The claw that grabs the striker, the ratchet it locks against, the push rod that releases it — low carbon strip, fine blanked to ±0.02 mm-class geometry, then surface hardened on the faces that wear.
Door lock blanks get case hardened on the locking surfaces, and the hardening recipe only works if the core stays tough and the case response is repeatable. That is exactly what low carbon strip delivers: soft enough to fine blank with a clean edge, lean enough to carburize predictably, and cheap enough to run in high volume.
SAE1010 blanks with the lowest force and cleanest edge, ideal for thin 1.5–2.0 mm links and pawls. SAE1035 gives a slightly stronger core after hardening where the claw carries the striker load directly.
Thin + low load → 1010; direct striker load → 1035.SPCC is the JIS cold-rolled commercial strip — controlled surface, consistent gauge, no aging at the skin-pass temper. For a lock blank that is carburized anyway, SPCC and SAE1010 are interchangeable in practice; the choice follows your drawing standard.
Both are stocked; pick per your governing standard.The locking flank of a claw sees sliding wear against the striker. A conventional stamping leaves a fractured edge that becomes a wear ridge and a stress raiser. Fine blanking gives a 100% burnished flank that case hardens evenly.
The fracture zone is not a surface you can harden.Indicative values from production door lock programs. Confirm the final spec against your drawing and durability test at RFQ.
| Parameter | Typical value | Why it matters |
|---|---|---|
| Strip thickness | 1.5 – 3.0 mm | Claw and ratchet are the thicker end; link plates and push rods run thin |
| Blanked positional tolerance | ± 0.02 mm class on critical features | Bearing holes must index the mechanism stack without slop or binding |
| Shear face | 100% burnished on locking flank | Wear surface must be smooth before hardening; no fracture zone allowed |
| Burr height after blanking | ≤ 0.03 mm (pre-deburr target) | Burrs drag on the sliding surfaces and break off into the mechanism |
| Flatness | 0.05 – 0.15 mm | Stacked sub-assemblies must not bind during assembly |
| Delivery condition | Annealed or skin-passed (soft) | Clean shear + predictable carburizing response |
| Surface hardening | Case 0.2 – 0.5 mm, 550 – 650 HV (typical) | Wear life on claw and ratchet locking faces |
| Core after hardening | Tough low carbon core (indicative) | Impact resistance when the door slams shut |
Durability validation (e.g. door slam and latch cycling per the OEM test) is a system result; the material input is repeatable chemistry, gauge and surface so the hardening and blanking results stay inside the validated band.
All supplied soft (annealed or skin-passed) and slit to your die width. Choose by thickness, core-strength need, and your drawing's governing standard.
| Grade | Typical C % | Why it is specified | Typical use in the lock |
|---|---|---|---|
| SAE1010 | 0.08 – 0.13 | Cleanest blanking, lowest force, best core toughness | Thin pawls, link plates, push rod blanks |
| SAE1020 | 0.17 – 0.23 | Slightly stronger core, still fully case-hardenable | Ratchets on light-duty side-door locks |
| SAE1035 | 0.32 – 0.38 | Higher core hardness for striker-loaded claws | Main lock claw, heavy ratchet |
| SPCC (JIS) | ≤ 0.12 | JIS cold-rolled commercial strip; controlled surface and aging behavior | Locks specified to JIS drawing standards |
| SPCD / SPCE (JIS) | ≤ 0.10 / ≤ 0.08 | Deeper drawing grades where a link plate is formed, not just blanked | Formed brackets and deep-drawn housings |
Chemistry shown is the typical band; confirm the delivered heat on the MTC. SPCC/SPCD/SPCE values are indicative of the JIS G3141 family — refer to the latest revision of the standard for the governing limits.
These are the failure modes that show up in lock programs, in order of how often we see them.
A burr on the claw flank drags on the striker and fails the pull-force test. Material side: consistent gauge and a clean annealed surface keep the die cutting a full burnish instead of tearing at the edge.
If thickness wanders across the coil, the die clearance changes and the hole pattern drifts. Solution: precision cold-rolled strip with a tight, agreed thickness tolerance and controlled camber for the feeder.
Chemistry scatter — especially Mn and residuals — shifts case depth and surface hardness. Solution: lean low carbon grades with a documented chemistry band so the carburizing line holds one recipe.
Thin 1.5 mm pawls can crack at the shear edge if the strip is over-hard from skin passing. Solution: controlled temper and softness band, with elongation confirmed on the inspection report.
The lock mechanism uses more than one steel family. Match your part to the line below and confirm at RFQ.
SAE1010–SAE1035 / SPCC annealed strip for claws, ratchets and pawls — the core of this page. Fine blanking range →
SPCD/SPCE or DC04 for formed brackets and housings around the mechanism. Low carbon family →
Some lock levers and springs run medium or high carbon where through-hardening beats case hardening. SAE1078 strip →
A typical side-door lock claw program, described the way it runs.
The part is a lock claw about 55 mm long, 2.5 mm thick, with a striker-receiving mouth on one end, a bearing bore in the middle and a spring hook on the tail. The drawing calls SAE1020 strip, 2.5 × 90 mm coil, carburized after blanking to 550–650 HV on the mouth and bore faces. The fine blanking line runs a progressive die — V-ring clamp, punch, counter-pressure — at 25–35 strokes per minute, holding the mouth profile and bore position inside ±0.02 mm. Shear face comes out fully burnished; burr stays under 0.03 mm before tumbling deburr.
Blanks go through the carburizing furnace with the other lock components, then the bore is reamed to final size. In the durability rig the claw cycles against the striker 100,000+ times; the wear limit is set by the case, and the case is set by chemistry consistency. Every coil of that 2.5 mm strip left our line annealed with the chemistry band on the MTC — which is the only way the carburizing line can hold one recipe for the whole production run.
If your drawing sits in the 1.5–3.0 mm low carbon envelope, the conversation is short: send the drawing, confirm the grade and case spec, and we quote a trial coil.
Related reading: fine blanking vs. conventional stamping — when the shear face has to be clean, and why chemistry scatter breaks your carburizing recipe.
These grade families share material, processing or application territory with the topic on this page.
SAE1078 / 65Mn / SK5 grades for hardened parts, springs and cutting edges.
65Mn / 50CrV4 / 60Si2Mn grades with high elastic limit and fatigue resistance.
SK5 / SK7 / T8A / T10A grades with wear resistance and edge hardness for cutting tools.
Send the drawing or part number, thickness × width, quantity and destination port. Our engineers reply within one working day with grade match, gauge tolerance and a trial-coil option.