Bits / Workshop reference
Compression bits & transition length
Understand where the upcut tip changes to downcut—and why shallow passes may still tear the top face.
In everyday language
Understand both faces of a plywood part
A compression bit combines an upcut section at the tip with a downcut section above it. The change between them is the transition.
Draw a plywood edge and mark where the bit changes direction. Check which cutting section touches each face during every planned pass.
What to notice: If only the upcut section reaches the top face, it may still lift the top fibers. The exact bit drawing matters.
Should you simply make the first cut deeper to reach the transition?
Only a setup within every tool, machine and holding limit is acceptable. Choose another bit or supported cutting strategy if the required depth is unsuitable.
No need to know the vocabulary first
A few words, explained
- Collet
- The gripping sleeve that holds the shank of a cutting bit.
- CAM
- Computer-aided manufacturing: software used to prepare the machine's cutting movements.
- Veneer
- A thin layer of wood, often bonded to another material.
- 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.
How it works
The lower upcut section and upper downcut section act toward one another. Both faces benefit only when the appropriate sections engage those faces.
When to consider it
Compare compression tooling for through-profiling double-sided veneered or laminated sheet goods supported by the tool specification.
Where it does not apply
Compression is not permission to cut full depth. A shallow pass with only the upcut section at the top face can still lift its fibers.
Before the first cut
- Read the exact upcut length and transition location from the tool drawing.
- In CAM, compare that transition with actual stock thickness and the engagement at every pass.
- If the required engagement exceeds the machine, tool or workholding limits, choose another tool or a supported multi-tool strategy; do not force a deeper cut.
Review collet engagement & stickout · Review material setup & zero
If the result looks wrong
Stop the machine and make it safe to inspect before checking the tool or workpiece.
Top veneer still tears
Check whether the top face is being cut by the upcut section, especially during entry and early passes.
Thin sheet has poor edges
Check that the transition can lie within the material; a different geometry may be required.
Use the matching calculator
Calculator outputs describe geometry, time or cost—not permission to operate at those values.
Make the setup repeatable
In Machine & Bit Settings, keep these details in the standard fields, additional fields and setup notes. Record a test date only after testing that exact setup.
- Upcut length / transition
- Actual sheet thickness
- Entry and pass strategy
- Top and bottom test results
No cutting settings are automatically supplied or saved by this guide.
References & exact specifications
These public references explain the tool families or software features. Locate your exact part number and machine manual before setup; product families are not interchangeable.
Guidance reviewed September 2026. Diagrams are original simplified explanations, not manufacturer drawings.