Introduction: A Precise Table Saw From an Electric Hand Saw
This photo is from 1972. It shows me using a table saw I made with an electric handsaw, also known as a circular saw.
Some will say, "Why bother?" since you can now buy an inexpensive table saw for the same amount of money. True, but the adaptation shown here allows the user to remove the saw from the table at any time and rip panels or frame houses, and then return the saw to its table precisely aligned and ready to do close fitting work. You cannot enjoy that dual purpose usage with an inexpensive commercial table saw.
This Instructable differs from similar Instructables because it offers that precise mechanism for automatically and exactly aligning the saw each time it is returned to its table. Details of this are in Step 16.
If you want yet another alternative for making your circular saw an accurate woodworking machine, see my earlier Instructable Get More from Your Circular Saw. Also, after 40 years I built another conversion of an electric handsaw to a table saw. You can see it here.
Step 1: Making the Miter Gauge
This is a good time to decide on the miter gauge you will use with your saw, and make or buy it. When I made this table saw conversion, I purchased a commercial miter gauge. The steps that follow will show you how to make a good miter gauge yourself.
If you choose to make your own, begin with a straight steel bar. The one shown is 1/4 x 3/4 inch and about a dozen inches long. It is what I had at the time. I would recommend a bar of 3/8 x 3/4 inch steel about 18 inches long, but 1/4 x 3/4 inch may be easier to find and works well, too. Round the edges at the ends a little with a grinder so the miter gauge moves more freely in the slots. The photos in this step and the next steps are from my previous Instructable titled Bench Saw Table for a Lathe.
Step 2: Drill Holes
Drill two holes for 1/4 x 2 inch screws. Make the holes 2 1/2 inches apart at the center. Countersink for the bevel heads.
Step 3: Attach the Bolts
Use lock-washers and nuts to secure the bolts in place.
Step 4: The Rest of the Miter Gauge
Cut a disc from 3/4 inch plywood that has a radius of 2 7/16 inches. I turned it on my lathe, but a bandsaw or jigsaw will also do the job. Slice away nearly half of the disc, but leave the center. Drill a 1/4 inch hole on center. Countersink the hole for the nut and washer. Glue and/or screw a face piece onto the disc. Glue on some fine sandpaper, if desired, to prevent work slippage on the face of the miter gauge.
Step 5: Finish the Miter Gauge
Assemble the miter gauge. Make a piece of 1/8 inch strap iron to fit as shown in the photo. Use a self-locking nut (with nylon insert) at the center pivot. Leave it just loose enough that the miter gauge can be adjusted easily. Place a wing-nut on the other bolt. Instructions for adjustment of the miter gauge will be given in a later step.
Step 6: Table Top
Now make the top for the saw table. I used 3/4 inch A-D fir plywood. A piece 24 x 36 inches is about right. (I no longer have the table saw I made, so I am using some images I made with Google Sketch-Up.)
Step 7: Opening for the Blade
You need more table in front of the blade than behind the blade. Cut an opening for the blade to come up through the table, but leave enough table behind the blade for clamping the rip fence and for a saw base.
Notice that the opening has a bevel on the left side. That is to accommodate the blade's position when the saw is set to rip a 45 degree bevel. Keep the blade opening as small as possible so scrap pieces do not fall down into it.
This design sacrifices 3/4 inch of cutting depth due to the thickness of the plywood table. Most of the time you will be cutting materials no thicker than 3/4 inch, so less than maximum cutting depth is not a problem. When I had to cut a 2 x 4 (1 5/8 x 3 5/8 inches), I simply turned it over after the first cut and made a second cut. It would be possible to mount the saw below a piece of steel plate. The details on that would require quite a few more frames in this Instructable and will not be covered here.
Step 8: Miter Gauge Slots
You need to cut two slots for your miter gauge. They should be equidistant from the upright blade on both sides of it. The slots should fit the bar of steel you use for your miter gauge so that it slides easily, but without looseness. The two slots must be exactly parallel to one another.
If you can borrow a friend's table saw, cutting slots for the miter gauge is easier, especially if he owns a dado blade attachment. An alternative method is shown in the next steps.
Step 9: Cutting the Slots
Set the saw's cutting depth to the thickness of your miter gauge's steel bar. Clamp a straight edge across the saw table. Here I used a framing square. Accuracy will be improved if you can leave the square undisturbed while cutting both slots. This involves using some shims. See the next step. (The photo is from an earlier Instructable I did titled Bench Saw Table for a Wood Lathe.)
Step 10: Making a Shim
The first shim needs to be the width of the steel bar on the miter gauge minus the thickness of the blade. Notice the red line. It aligns the left side of the bar with the left side of the saw blade's teeth. The temporary fence shown is clamped to the saw base so that the face nearer the blade's teeth aligns with the right side of the steel bar. The green arrow indicates the width of the shim needed.
Remove the steel bar. Turn the saw right side up and rip your shim from a straight piece of wood while holding the fence against the wood. Make the shim as long as your saw table is deep.
Step 11: Cutting a Miter Slot
The shim from the previous step needs to be rather precise. Make a test slot on some scrap wood before cutting on your saw table.
Make one cut with the base of the circular saw riding against the straightedge (first graphic). Then make a second cut with the shim against the straightedge and the saw riding against the shim (second graphic--The brown piece is the shim. Note the second cut to the left of the first cut. Thanks to Google Warehouse for the image of the circular saw. The image happens to show a left-hand drive saw, although most home circular saws are right-hand drive.). Make some freehand cuts to remove as much of the waste material between the two cuts as possible. Make the bottom of the slot smooth with a chisel or a rasp. Check to see how the steel bar from the miter gauge fits in the slot. Rub some paraffin in the slot to make the miter gauge slide more easily.
If the shim produces a test slot that is a little too narrow, cover one edge of the shim with a layer or two of black electrical tape and make another pass with the saw. If the test slot is a little too large, sand or plane the shim to narrow it a little.
Step 12: Make a Larger Shim
The second slot should be at least 12 inches off to the side of the first slot. You can make your own shim to offset the slot, or you can buy something that is reasonably certain to have parallel edges, like a piece of shelving. After the first cut for the slot has been made, use the smaller shim to cut the outer edge of the second slot, just as you did on the first slot. This allows you to leave the square undisturbed and gives a greater probability both slots will be exactly parallel to one another. (Note that this drawing is not to scale. The width of the shim (shown in shades of brown) in this graphic would be much greater than shown so that the second set of cuts would be much farther away from the first set.)
Step 13: Mounting Holes
I used two 1/4 inch bevel head screws to mount my saw. Countersink the heads so they are just below the surface of the saw table's top surface. Many circular saws will already come with two holes in the base. If your saw does not have these holes, you can drill your own mounting holes. Just be careful that the ends of the screws do not obstruct anything essential. Wing-nuts and lock-washers are adequate for securing the saw under the table.
Step 14: Temporarily Mount the Saw
Once the mounting holes for the saw have been drilled, mount the saw under the table and do some preliminary alignment of the blade to make it parallel with the miter slots. This is a necessary preparation for what needs to be done in Step 16. The miter gauge will be a key part of this preliminary alignment. Do not worry that there are no markings on the miter gauge as there are on a protractor, nor any positive stops. Set the miter gauge adjustments with a square. Later, if you need to cut at an angle, set the miter gauge with a "T" bevel angle finder.
Step 15: Preliminary Alignment
When checking the saw for alignment, place a square against the miter gauge and slide the other leg of the square against the saw blade. (The photo is from my earlier Instructable titled Bench Saw Table for a Lathe.)
Step 16: Built-in Micrometer-like Precision
In the previous step you aligned the saw so it is fairly well as it should be, but it still needs some tweaking.
Plans for saw conversions similar to this one were frequent in how-to magazines from the 1950's and 1960's. But, they all lacked a very useful feature, which was a positive way to align the saw and keep it aligned, even if it had to be removed for ripping a panel or otherwise being used as a hand circular saw.
I solved that problem with two 3/4 x 3/4 inch blocks mounted under the table at one side of the saw's base plate. The blocks are about 2 inches long and are glued or screwed to the underside of the table. A tightly fitting machine screw passes through a hole in each block and the tip rests on the edge of the saw's base at the front and the back of the saw's base. (See the two additional photos with this step.) Turning one of these screws in or out part of a turn aligns the saw with micrometer-like precision so the blade is exactly parallel to the miter gauge slots. You know the saw is aligned when the rear of the blade does not kick up chips, splinters, and sawdust while you are ripping a board. When I needed my saw for another job, I could remove the mounting bolts and take the saw with me in just seconds. Later I could attach it loosely with its mounting bolts, slide the base against the tips of the machine screws, and finish tightening the mounting bolts. The saw was perfectly aligned again. (I demonstrated this basic feature in another application. See my Instructable titled Radial Saw Table Alignment--An Easier Way.)
Step 17: Add a Base
The base for the table adds strength and rigidity to the table, especially since it has been weakened by the two miter gauge slots. The base also provides a housing for the circular saw and keeps your hands away from it. The front is not fully open because extra support for the saw table is needed across the front. The opening makes the saw accessible for adjustments and changing or removal of the blade. A power switch can be mounted on the front or the side near the front. You may also want to make an opening at the rear of the base for better access to the adjustment for cutting depth.
I added legs under the base. I also added 2 x 2 inch pieces under the front and back of the saw table to extend off to the right so I could saw pieces up to four feet wide. See the photo in the Introduction.
Step 18: Setting the Rip Fence
Use a square against the face of the miter gauge to place and align the rip fence. The miter gauge can be inserted backwards to gain extra clearance with the blade, if necessary.
I used a piece cut from the end of a sheet of plywood for my rip fence and clamped it to the front and back of the saw table with "C" clamps. ("G" cramps in the UK) My rip fence was about 4 inches wide. The factory edge on a sheet of plywood is very straight and true. In the photo some commonly available shelving serves as a rip fence.
Step 19: Safety Concerns
Always set the saw's cutting depth so the teeth just barely come through the top surface of the piece being cut. (See the photo.) The cut will be smoother and the piece being cut hides most of the blade to guard the user against damage in the event of an accident.. If there is an accident, you will have a cut you can heal with a common adhesive strip bandage, not a wound that goes down into bone.
Do not wear loose clothing and tuck long hair into your collar. You do not want these to become caught in the spinning blade.
Stand so you are well-balanced and not leaning on something for support.
I use pusher sticks a lot. The object is to keep my hands and fingers at least six inches away from a spinning blade at all times. Do not rely on blade guards alone. When extra safety devices are available, people take extra risks. That has been documented in studies.
A switch easy to reach at the front of the saw is also good to have, especially since you will need to tie the saw's switch in the "on" position for use.
Keep the saw properly aligned so the blade does not bind and throw work or pull you into the blade. Saw only dimensional lumber on this saw--no limbs for firewood.
If you are using a carbide tipped blade, stand to one side of the blade. Although not common, I have heard firsthand stories of a tooth thrown by one of these blades. Avoid sawing wood with a lot of sap or pitch in it to avoid the blade binding in the wood.
Wear approved eye protection when using the saw and be ever vigilant.
Disconnect the power whenever making adjustments to the saw, especially under the saw table.
Step 20: What Will It Do?
The most intricate project I built with my circular saw converted to a table saw was a Parsons table, actually four of them from one 4 x 8 sheet of 1/2 inch oak veneer plywood. Attached is a black & white photo of one of the four. I also recreated the design in Google Sketch-Up and edited it in MS Paint. The short straight black lines are to indicate the direction of the grain in the plywood. The inset at the lower left shows the detail for the joints where the sides met the top and where the legs met one another. A thin piece of wood joined the pieces in the kerf cut into each 45 degree bevel. The pieces all fit as tightly as the drawing of the table would lead you to believe. The tables were about 20 x 20 x 20 inches.
Mounting a hand circular saw adds accuracy and versatility to a basic tool. It also provides the home woodworker on a budget with a good alternative to buying a table saw. Had I not been able to buy a radial arm saw a few years after making my table saw conversion, I would still be using it. (My wife said, "You may have a radial arm saw, but you are not going to have two saws." I had to sell my circular saw and saw table. A couple of years later her parents did give me another circular saw.)