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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:Stainless Countersunk Screws
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Flat head
Drive:Phillips Cross
Thread:Partial Machine Thread
Point:Blunt
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:112-2
We make stainless countersunk screws in passivated stainless, a countersunk head with a cross recess, a plain guide shank and a partial machine thread, quoting them from M1 to M14. Shank, threaded length, cone and grade come from your drawing, and the first article is fitted to your own cover.
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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.
Stainless countersunk screws are machine screws with a countersunk head, a cross recess and a partly threaded shank: a plain guide length under the head and the thread below it. The head finishes flush in a countersink, the plain shank centres the part it passes through, and the thread engages only the nut or insert at the far end. This family is quoted from M1 to M14 with Number 112-2 in passivated stainless.
Countersunk head. A 90-degree cone under a flat top face, so the head sits inside the cover and self-centres in the hole.
Cross recess. A Phillips recess with tapered walls, for a standard driver.
Plain shank. An unthreaded length under the head that guides the cover without engaging it.
Partial thread. The thread starts below the shank, so it can only engage the part it was meant for.
Passivated stainless. No coating, so the cone and the shank are as machined.
Most countersunk screws are threaded up to the head, because the thread is the only thing that has to do work. Stainless countersunk screws with a plain shank are different: the shank has a job of its own, and the head is flush so that job can happen in a joint with nothing standing above the surface.
On stainless countersunk screws the job is guidance. Where a cover or a plate is located by its fixings, a plain shank of the right diameter centres the hole as the screw is offered up, and the thread only meets the nut or the insert below. If the thread ran all the way to the head it would cut or score the cover as the screw turned, and on a thin stainless cover that mark shows for the life of the product.
On stainless countersunk screws the flush head is what makes the arrangement usable. A guide shank needs the screw to be inserted straight, and a countersunk cone does exactly that: it pulls the head and the cover into line as torque is applied, so the shank finds its hole instead of fighting it. The two features work together, which is why this combination appears on covers that must locate precisely and sit flat.
On stainless countersunk screws there is a limit, and it is the thread length. A long plain shank means a short thread, and a short thread means fewer engaged turns in the nut. On a stainless screw into a stainless insert, where friction is high, that can be the difference between a joint that reaches its preload and one that strips the insert first. The threaded length is therefore a strength decision, not just a geometric one.
Stainless suits the form because the head is visible and the shank is a running surface. With no coating, the cone and the shank stay as machined, and a passivated surface resists the light corrosion of a damp interior without the risk of a plate wearing through at the shank where a cover slides.
The recorded range is M1 to M14, covering M1, M2, M3, M4, M5, M6, M7, M8, M9, M10 and M14. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For stainless countersunk screws the quotation carries head diameter, head height, cone angle, shank diameter and length, threaded length and the recess size, because the shank and the thread length are what the joint depends on.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Countersunk, 90-degree cone | Head diameter, height and cone angle |
| Recess | Phillips cross | Recess size and depth |
| Shank | Plain, as rolled or turned | Shank diameter and length |
| Thread | Partial machine thread | Threaded length and position |
| End | Blunt, chamfered | Chamfer cut, not deburred |
| Length | Overall, head included | Measured on the shop plate |
Thread length is the dimension most often left off drawings for this part, and the one that decides the joint. A drawing that gives only the overall length leaves the split between shank and thread to the maker; on a cover that is guided by the shank, that split is the whole point, and two batches can both be correct and behave differently.
Length is measured over the whole screw, head included, as on any countersunk part. The plain shank sits within that length, so a customer switching from a fully threaded countersunk screw to a partial-thread one usually needs the same length and gets a different grip — the thread is shorter, and the nut has to be closer.
Three features define this part: the plain shank, the countersunkhead and the stainless body. The first guides, the second seats, and the third keeps both as made in a damp interior or on a visible face.
| Feature | What it gives | What it costs |
|---|---|---|
| Plain shank | Centres the cover, protects the hole | Less thread length available |
| Countersunk head | Flush line, self-centring | Needs a matching countersink |
| Cross recess | Common driver, defined cam-out | Cam-out marks a visible head |
| Partial thread | Thread only where it is wanted | Thread length must be specified |
| Passivated stainless | Nothing to wear or chip | Galls against stainless |
On stainless countersunk screws the shank is a fit and should be toleranced like one. A shank a few hundredths oversize will not enter the cover; one that is undersize lets the cover wander and the flush line becomes uneven. Where the cover locates on the screw, the shank diameter is the locating diameter whether or not the drawing calls it that.
The flush head and the guide shank together make this a careful part to specify and a forgiving part to assemble. The operator does not have to hold the cover while the thread bites, because the shank already has it; and the head pulls everything into line as it seats. On a production line, that counts for more than the extra cost of the shank.
The recorded finish is passivated stainless with nothing added. On a part with a plain shank that is the right choice: the shank is a running surface, and a coating would be worn off it by the cover in a few cycles, leaving bare steel where the fit is. Passivation leaves the alloy’s own film in place and does not change the diameter.
| Option | How it protects | Effect on shank and cone | Typical use |
|---|---|---|---|
| A2 stainless, passivated | Passive chromium oxide film | As machined | General outdoor and indoor |
| A4 stainless, passivated | Passive film with molybdenum | As machined | Coastal and chemical |
| Steel, white zinc | Sacrificial zinc | Plate wears on the shank | Indoor painted panels |
| Steel, nickel plated | Barrier deposit, bright | Decorative; wears at the shank | Visible hardware |
| Brass, plain | Alloy resists corrosion | Softer shank, clean surface | Instruments and electrical |
Where stainless countersunk screws go into a painted steel cover indoors, a zinc-plated version is cheaper and works; the shank loses its plate over time, which matters less on a painted cover. Where the cover is stainless or visible, the stainless screw is the version that keeps the same surface as the part around it.
Galling is the behaviour that catches people on this part. A stainless shank in a stainless cover, turned under load, can seize before the head seats — and a seized countersunk screw has nothing to grip except the cross recess. A dry-film lubricant on the shank, or a slightly different alloy for the cover, removes the risk.
Three assemblies where stainless countersunk screws are the fixing:
| Where it sits | The screw holds a cover that has to be located by its fixings and sit flush, with the thread landing in an insert behind it. |
| When it goes wrong | A fully threaded screw scores the cover as it turns, and a shank that is off tolerance lets the cover move. |
| Why it happens | The cover locates on the screw, the face is flush, and the thread is in an insert. |
| What we control | Shank diameter and cone checked, first article fitted to the cover. |
| Where it sits | The screw passes through a plate that moves on the plain shank, with the thread clamping the assembly at the far end. |
| When it goes wrong | Thread in the moving part wears it, and too short a thread strips the nut before the joint is tight. |
| Why it happens | The plate moves on the shank, the head sits flush, and the joint is clamped. |
| What we control | Shank run checked, threaded length verified on the drawing. |
| Where it sits | The screw fixes a panel where the face must be flat, the environment is wet and a rusting head would be visible. |
| When it goes wrong | A plated screw loses its coating at the shank and rusts, and a proud head traps water. |
| Why it happens | The panel is stainless or painted, the face is visible, and the joint is wet. |
| What we control | Grade confirmed, cone and shank checked, passivation inspected. |
Four reasons that matter on a part with a guide shank, each tied to what the drawing has to prove:
|
Shank and thread length specified
The shank diameter, the shank length and the threaded length are confirmed separately, because the split between them decides whether the cover is guided and whether the thread is long enough. Basis: Shank and thread length agreed. |
Head, shank and thread in one route
The countersunk head and the recess are formed in the heading stroke, the shank is left plain and the thread is rolled on the lower length. Basis: One route from wire to passivated screw. |
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Fitted to the cover
The first article is measured on the shank and fitted to the customer cover, because the shank is a locating diameter and the fit is the function. Basis: First article fitted to the cover. |
First article fixes the setting
The first article fixes the wire, the cone and the thread start; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these stainless countersunk screws from stainless wire on single-die headers that cut the countersunk head and the Phillips recess in one stroke, leaves the shank plain, rolls the partial machine thread on the lower length and passivates the finished parts. The first part of every run is measured on the head, the shank and the thread start, driven with the production bit and entered into a thread gauge before the batch continues.
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On stainless countersunk screws the point where the thread starts is the tooling detail that matters most. It has to be a clean, square start at the drawing position, because a thread that begins early reaches into the cover and a thread that begins late leaves too little engagement. On a stainless part, where the thread is rolled and work-hardened, the start is also where a badly set roll leaves a burr that catches in the cover.
What decides whether stainless countersunk screws pass is the shank, the cone, the thread start and the alloy. The inspection agreement covers those, and the criteria come from the drawing.
Shank and cone on the projector |
Thread gauged per batch |
Hardness checked on the wire |
Salt-spray testing of the grade |
On stainless countersunk screws the shank is measured for diameter and length on the projector, and the thread start is measured rather than assumed — a batch that begins the thread a fraction early will pass every other check and score the cover it was made for. The cone is checked for angle, and the recess is driven with the production bit.
The thread is gauged per batch and the alloy is confirmed on the certificate. The first article is fitted to the customer’s cover, because on this part the shank is a fit and the fit is what the customer will judge.
Every shipment of stainless 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 a repeat order is made to the same thread start position that was approved.
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 part with a plain shank the first article is fitted to the customer’s cover, because the fit is the function. Buyers visit during the process to review samples and to see how the parts 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
|
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 |
It guides the cover or the moving part and keeps the thread out of it. A thread in that length would cut or score the hole as the screw turned.
Over the whole screw, head included. The plain shank sits inside that length, so switching from a fully threaded version changes the grip.
It can be. A long shank leaves fewer engaged threads, so the threaded length has to be checked against the insert rather than assumed.
The one that fits the cover. A shank that is a few hundredths out either will not enter or lets the cover move, so it is a fit and should be specified as one.
It can. A dry-film lubricant on the shank, or a different alloy for the cover, prevents the seizure.
Thread size, overall length, shank diameter and length, threaded length, head diameter, cone angle and the recess type.
How a stainless countersunk screw project runs from drawing to repeat delivery:
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1
Send the drawing and the cover it guides
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→ |
2
Shank, thread length and cone agreed
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→ |
3
First article fitted to your cover
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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, the overall length, the shank diameter and length, the threaded length, the head diameter and cone angle, and the grade.
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Thread size
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Overall length
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Shank dia.
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Threaded length
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Head diameter
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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
