ktscrew - Blog by King Tower

New Cold Heading Machines Online

Sat, 10 Oct 2026 03:33:40 +0000

New Cold Heading Machines Online | Custom Special-Shaped Screws, Bolts and Nuts Production Expanded

At hardware factory, we are pleased to announce the successful installation and commissioning of our new cold heading machines, marking another key upgrade to our manufacturing capabilities for specialty fasteners.

Cold forging (cold heading) technology is the core process for producing high-strength bolts, nuts and special-shaped screws. Unlike traditional machining, cold forming deforms metal wire at room temperature. This method preserves the intact metal grain flow of the raw material, delivering finished parts with superior mechanical strength, consistent dimensional accuracy and excellent surface finish. It is ideal for mass production of fasteners used across automotive, electronics, construction, renewable energy and machinery industries.

Our newly added cold heading equipment is specially configured for non-standard / special-shaped fasteners, alongside standard bolts and nuts. Many projects require custom-designed fasteners that cannot be sourced from off-the-shelf catalogs. Whether you need bespoke profile screws, irregular shoulder bolts, special nuts or other custom cold formed components, these machines allow us to flexibly develop and produce custom parts according to your drawings and samples.

With the expanded production line, we can now handle more orders for custom fasteners with shorter lead times while maintaining stable quality control. From raw material wire feeding, multi-station forming to in-process inspection, every production step is closely monitored by our technical team. Our engineers are on-site to fine-tune tooling and parameters, to ensure every batch meets international standards such as DIN, ISO and custom customer specifications.

We understand that reliable custom fasteners are critical to your end product performance. This equipment investment is our commitment to supporting global buyers: we can deliver both small-batch prototype runs and large-volume mass production for your special fastener projects.

If you have inquiries about custom shaped screws, specialty bolts or nuts, feel free to send us your drawings or samples for quotation. We are ready to support your next project with professional cold forging manufacturing solutions.

Send an Inquiry

Pre-Shipment Inspections for Non-Standard Screws

Fri, 09 Oct 2026 06:35:05 +0000

Pre-Shipment Inspections for Non-Standard Screws: What Every Buyer Should Verify

Non-standard screws are not off-the-shelf products. They are made to your drawings, samples, or specific application requirements, which means a pre-shipment inspection is not just a routine check—it is the last line of defense before your goods leave the factory. For custom fasteners, the margin for error is narrower, the stakes are higher, and the cost of a failed shipment is far greater than for standard parts.

This article walks through the key inspections that should be completed before non-standard screws are cleared for transport. Whether you are a sourcing manager, engineer, or importer, understanding these checkpoints helps you avoid installation failures, project delays, and unnecessary disputes. First, watch the video below to see the dimensional checks our factory performs when manufacturing custom screws.

Dimensional and Thread Verification

For non-standard screws, dimensions are not negotiable. Every critical measurement must match the approved drawing or sample, including head diameter and height, shank length, thread length, major and minor diameters, pitch, and thread angle . Even a small deviation in thread pitch can render an entire batch unusable in automated assembly.

Thread verification typically uses go/no-go gauges to confirm that the thread is within tolerance—the “go” gauge must pass through the full thread length, while the “no-go” gauge must not enter more than the allowed number of turns. For non-standard thread profiles, custom gauges or optical measurement tools may be required. Some manufacturers also use 2D/2.5D projectors or laser scanning systems to capture precise profile data.

Material and Chemical Composition

Non-standard screws are often specified with a particular material grade—carbon steel, alloy steel, stainless steel (such as SUS304 or SUS316), or a specialized alloy—because the application demands specific strength, corrosion resistance, or temperature performance. Before shipment, material verification should confirm that the actual raw material matches what was ordered.

Chemical composition analysis can be performed using spectrometer or optical emission spectrometry to check elements like carbon, manganese, chromium, and nickel . For stainless steel, a simple spot test can distinguish between grades like SUS304 and SUS201, though laboratory analysis provides more reliable documentation. If the order requires a material certificate, this documentation should accompany the shipment or be available before dispatch.

Mechanical Performance Testing

Mechanical properties determine whether the screw will perform under load without deforming or breaking. For non-standard fasteners used in structural, automotive, or equipment applications, pre-shipment inspection should include some combination of the following:

Tensile strength and proof load: Confirms the screw can withstand specified pulling forces without permanent deformation .

Hardness testing: Core and surface hardness correlate with strength and wear resistance.

Wedge tensile test: Evaluates the ability of the fastener to withstand tensile stress under a wedge-shaped load, simulating real-world off-axis loading.

Head soundness and impact test: Detects cracks or structural weaknesses in the head that could cause failure during installation.

The specific tests required depend on the material grade and application. For high-strength or safety-critical fasteners, these tests are not optional—they are essential documentation for acceptance.

Surface Treatment and Corrosion Resistance

Non-standard screws frequently receive specialized coatings—zinc plating, hot-dip galvanizing, Dacromet, Geomet, zinc-nickel, or custom finishes—to meet corrosion resistance requirements. Pre-shipment inspection should verify both the presence and quality of the coating.

Coating thickness measurement ensures the specified micron range is achieved; too thin and corrosion protection is insufficient, too thick and thread fit may be compromised . Adhesion testing, such as cross-hatch or scribe testing, checks whether the coating will flake or peel during handling and installation.

For applications exposed to moisture, salt spray, or industrial environments, salt spray testing provides a standardized measure of corrosion resistance. Neutral salt spray (NSS) is the most common method, with test duration ranging from 48 hours for standard protection to 1000 hours or more for marine or chemical applications . The test criteria should specify what constitutes failure—typically, red rust on the base metal, not white rust on the coating.

Additional Considerations for Non-Standard Parts

Because non-standard screws lack a universal reference standard, pre-shipment inspection should also confirm alignment with the approved sample or drawing revision. If the order was based on a sample, that sample should be retained and used as the reference during inspection.

Packaging should also be verified: correct quantities, proper labeling, rust-preventive packaging where required, and any specified assembly of washers or nuts. Inspection photos of packaging and labels can supplement documentation, though they do not replace dimensional and material verification.

Finally, confirm which inspection documents will accompany the shipment—certificate of conformity, material certificate, dimensional report, or inspection certificate according to EN 10204 3.1. These documents are often required for customs clearance, end-customer acceptance, or quality traceability.

Pre-shipment inspection for non-standard screws is a multi-layered process: dimensions and threads, material composition, mechanical performance, and surface treatment. Each layer addresses a different failure risk. Skipping any of them increases the chance that the goods arrive unusable or non-compliant.

For buyers, the key is to communicate inspection requirements clearly before the order is placed, not after production is complete. The clearer your specifications and the more specific your inspection expectations, the smoother the shipment will go.

Send an Inquiry

PPAP Documents for Hardware Orders

Wed, 05 Aug 2026 07:32:09 +0000

When Do You Need PPAP Documents for Hardware Orders

PPAP stands for Production Part Approval Process, a standardized quality package originated from the automotive industry. It is not a simple inspection report. Instead, it is a full set of quality evidence to prove that our mass-production process can stably manufacture fasteners fully matching your drawing, material, performance and surface-treatment requirements.

For custom bolts screws and safety-critical hardware parts, PPAP gives overseas buyers confidence before formal mass production starts.

When is PPAP required for fasteners

King Tower Hardware shall provide PPAP documents under these typical scenarios:

1. Brand-new custom fastener parts for first-time mass production;

2. Engineering drawing revision, material upgrade or surface-treatment modification;

3. New mould, new production line or production site transfer;

4. After long-term production stop (over 12 months) for the same part number;

5. Requested by customers for automotive, new-energy, heavy-equipment safety-related components.

Standard off-the-shelf commodity fasteners usually do not require full PPAP, subject to customer agreements.

Brief introduction to PPAP submission levels

There are 5 submission levels defined by AIAG, Level 3 is the most widely-used default for most automotive & new-energy projects.

- Level 1: Only Part Submission Warrant (PSW)

- Level 2: PSW + samples + partial supporting data

- Level 3: PSW + samples + complete supporting documents (common requirement)

- Level 4: PSW plus special documents specified by buyers

- Level 5: Complete data kept at manufacturer site for on-site audit review

A complete Level 3 PPAP package for fasteners generally includes drawing records, full-dimension inspection reports, material certificates, salt-spray test records, process flow, control plan, PFMEA and qualified production samples.

Why PPAP matters for overseas buyers

Many quality risks of fasteners happen not in sample stage, but in mass-production batches. PPAP validates process capability rather than only single-piece sample quality. It helps you avoid batch inconsistency, material mixing and performance failure in later volume orders.

As a fastener manufacturer, we are capable of preparing PPAP packages for custom and safety-critical hardware. Please tell us your required submission level at the project early stage, so we can arrange relevant records during pre-production.

If you need PPAP-supported custom fasteners or more quality-related documentation, feel free to contact our team for quotation and technical support.

Why a Strict Pre-Shipment OQC Inspection Standards Products Saves Buyers Quality Risks

Tue, 04 Aug 2026 09:37:07 +0000

Why Pre-Shipment QC Matters for Overseas Buyers

Pre-shipment inspection is the last quality barrier before delivery. It eliminates batch inconsistency, unqualified surface treatment, dimension tolerance errors and packaging problems. Buyers can receive consistent-quality fasteners every time, reduce return rates, and maintain stable supply chain reliability.

For overseas hardware and fastener buyers, pre-shipment quality inspection is the final quality gate before goods leave the factory. Unlike incoming material inspection that focuses on raw material quality,pre-shipment QC inspection verifies finished product consistency, compliance, and overall conformity to drawings, customer standards, and export requirements. A complete pre-shipment inspection report ensures stable batch quality and minimizes overseas after-sales risks.

What is Pre-Shipment QC for Fasteners?

Pre-shipment QC is a final sampling inspection for finished fasteners and metal accessories before packaging and shipment. It covers appearance, dimension, surface treatment, mechanical performance, environmental compliance, and packaging verification. All inspection items follow standardized factory SIP specifications to ensure every delivered batch meets export quality requirements.

Core Pre-Shipment Inspection Items

1. Visual & Appearance Check

Inspectors verify surface smoothness, no rust, oxidation, burrs, scratches, coating peeling or deformation. Threads are fully checked for complete crests, no missing threads, chips or damage. The overall appearance must match approved samples and drawing standards without cosmetic defects.

2. Key Dimension Inspection

Critical dimensions and tolerance parameters are sampled and measured using calipers, 2.5D measuring instruments, and go/no-go gauges. Star-marked key dimensions on drawings are fully verified to guarantee perfect assembly for customer end products.

3. Surface Treatment & Corrosion Resistance

Finished electroplated parts are checked for uniform coating thickness. For anti-corrosion required products, we review qualified salt spray test reports (typically 48H) to confirm no oxidation or discoloration, ensuring long service life for automotive, machinery and outdoor applications.

4. Mechanical & Mating Performance

Batch sampling is performed to test torque resistance and pull-out force according to drawing requirements. Mating fitting tests ensure no jamming, slipping or assembly failure, which guarantees stable mechanical performance in mass installation.

5. Environmental Compliance Verification

All export batches are confirmed RoHS and REACH compliant. XRF testing and compliance documents are provided to meet European and American import standards, avoiding customs clearance and audit risks.

6. Packaging & Labeling Standard

Final inspection includes quantity verification, batch labeling, and outer packaging checks. Each package is clearly marked with product specification, batch number, production date and compliance marks. Waterproof, moisture-proof and pressure-resistant packaging ensures safe long-distance sea shipment.

We provide complete pre-shipment QC inspection reports for every export batch, including dimension data, surface treatment records, salt spray test results, material certificates, and compliance documents. All quality data is traceable and fully matches customer drawing requirements.

If you need stable-quality custom fasteners with official pre-shipment inspection reports, contact us for detailed quality documents and quotation.

Rose Gold Carriage Bolts for Baby Strollers

Fri, 31 Jul 2026 09:36:59 +0000

Rose Gold Carriage Bolts for Baby Strollers: When Fastening Meets Aesthetics

In the world of baby strollers and pushchairs, every visible component must balance safety, durability, and design. Screws and bolts are no exception. Recently, we completed a custom fastener project for a German stroller manufacturer – a brand known for its premium infant carriages and attention to detail. The request was anything but standard:

“We need square neck carriage bolts in rose gold finish, with a reliable anti-loosening feature – and they must perfectly match our new stroller collection.”

Here is how we turned this requirement into a one-stop custom solution.

The Challenge: More Than Just a Bolt

Carriage bolts are typically hidden inside wood or metal structures. But on modern baby strollers, certain fasteners remain visible. That means they become part of the product’s appearance.

The German customer had three specific demands:

1.Square Neck for a Secure Fit

A standard round neck bolt can spin inside a square hole. The square neck under the round head locks into the stroller’s frame, preventing rotation during assembly. This is especially important for folding mechanisms and wheel attachments.

2. Special Rose Gold Surface Treatment

Most industrial carriage bolts are plain zinc-plated or black. But this stroller collection uses a warm rose gold accent.
We developed a custom electroplating process that delivers a consistent, scratchresistant rose gold color – not too pink, not too yellow – matching the customer’s Pantone reference.

3. Blue Nylon Patch for Anti-Vibration

Strollers are constantly shaken – over cobblestones, curbs, and rough sidewalks. Standard thread locking methods (like spring washers) can loosen over time.We applied a blue nylon patch on the threads. When the bolt is screwed in, the nylon compresses and creates a constant friction force. This makes the bolt vibration-resistant without damaging the mating thread or requiring glue during assembly.

Our One-Stop Custom Fastener Service

This project perfectly illustrates what we do best: taking a non-standard idea and turning it into a repeatable, high-quality product – all under one roof.

Shape customization – Square neck dimensions were adjusted to match the stroller’s specific mounting holes.

Size and tolerance – Length, thread pitch, and head height were optimized for compact folding mechanisms.

Surface finish – Rose gold electroplating with extra corrosion resistance .

Thread locking – Blue nylon patch applied precisely at the required position and coverage.

We handled everything from raw material sourcing to final 100% visual inspection. No outsourcing, no communication gaps.

Whether you make baby strollers, furniture, e-bikes, or agricultural equipment – if you need a fastener that doesn’t exist in any standard catalog, talk to us.

Get Started Now