WORKSHOP GUIDE · 03
Buy the grade. Build to the actual size.
A label such as 5/4 or 6/4 describes a nominal hardwood thickness. Your frame needs the usable size after milling. Those numbers should never be swapped without checking the stock.
A small face change that matters
Start with the floating-canvas example: 24″ × 18″ canvas, 1 1/2″ canvas thickness, 1/8″ gap, 3/8″ support ledge, 1/8″ setback, and 3/8″ retained ledge thickness. This time request a 5/8″ frame face.
The requested full blank width is 5/8″ + 1/8″ + 3/8″ = 1 1/8″. Its requested depth is 2″. In the default rough-lumber plan, 1/4″ is reserved for milling. A nominal 5/4 board (1 1/4″) would leave only 1″, which is too small under that assumption.
What the calculator does with 6/4
The next modeled grade is 6/4: nominal 1 1/2″, yielding 1 1/4″ after the selected allowance. The extra 1/8″ increases the face from the requested 5/8″ to 3/4″. The gap and ledge stay the same. The live result therefore has an outside size of 25 3/4″ × 19 3/4″, rather than the 25 1/2″ × 19 1/2″ implied by the original narrower face.
| Piece | Qty | Short point | Long point |
|---|---|---|---|
| Top + bottom | 2 | 23 1/4″ | 25 3/4″ |
| Left + right | 2 | 17 1/4″ | 19 3/4″ |
Use the adjusted cut list shown by the calculator. Do not mix the original sketch’s outside size with the wider final blank.
Surfaced is still an assumption until measured
The surfaced-lumber option models usable thickness as nominal thickness minus 1/4″: 4/4 → 3/4″, 5/4 → 1″, 6/4 → 1 1/4″, and 8/4 → 1 3/4″. This is a planning convention, not a universal S2S specification. A seller may offer a different final thickness; rough stock may need more cleanup than expected.
When you already know the true dimensions
Choose “Use boards I have” and enter measured usable thickness, width, length, and quantity after necessary cleanup. Add separate entries when boards differ. The tool combines only boards that can yield a common finished profile, and checks the four rail lengths with cutting allowances. A cross-section fit alone does not establish enough material; unknown lengths leave that question unresolved.
Before buying, confirm finished yield with the seller and inspect for bow, twist, splits, and knots. A waste percentage is a reserve, not a guarantee that each rail can avoid a defect.