3 Screws: Size Guide | Hebei Wotu Fastener Manufacturing Co., Ltd.
A request for 3 screws needs one clarification before any buyer can compare parts: does “3” mean a No. 3 screw size, an M3 metric thread, or a 3-inch length? Those choices describe very different fasteners, and mixing them up can lead to poor thread engagement, split material, stripped drives, or an assembly that simply does not fit.
For procurement, the useful starting point is the joint: the material being fastened, the required head style, the drive type, the thread form, the finish, and the length measured in the correct way for that head. Once those details are clear, Hebei Wotu Fastener Manufacturing Co., Ltd. can respond to a focused inquiry instead of guessing from an incomplete size description.
Brand: Wotu Surface: blue and white zinc plated Specifications: Chinese national standard 6#/8#/10#/12#/16#/20#, rod length 35mm~250mm full range of specifications in stock, supports nonstandard length customization Packaging: 25kg cartons, full pallets packed on wooden pallets, support neutral packaging, private-label customization
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Brand: Wotu Standard basis: German standard DIN934-1987, metric coarse thread/fine thread universal thread Surface: 304 stainless steel Specifications: M6～M24 full range of specifications Supporting equipment: same specification bolts, flat washer, spring washer complete set of shipment Packaging: 25kg standard carton, whole wooden pallet packaging
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Brand: Hengzuan Surface: blue and white zinc plated Specifications: in stock ST4.2/ST4.8full range of specifications, length 13~50mm in stock, support nonstandard length customization Packaging: 25kg cartons, solid wood packaging, support neutral packaging, private-label customization
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Brand: Hengzuan Surface: Color zinc plated, optional blue-white zinc plated, black oxide treatment Specifications: Chinese national standard ST4.2/ST4.8/ST5.5 specifications, rod length 13~50mm in stock, supports nonstandard length customization Packaging: 25kg export cartons, full wooden pallets wrapped with film, supports neutral packaging, private-label customization
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Brand: Hengzuan Surface: blue and white zinc plated, can be customized color zinc plated, black oxide plated Specifications: Comply with GB/T15856.2-2002 Chinese national standard, in stock ST4.2/ST4.8/ST5.5 full range of specifications, length 13mm~75mm optional, supports customized nonstandard rod lengths; drilling adaptation plate thickness 0.7~6mm Packaging: 25kg export cartons, full pallets wrapped with film, supports neutral export packaging, customer private-label customization
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Brand: Hengzuan Surface: blue and white zinc plated, can be customized color zinc plated, black oxide plated Specifications: in stock 3.5/3.9/4.2/4.8/5.5 mainstream wire diameter, rod length 13mm~75mm full size range, nonstandard length can be customized as needed Packaging: 25kg export cartons, full wooden pallets wrapped with film, supports neutral export packaging, private-label customization
Read MoreScrew specification factors
Relevant selection criteria for 3 screws include the meaning of the “3” in the specification, the material being fastened, head geometry, drive recess, thread form, point style, surface finish, and packaging needs. These details matter more than a short size label because they determine installation method, holding performance, and compatibility with the assembled part.
| Criterion | What To Check | Why It Matters | Buyer Tip |
|---|---|---|---|
| Confirm what “3” means in the specification | Ask whether the buyer means No. 3 screw gauge, 3 mm diameter, 3 inch length, or a pack quantity of three screws. | The same phrase can point to a very small screw, a metric size, a long fastener, or simply a quantity. Ordering from an unclear description can result in the wrong thread, length, or head size. | Send the drawing, sample photo, or full size callout and ask: “Does 3 refer to gauge, diameter, length, or quantity?” |
| Material being fastened | Identify whether the screw will go into wood, sheet metal, plastic, composite board, or a pre-threaded insert. | Thread form and point style need to match the base material. A wood or fiberboard screw will not behave the same as a self-tapping or machine screw. | Ask: “What materials and thicknesses will the screw join, and is the hole pre-drilled?” |
| Thread type and engagement | Compare coarse thread, fine thread, self-tapping thread, and machine thread against the pilot hole or mating thread. | Too little engagement can loosen; too aggressive a thread can split wood, strip plastic, or deform thin metal. | Ask for the pilot hole size, total clamping thickness, and required thread engagement depth before confirming the screw style. |
| Head style and drive recess | Choose between countersunk, pan, wafer, hex, Phillips, cross, or other drive types based on the assembled surface and tooling. | The head controls seating, appearance, load spread, and installation speed. The wrong drive can cam out or leave the head proud of the surface. | Ask: “Should the head sit flush, stand proud, or seal against a washer or panel?” |
| Finish and exposure conditions | Match the coating or material to indoor furniture, dry assembly, humid storage, roofing, or outdoor exposure. | A finish that works indoors may not provide enough corrosion resistance outside or near treated wood, moisture, or chemicals. | Ask: “Where will the assembled product be used, and is corrosion resistance or color matching required?” |
The most important distinction is diameter versus length. A No. 3 screw is a small screw size often used where space and material thickness are limited. An M3 screw is a metric machine screw thread. A 3-inch screw is a long fastener, usually selected for deeper timber, framing, or layered assemblies. They are not interchangeable, even if the word “3” appears in each description.
Thread type also changes the decision. Wood and fiberboard screws need threads that bite into softer material without excessive splitting. Self-tapping screws form or cut threads in a prepared hole. Self-drilling screws add a drill point for some metal applications. Machine screws usually need a matching internal thread or nut. Choosing between them depends less on the number in the name and more on the base material and how the joint will be assembled.
Start by naming the standard behind the size. If you need a No. 3 screw, say so clearly. If the part is metric, write M3 and include the thread pitch if it matters. If the length is three inches, state the diameter separately. A short note such as “M3 pan head machine screw” or “3-inch countersunk wood screw” prevents a common purchasing mistake.
Match the screw to the receiving material. For wood, MDF, particle board, and furniture panels, thread shape and point style affect holding strength and splitting risk. For sheet metal, confirm whether the hole is pre-drilled and whether the screw must tap its own thread. For metal-to-metal work, do not assume a wood screw or general-purpose tapping screw will perform correctly.
Check the head and drive against the assembly method. Countersunk heads sit flush when the material is prepared for them. Pan, wafer, hex, or washer heads leave a bearing surface above the material. Cross recess, Phillips, Pozi, hex socket, and external hex drives all affect installation speed, cam-out risk, and tool access. A technically correct screw can still be a poor choice if the installer cannot drive it cleanly.
For the next step, prepare a short specification: size standard, diameter, length, head style, drive type, thread type, point style, finish or coating, base materials, and expected assembly environment. If you already have a drawing, sample, or current part number, include it with the inquiry so the response can focus on fit and substitution options.
| Criteria | Importance | Description | Example Options |
|---|---|---|---|
| Meaning of the size reference | Essential because an ambiguous number can identify different dimensions or standards. | Separate a numbered screw size, a metric designation such as M3, and a length such as 3 inches. State the diameter and length independently when needed. | “M3 machine screw” and “3-inch wood screw” are different specifications, even though both contain the number 3. |
| Receiving material and thread form | High because threads must engage the material without poor holding, excessive damage, or an unsuitable installation method. | Match the screw to wood-based panels, sheet metal, solid metal, or a joint with an existing internal thread. Wood screws, tapping screws, and machine screws are not interchangeable by size alone. | A furniture-panel joint may call for a wood or fiberboard screw, while a pre-threaded metal assembly may require a matching machine screw. |
| Pilot hole and drilling method | High when the material requires a prepared hole or when installation speed affects the assembly process. | Confirm whether the screw forms or cuts threads in a pilot hole, or whether its point is intended to drill through the material. Do not assume a self-tapping screw and a self-drilling screw perform the same operation. | A pre-drilled sheet-metal assembly may use a self-tapping screw; an assembly requiring the screw to start through suitable metal may use a self-drilling alternative. |
| Head and drive combination | Important for flushness, bearing area, tool access, and reliable installation. | Select the head based on the mating surface and the drive based on the available tool and access. Countersunk heads need suitable material preparation if a flush result is required. | A countersunk head may suit a prepared furniture panel, while a pan or washer head may be better where the screw needs a visible bearing surface. |
| Length and thread engagement | Essential for fit and joint integrity; more length is not automatically better. | Measure length according to the selected head style and check how much thread will enter the receiving material. Avoid a length that causes breakthrough, interference, or insufficient engagement. | A layered panel joint may need a length that passes through the first component and engages the second without emerging from the far side. |
Related Options
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It may refer to a No. 3 screw size, an M3 metric thread, or a length of 3 inches. These descriptions identify different dimensions or standards, so confirm whether the number describes diameter, thread designation, or length before comparing quotations.
Choose a screw intended for wood-based materials, with a thread form and point suited to the panel. A countersunk head may be appropriate when the head must sit flush, but the pilot-hole requirement and risk of splitting should be checked for the specific material and thickness.
A self-drilling screw can make its own starting hole in some metal assemblies, while a self-tapping screw is commonly used in a prepared hole or a hole that matches its forming or cutting action. The choice depends on the material thickness, hole condition, access for the tool, and the required thread engagement.
No. Length must provide adequate engagement in the receiving material without passing through the assembly, striking another component, or causing splitting. Diameter, thread design, joint construction, pilot-hole size, and the material itself also affect the result.
State the size standard, diameter, length, head style, drive, thread type, point style, finish, base materials, and quantity. A drawing, sample photo, or existing part number is useful when the description could refer to more than one screw standard.
Send the intended meaning of “3” in your request, the materials being fastened, and the preferred head, drive, thread, finish, and quantity. A drawing, sample photo, or current part number will make the inquiry easier to answer.
