Tel：
+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:CSK Machine Screw
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Flat Head
Drive:Phillips Cross
Thread:Machine Thread
Point:Blunt
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:524-1
We make csk machine screws in passivated stainless with a countersunk head, a Phillips recess and a machine thread, quoting them from M1 to M14 with JIS head proportions. Head diameter, cone angle, recess and thread come from your drawing, and the first article is fitted into your own panel.
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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 CSK machine screw is a machine screw with a countersunk, flat head: the underside of the head is a cone that sits into a matching countersink, so the top of the head finishes flush with the surface. This family is made in stainless with a plain finish, a Phillips cross recess, a machine thread and the JIS head proportions recorded on the item, quoted from M1 to M14 with Number 524-1.
Countersunk head. A 90-degree cone under a flat top face. The cone centres itself in the hole and carries the clamp load on an inclined surface.
Phillips cross recess. A crossed slot with tapered walls. The driver seats on four inclined faces and is meant to cam out before the head is destroyed.
Machine thread. A rolled thread for a tapped hole or a nut, ending in a blunt chamfer.
JIS head proportions. The head diameter and depth follow the Japanese standard the item is filed under, which is not the same as a DIN or ISO countersunk head of the same thread size.
The most common problem with a csk machine screw has nothing to do with the thread. It is that the cone of the head and the cone of the countersink do not describe the same surface, so the screw either sits proud, sinks below the surface, or bears on the rim of the hole instead of on the full cone. That happens whenever a head made to one standard is dropped into a hole cut to another.
The head of a csk machine screw is defined by three numbers: the head diameter, the head height and the angle of the cone. The angle is 90 degrees in most metric standards, but the diameter and height are not interchangeable between JIS, ISO and DIN, and a JIS head is typically a little smaller in diameter and shallower than its DIN counterpart for the same thread. The difference is small on a drawing and very visible on a panel.
The practical test is on the part, not on the paper. Drop the csk machine screw into the countersink: it should settle with the full cone in contact and the top face flush. If it rocks, the angle is wrong. If it stops high, the cone is too shallow or the countersink is too small. If it falls below the surface, the head is smaller than the hole was cut for — the screw is still holding, but the edge of the hole is now a sharp lip waiting to be damaged.
The JIS recess is its own consideration. A JIS cross recess is a little different in wall thickness and corner radius from a Phillips recess, and a standard PH driver will turn it, but it does not seat as deeply and the corners take more of the load. Where the joint is assembled in volume with a torque-controlled driver, matching the bit to the recess is part of the specification.
On a flush head the load path also changes. A pan head clamps on a flat annulus; a countersunk head clamps on a cone, so the panel around the hole sees a radial component as well as the axial load. In a thin panel the countersink itself becomes the weak point, and a head that is slightly too large will crack the edge of the hole before the joint reaches its torque.
The family is quoted from M1 to M14, covering M1, M2, M3, M4, M5, M6, M7, M8, M9, M10 and M14 on the recorded item. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For a csk machine screw the head diameter, the head height and the recess size are quoted with the thread, because those three numbers decide whether the screw sits flush in the customer’s hole.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Countersunk, 90-degree cone | Head diameter, head height, cone angle |
| Recess | Phillips cross | Recess depth and size, driver fit |
| 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 | Overall, head included | Measured on the shop plate |
Length is measured over the whole csk machine screw, head included, because the head is inside the material. That is the opposite of a pan or cap head, where length is taken from under the head, and it is one of the fields that gets transcribed wrongly when a customer switches head styles on a repeat order.
The head diameter has a tolerance, and on a flush fixing the tolerance is what decides the appearance. A head at the low end of its range in a countersink cut at the high end leaves a visible ring; a head at the high end in a tight countersink sits proud on its cone and marks the panel. Where the fixing is visible, it is worth quoting the head diameter and the hole size together.
Three features define the part: the cone, the cross recess and the stainless body. The first removes the head from the surface, the second gives a drive a general-purpose driver can turn, and the third is why the fixing survives outdoors and in washdown.
| Feature | What it gives | What it costs |
|---|---|---|
| Countersunk cone | Flush surface, self-centring | Needs a matching countersink in the panel |
| 90-degree cone | Standard tooling for the hole | Any 100-degree hole will not seat it |
| Cross recess | Common driver, cam-out limit | Cam-out damages the recess over cycles |
| Flat top face | No projection to catch | Nothing to grip if the recess fails |
| Stainless body | No plating to chip at the rim | Galls against stainless |
The flush result is the reason the csk machine screw form exists. Anything that slides over the surface — a drawer, a cover, a sheet being fed through a machine — will catch a raised head and not a flush one. Where the fixing is on a wear surface, a countersunk head is not a cosmetic choice but a functional one.
The cross recess is the trade the form makes. It is fast to drive and available everywhere, and it is designed to cam out at a torque the head can survive. On a flush head that is a reasonable bargain, because the alternative — stripping the recess — leaves a screw with no projection and nothing to grip.
The recorded finish is plain, passivated stainless. On a csk machine screw that matters more than it does on a pan head, because the cone is a large inclined surface that sits in permanent contact with the panel and holds water against the cone. A passive stainless surface tolerates that; a plated surface wears through at the contact line and starts to rust exactly where nobody can see it until the panel is removed.
| Option | How it protects | Effect on the head | Typical use |
|---|---|---|---|
| A2 plain, passivated | Passive chromium oxide film | None; cone as cut | General indoor and outdoor |
| A4 plain, passivated | Passive film with molybdenum | None; cone as cut | Coastal, marine, chemical |
| White zinc on steel | Sacrificial zinc | A few microns; fit re-checked | Indoor panels, cost-driven |
| Black zinc on steel | Sacrificial zinc, dark passivation | A few microns; fit re-checked | Dark equipment and trim |
| Black oxide on steel | Thin conversion film, oiled | No measurable build | Internal machine parts |
Where the head is plated, the coating thickness enters the fit twice: on the cone, where it lifts the head out of the countersink, and in the recess, where it narrows the cross. Both are small and both are measurable, and on a flush fixing they are the two places where a coated screw stops behaving like the sample it was approved against.
Three assemblies where a csk machine screw is chosen because a flush head is the requirement rather than a preference:
| Where it sits | The screw closes a panel where the face has to stay flat because a cover, a drawer or a hand slides across it. |
| When it goes wrong | A proud head catches and wears, and a head that sits below the surface leaves an open countersink. |
| Why it happens | The panel is thin, the face is a working surface, and the fixing is repeated. |
| What we control | Head diameter and cone angle quoted with the thread, cone checked on the projector. |
| Where it sits | The screw fixes a front plate or a chassis panel where the face is visible and the head has to disappear into the material. |
| When it goes wrong | A head of the wrong standard leaves a ring at the rim, and the panel reads as unfinished. |
| Why it happens | The face is visible, the panel is thin, and the hole is already cut. |
| What we control | Head dimensions and recess checked, JIS or ISO fit confirmed against the hole. |
| Where it sits | The screw fixes a guard or a cover where anything projecting would catch clothing, a cable or a moving part. |
| When it goes wrong | A raised head is a snag point, and a damaged recess leaves nothing to remove it with. |
| Why it happens | The surface is a safety boundary and the fixing is serviced. |
| What we control | Cone angle and recess checked, thread gauged per batch. |
Four reasons that matter on a flush fixing, each tied to what the drawing has to prove:
|
Head standard confirmed before quoting
The JIS, ISO or DIN head proportions are confirmed against the customer hole, because a countersunk head made to the wrong standard will not sit flush no matter how good the thread is. Basis: Head standard matched to the hole, in writing. |
Head, recess and thread made in one route
The countersunk head and the cross recess are formed in the heading stroke, the thread is rolled and the parts are passivated in the same route. Basis: One route from wire to passivated screw. |
|
Cone and recess measured, not assumed
Head diameter, head height and cone angle are measured on the projector and the recess is driven with the production bit, because a recess that measures to the drawing can still refuse a worn driver. Basis: First article driven with the production bit. |
First article fixes the setting
The first article fixes the wire heat, the recess 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 csk machine screws from stainless wire on single-die headers that cut the countersunk head and the Phillips recess in one stroke, rolls the machine thread to a blunt chamfered end and passivates the finished parts. The first part of every run is measured on the head and the cone, driven with the production bit and entered into a thread gauge before the batch continues.
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The cone of a csk machine screw head is the part of the die that wears fastest, because it takes the full heading load on an inclined face. A worn cone flattens the angle at the rim, and a screw made with it will seat on the outer edge of the countersink rather than on the whole cone — the screw looks flush and moves under load, which is harder to diagnose than a screw that plainly does not fit.
What decides whether csk machine screws pass is the cone geometry, the recess, the thread and the alloy. The inspection agreement covers those, and the criteria come from the drawing.
Head diameter and cone on the projector |
Thread gauged per batch |
Hardness checked against the grade |
Salt-spray testing of the grade |
The head of every csk machine screw is checked for diameter and height against the standard, and the cone angle is checked against a countersink gauge or on the projector. That check is what a flush joint depends on, and it is the one that a batch made to the wrong standard will fail even though every other dimension is correct.
The recess is checked for depth, position and corner condition and then driven with the production bit; the thread is gauged per batch, and the alloy is confirmed on the certificate. First articles are kept so that repeat orders can be compared against the part that was approved.
Where a customer supplies their own panel or a sample hole, the first article is fitted into it before the batch is released. A flush joint cannot be proved on a screw alone.
Every shipment of csk machine 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 fixing the first article is fitted into the customer’s panel, because the seat is the function. Buyers visit during the process to review samples and to see how the heads and recesses are formed.
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8,678+
customers served
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87%
of orders from repeat customers
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56%
of orders through referrals
|
89
countries and regions shipped to
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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 |
Countersunk. The head is a cone under a flat top, so it finishes flush in a matching countersink. CSK and countersunk are the same part.
Not properly. The cone angle is the same in most metric standards but the head diameter and height differ, so the JIS head sits high or low in a DIN countersink.
Over the whole screw, head included, because the head sits inside the material. A pan or cap head is measured from under the head instead.
The countersink is larger than the head diameter, usually because the hole was cut for a different standard. The joint still clamps, but the lip of the hole is exposed.
No. A 90-degree cone in a 100-degree hole contacts only at the rim, and the joint is loose however tight the screw is turned.
Head diameter, head height, cone angle and standard, recess type and size, thread size, and the overall length including the head.
How a csk machine screw project runs from drawing to repeat delivery:
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1
Send the drawing and the countersink it goes into
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→ |
2
Head standard and cone angle confirmed
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→ |
3
First article fitted into your panel
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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 height, the cone angle and standard, the recess type, the thread size and the overall length including the head.
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Head diameter
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Head height
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Cone angle
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Recess type
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Thread size
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Overall 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
