# Laser Kerf Test & Press-Fit Gauge

> Cut a kerf test coupon and a press-fit comb, then turn your measurement into kerf and fit settings. Generate a kerf test frame (an opening divided into equal pieces) and a press-fit comb with engraved slot offsets for your material thickness. After cutting, push the pieces to one side, measure the gap and enter it: the tool divides it by the number of cuts and tells you the kerf compensation and the fit clearance to use for finger-joint boxes, slots and sliding lids.

Part of usefulweb.app (https://usefulweb.app/). Part of [Kerfwise](https://kerfwise.usefulweb.app/) (ownerApp: kerfwise). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://kerfwisekerftest.usefulweb.app/ (interactive tool at https://kerfwisekerftest.usefulweb.app/tool)
- JSON API: POST https://kerfwisekerftest.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://kerfwisekerftest.usefulweb.app/api/v1/tool)
- OpenAPI: https://kerfwisekerftest.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://kerfwisekerftest.usefulweb.app/mcp - tool `kerfwise_kerf_test`

## Inputs
- thickness (number): Material thickness (mm)
- pieces (integer): Pieces in the kerf frame
- pieceWidth (number): Piece width (mm)
- fitStart (number): First comb slot: thickness plus (mm)
- fitStep (number): Comb slot step (mm)
- fitCount (integer): Comb slots
- gap (number): Measured gap after pushing the pieces together (mm, 0 = not yet)
- slot (integer): Comb slot with the fit you want (0 = not yet)
- sheetWidth (number): Sheet or laser bed width (mm, 0 = no sheet) - With a sheet size the parts are nested onto as many sheets as needed; 0 lays every part out in one drawing.
- sheetHeight (number): Sheet or laser bed height (mm, 0 = no sheet)
- spacing (number): Gap between parts (mm) - For CNC routing use at least the cutter diameter.
- labels (boolean): Part names on a separate label layer
- paper (select): PDF pages

## Method
- The kerf frame has an opening of n × piece width, divided into n pieces by n − 1 cuts. Including the two sides of the opening, n + 1 cuts cross the strip and each removes one kerf, so pushed together the pieces leave a gap of (n + 1) × kerf: kerf = gap ÷ (n + 1).
- Comb slot k is cut at a nominal width of thickness + offset k; the laser widens it by one kerf. If slot k gives the fit you want, a slot that is kerf-compensated by the measured kerf needs a fit clearance of offset k + kerf to feel the same.
- Cut the test without kerf compensation. Numbers are engraved with a single-stroke font on the engrave layer. SVG files use millimetres (width/height in mm, 1 user unit = 1 mm) with one group per layer: cut (red #e4002b), score (blue #0067c5), engrave (black) and labels (grey). DXF R12 uses the same layers, millimetres, y up.

## Limits
- Laser cutters and CNC routers can start fires and release harmful fumes: never leave the machine unattended, use extraction, and never cut PVC, vinyl or other chlorine-containing plastics. Sizes, kerf and fit are starting points — check them with a test cut and follow your machine maker's safety rules.