Sawhorse – how to build a silent partner
We don’t have to tell you how handy sawhorses are in the shop. They act like silent partners, assisting us whenever we need extra support.
This design comes from James Krenov, and it’s simple yet quite ingenious. While studying at Rosewood Studio I made them not only as a shop aid but also as a way to reinforce lessons in joinery. The load is carried on a stout top straight down through the legs and onto the feet. Typical A-frame-style sawhorses have a tendency to splay with heavier loads and don’t always store neatly out of the way. All the pieces on this one are made from 3″-wide stock, and all but the legs are made from 1″-thick material. Hardwoods such as maple or white ash work best, take all the abuse we are going to throw at it and don’t cost an arm or a leg.
A few basic layout tools are all that’s needed to properly lay out the mortises. Accuracy here will assist with properly located joinery.
With a stop set, Der-Garabedian slowly raises his table saw blade to sneak up on a properly fitting mortise and tenon joint.
Tip it Up
Once the width of the tenon has been machined, tip the workpiece on its side to create the shoulders and cheeks. The height of the blade will have to be adjusted so the tenon fits the mortise.
Round it Over
With a file, Der-Garabedian rounds the corners of the tenons to fit the round mortise. Be careful not to cut into the shoulder, as it will show in the finished joint.
Ensure there’s no extra material to interfere with the joint seating precisely. Undercutting the shoulder slightly will help ensure a nice-looking joint.
Drill the Pin Holes
A spacer fitting snugly in the mortise will stop any blowout from happening on the inside of the mortise while the pin hole is being bored. Watch the underside of the workpiece as well.
A Little Tap
Using the same brad point bit with which the hole was drilled, and while the joint is fully assembled, insert the bit and lightly tap it. The resulting small hole will locate the center point, then that location can be offset slightly to create a drawbore joint.
Setting the Width
When cutting the tenons to width, Der-Garabedian cuts a very short tenon on the workpiece, then checks the fit against the mortise. Once the width is dialled in he cuts the entire length of the tenon to size.
Cut to Fit
With the stretcher on its side, equal cuts are made on both top and bottom of the stretcher. The resulting tenon dimension is checked against the mortise.
Create the Slot
Once the 1/8"-diameter holes are drilled near the base of the tenon, and the location of the slot is set, a band saw or hand saw will create the slot in the tenon.
Widen the Mouth
With a round file, Der- Garabedian expands the outer side of the mortise slightly. This will allow the wedge to press the outer edge of the tenon into the rounded end of the mortise, locking the joint in place.
Simple Wedge Jig
A rectangular piece of plywood with a notch the same shape and size as the required wedge is all that’s needed to cut many wedges.
Cut Some Wedges
Der-Garabedian uses a 1/8"-thick zero-clearance baseboard taped to his band saw’s table to stop the wedges from disappearing through his regular throat plate while he cuts the wedges.
With a leg standing on end, use your crosscut sled and two stop blocks to cut a notch the same width as the thickness of the top. A mating notch is created in the top so the two notches fit together.
Assemble the Wedged Joint
Once the mortise and tenon has been glued and clamped tightly, glue and tap in the wedges before letting the joint dry thoroughly.
A Slight Taper
Before trying to knock the pin into the offset holes, taper the leading end slightly. This will allow the pin to seat into the joint more easily.
Milling and sizing
I like to mark up, or map, my planks for projects so that I make sure to use the best possible grain in specific pieces and to cut back on waste. The top is sized at 27″ × 3″ × 1″. The legs work out to 29-1/4″ × 3″ × 3/4″, which allows for a 1-1/4″ tenon at the bottom. The stretcher comes in at 21-5/8″ × 3″ × 1″. The extra length here allows us to make the tenons on both ends slightly proud. Finally, the feet are 17″ × 3″ × 1″.
After milling and cutting the pieces to size, mark them with a cabinetmaker’s triangle. It’s a great way to keep track of what is the top or bottom as well as the inside and outside surfaces of the pieces.
Lessons in joinery
These sawhorses are created using the bread and butter joint of our industry, the mortise and tenon. While regular mortise and tenons will work, we’ll go the extra step and make both pinned and wedged styles. I typically use a router table to make my mortises then make matching tenons at the table saw using a crosscut sled. Use a method of cutting that you’re comfortable with and have the tools for. Mark up at least one of each piece to accurately set up tool fences or marking gauges, etc.
The mortises on the tops of the feet are 2-1/4″ long, 1-1/4″ deep and 3/8″ wide. When both feet are mortised, switch over to the legs. Making sure you pay attention to your triangle marks, cut these through mortises starting at 9-5/8″ from the bottom of the legs. They are 2-1/4″ long by 1/2″ wide.
Measuring without numbers
Next come the tenons on the bottom of the legs and both ends of the stretcher. I find that using the table saw to cut the tenons allows me to creep up to the perfect size. It’s just a matter of setting up a stop block for the depth and making multiple passes across the blade. Set the stop block 13/16″ away from the furthest edge of the blade. Next, roughly mark one end of the stretcher for the tenon’s width and length. Lower the blade below the mark for the width and make an initial cut at the tip, flip the board over and take another pass on the tip. Now hold up the stepped tip you created to the matching mortise and see how close you are. Adjust the blade height until you get a snug fit in the mortise. At this point, only the tip will fit in the corresponding mortise, but this is more than enough indication. Next, cut the one side of the tenon all the way to the stop, flip over and cut the opposite face. Since both ends of the stretcher need the same-sized tenon, repeat the procedure on the opposite end while the blade height is set. Do the exact same procedures for the length of the tenon. Make sure when testing the fit, you use the center portion of the mortise. A little extra material here won’t hurt when doing your final fitting.
The bottom of the legs will now need the same treatment. However, adjustments to the stop block and blade height will vary slightly, as the tenon will need to be 2-1/4″ long, 1-1/4″ deep and 3/8″ wide.
A little bit of cleaning
I find it easier to match the tenon to the mortise by rounding the ends. A safe edge file or a half round file work equally well here but take care to stay clear of the shoulders as any stray file marks will be visible after assembly. Start with the tenons on the bottom of the legs and test fit often. To make sure the shoulders fit nice and tight against the feet, slightly undercut the bottom of the tenons and chamfer the tops of the mortises. Do a dry fit to make sure that the tenons don’t bottom out.
The leg-to-foot assembly will also have the added insurance of a wood pin to hold it in place, and will serve double duty pulling the joint together a little tighter. To achieve this, first mark the position of the through holes in the feet. Centered on the mortise and 5/8″ down is a good spot. Mark this with an awl and place a sacrificial 3/8″ piece of wood in the mortise. Using a 3/8″ brad point bit drill through, making sure there’s another sacrificial piece of wood on the underside to prevent blowout. Next assemble the legs and feet using a clamp. Tap the brad point bit you’ve just used in the hole, and you have a perfectly centered mark on the leg tenon. If that mark is moved slightly closer to the shoulder of the tenon, it pulls the joint tighter as a dowel is driven through the hole. This offset should be less than 1/16″. After marking both tenons, use the 3/8″ brad point bit to drill the holes.
Now move your attention to the stretcher and leg pairing. Since these tenons poke through the legs, it should be slightly easier to make them fit, as you can sight down the mortises. This assembly gets a pair of wedges to lock it in place. Two things need to be accomplished for this to work. Slits need to be cut in the tenon, and the mortise needs to be flared. First, mark two lines 5/16″ in from the ends of the tenon, top to bottom. Using an awl, mark a point on the lines 1/8″ up from the shoulder. Drill a 1/8″ hole at these points to stop the slit from continuing to split and also act as a pivot point for the flared ends. Use a band saw or hand saw to cut the slits down to the holes.
Use a round file to flare the ends of the mortises. You only need to lightly touch the top and bottom and make them 1/8″ wider on the outside faces. Start the flare just short of the inside lip.
A simple wedge factory
Making duplicate wedges is not a hard process. Take a piece of 1/2″-thick plywood approximately 10″ long and 7″ wide. Draw two lines 1″ apart near the middle of the length. The 1″ comes from the length of wedge we will need. In this case 3/16″ for the thickest portion of the wedge is plenty. On the bottom line, draw a mark 3/16″ in from the edge and then join this mark to the beginning of the other line. Cut this shape out and there will now be a negative space in the shape of the wedge.
As the tenon is 1/2″ thick and the wedges need to be 1″ long, mill up some hardwood, keeping in mind the wedges need to run with the grain. A wider piece will make plenty and also keep your fingers away from the blade. In order for the wedges not to fall through the throat of the band saw, make a zero-clearance insert out of 1/8″ hardboard. Tape it in place, and you’re ready to make wedges. Place your wedge material in the jig and pass it through the blade. Once cut, pull back the jig, flip the material over, and cut again. In a matter of seconds you will have made more than enough to do the job.
The top and the legs slip into one another via notches that are 1″ deep. The notches in the top are spread 20″ apart, the same distance shoulder to shoulder of the stretcher, and are 3/4″ wide. The notches at the top of the legs are 1″ wide. These notches are easily cut on the table saw with the crosscut sled.
In order to make the sawhorse a little more stable, create two distinct pads on the bottom of the feet. I find sometimes that the sawhorse will rock if the bottoms of the feet are left straight. This can be done on the router table with stops and a 3/4″ bit set halfway into the fence. A band saw or a hand saw will also do the job. The clearance need only be 3/8″ from the floor. Finally, trim the top ends of the feet and lower corners of the top at 45°.
For final assembly I start attaching the legs to the feet. Apply glue and use a clamp to bring the two pieces together. Slightly chamfer the end of a contrasting dowel, in this case black walnut, and after adding a little glue, drive them in. You’ll see the joint get a little tighter. Let this dry for about an hour, then cut the dowels and flush them using a block plane.
Glue the tenons on the end of the stretcher and using a pair of clamps, one above and one below, attach it to the legs. Next add a little glue on the wedges and drive them home. Again, wait about an hour and flush the wedges and proud tenons to the outside of the legs. Lastly, slip the top onto the legs and tack it in place through the legs using a couple of wood screws.
Change the height of these workhorses to suit your needs. Don’t decrease the width and thickness too much, as this, along with the general design, are what gives it its strength. Make it your own, possibly by making the tenons on the stretcher longer and leaving them proud. Instead of straight 45° cuts on the tops of the feet and bottom of the top, make them round, or even leave them square. At Rosewood Studio, the basic design from student to student didn’t change, but little customizations made them unique. It doesn’t take long to make a pair and practice your mortise and tenon joinery.