Shapeoko 3 Base Board with T-Track

A replacement base board for a standard Shapeoko 3, with mounting holes for 5 T-tracks. It comes in two versions: 3/4" MDF with threaded inserts, or 1/2" 6061-T6 aluminum with tapped holes. The model is a parametric OpenSCAD file, and a small script exports DXFs you can send to a CNC or cutting shop.

Files

File	What it is
shapeoko3_baseboard_alu_cut.dxf	Aluminum, the file to order with. Outline and through holes only, one layer, mm
shapeoko3_baseboard_alu.dxf	Aluminum, one layer per operation (tap holes, counterbores)
shapeoko3_baseboard_cut.dxf	MDF, the file to order with. Outline and through holes only, one layer, mm. Works with 2D sheet-cutting quotes (e.g. Xometry)
shapeoko3_baseboard.dxf	MDF, one layer per operation, including the counterbores. For shops that read layers
baseboard.scad	Parametric OpenSCAD model (board, frame holes, T-track layout)
make_dxf.py	Runs OpenSCAD and writes both DXFs
reference_S3SBB_carbide3d.pdf	Carbide 3D drawing S3SBB (5/27/2016) that the frame holes come from
preview.png, preview_alu.png	3D renders of each version with the tracks

Board

• 717.55 x 580 mm (about 28.25" x 22.83")
• MDF: 19.05 mm (3/4"). Aluminum: 12.7 mm (1/2") 6061-T6, the same thickness as Carbide's aluminum table (S3P001).
• Origin is the front-left corner, top face. X runs left to right, Y runs front to back.
• 3 mm corner radius (the drawing doesn't give a size)

DXF layers (MDF)

shapeoko3_baseboard_cut.dxf has a single CUT layer: the outline plus 54 through holes (24 x 5.5 mm, 30 x 7.9 mm). Xometry's 2D quote only cuts through, so the counterbores are done by hand afterwards (see below).

shapeoko3_baseboard.dxf layers:

Layer	Qty	Operation
OUTLINE	1	Profile cut, through
HOLES_5.5_THRU	24	5.5 mm through (M5 clearance)
CBORE_10_X_6DEEP	24	10 mm counterbore, 6 mm deep, top face
INSERT_7.9_THRU	30	7.9 mm through, for the threaded inserts
INSERT_CBORE_12_X_1.2DEEP	30	12 mm counterbore, 1.2 mm deep, top face (insert flange)

Counterbores (if the shop only cuts through)

Do these on the top face after the board arrives, for example with Forstner bits on a drill press:

• Insert flanges, 30 holes: 12 mm, 1.2 mm deep. Needed, or the 1.1 mm flanges hold the tracks off the board.
• Frame screws, 24 holes: 10 mm, 6 mm deep, so the M5 button heads sit flush. Optional; none of them are under a track.

Aluminum version

shapeoko3_baseboard_alu_cut.dxf has the outline plus 54 through holes: 24 x 5.5 mm for the frame and 30 x 4.2 mm for the tracks. shapeoko3_baseboard_alu.dxf layers:

Layer	Qty	Operation
OUTLINE	1	Profile cut, through
HOLES_5.5_THRU	24	5.5 mm through (M5 clearance)
CBORE_10_X_6DEEP	24	10 mm counterbore, 6 mm deep, top face (optional)
TAP_M5_4.2_THRU	30	Tap M5 x 0.8 through

• Tapping: 4.2 mm is the standard M5 tap drill. If the shop taps the holes, check their tapping guide for the hole size they want drawn, set tap_d, and regenerate.
• Track screws: use M5 x 16 mm flat heads instead of 20 mm. With a track floor of about 3.2 mm, a 16 mm screw comes out roughly flush with the bottom of the plate, which keeps it clear of the endplate flange. M5 x 12 mm also works and still gives plenty of thread.
• Frame screws: without the counterbores, the M5 button heads sit on top of the plate at the front and rear edges, clear of the tracks. A counterbore tool with a 5.5 mm pilot can add them later. Check that the M5 x 25 mm screws don't bottom out in the thinner plate; M5 x 16-20 mm may fit better.
• Height: the plate is 6.35 mm thinner than the factory MDF, so the track tops sit 6.35 mm above the original board surface.
• Weight: about 14 kg (31 lb).

Tapping the holes yourself

Tools:

• M5 x 0.8 spiral point (gun) tap, for example this 2-pack on Amazon. Spiral point pushes chips out the bottom of through holes, so each hole is one pass.
• Tap wrench (T-handle), plus a tap guide block or a drill press to keep the tap square
• Cutting fluid (WD-40 or similar works in 6061)
• 4.2 mm drill bit, in case any cut holes come out undersized or tapered

Tap all 30 track holes from the top face. Keep the tap square, turn steadily, and back off if it binds.

Frame mounting holes

These come from Carbide 3D drawing S3SBB:

• Front and rear edges, 8 holes each. Six take M5 x 25 mm button head screws into the PEM nuts on the endplates. The outermost pair (x = 37.91 / 679.64) clears the leveling foot threads.
• Middle row, 8 holes. These were for the old cross straps and aren't needed on current machines. Set include_middle = false to leave them out.

T-tracks

Hardware (McMaster-Carr):

• T-track: 1850A11, 18" long, 3/4" wide, 1/2" tall, 6 holes at 3" center to center
• Screw: 93395A310, M5 x 20 mm flat head, 90 degree countersink, 10 mm head
• Threaded insert: 95596A204, M5, 13 mm, flanged, 7.9 mm drill

Layout:

• 5 tracks running front to back, starting flush with the front edge of the board
• 3.5" from each side edge of the board to the outer edge of the outer track
• Track centers at x = 98.4, 228.6, 358.8, 489.0, 619.1 mm (5-1/8" pitch)
• Holes at 1.5" from the front end of the track, then every 3" (1.5", 4.5", ... 16.5")

Notes:

• Mount each track with its 1.5" end toward the front. The end distances on these tracks may not match.
• The insert holes go all the way through because the screw tip ends up about 17 mm deep, past the end of the 13 mm insert.
• The factory track holes are sized for #8 screws. Drill them out to 5.5 mm (7/32") if an M5 doesn't pass, and countersink them so the screw heads don't block the T-slot.
• 7.9 mm is McMaster's drill size for softwood. Test in scrap MDF first; 8.0 mm may work better.
• The standard Shapeoko 3 moves about 425 mm left to right, so the outer tracks are mostly useful for clamping.

Regenerating

Requires OpenSCAD (the script expects /Applications/OpenSCAD.app) and Python 3 (no extra packages).

python3 make_dxf.py                          # MDF and aluminum DXFs
python3 make_dxf.py -D include_middle=false  # pass any OpenSCAD parameter override

make_dxf.py writes both the MDF and aluminum files. Main parameters at the top of baseboard.scad: material, tap_d, include_middle, include_tracks, track_n, track_margin, track_hole_end, track_hole_pitch, track_y0, insert_d, corner_r.

To render the preview:

OPENSCAD=/Applications/OpenSCAD.app/Contents/MacOS/OpenSCAD
$OPENSCAD -o preview.png --imgsize=1600,1200 --camera=358,200,-10,50,0,25,1450 \
  --colorscheme=Tomorrow -D 'part="3d"' baseboard.scad
# add -D 'material="aluminum"' and -o preview_alu.png for the aluminum render

Sources

• Carbide 3D Community: Wasteboard plans? (S3SBB drawing)
• Carbide 3D Community: Shapeoko 3 Bed DXF
• Shapeoko 3 Assembly Guide