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+86 13143444311
Email：sst@szsst88.com
Fax：+0086-755-27322278
Address：Building 9, First Industrial Zone, Tantou Industrial City, Songgang Street, Baoan District, Shenzhen 518105, Guangdong, China
Type:Flat Head Socket Screw Stainless Steel
Materials:Stainless steel
Surface treatment:Plain
Head Type:Csk Head
Drive:Hexagon socket (Allen)
Thread:Self-tapping
Point:Sharp, tapered
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:578
We make flat head socket screws in passivated A2 stainless, with a countersunk head, a hexagon socket and a self-tapping point, quoting them from M1 to M14. Cone angle, socket depth, point and pilot hole come from your drawing, and the first article is seated and driven in your part.
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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.
These flat head socket screws are countersunk, hex-driven self-tapping screws in passivated A2 stainless, quoted from M1 to M14 with Number 578. The cone seats in a countersink so the head finishes flush, the socket drives it, and the sharp thread-forming point makes its own thread in the material.
Flat countersunk head. A 90-degree cone that seats in a matching countersink and leaves no edge above the surface.
Hexagon socket. An internal hexagon cut into the flat top, driven with an Allen key.
Self-tapping point. A sharp, thread-forming end that cuts or forms its own thread as it enters.
Passivated stainless. A2 grade, uncoated, so the socket, the cone and the thread are as made.
Flat head socket screws are used where the fixing has to vanish into the surface and the far part cannot be tapped: guards, covers and thin-sheet assemblies that are closed flush and driven with a key.
A flat head socket screw combines three decisions that each remove something. The countersunk head removes the edge above the surface, so the fixing leaves a plane; the socket removes the outside drive, so the head has no flats for a wrench; and the self-tapping point removes the tapped hole, so the screw threads the far part as it enters.
The combination is demanding because none of the three has a fallback. A head with no edge cannot be gripped with pliers if the socket fails, and a self-tapping screw has to be driven hard enough to form a thread — which is exactly the load a countersunk head and a hexagon have to carry together. That is why the socket depth is the number that decides the part, and why a worn key is the usual cause of failure.
The cone is the seat and the alignment. It centres the screw as it tightens and carries the clamp on its face, and its angle has to match the countersink in the part; a mismatch leaves the head flush at one side and proud at the other, and on a flush fixing that is visible immediately.
Stainless keeps all three features as made. There is no coating to narrow the socket, round the cone or blunt the point, and on a self-tapping screw the point matters: a blunted point stalls before the thread is formed. The trade is galling, which on a screw that is driven hard is worth managing with a lubricant.
What the part gives is a fixing that disappears. A guard, a cover or a plate can be closed to a flat surface with nothing standing above it and no tapped hole behind, which is often the only way to hold a thin sheet or a casting that cannot be threaded.
The recorded range is M1 to M14, with lengths made to the drawing. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For flat head socket screws the quotation carries head diameter and cone angle, socket size and depth, overall length, point and the pilot hole.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Countersunk, 90-degree cone | Head diameter and cone angle |
| Socket | Internal hexagon in the flat top | Across flats, depth and corners |
| Length | Overall, head included | Length tolerance and point length |
| Thread | Self-tapping | Thread form and crest condition |
| Point | Sharp, tapered | Point length and concentricity |
| Material | A2 stainless | Grade and heat number on the certificate |
| Finish | Passivated | Surface condition and socket edges |
Socket depth is quoted with the head height, because the flat head leaves the socket less room than a cap head and the forming thread needs torque. A shallow socket in a countersunk head is the limiting feature of the whole part.
Pilot hole diameter belongs on the assembly drawing. The point forms the thread, and the size of the hole decides whether it forms cleanly, splits the material or stalls.
Three features define the part: the countersunk seat, the hexagon socket and the self-tapping point. The first makes it flush, the second is the only drive, and the third removes the tapped hole.
| Feature | What it gives | What it costs |
|---|---|---|
| Countersunk seat | Flush finish, self-centring | Seat angle and depth must match |
| Socket drive | Torque without cam-out | The only drive; a worn key rounds it |
| Self-tapping point | No tapped hole behind | Pilot hole must be right |
| Stainless body | Socket and point as made | Galls dry; softer than steel |
| No edge to grip | Nothing to catch or turn | Cannot be removed if the socket fails |
The flush seat is the reason the head form is chosen. A countersunk screw leaves the surface continuous, so a panel can slide, seal or be cleaned across it without catching on a head.
The socket is the reason the part works. A self-tapping thread needs torque, and a countersunk head cannot offer an outside drive; six flats under a key are what makes the joint possible at all.
The recorded finish is passivation with no coating on A2 stainless. On a self-tapping screw that matters at the point as much as in the socket: a coating thick enough to protect the thread would round the point’s crest and stop it forming cleanly.
| Option | How it protects | Effect on socket and cone | Typical use |
|---|---|---|---|
| A2 stainless, passivated | Passive chromium oxide film | Socket and cone as made | Wet and outdoor assemblies |
| A4 stainless, passivated | Passive film with molybdenum | Socket and cone as made | Marine and medical |
| Steel, black oxide | Conversion film, oiled | No measurable build | Internal mechanisms |
| Steel, zinc plated | Sacrificial zinc | Thin build; socket re-checked | General indoor work |
| Steel, black zinc | Sacrificial zinc, dark | Thin build; wear visible | Dark panels |
Where the joint is wet, A4 is the grade, and the socket is the reason: a rusted hexagon cannot be re-entered, and a countersunk head has nothing else to grip.
Where the joint is dry and hidden, a coated steel screw works for less, but the socket has to be gauged after plating — on a countersunk head the socket is already shallow.
Three assemblies where flat head socket screws are the fixing:
| Where it sits | The screw holds a panel flush where a hand or a cable passes over the surface and nothing may stand proud. |
| When it goes wrong | The socket rounds, and a flush head with no edge cannot be removed. |
| Why it happens | The joint is flush, the drive is a key, and the far part cannot be tapped. |
| What we control | Socket depth checked; first article driven at the joint torque. |
| Where it sits | The screw closes a panel that is cleaned or rained on, where a stainless body is required and the seat must stay flat. |
| When it goes wrong | A plated screw corrodes in the socket, and the panel cannot be serviced. |
| Why it happens | The joint is wet, it is flush, and the drive is a key. |
| What we control | Grade confirmed; first article assembled and released. |
| Where it sits | The screw forms its own thread in a thin sheet or a soft extrusion where a tapped hole or an insert would cost another operation. |
| When it goes wrong | A pilot hole that is too small splits the material, and one that is too large never holds. |
| Why it happens | The sheet is thin, the seat is formed, and the thread is formed by the screw. |
| What we control | Pilot hole agreed; first article driven into a sample sheet. |
Four reasons that matter on a flush socket-driven forming screw, each tied to what the drawing has to prove:
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Cone, socket and point agreed
Cone angle, socket depth, point and pilot hole are agreed as a set, because on flat head socket screws each has to leave room for the others. Basis: Cone, socket and point agreed. |
Formed, threaded, passivated in one route
The cone and socket are formed in one stroke, the thread rolled and the point cut before passivation. Basis: One route from wire to passivated screw. |
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Socket driven at torque
The first article is driven with the production key at the joint torque, because a shallow socket rounds at exactly the load the thread needs. Basis: First article driven at torque. |
First article in the seat
The first article is seated in the customer countersink, because flushness and the pilot hole are both properties of the pair. Basis: First article seated in the part. |
Shi Shi Tong forms these screws on single-die headers that form the countersunk head with the hexagon in its flat top, rolls the self-tapping thread and cuts the sharp point before passivating the parts. The first part of every run is measured on head diameter, cone angle, socket depth, thread and point.
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Cutting a hexagon into a countersunk head is the hardest part of the form. The flat face is small, and the socket has to reach full depth without breaking through toward the cone; a punch that is slightly deep leaves a head that measures correctly and a socket that sits over thin metal, which fails at the torque the thread needs.
What decides whether flat head socket screws pass is the cone, the socket, the point and the thread. The inspection agreement covers those, and the criteria come from the drawing.
Cone and socket on the projector |
Thread form checked |
Hardness checked on the wire |
Salt-spray testing of the grade |
The cone is checked for angle and contact, the socket for across flats and depth, and the point for length and concentricity. The thread is gauged, and the socket is checked again on the finished part for burrs that would stop the key.
The first article is driven into the customer material at the joint torque and then released. A socket that survives being driven but not being removed is still a part that fails, and on a flush head there is no second way in.
Every shipment of flat head socket screws is traceable to the wire it was made from and to the passivation batch. 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 grade. The documents carry the drawing revision and the batch number, so a repeat order keeps the same cone angle and socket.
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 flat head socket screw the first article is seated and driven in the customer part, because the seat and the pilot hole are both properties of the pair. Buyers visit during the process to review samples.
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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 headers and the passivation 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 |
With an Allen key in the hexagon. There is no outside drive; a flush countersunk head has no edge to grip.
Yes. The sharp point forms its thread in a drilled pilot; without one it will not start cleanly in sheet or soft material.
A countersunk head has less material above the cone than a cap head, so the hexagon is shallower and the torque is lower.
The head cannot be gripped afterwards. Use the correct key and set the torque to what the socket will take.
Yes. A2 covers ordinary exposure and A4 the chlorides; nothing is plated that could blunt the point.
Head diameter and cone angle, socket size and depth, overall length, point and the grade.
How a flat head socket screw project runs from drawing to repeat delivery:
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1
Send the drawing and the countersink
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→ |
2
Cone, socket and point agreed
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→ |
3
First article seated and driven in your part
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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 head diameter and cone angle, socket size and depth, overall length, point and the grade.
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Head diameter
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Cone angle
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Socket size
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Socket depth
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Overall length
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Grade
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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
