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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:Hex Socket Countersunk Screw
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Flat Head
Drive:Allen Socket
Thread:Machine Thread
Point:Blunt
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:SST
We make hex socket countersunk screws in passivated stainless with a flush cone and a deep hexagon, so a head with nothing to grip can still be torqued. Cone angle, socket depth, thread and grade come from your drawing, and the first article is seated in your countersink and turned with your key.
Watch the factory video·Email sst@szsst88.com
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 hex socket countersunk screw is a flush-head screw driven with a hex key through a socket in the middle of a countersunk cone, so it can be tightened hard in a head that offers nothing to grip outside. The recorded item is stainless with a plain finish, a flat head and a hex socket, quoted from M1 to M14.
Countersunk head. A cone that seats in a matching countersink and finishes flush or below the surface. It centres the screw as it turns and bears on the cone over its whole area.
Hex socket. An internal hexagon deep enough for a hex key to seat fully. On a flush head this is the only way in: there are no flats outside and no slot cut into the cone.
Machine thread. A rolled thread with a blunt chamfered end, made for a tapped hole or a nut. It runs in and out without cutting into the part.
Stainless, plain. Passivated and uncoated, so the cone seats exactly as formed and the socket is as deep as it was cut.
A flush head has no outside surface to grip and, on this form, no slot across it either. That leaves the socket as the sole means of turning the screw, which is why the depth of the socket and the condition of the key matter more here than on any other head. A rounded socket on a countersunk screw cannot be recovered by gripping the head, because there is nothing to grip.
The countersunk cone and the socket cooperate rather than compete. The cone takes the lower part of the head and carries the clamp load; the socket sits in the material above it and carries the torque. Because the head is a cone with material at its centre, the socket can be deeper than on a pan head of the same diameter — which is what allows a flush screw to be driven to a real torque.
The countersink depth in the part is part of the specification. A countersink that is exactly the head height leaves the head flush; one that is deeper leaves the head below the surface, which is what a machine table or a fixture wants so that nothing stands proud; one that is shallower leaves the head standing up and the joint riding on the rim of the cone.
Thin sheet is the limit of the form. A countersink that has to swallow the head can break through a thin panel, and once it does, the cone has nothing to bear on. Where the sheet is thin, the choice is a shallower head, a thicker sheet, or a different head form — not a deeper countersink.
Plain stainless is passivated after the socket is cut. The cone is the largest visible surface and the socket is the only drive, so free iron left by the tools shows either as a bloom on the cone or as a rust spot inside the socket, and both are read as material failures.
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 hex socket countersunk screws the cone angle, the socket size and the thread length are quoted together, because the head carries both features.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Countersunk cone, flush top | Cone angle, diameter and concentricity |
| Socket | Internal hexagon | Across flats and depth, key tried on the part |
| Thread | Machine thread | Pitch and length, gauged per batch |
| End | Blunt, chamfered | Chamfer cut, not deburred |
| Finish | Plain stainless, passivated | Surface condition and film |
| Length | From the top of the head to the end | Measured on the shop plate |
The cone angle has to match the countersink, and on a fixture that has been re-cut or a sheet that has been formed the angle is often a degree or two off. The first article is seated in a sample of the customer’s part for that reason, because a cone that is out seats on a line and looks flush from above.
Length is measured from the top of the head, because a flush head finishes at the surface and the top face is the datum that shows. Measuring from the start of the cone gives a screw short by the head depth, and on a shallow counterbore that is the whole engagement.
Three features define this part: the countersunk cone, the hex socket and the stainless body. The first two make a flush fixing that can be torqued, and the third is what lets it sit in a wet or washed machine.
| Feature | What it gives | What it costs |
|---|---|---|
| Countersunk cone | Flush or below-flush finish | Bears on the panel; thin sheet is the limit |
| Hex socket | High torque in a flush head | The only way in if it rounds |
| Socket depth | Deeper than on a pan head | Needs a full-depth countersink |
| Stainless | No coating to chip at the cone | Galls in a stainless countersink |
| Plain finish | Cone and socket as formed | Pitting in chloride at the socket |
The comparison that matters is with a slotted or cross flush head. Those drives are shallower and cam out earlier, which on a flush head means the driver climbs and marks the cone — the one visible surface. A socket carries the torque without leaving the recess, and where the joint needs a real clamp load it is the only flush drive that will deliver it.
The cost arrives when the socket fails. A hex key that is worn, or one that is a size small, rounds the socket at its corners; the head then cannot be turned by any tool, because there is no outside surface and no slot. On a fixture that has to come apart, that is the difference between a repair and a drilled-out screw.
The recorded finish is plain, passivated stainless. Nothing is added, so the cone seats exactly as formed and the socket keeps its depth; a coating would change where the head stops in the countersink, and on a below-flush fixing that is the visible dimension.
| Option | How it protects | Effect on cone and socket | Typical use |
|---|---|---|---|
| Stainless A2, plain | Passive chromium oxide film | None; gauged as formed | Machine tools and fixtures |
| Stainless A4, plain | Passive film with molybdenum | None; gauged as formed | Coastal and washdown |
| Zinc plated steel | Sacrificial zinc | A few microns; both re-checked | Indoor, cost-driven work |
| Black oxide on steel | Thin conversion film, oiled | No measurable build | Fixture plates and tooling |
| Dacromet on steel | Zinc-aluminium flake layer | Film builds; socket re-checked | Outdoor steel structures |
Stainless has one behaviour that a countersunk joint has to plan for: galling. A stainless cone driven into a stainless countersink can seize before the head seats, and a seized flush screw has only the socket left to turn it with. A lubricant on the thread, or a different grade for the part, prevents it.
Where the joint is wet, the socket is the weak point. Water sits in a hexagon, air is excluded, and the passive film struggles to rebuild — so an A2 screw in chloride pits inside the socket before anywhere else. The grade is the answer, and where the service is severe the socket is left uncoated and bare so that the alloy does the work.
Three assemblies where hex socket countersunk screws are the fixing:
| Where it sits | The screw clamps a jaw, a stop or a plate below the surface of a table so that nothing stands proud of the working face. |
| When it goes wrong | A head that is flush but not below leaves a burr that marks the workpiece, and a rounded socket ends the adjustment. |
| Why it happens | The face is a datum, the head is buried, and the fixing is re-set often. |
| What we control | Cone and socket checked, socket driven with the production key, counterbore depth matched. |
| Where it sits | The screw fixes a mount or a stage where the head must sit below the surface and the torque has to be repeatable. |
| When it goes wrong | A cross recess in a flush head cams out and marks the cone, and a shallow countersink leaves the head high. |
| Why it happens | The joint is adjusted, the head is buried, and the part is small. |
| What we control | Cone seated in a sample, socket depth checked, thread gauged. |
| Where it sits | The screw closes a cover or fixes a fitting where the surface must be flat for cleaning and the joint is washed. |
| When it goes wrong | A proud head traps residue, and a plated screw rusts at the cone where water sits. |
| Why it happens | The surface is cleaned, the head is flush, and the fixing is serviced. |
| What we control | Grade confirmed, socket and cone checked, passivation inspected. |
Four reasons that matter on a flush socket head, each tied to what the drawing has to prove:
|
Cone, socket and counterbore reviewed together
The cone angle, the socket depth and the depth of the countersink are reviewed as one set, so a head that would stand proud or a socket too shallow for the key is raised before the die is cut. Basis: Cone, socket and counterbore reviewed as one set. |
Heading, socketting and passivation in one route
The countersunk head and the hex socket are formed in one stroke, the thread is rolled and the parts are passivated in the same route. Basis: One route from wire to passivated screw. |
|
Key tried, cone seated
The socket is turned with the production key and the cone is seated in a sample part on the first article, because both features are proved in use. Basis: First article keyed and seated. |
First article fixes the setting
The first article fixes the wire heat, the socket punch and the passivation; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these hex socket countersunk screws from stainless wire on single-die headers that cut the countersunk cone and the hexagon in one stroke, rolls the machine thread to a blunt chamfered end and passivates the parts. The first part of every run is measured on the cone, turned with the production key and seated in a sample countersink before the batch continues.
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The socket punch works inside a head the cone has already thinned, so the tool has less room than on a cap head. A worn punch leaves a hexagon that is shallow at the corners, and a shallow hexagon on a flush screw rounds under a key with no visible warning on the outside of the product — by the time it is noticed, the screw is already tight and cannot be removed.
What decides whether hex socket countersunk screws pass is the cone, the socket, the thread and the alloy. The inspection agreement covers those, and the criteria come from the drawing.
Cone and socket on the projector |
Thread gauged per batch |
Hardness checked on the formed head |
Salt-spray testing of the stainless grade |
The cone is checked for angle, diameter and concentricity, and the socket for across flats and depth; the first article is then seated in a sample countersink and turned with the production key. Seating is read with a light behind the head, which is the customer’s acceptance test on a flush joint.
The thread is gauged per batch, and the alloy is confirmed on the certificate. On a stainless part the socket is also inspected for a rust bloom, which is the sign of free iron left by the punch.
Every shipment of hex socket countersunk 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 or the passivation. 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 flush socket head the first article is seated in the customer’s fixture plate, because the countersink depth is the variable that decides whether the head sits below the surface. Buyers visit during the process to review samples and to see how the heads and sockets 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 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 |
A flush head has no outside surface to grip and no slot, so the socket is the only way to turn it. The socket can be deep because the cone leaves material at the centre of the head.
That is set by the depth of the countersink. A countersink equal to the head height leaves it flush; deeper leaves it below the surface, which is what a fixture plate needs.
Nothing can turn the screw, because there is no outside surface or slot. The socket is checked with the production key on the first article for that reason.
Only if the sheet can take the countersink without breaking through. If it cannot, a different head form or a thicker sheet is the answer, not a deeper countersink.
A stainless cone in a stainless countersink can seize before the head seats. A lubricant on the thread, or a different grade for the part, prevents it.
Cone angle and diameter, socket across flats and depth, thread size and length, length from the top of the head, and the stainless grade.
How a hex socket countersunk screw project runs from drawing to repeat delivery:
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1
Send the drawing and the countersink sample
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→ |
2
Cone, socket and thread review
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→ |
3
First article keyed and seated
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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 cone angle and diameter, the socket across flats and depth, the thread size and length, the length from the top of the head and the stainless grade.
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Cone angle
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Head diameter
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Socket size
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Socket depth
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Thread and length
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Stainless 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
