No need to know the vocabulary first
A few words, explained
- Spindle
- The rotating assembly that turns the cutting tool.
- CAM
- Computer-aided manufacturing: software used to prepare the machine's cutting movements.
- CNC
- Computer numerical control: a computer directs a cutting machine.
- Stock
- The wood or other material you start with.
- Workholding
- The way you keep a piece securely in place while working on it.
- Toolpath
- The route a cutting tool follows through a job.
3 more words used on this page
- Work zero
- The starting reference point used to locate a job on the machine.
- Feed rate
- How quickly a cutting tool moves along the material.
- Grain
- The direction and pattern of the wood's fibers.
Before you begin
Machine and controller manuals, a CAM preview, and an unpowered setup review. Physical testing requires machine-specific instruction.
What this lesson covers
- Tell machine home apart from the job's work zero.
- Compare stock size, origin, and units across the workflow.
- Explain why simulation cannot prove the physical setup is safe.
Recommended preparation
01 / Understand
How it works
Accurate CNC work depends on the drawing, toolpath and physical setup using the same dimensions and reference points. This lesson covers the stock, tooling and coordinate checks to make before the spindle starts.
Prepare stock that matches the plan
Confirm thickness, flatness, grain or face orientation, and the usable machine area. A warped board or a sheet that is not supported can turn correct toolpaths into inaccurate parts.
Match the coordinate system to the setup
Know where your design origin is, where the machine expects the work origin, and which corner or center you actually zeroed. These three references must agree before you start.
Check the setup before production
Use preview or simulation, confirm the tool and offsets, then use a controller-appropriate temporary Z offset or air-cut reference to prove clearance, or make a controlled test piece. Restore and re-verify the intended work zero before the production cut.
Key points
- A drawing origin, CAM origin, and machine zero must describe the same physical point.
- Flat stock and secure workholding help maintain accurate dimensions.
- Simulation checks the planned toolpath; a controlled test also checks the physical setup and resulting part.
02 / Worked example
A mismatch between CAM origin and work zero
A 200 × 100 mm example blank uses a lower-left CAM origin. The operator instead intends to zero at its center. Compare the references before any motion.
| Reference | CAM plan | Physical setup |
|---|---|---|
| X/Y origin | Lower-left corner | Center: mismatch, stop |
| Z reference | Stock top | Must match the CAM choice |
| Units | Millimeters | Verify controller and file units |
| Resolution | One approved setup sheet | Restore agreement and recheck |
03 / Try it with your project
Apply the method
Work through the drawing or setup review first, then use a sample that matches your project. Check the equipment and safety requirements above before starting any machine work.
- Use a scrap rectangle and mark its show face.
- Set the intended X/Y/Z work zero, then use your controller’s documented temporary Z offset or air-cut zero to prove clearance—do not assume the programmed path will remain above the stock.
- Restore and re-verify the intended work zero, then measure the controlled test against the drawing before the first production run.
Common mistakes
- Zeroing from a different corner than CAM expects.
- Ignoring stock thickness or a bowed board.
- Failing to check clamp positions against the toolpath.
Take it further
Build a setup sheet another trained operator could review without guessing: file revision, units, stock, tool, origin, holding, clearance, and first-part acceptance.
Workshop checklist
Use this topic checklist alongside your machine’s full setup procedure.
- Verify material thickness and usable area.
- Confirm bit type, diameter, condition, and secure installation.
- Confirm workholding and clearance for clamps or screws.
- Set and verify the intended work zero.
- Preview the toolpath and use a controller-appropriate air-cut or controlled test when appropriate.
04 / Review questions
Review the key decisions
Consider each question, then compare your answer with the explanation. Return to the worked example whenever you need it.
1. Does homing the machine establish the correct work zero for every job?
View hint
Machine coordinates and job coordinates serve different purposes.
View explanation
No. Homing establishes the controller's machine reference. The job's work origin still needs to match the CAM setup using the controller's documented procedure.
2. What must happen after a documented temporary air-cut offset?
View hint
Check which work zero the production file expects.
View explanation
Restore and verify the intended work zero using the controller manual, then complete the setup checks before production.
05 / Project notes
Notes for your next project
Check off the topics you have reviewed and record anything useful for your next build. This tracks your learning progress; use your equipment’s setup procedure for machine checks.
Record: Material, thickness, bit, work zero, hold-down method, test result, and any correction you made.
No notes recorded. Use this space for your observations.
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Check each topic above to mark the lesson as reviewed. You can browse any lesson at any time.
Related calculators
Use your project measurements and costs in the calculators below. Check the results against the stock, equipment and requirements of the job.
Practice with a complete project
Apply the lesson to measured dimensions, then keep the drawing, material list and build checks together.
Sources & further study
WoodWorkCalc writes the exercises and illustrative examples. Named historical cases are attributed separately. These sources support the principles identified in the lesson; their publishers do not endorse WoodWorkCalc. Guidance and platform features can change. Sources retain their own copyright and licensing terms.
- ShopBot Tools — CNC Documentation (opens new tab)
Manufacturer's documentation directory for model-specific CNC setup, software, and accessories. Use the manual for your own machine; ShopBot procedures are not universal.
ShopBot Tools. Support Resources. Accessed September 10, 2026.
- Occupational Safety and Health Administration — Woodworking eTool (opens new tab)
Public overview of common woodworking-machine hazards and controls.
Occupational Safety and Health Administration. Woodworking eTool. Accessed September 2026.