"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
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
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
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
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
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
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
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
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!
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!
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.