Newcomers to
milling often face these questions: Why do workpieces processed with the same tool have varying surface finishes—some smooth, some covered in tool marks? Why do identical parameter settings result in tools lasting a week for some, but breaking within a day for others? The problem may lie in a fundamental choice—have you selected the right “climb milling” or “conventional milling”?
Today, we’ll clarify the differences between climb process and conventional milling using practical cases, focusing on 5 key dimensions that confuse new machinists most!
The rotation direction of the cutter’s cutting edges is exactly the same as the workpiece’s feed direction (e.g., the workpiece moves toward the cutter). For example, if the cutter rotates clockwise, the workpiece also moves clockwise—they “cooperate seamlessly,” making cutting smoother.
Intuitive judgment: At the point where the cutter contacts the workpiece, the cutting edges “push the workpiece forward” rather than “holding it back.”
The rotation direction of the process cutter is opposite to the workpiece’s feed direction. For example, if the cutter rotates clockwise, the workpiece moves counterclockwise—equivalent to the cutter “pulling back” the workpiece, creating a “counterforce” between them.
Intuitive judgment: When the cutting edges contact the workpiece, they “scrape the surface” with a noticeable “friction feel.”
Climb milling is “cooperative cutting,” while conventional process is “oppositional cutting”—this is the root of all differences.
At the moment of cutting into the workpiece, the cutting edges “bite off” a thicker chip (e.g., 0.2mm) in one go. As the cutter advances, the chip gradually thins and finally detaches gently from the workpiece.
Advantage: Thick chips quickly carry away cutting heat, reducing friction between the tool and workpiece. The workpiece surface is less likely to have scratches, making it suitable for finish machining (e.g., parts requiring a surface finish of Ra≤1.6μm).
Note: If the tool is not sharp enough, thick chips may cause the cutting edges to “jam” and chip.
When cutting in, the cutting edges first “scrape lightly” across the workpiece surface, producing chips as thin as paper (even only 0.05mm). As the cutter penetrates deeper, the chips gradually thicken, reaching maximum thickness when exiting.
Advantage: Thin chips avoid the hard skin on the workpiece surface (e.g., oxide layers on castings), preventing the cutting edges from directly hitting hard spots and chipping—ideal for rough machining.
Disadvantage: Initial “scraping” heats the tool, leading to rapid dulling over time and potential fine marks on the workpiece surface.
The main cutting force of climb process points toward the inside of the worktable (i.e., the fixture direction), essentially “pressing” the workpiece against the fixture. As long as the fixture clamping force is sufficient, the workpiece will barely loosen.
The main cutting force of conventional process points toward the outside of the worktable, essentially “pulling” the workpiece away from the fixture. If the fixture is not tightly clamped, the workpiece is prone to loosening and vibration.
Impact force at the moment of cutting is the “number one killer” of tool damage for new machinists—and the difference between climb and conventional milling is significant:
When cutting in, thick chips require the cutting edges to “bite off” more material in an instant, resulting in a large impact force (e.g., up to 500N) but a short impact duration. As long as the tool is made of cemented carbide (wear-resistant and impact-resistant) and the machine tool has sufficient rigidity (no wobble), stability is quickly restored.
Taboo: Using high-speed steel tools (low hardness) for climb milling of hard materials (e.g., 45# steel) is prone to chipping.
When cutting in, thin chips allow the cutting edges to “scrape into” the workpiece slowly, resulting in a small impact force (e.g., only 100N). However, as the chips thicken later, the cutting force increases continuously and lasts longer (e.g., 2-3 times longer than climb milling), easily causing tool “fatigue.” For example, long-term conventional process with high-speed steel tools will gradually curl the cutting edges.
Taboo: Too high a feed rate during conventional milling turns “long-term load” into “long-term impact,” drastically reducing tool life.
Core Features:
1.Small cutting force directed vertically downward, ensuring stable workpiece stress, minimal deformation, and low machine vibration.
2.No sliding friction when cutting edges enter the material, resulting in low surface roughness (smaller Ra value) and high machining precision.
3.Uniform tool wear and longer service life.
Application Scenarios & Conditions:
1.Suitable materials: Ductile materials (e.g., aluminum, copper, low-carbon steel, stainless steel) and high-precision parts.
2.Suitable working conditions:
- Finish machining or semi-finish machining (requiring surface quality Ra≤1.6μm)
- Firmly clamped workpieces (e.g., rigidly fixed with vices or pressure plates) to avoid displacement due to cutting force.
- Machine tools with high-precision feed systems (no backlash or compensable backlash) to prevent “creeping.”
3.Notes: Use sharp tools to avoid material adhesion; the machine tool must have sufficient rigidity to prevent vibration.
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Core Features:
1.Large upward cutting force, causing the workpiece to tend to “lift” and resulting in poor stability.
2.Sliding friction between cutting edges and the workpiece surface before cutting in, prone to built-up edge formation and high surface roughness.
3.Cutting edges first contact the workpiece’s hardened layer (oxide scale, burrs from previous processing), protecting the tool tip.
Application Scenarios & Conditions:
1.Suitable materials: Brittle materials (e.g., cast iron, cast steel, non-metallic materials) and high-hardness materials (HRC＞35).
2.Suitable working conditions:
- Rough machining (removing large amounts of stock, prioritizing efficiency over precision).
- Weakly clamped workpieces (e.g., thin-walled parts, slender shafts)—the “scraping” action of conventional c reduces deformation risk.
- Workpieces with surface oxide scale, rust, or burrs (avoids direct impact of the tool tip on hard spots during climb milling).
- Machine tools with large feed system backlash (cutting force of conventional milling offsets part of the backlash, avoiding “creeping”).
3.Notes: Reduce cutting speed to minimize tool wear; use cutting fluid if necessary to reduce frictional heat.
There is no absolute “good” or “bad” between climb milling and conventional milling—only “suitability.”
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