Friday I set out to make a set of saw horses for my workshop. I have two large, heavy, A-frame saw horses that my dad built. I wanted some horses more suited for shop use – nimble and lightweight, yet still sturdy. I felt that this design popularized by the late James Krenov fit the bill. This photo illustrates another advantage of this style of horse – if you look closely, you will see that there is not just one horse there, but actually four. The nesting ability is not only great for storage, but also when dealing with shorter stock.
Since I’ve never seen a horse of this design in person to critique it, so rather than make my first set out of expensive materials, I opted to go with cheap spruce. I went down to the local lumberyard to select some materials. I decided to use 1″x3″ stock (that’s 1×3″ dressed, not 1×3 dimensional lumber which measures 3/4″ thick and 2-1/2″ wide) so went straight to the 2x4s which, when dressed, would yield straight, flat, defect-free stock 1″ thick and 3″ wide.
All the eight-footers had large diameter knots and were deemed unsuitable, so I looked at the ten-footers. I found five relatively clear (knot-free) 2x4s without the pith included – enough for four horses. Some even had nice colouring and streaking. I proceeded to the check-out with them and handed over $15. I loaded up my truck and headed home.
Back home, the first thing I did was put the 2x4s across my old horses to layout the cuts. I cut the feet 18″ long and the uprights long enough to make the completed horses 30″ tall. I made the required cuts with my miter saw using a stop block to ensure uniformity.
Once all the cuts were made, I flattened one face and squared an edge on the jointer, then brought the stock down to its finished size with my thickness planer. The uprights have 1″ long tenons on their ends which slip into matching mortises in the feet.
It’s always easier to fit the tenons to the mortises rather than the other way around, so I started by picking out a spiral router bit to make the mortises with. I like to use a spiral bit for mortising because the spiral does a good job of clearing the chips from the cavity. I installed the bit in my plunge router and attached its fence.
Since I was making eight feet, I decided to make a jig – a mortising block – to ensure repeatability and make it easier to balance the router. The jig is simply a 4×4 with stops screwed onto it’s faces. Two stops on the top limit the router’s lateral movement and align the workpiece flush with the top of the jig. The workpiece butts against the third stop screwed onto the front. It is positioned so that the mortise is centered along the length of the foot, and the router’s fence centers the bit on the thickness of the stock.
To rout the mortises, I worked with the fence towards me and started with the router against the left stop. I set the depth stop to 1-1/16″ – the extra 1/16 prevents the 1″ long tenon from bottoming out and provides some room for any excess glue. I made a full-depth plunge cut, retracted the router, then moved to the right to overlap the last cut by about 1/3-1/2 and made a second cut, continuing until I reached the other stop. I noticed that some of the sawdust I created ended up on the jig and would have prevented the router from bearing against the stop, so I had to blow it out of the way before making the final plunge cut.
Once the series of plunge cuts was complete, I was left with a series of overlapping circles. To transform the circles into a parallel-sided mortise, I returned the router to the beginning, plunged the router to full depth, and moved the router across to the other stop before finally retracting the router and switching it off. I prefer this method to making multiple shallow, full-width passes because it results in straight-sided mortises without steps. It also puts less lateral strain on the router spindle and bit, resulting in less deflection. In fewer words, I think that this method makes for a better mortise.
With the mortises routed, the next step is to cut the tenons to fit. I like to cut my tenons on the table saw using a dado stack. The table saw has more power than a router and I feel I have more control. Part of this is that the cutting force applied from a table saw is linear – directly back towards me.
On a router table, the cutting force is lateral and harder to control. However, with the combination of a miter gauge and fence, the direction of cutting force is really a non-issue. What is an issue, however, is the power. On the table saw, I have no problem taking a 3/4″ wide cut deeper than 1″ in a single pass. Not the case with a router. However, a router will leave a smoother surface, but I don’t feel that it is paramount to have a smooth surface on the face of a tenon. If I did, it would be a simple matter to smooth the faces with a shoulder plane. The same tool could be used to fine-tune the fit if required.
To cut the 1″ long tenons, I installed a 5/8″ stacked dado blade on my table saw. I could have made a wider stack, to a maximum width of 13/16″, but that would have required a slower feed rate than the 5/8″ stack. The 5/8″ stack is still wide enough to cut the required width while allowing enough overlap to not require ultra-precise positioning for the second cut.
I positioned the fence 1″ from the left side of the dado stack and locked it down. I then set the blade a little lower than required to create a too-fat tenon. I used the set-up to cut both cheeks and tested the fit against a mortise.
As expected, it was too tight. I raised the blade a bit more and ran the same test piece over again. The tenon was almost the right size – it would start to go in, but would require a little tuning to perfect. Because I was cutting a number of tenons, I took the extra time to tweak my setup and get the fit perfect. Before starting on my work pieces, I checked that my miter gauge was square to the fence (and thus, the blade). A zero-clearance backer on the miter gauge prevents blowout on the back end of the stock.
Once I had the setup just right, I began cutting the tenons. Being diligent to keep the stock firmly on the table, I made the first cut at the end of the workpiece, then slid the workpiece against the fence for the second cut. Using this sequence of cuts ensures that any sawdust build-up on the table won’t keep the stock from bearing fully against the fence. I rotated the stock 90-degrees and repeated the pair of cuts and continued until all eight uprights had a four-shouldered tenon on the lower end.
I took a break from the noise of machinery and moved from the machine shop to the bench room to square the ends of the router-cut mortises in the feet. I dropped a scrap piece of wood over the steel guide rods of the vise wide enough to make the top surface of the foot sit proud of the vise jaws. This scrap of wood effectively transfers the force of the chisel right through it to the vise and bench. Without it, every blow with the mallet would try to knock the workpiece down in the vise.
For the sake of efficiency, I could have clamped all eight feet in the vise at the same time. That’s one of the benefits of having a vise that opens up nice and wide. I set a chisel as wide as the mortise tangentially to the rounded ends and chopped the ends square with a few blows with my carver’s mallet. I like urethane head of my carver’s mallet because it is a quieter than a wooden head. Once I’d reached the bottom of the mortise, I levered the chisel handle downwards and removed the foot from the vise to scrape out the chips.
You can watch a short, two-minute video of me cutting the mortise and tenon, then squaring the mortise and fitting the joint.
I returned to the machine shop to cut the tenons on the ends of the stretchers and matching mortises in the faces of the uprights. I used the same equipment before, using the same procedures, only these tenons were to go clean through and would later receive wedges to lock them in place so I cut them a little long to allow them to be trimmed flush later.
When I returned to the bench room to square the mortises, I again placed a scrap between the mortised stock and the vises steel guide rods. The scrap again prevents the work from being driven down in the vise, but also serves as a sacrificial backer to prevent blow out on the underside of the through-mortise. I chopped the mortises square, then moved the chisel about 3/16″ farther from the mortise and angled it to create a tapered mortise to allow the tenon to be wedged.
To allow the tenons to be spread to fill the tapered mortises, I sawed a pair of slots down to the shoulder about 3/16″ from the end. From some stock the same thickness as the tenons, I sawed a handful of wedges with my dovetail saw. The last step before gluing up is to fit the top cross-pieces. I cut a 1″ square notch in the top of the uprights and a matching notch in the underside of the cross-pieces. I cut the notches in the uprights with a dovetail and coping saw, then cut the notches in the cross-pieces with the table saw.
Glue-up time. As a relatively simple assembly, the glue-up wasn’t very stressful. I put together one horse at a time, starting by gluing the feet onto the uprights, applying glue to the cheeks of the tenons and a bead around the inside edges of the mortise. I put them together, then went to work on the stretchers. I applied glue to the cheeks of the tenon and pressed them into their respective mortises.
Next, with the horse on its side, I applied glue to the wedges and inserted them in each slot and tapped them in place with alternating taps from a steel hammer until the tenon expanded to fill the tapered mortise. I flipped the horse over and knocked the wedges in the opposite end. Then, I slipped in the top cross-piece and screwed it in place (no glue). Finally, I set the horse on my table saw top which I know is flat and ensured that the feet sat flat before letting the glue set.