When screw length or length-to-diameter ratio moves beyond practical catalog options, the manufacturing route matters as much as the nominal size. Shi Shi Tong reviews the complete drawing—including shank, thread zones, head, drive, material, strength, finish and inspection requirements—before sampling and repeat production.
Extra-long is not one universal length category. A screw becomes an extra-long manufacturing project when its total length or length-to-diameter ratio begins to change forming stability, thread production, handling, heat-treatment behavior or inspection strategy.
Shi Shi Tong evaluates extra-long projects across an overall diameter range of M1.4–M12, with lengths up to 2000 mm subject to the complete design. Diameter, geometry, material, thread coverage, strength, surface treatment, tolerance, quantity and validation requirements determine the feasible combination.
| Nominal diameter | Approximate length that commonly triggers extra-long review | What changes in the review |
|---|---|---|
| Up to M2 | Above 50 mm | High length-to-diameter ratio, handling, shank condition and measurement references become more sensitive. |
| M2–M3 | Above 80 mm | Forming route, thread coverage, bending risk and inspection setup require closer evaluation. |
| Above M3 | Above 150 mm | Geometry, material, production route and effective thread length determine whether catalog-style processing remains practical. |
These values are Shi Shi Tong’s initial project-screening references, not an industry standard or an automatic feasibility limit. Designs around 200–300 mm and above are a particularly relevant custom-manufacturing direction, while every final decision remains drawing-specific.
Use these groups to identify the closest starting point. Final manufacturability is confirmed from the drawing, assembly conditions and required production volume.
For projects that exceed standard catalog lengths or require a non-standard combination of diameter, head, drive, thread and material. Lengths up to 2000 mm can be evaluated within the confirmed M1.4–M12 range.
For high length-to-diameter designs and narrow assembly spaces where a long fastener must remain compatible with a small nominal diameter. Geometry, handling, thread formation and inspection references are reviewed together.
Custom metric or inch machine screws can be evaluated with socket, external-hex, Phillips, slotted or combination-drive concepts. Head geometry, recess depth, thread fit, point style and effective engagement must be defined by the applicable standard or approved drawing.
Full thread supports extended engagement or adjustment, while partial thread provides a defined shank for location, clearance, bearing or clamping. Extra-long shoulder and stepped-shank configurations can also be evaluated when the drawing defines each diameter, transition and functional length.
For projects with defined strength, hardness or heat-treatment requirements. 12.9-grade requests can be evaluated against the applicable standard, diameter, material, geometry, coating and hydrogen-embrittlement controls; the grade is not assumed for every long-screw design.
Carbon steel, alloy steel, stainless steel, titanium, copper, brass and aluminum options can be reviewed according to strength, corrosion, weight, conductivity, appearance, forming and machining requirements. Not every material is feasible in every dimension or forming route.
Security drives, thread-locking treatments, nylon patches, extra-long set screws and extended-tip configurations can be evaluated for removal control, vibration resistance, positioning or retention. Define tip geometry, mating contact, installation torque, removal and reuse conditions before production.
Head height, diameter, bearing face and drive geometry can be adapted to installation space, torque transfer, flush mounting or appearance requirements. Available concepts include socket cap, pan, truss, flat or countersunk, washer-style and drawing-specific heads, subject to forming, tooling and rights review.
Long self-tapping screws are not a standard stock family in Shi Shi Tong's range. Selected industrial designs can be evaluated when an extended-length screw must form or cut a mating thread in a compatible substrate or prepared hole.
Feasibility depends on the complete drawing, length-to-diameter ratio, thread and tip geometry, substrate, starting-hole condition, material, finish, quantity and validation requirements.
Past samples include stainless steel and black-finished carbon-steel designs with a Phillips pan head, extended unthreaded shank, partial self-tapping thread and pointed tip. These samples show a completed customization route, not a stocked size range.
Review: overall length, shank diameter, thread length, point geometry, Phillips recess, substrate and starting hole.
A past sample combines an internal hex socket head, long partial-thread shank and flat tip. A flat tip is not suitable for every substrate; the starting hole, thread engagement and installation method must be reviewed for each new design.
Review: socket and head dimensions, shank length, thread length, starting hole, tip style, material and finish.
Other head, drive, thread and tip concepts are considered only from a complete drawing or representative sample. The mating material, starting hole and installation process determine whether the thread and tip are suitable.
For an initial review, provide the screw's overall and threaded lengths, shank diameter, head and drive, thread and tip geometry, substrate, hole diameter and depth, material, finish, expected quantity and critical inspection requirements. The M1.4–M12 and up-to-2000-mm figures describe the overall long-screw evaluation range, not every possible self-tapping combination.
A self-tapping screw forms or cuts a mating thread in a suitable substrate or prepared hole. A self-drilling screw uses a drill point to create the starting hole before forming the thread. The custom option shown here does not include drill-tail, drill-point or TEK screws.
This option is for selected industrial drawing-based projects. It is not a range for wood, decking, drywall, roofing, structural timber, masonry or anchors.
| Field | Available direction | Selection implication |
|---|---|---|
| Diameter and length | M1.4–M12, with lengths evaluated up to 2000 mm. | The feasible combination depends on diameter, length-to-diameter ratio, geometry, material, strength, tolerance and process route. |
| Thread system | Metric or inch machine threads; selected drawing-defined long self-tapping projects may be evaluated. | State the applicable thread standard or full profile, mating material and starting-hole condition. Self-drilling and TEK screws are outside this page's scope. |
| Thread and point style | Full thread, partial thread, project-specific thread zones, machine-thread pointed ends, reduced or tapered ends, and selected self-tapping tip concepts reviewed from drawings. | Define effective thread length, point geometry, mating engagement and the dimensional reference on the drawing. |
| Shank geometry | Straight shank, long unthreaded shank, shoulder and stepped-diameter concepts. | State each diameter, transition, functional length and datum; do not describe a shoulder or step only through a product photo. |
| Head style | Socket cap, pan, truss, flat or countersunk, washer-style, external hex and drawing-specific heads. | Head height, diameter, bearing face and forming volume must be reviewed together. |
| Drive style | Phillips, slotted, combination, hex socket and selected security-drive concepts. | Tool access, torque transfer, recess depth, proprietary rights and matching tools must be confirmed. |
| Cold-headed external hex | Recessed external-hex and cold-headed flat-face external-hex concepts can be evaluated for designs that do not use trimmed hex flats. | Across-flats dimension, head height, bearing face, corner form and appearance acceptance must be defined by the drawing and approved sample. |
| Material | Carbon and alloy steel, stainless steel, titanium, copper and copper alloys, brass, or aluminum. | Confirm exact grade and condition. Not every material is feasible at every diameter, length, head volume or forming route. |
| Strength and hardness | Project-specific strength class, hardness, heat treatment and mechanical verification. | High-strength and 12.9 requests require the applicable standard, material, geometry, coating and test requirements; the grade is not assumed across the range. |
| Surface and function | Project-specific finish, passivation, anodizing, thread locking, nylon patch and security features. | Base material, coating thickness, thread fit, corrosion target, test method and high-strength embrittlement controls must be reviewed together. |
| Inspection and documents | Dimensional, thread, geometry, hardness, torque, material and project-specific inspection options. | Agree datums, gauges, sampling, records and traceability requirements before production. |
| Packaging | Neutral cartons, pallets or custom wooden cases can be evaluated with project-specific labels and export documents. | Long parts may require protection against bending, scratching, movement and mixed-part packing; the final pack is confirmed by part length and shipment needs. |
Note: An extra-long screw is not defined by total length alone. Review the diameter, length-to-diameter ratio, head, shank, thread zones, point, material, treatment and inspection references as one manufacturing system.
As diameter decreases and length increases, the part becomes more sensitive to handling, shank condition, forming stability, thread production and measurement setup. Shi Shi Tong reviews the complete geometry and agrees the functional references before selecting a process route.
An unnecessarily long full-thread zone can add processing difficulty without improving the joint. Effective engagement, clamping, location and adjustment requirements should determine whether the design uses full thread, partial thread or a controlled unthreaded shank.
Material, heat treatment, target hardness and coating interact with geometry and thread fit. High-strength extra-long screws require project-specific review of core properties, deformation risk, mechanical verification and hydrogen-embrittlement controls where applicable.
Material, hardness, thread designation, dimensional references, finish, inspection and packaging requirements must be aligned before quotation and sampling. One approved specification gives engineering, production, quality and purchasing teams the same acceptance basis.
Extra-long fasteners often fail at the interfaces between geometry, process and inspection. Shi Shi Tong brings those decisions into one drawing-based review before the project moves into repeat production.
Projects can be evaluated from M1.4 to M12 and up to 2000 mm in length, giving engineering teams a practical starting range for thin, stepped, partially threaded and ultra-long designs. Each combination remains subject to manufacturability review.
Single-die cold heading, multi-station forming, open-die forming for selected extra-long designs, thread rolling and CNC secondary machining are considered according to the part rather than presented as one universal route.
Thread fit, effective thread length, head and recess features, stepped diameters, concentricity, hardness and other critical characteristics can be tied to agreed datums, gauges and project-specific inspection requirements.
Drawing review, process planning, sample or first-article validation and production inspection keep the approved requirements visible as the project moves from development to repeat manufacturing.
Material selection for an extra-long screw should balance strength, corrosion exposure, weight, conductivity, appearance, manufacturing route and cost. Availability is confirmed by exact grade, condition, geometry and order requirements.
Carbon & Alloy Steel — broad strength and heat-treatment options; coating choice must account for thread fit and, for high-strength projects, hydrogen-embrittlement controls.
Stainless Steel — selected for corrosion resistance and application-specific strength; exact grade and cold-heading or machining route must be confirmed.
Titanium — useful when low weight, corrosion resistance or strength-to-weight ratio is important; grade and manufacturability remain project-specific.
Copper & Brass — evaluated for conductivity, formability, machinability or appearance according to the selected alloy and finish.
Aluminum — a lightweight option compatible with selected anodizing routes; alloy, temper, strength and thread requirements must be reviewed.
For a 12.9-grade extra-long screw request, provide the applicable standard, diameter, thread, material, heat treatment, coating, hardness or mechanical-test requirement and installation conditions. Shi Shi Tong will evaluate whether the target is practical for the specific geometry.
Do not select a finish by color alone. State the base material, corrosion or appearance target, coating thickness or test method, mating fit and failure criteria. Salt-spray performance is confirmed only for a defined treatment system and test specification.
For saltwater, coastal or chloride-bearing environments, define chloride exposure, immersion or splash conditions, temperature, cleaning chemicals, mating materials, crevice conditions, target service life and the applicable corrosion test. Grade 316 or 316L stainless steel, titanium or another material-and-finish system may be evaluated, but the complete assembly and galvanic-corrosion risk must be reviewed.
Shi Shi Tong does not force every extra-long screw through the same process. The route is selected after reviewing geometry, length-to-diameter ratio, material, tolerances, quantity and the intended assembly.
Evaluated for relatively simple geometries when the dimensions, material and production requirements suit the process.
Used when the design needs greater material movement, stepped features, reduced shanks or more complex formed geometry.
This route can be evaluated for selected extra-long screw geometries when conventional forming is not the best fit. The drawing determines whether secondary operations, special handling or another process combination is required.
Thread rolling is planned around the required thread zone and fit. CNC is used only as a confirmed secondary process or selected route.
Treatment allowances, thread fit and critical dimensions are reviewed before final inspection and release.
The inspection plan is agreed from the approved drawing, manufacturing route and assembly risk. Available coverage includes dimensional inspection, thread GO/NO-GO checks, pitch, depth, radius, angle and concentricity measurement, optical measurement, metallographic inspection, Rockwell or Vickers hardness, torque testing, material verification and project-specific checks.
Extra-long screw projects typically begin when a standard catalog part no longer matches the assembly, or when an existing supplier cannot combine the required length, diameter, structure, material and validation plan.
Engineering and purchasing teams use drawing-based extra-long screws for deep-reach fastening, long through-connections, restricted tool access and controlled shank or thread zones in equipment and mechanical assemblies.
Distributors can use one technical review to clarify a downstream customer’s non-standard geometry, documents, packaging and repeat-order requirements before committing to a supply route.
Another fastener producer may need support for a thin, ultra-long, high-strength, special-material or complex-shank design that falls outside its current forming range. Drawing control and confidentiality remain part of the project discussion.
Early projects can begin from a drawing, sample or assembly function. Material, geometry, manufacturing route, validation and any product-level compliance requirements are reviewed before repeat-production assumptions are made.
Deep-reach fastening in industrial equipment and mechanical assemblies
Long through-connections where a controlled shank and thread zone are required
Narrow assemblies that need a small-diameter, high length-to-diameter fastener
Custom housings, frames, fixtures or equipment components with restricted tool access or special head requirements
Application Boundary: Application suitability depends on the drawing, load, mating parts, environment, installation method and any applicable product-level standard. Ordinary catalog long screws, threaded rods and studding are separate product decisions. This offer does not claim construction-code approval or suitability for wood, decking, drywall, ledger-board, roofing, masonry, anchors, electrical outlets or self-drilling applications.
Shi Shi Tong is a custom fastener engineering partner focused on complex geometry, special materials, precision requirements and repeatable production—not a catalog reseller.
50+ primary production machines and 10+ professional inspection devices support current operations. Manufacturing capacity is matched to the screw size, geometry, material, process and program requirements.
Share the drawing, sample, mating parts and operating conditions.
Confirm geometry, thread, material, finish, critical dimensions and measurement references.
Evaluate forming, thread rolling, secondary machining, heat treatment and surface treatment needs.
Set gauges, test methods, sample plan, documents and acceptance criteria.
Review the physical part against the approved drawing and assembly needs.
Apply the agreed production, inspection, packaging and traceability requirements.
There is no universal millimeter threshold for every diameter. The designation becomes useful when total length or length-to-diameter ratio changes forming stability, thread production, handling or inspection. For initial review, Shi Shi Tong commonly treats designs above 50 mm up to M2, above 80 mm from over M2 to M3, and above 150 mm over M3 as extra-long candidates; these are screening references rather than an industry standard or an automatic feasibility limit.
Projects can be evaluated up to 2000 mm within an overall M1.4–M12 diameter range. Feasibility depends on the complete combination of diameter, geometry, material, thread coverage, strength, surface treatment, tolerance, quantity and validation requirements.
Full thread is useful for extended engagement or adjustment. Partial thread provides a controlled shank for location, clearance, bearing, clamping or load transfer. The best choice comes from required engagement and function; adding thread where it is not needed may increase processing difficulty without improving the joint.
These configurations can be evaluated when the drawing defines every diameter, transition, functional length, thread zone and tip contact. Extra-long set screws, extended tips, shoulders and stepped shanks are not interchangeable, so the assembly function must determine the geometry.
A 12.9 request requires the applicable standard, diameter, geometry, material, heat treatment, hardness or mechanical-test requirement, coating and installation conditions. The target can be evaluated for the project, but a property-class label is not assumed to be feasible for every extra-long geometry. Coated high-strength steel also requires thread-fit and hydrogen-embrittlement review.
No material is automatically best for every corrosive environment. Define immersion, splash or atmospheric exposure, chloride level, temperature, chemicals, mating materials, crevice conditions, target service life and test method. Grade 316 or 316L stainless steel, titanium or another material-and-finish system may be evaluated after galvanic and assembly conditions are considered.
Use one approved drawing to control material, strength, head, drive, shank, thread and point geometry, surface treatment, critical dimensions and inspection methods. Also confirm sample approval, packaging, labeling, required records and expected order demand so the repeat-production basis is clear.
Selected long self-tapping screw projects can be evaluated from a complete drawing, sample and assembly information. Past examples include long Phillips pan head and socket head designs with partial self-tapping threads.
This is a project-based customization option, not a standard stock range. Feasibility depends on length-to-diameter ratio, thread and tip geometry, substrate, starting hole, material, finish, quantity and validation. Wood screws and self-drilling or drill-point screws are outside this scope.
Send the drawing, sample or assembly conditions for a focused review of geometry, material, manufacturing route, critical dimensions, inspection and expected production demand.
"If a drawing is not yet available, share the diameter, required length, mating parts, thread and point, head or drive, material, environment, quantity and the problem with the current fastener."
