside joints gave me some difficulty. The band saw is not made to do sharp turns (especially with a wider blade that I had) and my pieces were long enough and wide enough that I couldn't cut into the joint the reverse way because they hit the band saw arm. I had to line out the joints on the reverse side on every piece to be able to flip them over and cut into them.
Note: at one point I set a guard to run my pieces against to keep the depth of the groove consistent. Unfortunately there is also a little give to most band saws and I didn't end up with the most clean cuts.
Step 5: Sanding the Edges
When jumping on a box for box jumps the last thing you want are sharp corners for your shins to get ripped up on. The other thing you will notice is the "stings" attached to the board. I cleaned up the edges of all my boards with a belt sander set at 90 degrees.
I also 'rounded' the edges of all my outside corners to prevent the above-mentioned shin damage. To do this I set the disc sander to 45 degrees and applied the edges to the disc sander. Safety Note: When putting wood onto a disc sander make contact with the disc on the downward side. If you come into contact with the other side first your material can flip up out of your hands and hurt you.
Step 6: Assembly...almost
I fit the box together a realized the inaccuracies of the band saw were going to be an issue. There were some gaps at most of the joints because I didn't get the depth of the grooves exact. I put the box together with some clamps and drilled all my holes with the pieces lined up against the table. This way that once the screws were inserted the box would be flush on the outside, if not necessarily everywhere else.
I also used a countersink bit after I drilled all the initial holes. This will allow for the screws to sit flush and won't catch on a shoe or clothes.
Step 7: Laser Engraving for Fun
Another limitation I had with the shop was no jig saw or scroll saw. I decided I would laser engrave a pattern on the side of the box and try to cut the handles through the wood. The wood proved to be too thick but the rastering turned out nice.
Here are the specs on my laser settings:
Raster: Speed/Power - 45/90
Vector: Speed/Power/Freq - 10/90/500
Note: Do not cut through wood more than 1/4" thick. As you can see in my pictures, I burned the wood pretty badly. The laser is not meant to cut through thick wood. I tried to fudge it by nudging the table of the laser up, thinking it would just engrave deeper. It did, but not as neatly as I thought it would.
Step 8: Cutting the Handles
I drew the outline of the handle that I wanted to cut and drilled a hole through the middle of the wood that would be discarded. This hole allowed me to use a hand jig saw to cut the handles out. I did a rough cut and didn't worry about being too neat. I used sandpaper to clean up my edges and smooth the edges of the handles so I wouldn't get splinters.
If I had wanted to be super neat I would have laser engraved the outline for where to cut.
Because of my failed attempt to laser cut through the wood I had to clean up my burnt edges with the jig saw.
Step 9: Final Assembly
Some of the gaps that were visible initially were closed in part by the screws. There were still some gaps in general.
To assemble the box I interlocked all the pieces and started screwing from the top, down. The pre-drilled holes really helped line up the edges of the box. Sanding the edges of the box after it is fully assembled will help keep the jumping surface as smooth as possible.
...and remember, I made it at TechShop!