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+86 13143444311
Email：sst@szsst88.com
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Address：Building 9, First Industrial Zone, Tantou Industrial City, Songgang Street, Baoan District, Shenzhen 518105, Guangdong, China
Type:Flange Head Socket Cap Screw, External Hexagon with Internal Hexagon Socket, Full Thread (Non-Standard)
Materials:Carbon Steel
Surface treatment:Black Oxide (conversion film, oiled; no build-up coating)
Head Type:Flange Head (external hexagon body with an integral serrated flange at the base)
Drive:Two interfaces: external hexagon across flats, plus an internal hexagon socket sunk in the head face
Flange:Integral flange about 2.1 x thread diameter, radial serrations headed into the underside, not milled
Thread:Machine thread, rolled 60 degree, full to the flange bearing face; no plain shank
Point:Blunt end with a small chamfer; no taper, no drill point
Forming:Multi-station heading, thread rolling, black oxide, oiling and sorting
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:246
We manufacture flange head socket cap screws with a dual drive: an internal hexagon socket and an external hexagon, an integral radial serrated flange and a full thread to the flange face, in carbon steel with a black oxide finish. Flange diameter, head height, socket and length are taken from your drawing.
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ISO 9001:2015 · Manufacturing since 1998 · 8,678+ customers · 89 countries and regions
Made to order – there is no stock catalogue. Each part is produced to your drawing, and production starts after drawing review and first-article approval.
A flange head socket cap screw is a machine screw with an integral flange at the base of the head, a hexagon socket sunk in the top face, and a full thread to the flange. The recorded item on this page is the dual-drive version: an external hexagon body plus an internal socket, with a radial serrated flange about 2.1 times the thread diameter, in carbon steel with a black oxide finish, quoted from M1 to M14 with Number 246.
Flange head. The flange is formed with the head in the same heading operation, not welded or pressed on. It widens the bearing area under the head, so a flange head socket cap screw spreads its clamp load over a patch more than twice the thread diameter without a separate washer.
Serrated flange. The underside carries radial serrations headed into the face. They bite the mating surface as the screw tightens and give the joint resistance to loosening under vibration — the reason this part is also filed as a self-locking screw.
Two drives. An internal hexagon socket in the top face for a key, and an external hexagon on the body for a wrench. Either will turn the screw, and that is not redundancy: the socket is for speed and for working inside a recess, the external hex is for torque and for the case where the socket has rounded.
Full thread. There is no plain shank. The thread runs from the blunt chamfered point to the flange face, so the screw engages a tapped hole over its whole length.
Together these decide the joint: the flange spreads the load, the serrations resist loosening, the two drives cover assembly and service, and the black oxide keeps the finish dark and dimensionally neutral.
The body is carbon steel wire, with grade and heat number on the batch record. The head is formed on a multi-station header: the flange is upset first, then the hexagon body, then the socket is punched into the top face. Doing it in that order is what keeps the socket concentric with the flange and the shank.
The serrations are formed, not cut. The die that upsets the flange also imprints the radial teeth into the underside, which is why the teeth on a flange head socket cap screw are shallow, even and continuous around the face. Milled serrations leave burrs at the ends of each cut and a land between teeth that does not bite.
The flange thickness is set against the tooth depth. A flange that is too thin dishes when the teeth bite and the screw loses preload; one that is too thick lifts the head and wastes height. The two dimensions come off the same die and are checked together.
The socket depth is set against the head height, and on this part the head height also has to leave room for the external hexagon. The socket is deep enough for the key to seat fully, and the hexagon around it has enough wall to take a wrench without collapsing into the socket.
The thread is rolled from the point up to the flange face. Black oxide follows as a conversion treatment, so the thread, the socket and the serrations keep their dimensions; the parts are lightly oiled before packing, because the oxide film on its own is not a lubricant.
The family is quoted from M1 to M14, with M1, M2, M3, M4, M5, M6, M7, M8, M9, M10 and M14 in the recorded range. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission; on a flange head socket cap screw the flange diameter and the head height together decide how much room the joint needs.
| Item | How it is defined | What we control |
|---|---|---|
| Thread | Metric machine thread, coarse pitch for the size | Gauged per batch |
| Head across flats | External hexagon on the body | Checked with a wrench on the first article |
| Socket | Internal hexagon in the top face | Depth and across-flats checked |
| Flange diameter | About 2.1 times the thread diameter | Measured on the projector |
| Flange thickness | Set against the serration depth | Checked on the section |
| Serrations | Radial teeth formed into the underside | Checked for continuity on the first article |
| Length | From the flange face to the tip | Measured on the shop plate |
Length on this part is measured from the flange face, which is the surface that bears on the joint. That is not the same as measuring from the underside of the head body: the flange adds its own thickness, and a screw quoted the other way will be short by that amount in every joint.
The flange diameter is the dimension that decides whether the head will clear the surrounding part. At about 2.1 times the thread diameter it is wider than a plain cap head of the same size, so a counterbore cut for a standard cap head will not take it. The drawing states the flange diameter and the counterbore together.
The flange head socket cap screw is specified when a joint has to be tightened hard, hold under vibration, and still be openable in service without a special tool. Each of the three features answers one of those needs.
| Feature | What it gives | What it costs |
|---|---|---|
| Integral flange | Bearing area without a separate washer | Wider head; needs a larger counterbore |
| Radial serrations | Bite that resists loosening under vibration | Marks the mating surface; not for a soft or painted face |
| Internal socket | Fast assembly with a key, works in a recess | Socket can round if the key is worn |
| External hexagon | High torque with a wrench when the socket is not enough | Needs clearance around the head |
| Full thread | Engagement over the whole length | No plain shank to protect a clearance bore |
The two drives are the feature buyers ask about most. An internal socket alone limits the torque to what the key can transmit, and on the smaller sizes that is not much. The external hexagon lets the same screw be driven with a socket wrench or a spanner at a torque the internal key could never reach, which is why the dual-drive version is used where a joint is both tight and serviceable.
The serrations are a locking feature with a limit. They work by cold-forming shallow grooves into the mating surface, so they hold well on steel and castings and badly on aluminium, plastic or a painted face, where they cut rather than grip and leave a mark that reads as damage. Where the joint is soft, a flange without serrations or a plain cap head with a hardened washer is the better choice.
The flange itself is not a substitute for a washer in every case. It spreads load and it cannot be forgotten or dropped, but it is fixed to the screw: once the flange is deformed, the whole screw is scrap, whereas a washer can be replaced.
The recorded configuration is black oxide, lightly oiled. The treatment darkens the steel by converting the surface rather than adding a layer, so the flange face, the serrations and the thread keep the dimensions they had before the finish went on.
| Finish | How it protects | Effect on flange and thread | Typical use |
|---|---|---|---|
| Black oxide, oiled | Thin conversion film plus oil | Almost no dimensional change | Indoor machinery and dark assemblies |
| Zinc phosphate, oiled | Conversion coat with oil retention | Thin; serrations unchanged | Machine tools and general machinery |
| White zinc | Sacrificial zinc, blue-white passivation | A few microns; gauged after | Indoor general assembly |
| Zinc nickel | Alloy layer, higher corrosion resistance | Thicker; thread and socket re-checked | Wet or industrial service |
| Dacromet | Zinc-aluminium flake layer, cured | Thin film; serrations re-checked | Outdoor and wet assemblies |
Where a coating builds up, the serrations are the first feature to suffer: a heavy deposit rounds the teeth and the locking action goes. That is why a zinc-nickel or Dacromet version is checked on the teeth and not only on the thread, and why the first article is driven into a sample plate to confirm the bite.
The oil on a black oxide part matters for the same reason it matters on any steel fastener: it is the barrier that stops the oxide film from rusting in storage. Parts that will sit for months before use are supplied oiled and bagged, and the packing note says so.
Three assemblies where a wide serrated bearing face and two drives do the work:
| Where it sits | The screw holds a bracket, a guard or a bearing block to a steel frame, tightened hard and expected to stay tight with the machine running. |
| When it goes wrong | A plain head on a frame that vibrates loosens, and a washer adds a part that can be left out or lost in the assembly. |
| Why it happens | The joint is steel on steel, it vibrates, and it is serviced on a schedule. |
| What we control | Serration continuity and flange flatness checked, thread gauged per batch. |
| Where it sits | The screw fixes a track section, a clamp or an anti-skid plate where the head sits in a shallow recess and the joint sees repeated load. |
| When it goes wrong | A head without a flange dishes the plate, and a joint that cannot be opened with a standard wrench slows down track maintenance. |
| Why it happens | The parts are heavy, the surfaces are exposed, and the joint is maintained in the field. |
| What we control | Flange diameter and head height checked against the recess, socket and hexagon both driven on the first article. |
| Where it sits | The screw fixes a panel, a link or a guard on equipment that runs outdoors and is washed or caked in mud. |
| When it goes wrong | A coated head that rounds its serrations loses its grip, and a socket that fills with dirt cannot be driven in the field. |
| Why it happens | The joint is exposed, the service is rough, and the same fixing is used many times. |
| What we control | Finish checked on the serrations, and both drives tried with the tools used in service. |
Four reasons that matter on a serrated flange screw, each tied to what the drawing has to prove:
|
Flange and counterbore reviewed together
The flange diameter, flange thickness and head height are reviewed against the recess, so a head that will not seat is raised before the die is made. Basis: Flange and recess reviewed as one set. |
Flange, socket and thread in one route
The flange and its serrations are headed first, the hexagon and socket are formed after, and the thread is rolled to the flange face on the same machine. Basis: One route from wire to oiled screw. |
|
Serrations and socket checked on the part
The teeth are checked for continuity, the flange for flatness, and both drives are tried with the tools used in service. Basis: First article driven with both drives. |
First article to repeat production
At the first article the drawing revision, wire heat, die set and thread roll are recorded, and that record governs repeat orders. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these flange head socket cap screws on a multi-station header: the flange and its radial serrations are upset, the hexagon body is formed, the socket is punched into the face, and the machine thread is then rolled to the flange face. The parts are black oxide finished and oiled. The first part of every run is measured on the flange, the hexagon and the socket, and tightened into a sample plate, before the batch continues.
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The multi-station route is what makes the part possible. A single-die header cannot form the flange, the hexagon and the socket at once without the flange going out of round, so the work is split across stations and the part is transferred between them in the tool. The last operation before rolling is the socket, which is why the socket and the flange stay concentric.
What decides whether a flange head socket cap screw passes is the flange diameter and thickness, the serrations, the head across flats, the socket, the thread and the finish. The inspection agreement covers those, and the criteria come from the drawing.
Flange and head on the projector |
Thread gauged per batch |
Hardness testing against the property class |
Salt-spray testing where a coating is specified |
The serrations are checked as a feature, not as surface texture. The teeth are inspected for continuity around the face and for depth on a section from the first article, and the finished screw is driven into a sample plate at the joint torque and then removed to see the impression it leaves. An even ring of marks is a pass; a partial ring means the flange is not flat.
The socket and the hexagon are checked with the tools used in service. A socket that measures correct but bottoms out on the key will round under load, and a hexagon that is slightly undersize will let a spanner slip and damage the flange edge, so both are driven on the first article rather than only gauged.
Every shipment of flange head socket cap screws is traceable to the wire it was made from. The grade and heat number are recorded on the material certificate supplied with the parts, and the inspection records follow the criteria agreed on the drawing.
ISO 9001:2015 |
RoHS test report |
Registered trademark |
Patent: security screw and driver |
With each batch we supply the material certificate, the inspection record for the criteria on the drawing and, where it is listed, the third-party report for the material or the finish. The documents carry the drawing revision and the batch number, so the paperwork can be matched to the parts.
More than 8,678 customers in 89 countries and regions have ordered from Shi Shi Tong; 87% of orders come from repeat customers and 56% through referrals. Most projects follow the same route: drawing review, first-article approval, then batches checked against that sample. On a serrated flange the first article is tightened into a sample plate, so the bite is signed off with the torque rather than on the bench. Buyers visit during the process to review samples and to see how the flanges are formed.
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8,678+
customers served
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87%
of orders from repeat customers
|
56%
of orders through referrals
|
89
countries and regions shipped to
|
Buyers and quality engineers visit for sample review, process discussion and supplier audits; the visit is arranged around production so the header and the finishing line can be seen on the day the parts run.
Customer group visit – sample review |
Customer group visit – process discussion |
Customer group visit – factory tour |
Customer visit – project kick-off |
Danish customer – drawing review |
Industry exhibition – meeting customers |
A machine screw with an integral flange at the base of a hexagon head and a hexagon socket in the top face. The flange spreads the load and the socket drives it.
The internal socket drives it quickly and inside a recess; the external hexagon takes a wrench when more torque is needed or the socket has rounded.
They bite the mating surface as the screw tightens and resist loosening under vibration. They hold well on steel and castings and badly on soft or painted surfaces.
From the flange face, which is the surface that bears on the joint. It is not the same as the underside of the head body, because the flange adds its own thickness.
It is filed as one because of the serrated flange, but the locking action depends on the mating surface. On a soft or painted face the teeth cut rather than grip.
Thread size and pitch, head across flats, socket size, flange diameter and thickness, serration spec, length and datum, material and finish.
How a flange head socket cap screw project runs from drawing to repeat delivery:
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1
Send the drawing or sample
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→ |
2
Flange and recess review
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→ |
3
First article tightened in a sample plate
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→ |
4
Batch production and repeat orders
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Each step is confirmed with you before the next one starts; the drawing revision from the first article is what repeat orders are checked against.
For a quotation, send the drawing with the thread size and pitch, head across flats, socket size, flange diameter and thickness, the serration spec, length and datum, material and finish.
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Thread and pitch
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Head across flats
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Socket size
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Flange diameter
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Serration spec
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Length and datum
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Sending a drawing? The form below does not take attachments. Email the PDF, DXF or STEP file to sst@szsst88.com with the part name and quantity in the subject line – the drawing is reviewed and a quotation follows.
+86 13143444311
sst@szsst88.com
