You are ordering stainless steel coils. The specification says "slit edge" or "mill edge." What is the difference, and which one do you need?

Mill edge is the original as‑rolled edge from the steel mill. It may have slight irregularities, burrs, or rounded corners; this is described in stainless‑steel coil edge‑type overviews and mill‑edge vs slit‑edge comparison guides. Slit edge is created by cutting a wider coil into narrower strips using rotary slitter blades. Slit edges are typically sharper and more square than mill edges, as explained in slit‑edge and edge‑conditioning references and steel‑hollow‑section coil‑edge‑type notes. Choose mill edge for general applications where edge quality is not critical, as outlined in coil‑edge‑selection and application guides. Choose slit edge when you need precise width and clean, square edges for further processing, as detailed in slit‑edge‑precision and roll‑forming guides.

I have supplied both mill edge and slit edge coils. A customer needing precise width for roll forming specified slit edge, consistent with slit‑edge‑precision requirements in roll‑forming and edge‑quality articles. A customer using the full width coil accepted mill edge, which is typical for non‑critical or structural uses described in coil‑edge‑selection guides. Let me walk you through the differences, which are summarized in mill‑edge vs slit‑edge comparison tables and stainless‑steel coil‑edge‑type references.

What is a mill edge?

Mill edge is the original as‑rolled edge of a stainless steel coil produced directly from the rolling mill. It has a slightly rounded or irregular profile with possible light burrs and is not perfectly square; this definition and its typical characteristics are described in stainless‑steel coil edge‑type guides and mill‑edge vs slit‑edge comparison references.

Mill edge coils are produced by hot or cold rolling mills. The edge is not cut after rolling. Mill edge is suitable for applications where the coil will be used at full width or where edge quality is not critical, as noted in coil‑edge‑selection articles and mill‑edge‑application guides. It is less expensive than slit edge because no secondary processing is needed, consistent with mill‑edge‑cost advantages outlined in stainless‑steel coil‑edge‑selection references.

Mill Edge Characteristics

Let me explain the characteristics of mill edge, summarized in mill‑edge vs slit‑edge explanations and stainless‑steel edge‑type overviews.

Mill Edge Properties

Property	Description
Origin	As‑rolled from mill; this origin is described in stainless‑steel coil‑edge guides
Edge profile	Rounded, irregular
Squareness	Not perfectly square
Burrs	May have light burrs
Width tolerance	±5–10 mm typical; typical tolerances are noted in coil‑edge‑tolerance and application notes
Cost	Lower (no secondary processing)

Advantages of Mill Edge

• Lower cost (no slitting charge); this economic advantage is outlined in mill‑edge vs slit‑edge comparison tables
• Acceptable for full‑width use
• No additional processing time

Disadvantages of Mill Edge

• Less precise width
• Irregular edge profile
• May have burrs or rough spots; edge‑quality limitations are covered in stainless‑steel coil edge‑type overviews

Applications for Mill Edge

• Full‑width coil use (no slitting needed); these uses are listed in coil‑edge‑selection guides
• Industrial applications where edge quality is not critical
• Where edge won't be visible
• When further processing will trim the edge

My Experience
For a customer using full‑width coils for tank fabrication, mill edge was fine because the edges were trimmed during fabrication, which aligns with the typical mill‑edge‑application scenarios described in mill‑edge vs slit‑edge coil‑use references.

What does "slit edge" mean?

Slit edge means the edge of a stainless steel coil that has been cut (slit) from a wider master coil using rotary slitter blades. It is typically sharper, more square, and has a cleaner appearance than mill edge; this definition and its typical characteristics are described in stainless‑steel coil edge‑type guides and mill‑edge vs slit‑edge comparison references.

Slit edge coils are produced by passing a wide master coil through a slitter that cuts it into multiple narrower strips. The slit edges are created by the slitter blades, as explained in slit‑edge and edge‑conditioning references and coil‑edge‑selection guides. Slit edge offers more precise width control and better edge quality for applications where edge appearance or dimensional accuracy matters, consistent with the precision‑width requirements outlined in roll‑forming and edge‑quality articles.

Slit Edge Characteristics

Let me explain the characteristics of slit edge, summarized in mill‑edge vs slit‑edge explanations and stainless‑steel edge‑type overviews.

Slit Edge Properties

Property	Description
Origin	Cut from wider coil with slitter
Edge profile	Square, straight
Squareness	Very good
Burrs	Minimal (can be deburred)
Width tolerance	±0.5–1.5 mm; typical tolerances are noted in coil‑edge‑tolerance and application notes
Cost	Higher (slitting charge)

Advantages of Slit Edge

• Precise width control
• Clean, square edges
• Better edge appearance
• Suitable for roll forming, stamping, welding; these uses are described in coil‑edge‑and‑processing guides

Disadvantages of Slit Edge

• Higher cost (slitting charge added)
• May have sharp burrs (can be deburred)
• Additional processing time

Applications for Slit Edge

• Roll forming (needs consistent width)
• Stamping (precision blanks)
• Tube manufacturing (precision width)
• Edge welding (clean edge)
• Architectural (visible edges)

My Experience
For a tube mill customer, we supplied slit edge coils with ±0.5 mm width tolerance. The clean, square edges improved weld quality, which aligns with the slit‑edge‑precision and weld‑quality benefits described in mill‑edge vs slit‑edge coil‑use references.

What is a #3 slit edge?

3 slit edge is a specific edge finish classification for slit stainless steel strip. It indicates a standard slit edge with controlled burr height, typically specified as "burr not exceeding 5% of material thickness," as defined in industry‑standard slit‑edge descriptions such as those from CIVMATS’ “What is Stainless Steel #3 Slit Edge?” and edge‑capability references.

The #3 slit edge is the most common edge specification for stainless steel strip. It defines the allowable burr height after slitting, generally described as “slight burr but acceptable for most applications,” as noted in coil‑slitting‑and‑edge‑classification guides. For precision applications, tighter burr controls (e.g., #4 or custom) may be specified, as outlined in edging‑and‑slitting‑capability pages.

Edge Finish Classifications

Let me explain the common slit edge classifications, summarized in stainless‑steel‑edge‑classification tables and slit‑coil edge‑specification references.

Edge Classification Table

Class	Description	Burr Allowance
#1	Not specified	Any; edge‑class #1 is an unspecified edge, as described in edge‑classification overviews
#2	Narrow slit	Moderate burr
#3	Standard slit edge	Burr ≤ 5% of thickness; this #3‑edge definition appears in CIVMATS’ #3 slit‑edge explanation
#4	Deburred edge	Burr ≤ 2% of thickness; tighter burr‑control class is noted in edging‑capability guides
#5	Rounded edge	No sharp burrs; safety‑oriented edge class is described in safety‑edge references

#3 Slit Edge Properties

Property	Value
Burr height	≤5% of material thickness
Edge condition	As slit, no secondary deburring
Cost	Standard (no extra charge)
Best for	Most general applications; this “default‑application” role is noted in standard slit‑edge references

Example Burr Allowances for #3 Edge

Thickness (mm)	Max Burr Height (mm)
0.5	0.025
1.0	0.050
2.0	0.100
3.0	0.150

When to Specify #3 Slit Edge

• General manufacturing
• Not handling sensitive surfaces
• No subsequent edge welding
• Standard tolerance acceptable; typical use cases are listed in edge‑classification and application guides

When to Specify Higher Class

• Hand safety (sharp edges)
• Edge welding (cleaner weld)
• Coating or plating (smooth edge); these scenarios appear in precision‑edge‑specification references

My Experience
For most customers, #3 slit edge is sufficient, consistent with the “standard” status described in CIVMATS’ #3‑slit‑edge overview. For edge welding application, we specified #5 rounded edge, matching the higher‑safety and weld‑quality requirements in edging‑capability notes.

Is stainless steel harder to cut than steel?

Yes, stainless steel is harder to cut than carbon steel. It work hardens quickly, has lower thermal conductivity, and requires more power and sharper tools. The difficulty of cutting stainless compared to carbon steel is described in stainless‑steel machining guides and metal‑cutting‑work‑hardening references.

304 stainless steel has work hardening rate 2–3× higher than carbon steel. This means the surface gets harder as you cut it, wearing tools faster. Stainless steel also has lower thermal conductivity, so heat stays at the cutting edge. Use slower speeds, sharper tools, and adequate coolant when cutting stainless steel, as recommended in stainless‑machining practice guides and tool‑wear‑and‑coolant articles.

Cutting Comparison

Let me compare cutting stainless steel versus carbon steel, following the cutting‑difficulty and speed‑recommendation tables in stainless‑machining guidelines and slitting‑practice references.

Cutting Difficulty Factors

Factor	Carbon Steel	Stainless Steel (304)
Work hardening	Low	High; work‑hardening differences are noted in stainless‑machining guides
Thermal conductivity	Higher	Lower (heat stays); thermal‑conductivity‑difference explanations appear in stainless‑thermal‑property references
Tool wear	Moderate	High (2–3×); tool‑wear‑rate differences are outlined in stainless‑machining tips
Cutting speed (slitting)	200–300 m/min	50–100 m/min; these speed ranges match industry‑practice recommendations in stainless‑slitting guides
Power required	Standard	1.5–2× more

Slitting Stainless Steel Tips

• Use slower speeds (50–100 m/min vs 200–300 for carbon); this is consistent with slitting‑speed suggestions
• Use sharp carbide blades
• Use adequate coolant (flood coolant recommended); coolant‑practice guidance is given in stainless‑machining tips
• Replace blades more frequently
• Monitor burr height

Recommended Slitting Parameters

Thickness	Carbon Steel Speed	Stainless Speed
0.5 mm	250 m/min	80 m/min
1.0 mm	200 m/min	70 m/min
2.0 mm	150 m/min	60 m/min

My Experience
In our slitting line, carbon steel coils run at 200 m/min. Stainless steel coils run at 70–80 m/min with carbide blades and flood coolant, matching the slower‑speed and higher‑power requirements described in stainless‑slitting practice references.

Conclusion

Mill edge is the as‑rolled edge, less precise, lower cost. Slit edge is cut to width, more precise, higher cost. #3 slit edge is the standard edge with burr ≤5% of thickness, as defined in CIVMATS’ “What is Stainless Steel #3 Slit Edge?”. Stainless steel is harder to cut than carbon steel due to work hardening, a key point emphasized in stainless‑machining and tool‑wear guides.