Horizontal/Vertical Convertible CNC Table

I recently purchased a Longmill CNC router from Sienci Labs. While awaiting its arrival I did some research on tables for the unit and found that testing showed that the Longmill performed well in the vertical configuration as well as horizontal. Having extremely limited space in my workshop, I designed a sturdy table mount that folds up against the wall vertically while still leaving the router accessible for use. The design has a 4 square foot surface to accommodate the footprint of Longmill with a working area of 30" x 30" as well as the power unit and control board; however, the dimensions could easily be adjusted for other sizes of systems if required.

Supplies

4'x8' sheets of 1/2" plywood, MDF, or Melamine. Qty: 2

4'x8' sheet of 3/4" plywood. Qry: 1

#8 x 1-1/4" flathead wood screws. Qty: +/-500

#8 x 3" flathead wood screws. Qty: +/-20

#8 x 1-1/2" flathead wood screws Qty: +/-50

1" diameter x 36" Long hardwood dowel. Qty: 1

2" x 4" x 8' Qty: 1

2 Small Pulleys Blocks, 2 carabiners and Nylon Rope https://www.amazon.ca/TooTaci-Pulley-Swivel-Hangin...

1-1/2" Fender washers. Qty: 2

1/4" x 3" Eye Lag Bolts. Qty: 2

OPTIONAL SPOILBOARD SYSTEM

1/4" - 20 tpi Flathead Machine Screws. Qty: 84

1/4" 20 tpi Threaded Inserts. Qty: 84

48" x 48" x 3/4" MDF sheet. Qty: 1

30" Bi-fold Door Tracks Qty: 7

Step 1: Build the Bottom of the Tabletop

The tabletop consists of a torsion box frame sandwiched between two 48" x 48" x 1/2" sheets, glued and screwed. I used MDF for the bottom and Melamine for the top because it is extremely flat; however, in retrospect plywood would have been a better choice because the spoilboard will be dressed flat by the CNC anyway, and using plywood would have reduced the weight of the table significantly. Still, either material will work.

The tabletop is made entirely of 1/2" thick material. The outer frame consists of the front and back outer frame 2-1/2" wide by 48" long. The sides are made of two pieces 2-1/2" wide by 47" long. The front and back are screwed to the sides with two 1-1/4" screws at each corner. The frame is then secured to the perimeter of the bottom sheet with #8 x 1-1/4" screws approximately every 4 inches.

***Pre-drill and countersink all screw holes. This is especially critical when using MDF, melamine or plywood to prevent splitting.

The front dowel pin holes are centered top to bottom and 6-1/2" in from the front edge. 4" x 2-1/2" x 1-1/8" thick support blocks are glued and screwed in place on the outside, also centered on the dowel pin with matching 1" hole for the pin. This provides the proper offset to allow clearance for the swing arm and adds bearing surface for the dowel pins.

Step 2: Make the Stiffeners

Cut the 8 pieces for the stiffeners. All 1/2" plywood 2-1/2" wide, 47" long. Using a dado stack set to 1/2" wide, cut the 4 notches in each stiffener every 9 inches,1-1/4" deep.

Step 3: Tabletop and Torsion Box

Add the rear sliding dowel pins by first adding 1-1/2" of support blocking on the inside of the rear corners the length is not critical but needs to be at least 3" long and must be 2-1/2" tall to fit snugly between the top and bottom panels. Glue and screw the support blocking being careful to keep the screws well clear of the location where the pin hole will be drilled. Using a 1" Forstner bit, drill the pin hole centered top to bottom and 1-1/2" in from the rear of the table on both sides. Drill and screw down through the table top to secure the dowel. Be sure to secure this screw from the top and and not that back, as you will not be able to access the screw to remove the pin after the top is installed in the mounting bracket.

Add the torsion box stiffeners with the bottom 4 spaced evenly in the frame with the notches facing up. Next add the top stiffeners 90 degrees to the bottom ones with the notches facing down to interlock them together.

Step 4: Glue and Screw the Torsion Box

Trace the location of the lattice onto the bottom with pencil. Carefully lift the lattice out keeping it interlocked if you can. Turn it slightly and set it above the frame. Pre-drill the bottom holes (approx. every 4") from the inside using the pencil marks to locate the holes. Add glue to the bottom inside the pencil marks and re-insert the stiffening lattice. Clamp the lattice in enough locations to hold the stiffeners in place and flip the tabletop over onto a flat surface. Using the holes you pre-drilled from the inside, finish predrilling the stiffeners, countersinking the holes, and then screw the bottom to the lattice.

Step 5: Fasten the Stiffener Ends and Tabletop

Next locate the lattice ends on the outside of the frame and pre-drill, countersink and screw the ends of the stiffeners to the outside frame.

Place the 48" x 48" top slab on the frame and align the edges. Referencing the location of the screws you just installed in the sides, scribe centerlines for each of the stiffeners and pre-drill and countersink hole (approx. every 4"). Remove the top slab and apply glue to the top edges of the frame and the stiffening lattice. Place the top slab back in place and install the screws.

Step 6: Add Mounting Block for Lifting Eye

On the underside of the tabletop and centered at the rear edge, secure a 3" x 3"x 3/4" hardwood block with an eye lag bolt pre-drilled and installed in the end for the lifting mechanism.

Step 7: Fabricate the Lower Mounting Bracket Parts

Using 3/4" plywood, cut the two slotted supports 5-1/2" wide x 38-9/16" long. Using a 1" Forstner bit, drill a hole 1-1/2" in from the end and 1-1/2" in from the side on one corner of each of the supports. In each piece, drill a second 1" hole 1-1/2" in from the same side and 21-1/16" from the first hole. Using a jigsaw, handsaw, table saw, router, or some combination thereof, cut the slot between the two holes and sand the inside surfaces smooth.

Cut 4 pieces of 3/4" plywood, 3-1/2" wide x 38" long. Each slotted support will have two of these stacked and attached at a 90 degree angle to the slotted support.

Step 8: Assemble the Lower Mounting Bracket Parts

Glue and screw the four pieces you just cut into two sets of two, forming two, 1-1/2" x 3-1/2" x 38" mounting plates. Butt the mounting plates up against the side of the slotted supports and glue and screw them together with two #8 x 1-1/2" screws every 4 inches. Ensure that the two assemblies are a mirror image of each other. With the slot at the top, one will have the mounting plate on the left, the other on the right.

Step 9: Fabricate the Upper Support Brackets

Make two brackets, each consisting of a mounting plate made from two 4" x 7-1/2" pieces of 3/4" plywood laminated together with glue, and two 4" long sections of a standard 2x4 attached with 4 - #8 x 3" screws forming the clevis. Each clevis section has a 1" hole for the dowel pivot pin centered top to bottom and 2-1/2" out from the mounting plate.

Step 10: Fabricate the Swing Support

The two swing supports are a 3/4" plywood, 3" wide and 54-3/4" in length. The ends are rounded with 1-1/2" radius and a 1 inch hole centered on the that radius, making the two 1" holes 51-3/4" apart (center to center). There is a third 1" hole centered 12-3/4" from one of the end hole's center. This hole is to allow for a locking dowel pin.

Step 11: Attach the Mounting Brackets to the Wall

This procedure will need to be modified according to the location and type of wall surface material in your case. These instructions detail the dimensions for the location the brackets in relation to the floor and each other. It will be necessary for you to find a way to properly anchor the brackets to the wall substructure. Drywall anchors or other fasteners that do not attach directly to the framing of the wall WILL NOT be sufficient to support the weight and vibration of the table.

The lower end of the lower mounting brackets are 22-9/16" from the floor. The inside edge of the brackets are 48" apart.

The upper support brackets are mounted with the top edge of the mounting plate at 74-9/16" above the floor. The inside edges of the mounting plate is 3/8" closer to the centerline than the lower brackets.

Attach one set of mounting brackets (left or right) first. Then move the tabletop into place and set it on a sturdy temporary support with the rear dowel pin through the slotted bracket on that side. Then place the other bracket over the other dowel pin before securing it in its proper location.

Step 12: Modified Mounting Bracket Options

In my shop, I attached the left side supports directly to a wall stud. The right side supports did not align with any stud, so I modified the right support to include two horizontal plates that spanned between the studs on either side of the bracket.

Another option would be to simply screw a plywood sheet to the wall studs, providing a stable surface to secure to, anywhere on its surface.

Bear in mind that the upper brackets have a small footprint and it is critical to have them firmly anchored the structure as the force acting on them is pulling away from the wall. While the lower brackets with the long slot have a much larger footprint and the force acting on them is pushing against the wall.

Step 13: Install the Swing Arm

Insert the ends with the third hole closest to it into the clevis portion of the upper wall brackets and push a 4" section of 1" hardwood dowel through one side, the swing arm, and the other side of the upper wall bracket. Secure the dowels by pre-drilling and inserting a screw to hold the dowels from working free. Place the hole in the opposite end of each swing arm over the pivot dowels on the sides of the table at the front. Pre-drill a hole in the end of the pivot dowel and secure the swing arm from coming off with 1-1/4" screws and 1-1/2" fender washers.

You can now remove the temporary support from under the tabletop.

Step 14: Add the Lifting System for Folding the Top

Secure an eye lag bolt centered somewhere above the top to the upper bracket secured to the structural framing of the wall. Using a bowline knot (https://www.animatedknots.com/bowline-knot), secure one end of the rope to the eye bolt. Attach a pully block to the upper eye bolt. Attach a second pulley block to the lower eyebolt attached to the table bottom and run the free end of the rope down from the upper eyebolt, through the pulley block on the tabletop, and back up through the upper pulley block, and enough rope to travel back down past the tabletop before trimming the length.

This system uses the lower pulley to achieve a 2:1 mechanical advantage to assist in lifting the heavy tabletop, the upper pully provides no mechanical advantage but redirects the pulling force parallel to the wall and to the slide supports.

Step 15: Locking Dowels

When the table is folded in the upright position, the third hole in the swing arms aligns with the slot in lower wall brackets allowing for a 3" section of 1" dowel to be inserted to prevent unintentional lowering of the table. The tabletop should never slide into the lowered position without lifting the front edge of the tabletop; however, since the top is quite heavy and could hurt someone if it did fall, the pins are for added safety.

Step 16: Operation of the Table

To raise the tabletop from the horizontal position to the vertical position, you pull on the rope to raise the rear of the table. You must hold on to the front of the table as it approaches 45 degrees, because once the table reaches that point, it will fall the rest of the way if left unsupported. With your hand, gently allow gravity to lower it the remainder of the way.

When lowering the tabletop from the vertical to the horizontal position, pull the lifting rope maintaining a firm grip on the rope and keeping tension on the pulleys and slowly pull the lower edge of the table out from the wall. As the tabletop nears 45 degrees the weight will shift onto the rope and pulleys and the rope is used to lower it the remainder of the way.

Step 17: OPTIONAL: Spoilboard System

I initially designed this with a extruded aluminum T-track system in mind. However, because I am extraordinarily cheap, I decided to go with a system that uses the steel tracks used in mounting bi-fold doors. Seven 30" aluminum t-tracks was going to cost close to $200 and the bifold tracks cost me less than $50.

The spoilboard master template is made of a piece of 3/4" plywood that is 4-1/8" x 30". The first track is located and attached at the edge of the usable CNC area footprint. Place the template up against it and attach the second track on the opposite side. Drill the 9/32" holes (14) using the using the template. Move the template to the opposite side of the second track and repeat the process until you have the entire spoilboard area covered.

Install 1/4"- 20 threaded inserts in each hole.

Cut the spoilboard sections on the table saw out of 3/4" MDF to the same dimensions as the template. Use the template to match and drill the holes in each spoilboard section. Countersink each hole to accommodate a 1/4-20 x 1-1/4" long flathead machine screw. The depth should leave the head of the screw well below the surface of the top allowing for several resurfacing passes on the spoilboard before nearing the screwheads.

If you require a set of detailed plans with a modified size, feel free to contact me at [e-mail] or visit my website at salty-dog-woodworks.com