I wanted a way to clamp 2x4s in my [Toughbuilt sawhorses](https://www.toughbuilt.com/sawhorses) (C650s in my particular case) to ensure stability when building a work table to use with these sawhorses, and without any modification to the sawhorses themselves. Fortunately the geometry of the endpieces made this relatively easy.
I have included a .skp (Sketchup) drawing that includes dimensions (for those who are fractionally challenged .4375" equals 7/16") for the blocks themselves. These clamping blocks are intended to be made from scraps of 2x4 (using a circular saw, drill, and a grinder with a flap disc), but these could theoretically be 3D printed. If one were to attempt to do so the geometry for the hex nut and bolt would need to be altered.
1. Start by ripping a piece of 2x4 to three inches wide. If making multiple blocks I suggest using a long enough piece of wood to cut the number of desired blocks from. If a little extra clearance is desired rip the board to 2 15/16".
<img src="https://www.youmagine.com/uploads/image/file/190731/carousel_01.jpg" alt="01" width="640" height="480">
<img src="https://www.youmagine.com/uploads/image/file/190711/carousel_02.jpg" alt="02" width="640" height="480">
2. Next change the angle of your saw to 45° and cut the end of the board at a 45° angle.
<img src="https://www.youmagine.com/uploads/image/file/190712/carousel_03.jpg" alt="03" width="640" height="480">
<img src="https://www.youmagine.com/uploads/image/file/190713/carousel_04.jpg" alt="04" width="640" height="480">
3. Measuring from the acute angle formed by the cut (the long side of the completed trapezoid) mark a line at 5 7/16".
<img src="https://www.youmagine.com/uploads/image/file/190714/carousel_05.jpg" alt="05" width="640" height="480">
Depending on the direction one wishes to cut from it may be necessary to transfer this mark to the other side of the board. To do so, continue the mark on the side of the board, then measure back (toward the angled cut) 1 1/2" (the thickness of a 2x4), then continue the mark on the front of the board.
<img src="https://www.youmagine.com/uploads/image/file/190715/carousel_06.jpg" alt="06" width="640" height="480">
<img src="https://www.youmagine.com/uploads/image/file/190716/carousel_07.jpg" alt="07" width="640" height="480">
If the mark has been transferred to the front of the board it can be sanity checked, and will come in just under 2 1/2" (2 7/16" to be precise, which can be easily calculated since the ratio of the non-hypotenuse sides of a triangle with a 45° angle is one to one. Since the board is 1 1/2" thick and there are two cuts, multiply 1 1/2 by two [three] and subtract the result from the starting measurement [5 7/16 - 3 = 2 7/16].)
<img src="https://www.youmagine.com/uploads/image/file/190717/carousel_08.jpg" alt="08" width="640" height="480">
3. Cut the board at 45° with the angle opposite to the first. The cutoff piece should be a trapezoid with the long side 5 7/16".
<img src="https://www.youmagine.com/uploads/image/file/190718/carousel_09.jpg" alt="09" width="640" height="480">
Note that if making multiple clamping blocks, the cuts can be alternated to minimize waste.
4. There are welds in the corners of the end pieces that will prevent the block from seating on the angled edges made by the cuts.
<img src="https://www.youmagine.com/uploads/image/file/190719/carousel_10.jpg" alt="10" width="640" height="480">
This is not optimal, so these edges need to be radiused or chamfered. The acute edges will be prone to chipping, so they should be radiused or chamfered as well. The remaining edges should be radiused or chamfered, and the corners radiused or chamfered to match. Before doing this marks for the holes for the clamping bolt (or bolts if a different configuration is desired) should be made while there are still well defined edges to work from. Mark the center of the block.
<img src="https://www.youmagine.com/uploads/image/file/190720/carousel_11.jpg" alt="11" width="640" height="480">
5. Drill a small pilot hole all the way through the block. The size is not critical but should be relatively small (I used an 1/8" drill bit). Be sure to keep both the block and drill level while drilling so the hole is perpendicular to the original (non-cut) surfaces.
<img src="https://www.youmagine.com/uploads/image/file/190721/carousel_12.jpg" alt="12" width="640" height="480">
6. Use a grinder and a flap disc to radius the edges and corners of the block. These radii do not have to be perfect.
<img src="https://www.youmagine.com/uploads/image/file/190722/carousel_13.jpg" alt="13" width="640" height="480">
Note that a significant amount of material needs to be removed to provide sufficient clearance of the welds in the end pieces. I used a radius of approximately 1/4", though this was not measured. Use whatever radius or chamfer is preferred as long as it provides sufficient clearance.
<img src="https://www.youmagine.com/uploads/image/file/190723/carousel_14.jpg" alt="14" width="640" height="480">
7. Once the block has been radiused measure the thickness and width of the hex nut(s) being used. In my case I used 1/2" bolts and nuts, the hexes of which measure 3/4" across the flats (note that this measurement will probably be the equivalent of whatever wrench fits the nuts / bolts).
<img src="https://www.youmagine.com/uploads/image/file/190724/carousel_15.jpg" alt="15" width="640" height="480">
Use a spade or paddle bit (do not attempt to use a hole saw or jobber bit) that is the same size as the width across the flats of the hex nut to drill a hole as deep as the hex nut is thick. The depth can be marked with a drill bit stop, or if one is not available using any number of field expedients. In my case I used a piece of masking tape.
<img src="https://www.youmagine.com/uploads/image/file/190725/carousel_16.jpg" alt="16" width="640" height="480">
<img src="https://www.youmagine.com/uploads/image/file/190726/carousel_17.jpg" alt="17" width="640" height="480">
Note that we will be seating the nex nut into this recess later, and when we do the corners of the hex nut will cut their shape into the block, preventing the nut from rotating while in use. If a tighter fit is desired, a smaller bit can be used, but this will run the risk of cracking the block when the nut is seated. Also note that this is somewhat dependent on the size of the hex nut being used.
This is also the reason for using a spade or paddle bit. The bottom of the hole must be flat in order for the hex nut to have good surface contact when compressive forces are applied as the bolt is tightened.
7. Measure the diameter of the bolt's shank, and start a hole at the bottom of the relief for the hex nut. This hole does not have to be very deep, but should be deep enough for the hole to be fully formed with some additional clearance (I would suggest at least an additional 1/8" after the maximum diameter of the bit is formed).
<img src="https://www.youmagine.com/uploads/image/file/190727/carousel_18.jpg" alt="18" width="640" height="480">
8.) Flip the block over and finish drilling the bolt hole from the other side. This will provide nicely finished holes without blowing out pieces of the block.
<img src="https://www.youmagine.com/uploads/image/file/190728/carousel_19.jpg" alt="19" width="640" height="480">
9.) Use a razor knife, piece of sandpaper, or a large countersink to clean up the edges of the drilled holes. Aside from being the mark of a civilized human being, this will be help seating the hex nut in the next step.
10.) Place a hex nut over the recess drilled in step six. If the edges of the hole were properly cleaned up, pressing on the nut will cause it to self-center (the faces of the hex nut have a slight taper around the outside edges). If the nut does not stay self centered do not worry. Note that the nut can be seated directly with a hammer, but I recommend using a scrap piece of wood to prevent marring and reduce the possibility of splitting the block. Apply firm pressure to the hex nut using the scrap piece of wood and strike it firmly with a hammer. The nut should be seated in a single blow (It is possible to crack the block or the scrap piece of wood if too much force is applied, but this generally is not a problem unless the block is struck with a quite a bit of force).
The hex nut should be seated into the block with the top surface flush with the outside of the block. Insert the bolt into the hole opposite the hex nut and make sure the bolt can be started in the hex nut (the bolt may need to be removed to install the block in the end piece of the sawhorse).
<img src="https://www.youmagine.com/uploads/image/file/190729/carousel_20.jpg" alt="20" width="640" height="480">
The block is now finished. Insert the block into the endpiece of the sawhorse and tighten against the material of choice.
<img src="https://www.youmagine.com/uploads/image/file/190730/carousel_21.jpg" alt="21" width="640" height="480">