Components after cutting and sanding. The leg tenons are slotted diagonally with a hand saw
The purpose of this project was to build an improved copy of a traditional wooden stepstool with the CNC (that used to be made by hand tools only).
The sample here is made from cherry (due to availability), ideally it should be made from white oak, maple, hickory or other higher strength hardwood.
See instructions and recommendations at the bottom of this page.
Instructions / Recommendations
Both .crv files are double sided VcarvePro projects with z-zero on the board surface for the top tool paths and z-zero on the spoilboard/table for the bottom tool paths.
The sample here is made from cherry (due to availability). A better choice may be white oak , hard maple, hickory or other higher strength hardwood.
There are 2 CNC files: one for the 4 legs (requires a 550x230x32mm / 22x9x1.25" board) and one for the seat plate (requires a 500x230x32mm / 20x9x1.25" board). The boards can be slightly thicker.
For both files:
Top tool paths are best cut by clamping the blank corners onto the spoilboard (optionally on spacer blocks). If the boards are not flat within ~0.25mm / 0.01" they should be surfaced first.
After the top cuts, before flipping and re-mounting, hand drill 4 screw holes (e.g. 0.2") in the remote corners of the blanks.
Drill the alignment holes into the spoilboard with a 1/4" end mill or drill bit (they will go 10mm or 3/8" deep when zeroed on the spoilboard surface). Tool path is "TableAlignDrill".
Flip the blank, set onto spoilboard with 1/4" dowels and screw down using the corner holes (or use another work holding method of your choice).
If the bottom side of the blank as mounted is not flat within 0.25mm / 0.01" then surface the board again to make it so. The resulting thickness should not be less than 31.5mm / 1.23" . If it is much thicker than 32mm / 1.25", reduce thickness with appropriate machining (there is a tool path included that can be used for that).
The 1/4" endmill used should ideally have a flute length of 1.5". A 1" bit may work if the alignment holes are drilled with a drill bit
Leg File Top:
Zero 1/4" end mill on the blank surface and make the alignment holes and the waste pocket
Zero 1/4" ballnose on the blank surface and cut the "swept profile 1" edge bevels
Leg File Bottom:
If required: Zero 1/4" end mill on the spoilboard and cut the surface flat with "Thickness Pocket". Or use a bigger bit for a faster cut. Ideally end thickness is 1.25" approx. 32mm
Zero the 1/4" ballnose on the spoilboard and cut the edge bevels with "swept profile 2"
Change back to the 1/4" end mill and cut out the tenon and foot with "Endcut". This will leave generous tabs on both ends.
Remove the board, cut the tabs and sand everything to desired smoothness
Now measure the final thickness of the tenons with a caliper and adjust (if necessary) the width of the mortises in the seat plate file. The recalculate the mortise tool paths.
Seat File Top:
Zero 1/4" end mill on blank surface and drill the alignment holes, the wedge peg holes, the handle pocket and the perimeter relief cut.
Swap to 1/4" ballnose, zero on blank surface and cut the decorative groove (if desired), the handle hole bevel and the perimeter bevel.
Seat File Bottom:
Zero 1/4" end mill on spoilboard and cut the mortise rough and finish cuts. Check with the legs that the mortise is reasonably tight. If it is too tight, run the tool path again with a small allowance.
Screw down the blank through the peg holes in the mortise into the spoilboard (I used 8 screws). That way no tabs are needed. This must be done before any other tool path is run or the seat will get loose.
Run the relief cut. Then remove the blank corner screws and remove the waste.
Swap to 1/4" ballnose, zero on spoilboard and cut the chmfer and the two bevel tool paths. Remove the seat plate and sand as desired.
Mark how the wedge peg holes are located on the leg tenons and cut a diagonal slot through the tenons with a hand saw or band saw (to allow the pegs to be hammered in and expand the tenons)
Cut 2" dowels from 1/4" rod and sand a sharp wedge into one end.
Hammer the leg tenons into the mortises with ample glue until the shoulders are seated and confirm the stool does not rock much
Pre-drill through the wedge peg holes with 5.5mm bit into the tenons about 3/4" deep. Hammer the wedge pegs in with glue, making sure the wedge is aligned with the diagonal slot. This must be done carefully as to not split the legs or the seat plate.
Let dry, sand and finish
Seat underside with mortise cutout
1/4" wedge pegs (3 per leg) to be hammered in and expand the slotted tenons
Original handmade step stool (50+ years old)
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CNC machined and tweaked copy