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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:Flat Head Hex Socket Screw
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Flat (countersunk) socket cap
Drive:Hexagon socket (Allen)
Thread:Machine thread
Point:Plain, chamfered
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
We make flat head hex socket screws in stainless steel, quoting them from M1 to M10 with lengths made to the drawing. The countersink angle, head height and socket depth are agreed with your key, and the first article is seated in your plate.
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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 flat head hex socket screw is a countersunk machine screw driven with a hex key from inside the head. The part recorded here is stainless steel with a plain finish, quoted from M1 to M10 with lengths made to the drawing.
Flat head. A cone that seats in a countersink so nothing stands above the surface of the machine.
Hexagon socket. An internal hexagon, the drive most people mean when they say an Allen key.
Stainless body. No coating, so the socket keeps its cut geometry and the thread does not rust into the tapped hole.
Machine thread. A uniform thread for a tapped hole or a nut, with the length measured over the head.
They are used on machine beds, covers, guards, tooling plates and equipment where the fixing must be flush and the drive must be internal, so the surface stays clear and the tool is a key rather than a bit.
The reason a machine is often specified with flat head hex socket screws is not the head: it is the tool. A service engineer can carry one set of hex keys and open every fixing on the machine, whatever its size, instead of carrying a driver set. That is a real advantage on equipment maintained in the field.
The advantage stops where the sizes do. One key set covers many diameters, but not one key: an M4 socket needs one size and an M6 needs another, and the set is what travels, not the single key. The socket depth is also bounded by the head height, so the key has to reach the floor without damaging the corners.
That last point is the practical limit of the form. A countersunk head spends its height on the cone, so the hexagon is cut into a thin disc; a key that only enters part way bears on a shorter run of each flat and the corners mark first. The fix is a key in good condition and a socket depth that was specified and measured, not assumed.
The flush result is the second reason the form is chosen. Where a plate, a seal or a slide passes over the fixings, nothing may stand proud, and a countersunk head is the only way to keep the internal drive and still finish level. That does mean the countersink has to be cut into the top member, at the right angle and to the right depth, and only into that member: everything below is a clearance hole.
Stainless is the finish that keeps the drive usable over time. A plated countersunk socket has a film inside the hexagon that changes which key seats, and at the small sizes that film is a measurable part of the socket. A plain stainless part keeps the socket as cut, which is why these screws are often specified in stainless even where corrosion is not the driver.
The recorded range is M1 to M10, with lengths made to the drawing. Custom lengths up to 2,000 mm are subject to the drawing submission and DFM review. The quotation for a flat head hex socket screw carries the head diameter, the countersink angle, the head height, the key size and socket depth, the thread pitch and the overall length.
| Item | How it is defined | What we control |
|---|---|---|
| Cone | Countersink angle, usually 90 degrees | Angle and concentricity |
| Head diameter | Widest point of the cone | Diameter and rim form |
| Head height | Top face to the cone top | Height and face flatness |
| Socket | Hexagon, key size per diameter | Depth and floor thickness |
| Thread | Machine thread in stainless | Pitch, length and start |
| Length | Overall, head included | Length tolerance |
The key size follows the diameter, and it is worth writing it on the drawing rather than leaving it to a table. A customer who buys parts across several sizes needs to know which keys the machine will require, and that is a purchasing decision as much as a technical one.
Socket depth is the number that pairs with head height. On a countersunk screw the disc above the cone is thin, so the socket has to be cut as deep as that disc allows and no deeper; the depth is measured on the first article and proved with the key.
The countersink angle belongs on the mating part’s drawing. A 90 degree head in an 82 degree seat bears on the rim and stands proud however hard it is driven, and on a flush machine surface that is visible immediately.
Four properties decide flat head hex socket screws, and each one carries a cost:
| Property | What it gives | What it costs |
|---|---|---|
| Flush cone | Nothing above the surface | Head height spent on the cone |
| Hexagon socket | Internal drive, one tool family | Key must reach the socket floor |
| Stainless body | No coating inside the socket | Lower strength than a graded steel part |
| Plain finish | Socket keeps its cut geometry | Surface darkens in salt air |
The value is a machine with a clean surface and a single tool family for service. On equipment that is maintained in place, that combination saves more time than the screws cost.
The cost is the shallow socket. A flush head cannot give the depth of a cap head, so the drive is the feature to prove on the first article rather than to assume.
The trade is a flush head driven by a socket, with no room for a wrench on the outside.
The recorded finish is plain. On a countersunk socket screw that matters at two surfaces: the cone, which is the bearing face, and the hexagon, which is the drive. A coating on either changes how the joint seats or how the key fits.
| Option | How it protects | Effect on cone and socket | Typical use |
|---|---|---|---|
| Passivated, plain | Removes free iron; rebuilds oxide | No build; cone and socket as cut | Default for stainless |
| Electropolished | Levels the surface | Socket edges softened; cone brighter | Food and medical equipment |
| Black oxide on stainless | Colours the surface | Thin film; key fit unchanged | Dark machine beds |
| Nickel plated | Hard bright barrier | Build in socket; re-gauged | Where a bright finish is wanted |
| Zinc plated steel equivalent | Sacrificial zinc | Build on cone; seating changes | Where stainless is not needed |
Where a coating is applied, the socket is gauged after plating and proved with the key. On a flush head the socket is shallow, so a film that would be irrelevant on a cap head changes which key seats.
Black oxide on stainless is the usual way to get a dark flush head without adding anything to the socket. It keeps the drive as cut and gives a colour, which is often what the application actually needs.
Three settings where a flush surface and an internal drive meet:
| Where it sits | The screw closes a plate where the surface is machined flat and must stay usable. |
| When it goes wrong | A head that is not flush marks the workpiece or lifts the plate. |
| Why it happens | The surface is machined, the fixings are numerous, and the joint is dismantled. |
| What we control | Cone angle and socket depth checked; first article seated in the plate. |
| Where it sits | The screw holds a cover that a seal or a scraper passes over. |
| When it goes wrong | A proud head wears the seal and the joint begins to leak. |
| Why it happens | The joint moves or is sealed, and the surface is finished. |
| What we control | Head height measured; first article assembled and cycled. |
| Where it sits | The screw fixes cladding that must present a flat face to operatives and cleaning. |
| When it goes wrong | A raised drive traps debris, or a cross recess fills and cannot be cleaned. |
| Why it happens | The surface is visible, the machine is washed, and the joint is serviced. |
| What we control | Socket proved with the key; first article fitted on the cladding. |
Four reasons that matter on a part whose drive has no reserve, each tied to something the drawing or the first article has to prove:
|
Key size and socket depth stated
The key size and the socket depth are written on the drawing, because a flush head has little height to give and the key has to reach the floor to carry torque. Basis: Key size and depth stated. |
Headed, broached, threaded and passivated
The cone and head are formed, the hexagon broached to depth, the thread rolled and the batch passivated so the socket stays as cut. Basis: One route, socket as cut. |
|
Socket proved with your key
The socket is driven with the key the customer uses at the joint torque, because a shallow socket marks before the head seats and cannot be recovered. Basis: Driven with your key. |
Same key across orders
The broaching punch and its depth are recorded with the drawing revision, so a repeat order takes the same key with the same engagement. Basis: Same key fit across orders. |
These screws are headed on single-die machines that form the cone and the top face in one stroke, broached with a hexagonal punch, thread rolled on the stainless shank and passivated. The first part of every run is measured on head diameter, cone angle, head height, socket size and depth, thread and length.
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|
Forming the cone leaves a thin disc for the socket, so the two operations are tied together: a cone pressed a little too deep leaves the disc too thin to hold a hexagon, and a cone pressed shallow leaves a head too tall to finish flush. Both are measured on the first article because each one alone can look acceptable.
Broaching the hexagon is the operation with the least room. The punch displaces material downward and sideways into the cone, so the floor thickness is set by the broaching depth rather than by head height alone; a punch a few hundredths deep leaves a floor that yields at the first drive.
Passivation reaches the socket. That is the smallest feature on the part and the one where contamination stays, so a batch checked only on the head can pass and still show rust at the socket floor.
What decides whether flat head hex socket screws pass is the cone, the head, the socket and the thread. The inspection agreement covers those, and the criteria come from the drawing.
Cone and socket on the projector |
Thread and start checked |
Hardness against the stainless spec |
Salt-spray testing of the socket |
Cone angle, head diameter and head height are measured as one set, then the socket depth is read against them. The socket is proved with the production key at the joint torque, and the floor is inspected under magnification afterwards.
A sample from every batch is seated in a countersunk plate of the agreed angle and checked for rocking and proudness, then driven and removed. That cycle is what catches a head height that does not match the seat.
The thread and the length are checked as on any machine screw, with the length measured over the head so the datum agrees with the countersink.
Every batch is traceable to the heat of stainless it was made from. The grade and heat number appear on the material certificate supplied with the parts, and the inspection record carries the measured cone and socket against the drawing.
ISO 9001:2015 |
RoHS test report |
Registered trademark |
Patent: security screw and driver |
With each shipment we supply the material certificate, the inspection record for the dimensions on the drawing including the socket depth, and the passivation records for the batch. The documents carry the drawing revision and the batch number, so a repeat order of flat head hex socket screws takes the same key.
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 flush socket head the first article is seated in the customer plate and driven with the production key. Buyers visit during the process to review samples.
|
8,678+
customers served
|
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 broaching station 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 |
Yes. Allen is the common trade name for a hex socket drive; the part is a socket screw with an internal hexagon.
The cone uses most of the head height, so the hexagon is cut into a thin disc. The key still has to reach the floor.
No. A key set covers the range, but each diameter needs its own size, and the depth available differs between head forms.
Only in a countersink of the same angle. A 90 degree head in an 82 degree seat bears on the rim and stands proud.
M1 to M10 in this range, with the key size stated per diameter on the drawing.
Head diameter, countersink angle, head height, key size and socket depth, thread pitch and overall length.
How a flush 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 angle and key size agreed
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→ |
3
First article seated and driven
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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, countersink angle, head height, key size and socket depth, thread pitch and overall length.
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Head diameter
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Cone angle
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Head height
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Key size
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Thread pitch
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Length
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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
