When a slit coil arrives at your press shop, it should be ready to feed into your die without adjustment. Width should be within spec. Edges should be clean. The strip should run straight. If any of these are off, you're either scrapping parts or adjusting your process to compensate — both of which cost money. These five questions will help you separate serious coil slitting vendors from those who will cause problems on your production line.
Width Tolerance — What's Achievable?
Width tolerance is the most critical quality parameter for press shop buyers. A slit strip that is 0.5mm wider than specified may not feed correctly through a progressive die, causing misregistration, scrap parts, or die damage.
Industry standard for general HR slitting is typically ±0.3mm to ±0.5mm. For CR coil slitting serving auto stamping applications, buyers should expect ±0.1mm to ±0.2mm from a competent vendor.
Ask your vendor: What tolerance do you guarantee on this material and thickness? Can you provide a sample order before full volume commitment?
Edge Burr Height
Burr is the small raised edge created when the slitter knife shears through the steel. Excessive burr causes problems downstream — it can scratch mating surfaces during press feeding, cause edge cracking when the strip is formed, and create handling injuries.
Burr height acceptable levels depend on thickness and application. For thin CR material going into auto components, buyers typically require burr height under 10% of material thickness. For heavier HR material in general fabrication, the tolerance is wider.
Ask your vendor: What burr height can you achieve on this gauge? How frequently do you change blades?
Camber (Lateral Bow)
Camber is the lateral curvature of a slit strip — the tendency for it to curve sideways along its length rather than running straight. It's measured as the deviation from a straight line over a given length (typically mm per metre or mm per 2 metres).
Camber causes significant problems on coil-fed progressive die lines. If a strip runs crooked into the die, parts are stamped off-centre, pilot pin registration fails, and scrap rates climb. On roll forming lines, camber causes the formed section to twist.
Ask your vendor: What camber spec do you achieve? How do you control tension to minimise camber on narrower strips?
Surface Condition
For CR and SS coil slitting, surface integrity matters. Scratches, oil stains, and contact marks on the slit strip surface can cause problems in painting, plating, and visible components.
HR coil slitting is less sensitive to surface condition since the mill scale already creates a rough surface, and downstream applications (welding, structural assembly) are generally unconcerned with surface scratches.
Ask your vendor: How do you protect CR and SS surfaces during slitting and recoiling? What separator paper or interleaving do you use?
Material Traceability and Test Certificates
For auto component suppliers working within an OEM quality system, material traceability is non-negotiable. The steel grade, mechanical properties, and chemical composition must be documented and traceable to the source mill.
A Mill Test Certificate (MTC) accompanies the original coil from the steel mill and records this information. When you send your coil for job work slitting, the MTC should be available for reference against the slit coils returned to you.
Ask your vendor: Do you maintain processing records? Can you facilitate MTCs on material you supply? Do you have any traceability system for job work material?
Bonus: How to Evaluate a Vendor's Equipment
A vendor's equipment condition directly affects their output quality. When visiting or asking about a facility, check:
- Slitter type — arbor-based multi-blade slitters give better consistency than single-pass disc cutters
- Blade condition — dull blades increase burr. Ask how frequently they are changed or reground
- Tension control — proper entry and exit tension control reduces camber, especially on narrow strips
- Coil handling — adequate mandrel and recoiler capacity for your coil weights
Request a Sample Order from MVEE Industries
We welcome sample orders before full volume commitment. Send us your coil spec and we'll demonstrate our quality on a trial run.