Both projects assume the workflow and the feed formula in the CNC router guide, a machine with at least 10 × 6 in of travel, and one 1/4 in two-flute end mill. They are drawn rather than supplied as files, so the first job is to draw each part in your own CAD program from the dimensions here.
The two projects at a glance
| Item | Slot-together organizer | Pocketed tray |
|---|---|---|
| Stock | 1/2 in nominal plywood, actual thickness measured | A 3/4 × 5 × 12 in board |
| Parts | One 10 × 6 in base, three 6 × 5 in dividers with tabs | One piece |
| Bit | 1/4 in end mill | 1/4 in end mill |
| Toolpaths | Through-mortises with dogboned corners; outside profiles | Three pockets 1/2 in deep; outside profile |
| Teaches | Square inside corners; fitting tabs to real plywood | Pocket depth, floor thickness, corner radius |
BenchRoot designs. Plywood sold as 1/2 in is often thinner; see the plywood thickness chart.
Why inside corners need dogbones
A plain pocket's corner leaves the bit's centre r from each wall — √2 × r from the corner. A dogbone carries it on along the bisector until it is only r from the corner, so its edge just touches the corner point; the extra travel is r(√2 − 1). Dogbones can be drawn into the part, or added to the toolpath where the CAM program offers it; they leave a small, visible overcut beyond each corner.
Project 1: a slot-together organizer
The layout adds up: the three divider centrelines sit 1-1/2 in from each end with 3-1/2 in between them, 1-1/2 + 3-1/2 + 3-1/2 + 1-1/2 = 10 in. Along each divider's 6 in bottom edge, the two 1-1/2 in tabs leave 1 in at each end and 1 in between: 1 + 1-1/2 + 1 + 1-1/2 + 1 = 6 in. Each tab is as long as the base is thick, so it finishes flush underneath. That is six mortises and 24 dogboned corners.
Cutting the organizer
Measure the plywood
Measure the sheet's actual thickness, t, with calipers in several places, and draw the mortises and tabs to that figure.
Test the fit
Cut one mortise and one tab in an offcut and adjust the mortise width until the tab slides in snugly by hand; use that allowance for all six.
Toolpaths
Mortises as through pockets with dogboned corners, cut before the outside profiles so the parts stay held; outside profiles last, with holding tabs left in the path.
Workholding and run
Screw or clamp the sheet outside every toolpath, set zero, preview, and run with someone at the machine throughout.
Assemble
Cut the parts free from their holding tabs, sand the edges, glue the divider tabs into the mortises and check each divider is square to the base.
Project 2: a pocketed tray
Along the board: 1/2 + 3-1/2 + 1/2 + 3-1/2 + 1/2 + 3 + 1/2 = 12 in. Across it: 1/2 + 4 + 1/2 = 5 in. The pockets cover 4 × (3-1/2 + 3-1/2 + 3) = 40 sq in at 1/2 in deep, so 20 cu in of wood comes out, leaving a 1/4 in floor under a 3/4 in board. Rounded pocket corners are fine in a tray, so no dogbones are needed here.
Cutting the tray
Prepare the board
Flatten and thickness the board to 3/4 in so the floor comes out even; a planer does it.
Draw and set depth
Draw the three pockets and the outline; set the pocket depth to 1/2 in, measured from the top surface zero.
Work out the feed
Take the chip load for your bit and wood from the bit's maker and the speed from your router's manual; feed = RPM × flutes × chip load. Cut the depth in passes as the bit maker advises; Amana's chart, for example, assumes one tool diameter per pass.
Run the pockets
Clamp the board outside the toolpaths, set zero on the top surface, preview and run the pockets, then the outside profile with holding tabs.
Finish
Cut the tabs, sand, and finish; finishing oils suit a desk tray.
Safety— At the machine
Carbide 3D's rules apply to any machine: never leave it running unattended, wear eye and hearing protection and a respirator suited to the dust, keep hands out of the working area while it runs and clamps out of every toolpath. General rules are in woodworking safety rules.
Before cutting either project
- Plywood thickness measured and the drawing set to it
- Tab fit proved in an offcut
- Chip load from the bit's maker and the feed worked out
- Clamps and screws outside every toolpath; zero set and previewed
- Eye and hearing protection on and someone at the machine
Sources
Both are BenchRoot designs; every dimension is on the drawings, and the dogbone and layout arithmetic is exact. No feed, speed, depth per pass or fit allowance is given as a figure: feeds come from the bit maker's chip load by its formula, speeds from the router's or spindle's manual, and the fit of the tabs from a test cut in the actual plywood. No cut files, DXF, SVG or G-code are offered. Neither design was cut for this page, and neither carries a load rating.
- 1.
AMS-126 Speed Chart: 2 Flute Solid Carbide Spiral Flute Plunge Inlay Router Bits. Amana Tool.
Used for: Feed rate = RPM × number of flutes × chip load, with chip loads from the bit maker; chart values at a depth of cut of one tool diameter, the feed reduced 25% at two diameters and 50% at three; all values recommendations.
- 2.
Machine Safety. Carbide 3D.
Used for: Never leave the machine unattended; eye and hearing protection; a respirator suited to the dust; never reaching into the working envelope while it runs; care handling end mills.
About this guide
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