"Yeah, it's strange that they don't make a circular saw that just snaps into a table so you can use it as a table saw."
And thus the seed was planted. I remember at the time I brushed it off, but a few days later a friend and I decided to sketch the plans out for one and try to make one with three criteria:
1) Make it cheap.
2) Design it so that all you need to build it is a drill and a circular saw.
3) Design it so that you can easily remove the circular saw when needed.
The video below is a time-lapse of us building our Circular/Table Saw over the course of ~4.5 hours. We were planning as we built, so I am confident that this could easily be replicated in 2-3 hours.
Step 1: Materials
Circular Saw (More on this ahead)
1/4" 20 Machine Screws
1/4" 20 Wingnuts
1/4" Lock Washers
2" Wood Screws
3" Wood Screws
3 2x4's (Pine)
2 1/2x1's (Pine)
2' by 4' sheet of particle board
Everyone has their own method of selecting lumber, we like to look down the length of the wood and search for warping. Sometimes I like to lay the wood on the ground and see if it rocks or falls over, but this method requires the floor is even. Finally, make sure there aren't too many knots.
All in all, this project should cost less than $70. That's including the cost of the circular saw and all components (but assumes you own a drill and the necessary drill bits).
Step 2: Examining the Circular Saw
You can use pretty much any circular saw, but I prefer the Craftsman evolv for three reasons:
1) It's light. At around 7lbs, this saw is at least half as light as other circular saws. Since we are planning to suspend this saw upside down, we want it to be as light as possible.
2) It's cheap. Hey, if I wanted to spend big bucks, I would blow it on a top of the line table saw and a separate circular saw. I'm not a professional contractor, just a guy that likes to work with wood and has limited space/budget. At $39.99, the evolv definitely meets my needs.
3) It's CRAFTSMAN. Sure, I could have saved a few bucks by buying a Harbor Freight circular saw, but I want my tools to last. I've had good experiences with Craftsman, so I'll stick to them when I can.
Reasons explained, we have a fairly standard circular saw. It's nice and light, and uses a 7" diameter blade.
Step 3: Cutting the Tabletop
The first thing we want to do is measure and cut our tabletop. We want the working surface (right of the blade) to be larger so that we can rest wider objects (such as plywood) on it when cutting.
As shown below, we marked out a 20" length and set up a guide with a piece of angle aluminum and a few table clamps. What did we cut it with? The circular saw, of course!
Step 4: Modifying the Circular Saw
This is where things can start to get a little dicey. We need to drill some holes in the guard plate of the circular saw so that we can secure it to the bottom of the tabletop. Start by removing the saw blade so that you can retract the guide and lay it flat on some scrap wood.
Use a 1/4" drill bit to drill holes in the four corners (more or less) of the guide plate. Make sure to deburr the holes after drilling; failure to do so could keep the circular saw from sitting flush against the underside of the tabletop. If you do not have a deburring tool, you can use a larger drill bit in it's place.
Step 5: Mount the Circular Saw to the Tabletop
We want to mount the circular saw to the larger tabletop piece, so we'll start by marking out the center. Since we'll be mounting the saw to the bottom side of the tabletop, make sure you make all your marks on the rough side (if there is one).
A table saw with a blade that won't angle isn't very useful, so we'll set the blade to the deepest angle desired (in our case, it was 30), and push it against the edge of the tabletop. We then clamped the circular saw to the tabletop and drilled through the tabletop (using the holes we drilled in the guard earlier as a guide).
We then did a test fit of the 1/4" 20 machine screws and wingnuts. Everything should be nice and tight, with no wiggle (or wobble, obviously). If there is a vibration, flip the board around and use the other end. Having a wobbly blade on a table saw is just a bad idea, so do it right!
Step 6: Build the Frame
Now that we have an idea where the circular saw will be mounted, we can build the frame for the underside of the table. Start by measuring and marking out the distance in from the edges of the table you want the frame to be. We went with 2" on the long edge, and 6" from the ends.
We are just making a simple box frame, so you can either detach your circular saw to cut the 2x4's to length, or use a chop saw (as we did). Once you have the 2x4's cut to length, square up the outer frame and drill some holes to prevent the screws from splitting the wood. Using a piece of scrap wood to keep things in line on the outer edge can be extremely useful.
Once you have the outer frame, attach the inner supports. Make sure you leave enough clearance for the saw blade to tilt and angle. Finally, put the support beam that will be attached to the smaller side of the tabletop close to the edge, to provide additional support.
Step 7: Cut and Attach Legs
This is where it's nice to have a friend to help you. Start by cutting 2x4's to length, with a 15 degree cut on one end. Standard work surfaces are 32" high, so we settled for 31" long segments of 2x4 (from longest end to end).
Line the square end up to the frame as shown below and secure it with a single screw. Repeat for all four legs, and then make small adjustments until everything is level. Have your friend hold everything steady while you add a second screw to each leg.
Step 8: Brace the Legs
Next, we want to brace the legs with the 2x1's. Start by cutting a piece to length that will span the gap between adjacent legs (on the short side). Make sure everything is level, mark it off, and screw them into place. Don't forget to pre-drill your holes to prevent splitting!
In order to prevent torsional motion, we decided to cross brace the back side of the table. For some reason, I don't have a good photo of this, so I've grabbed a screenshot from the time lapse. We found it easiest to use a full 8' length of 2x1, screw it to the frame, and cut off the excess with a hand saw. The front end of the table is braced with a single horizontal beam.
Step 9: Tabletop
First, sand the edges. We don't want any rough edges catching wood we are trying to cut. Keeping in that mindset, we will need to countersink the screws to keep the surface smooth. As shown below, choose a drill bit that is the slightly larger than the head of the screw, then mask the required depth with a piece of tape. If you aren't careful to gauge the depth, the tabletop will not support the circular saw. To keep from drilling too deep, we filed the ends of the 1/4" 20 screws down by a couple of millimeters.
Next, we need to attach the circular saw to the other table surface. Flip the tabletop over and measure an appropriate gap (we went with 3/4"), then drill the necessary holes using the holes we drilled in the guard plate as a guide.
After this is done, flip the tabletop back over and position it in the correct place. Then, mark out the position of the wood screws to correspond to bottom frame, pre-drill your holes, countersink them, and secure the tabletop with wood screws.
Step 10: Running It!
First, we need to use a zip tie to keep the safety switch and trigger depressed so that the circular saw is in the ON position at all times. The switch will be upstream at the cord (more about this later).
We set up a simple guide with a piece of scrap angle aluminum and some hand clamps, but you could easily use a piece of 2x4. In the future we would like to cut a slot with a router to allow for use of a push guide.
Now all there is to do is set the correct depth/angle and let it rip! Be sure to wear safety goggles and keep your hands away from the blade.
Step 11: Safety!
In lieu of a safety guard, we are simply retracting the blade into the table while not in use. Alternatively, we could remove the circular saw from the table and attach it only when needed.
The morning after we built the table, I bought a foot switch to plug the circular saw into and mounted it with quick ties onto the frame. This not only keeps the cords out of the way, but gives a visual indication of whether or not the system is plugged into the wall. Additionally, the huge red button is a good emergency switch. Unfortunately, I do not have photos of our final setup, but will post them as soon as I can make it back to campus.
Remember, all the safety precautions in the world are worth nothing without common sense. Be sure to let someone know if you are planning on working with the table saw and always wear proper safety equipment. I hope this instructable has been informative and look forward to comments and suggestions.