Side Panels (four)
1) All dimensions shown are in inches. Cut four 20" x 60" rectangles from your plywood. You want them to be as square and consistent as possible.
Adjustable Access Panel (one)
Cut one access panel. The 30" length is not critical, but don't go over 30". The holes need to match the holes in the "side panel with access cutout" (shown below) as the access panel moves up and down, so make them carefully. Keeping the pairs of holes 27" center to center is most critical.
Side Panel with Access Cutout (one)
Pick one of your side panels and drill eight additional 1/4" holes as shown. If you clamp the access panel onto the side panel so that it is centered between the handle holes and the top edges are aligned, you can use it for a drilling jig.
Mark the 8" x 24" cutout and rough it out with a saw. Use wood strips as shown in previous steps to make guides for your router and rout the opening to finish size.
Round off the two sharp corners. A sander will do it very quickly.
The shape of the seat is not critical, but the sides should not be over 11-1/2" in order to avoid interfering with the side panel handle holes. Round one corner for safety. After carefully making the first seat, if you have a 1/2" flush trim router bit you can use the first seat and your router to cut the final three to finish size. Just clamp the first seat on top each subsequent panel and follow the edge.
The two 1/4" holes can be difficult to position accurately, so wait to drill them until after your test assembly.
Pig Rail (four)
The pig rails are made from 2x4's. Rabbet each end so that the ends of two pig rails can cross and be the same thickness as the original 2x4. If you rabbet alternate sides as shown, the four pig rails will be interchangeable. If you make both rabbets on the same side, you will have two different kinds of rails when you drill them after test assembly.
Rounding The Edges
Keep the full surface of your wooden edge wherever two pieces come together, but round off everything else with your 3/16" roundover bit. Make sure that you are consistent when rounding the outside end of the side panels. If any holes need to be filled with wood filler, this is the time. Sand all parts, except for the seats.
Inserting Tee Nuts Into Side Panels
With care, tee nuts can be simply pounded into place with a hammer. The key is to hammer them just enough to make the head touch the wood. If you try to smash the flat head into the wood, you will break the surface wood fibers and raise some very nasty splinters. When you assemble the whelping box, tightening the screws will pull the tee nuts tighter. A better method, if you have a drill press, is to put a 1/2" rod into the drill chuck and use it to press the tee nuts into the holes.
On all side panels, the eight corner bracket tee nuts are on the outside surface. This surface has one end rounded with the router.
Test Assembly and Marking the Seats and Pig Rails
Screw the corner brackets to the side panels. You may find it helpful to screw them on loosely until everything is together and then snug the screws.
Set each seat on a corner. Line up the edges of the seat with the outside of the side panels. Holding the seat in place, use a pencil to trace the hole positions from the corner bracket onto the underside of the seat.
Set the pig rails in position on top of the lower corner brackets. The rounded edges should be toward the inside. Push the rails against the side panels and use a pencil to trace the hole position nearest the end of the lower rail
The pig rails are made 1/8" shorter than the inside of the box in order to make it easy to get them into position, so the hole in the bottom rail will be drilled oversize to provide some wiggle room.
Drilling the Seats
Since people will be sitting on the seats, you need to recess the tee nuts into the wood to avoid the edges. Begin by drilling two1/16" diameter holes through the seat using the circles you drew on the bottom for positioning. Next, make flat bottomed counterbores about 1/16" deep in the top. The counterbores need to be at least 45/64" and may be up to 3/4" diameter. You can use a sharp spade bit or a forstner bit. After you make the counterbores, drill through from the bottom with your 1/4" wood bit.
Drilling the Pig Rails
Hold a top and bottom pig rail together as they were in the whelping box. Begin by drilling a 1/16" diameter hole through both boards. This marks your hole positions.
Drill a 1/2" hole through the bottom rail. This clearance hole will provide some wiggle room.
Counterbore the top surface of the top rail as you did on the seats, but 1/4" deep. This will allow a 1-1/4" screw to get full thread engagement in the tee nut. Drill a 1/4" hole through.
Sand your seats and pig rails, and go over your other parts to make sure that they are smooth and ready to finish.
If you plan to brush on polyurethane varnish, you can save some time by turning screws into the tee nuts and using them as feet. This will allow you to flip the side panel and varnish the second side immediately after the first side.
You will get a much smoother finish if you lightly sand the first coat and apply a second coat of varnish.
Construction Plans for the McEmn Mark III Whelping Box