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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:Stainless Steel Machine Screws Countersunk
Materials:Stainless Steel
Surface treatment:Plain
Head Type:Flat (countersunk)
Drive:Phillips cross recess
Thread:Machine thread
Point:Plain, chamfered
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
We make stainless steel machine screws countersunk with a cross recess and a plain finish, quoting them from M1 to M10 with lengths made to the drawing. The cone angle and the seat in your plate are agreed together, and the first article is seated in it before the batch runs.
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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 steel machine screws countersunk are machine screws with a conical underside that seats in a countersink, made in stainless and left plain. The part recorded here has a cross recess and a machine thread, quoted from M1 to M10 with lengths made to the drawing.
Countersunk head. A 90 degree cone that seats in a matching countersink so the head finishes level with the surface.
Cross recess. Four tapered arms driven by a matching bit, cut into the small disc left above the cone.
Stainless body. No coating, so the cone is bare metal meeting bare metal, which is what a seated joint needs.
Machine thread. A uniform thread for a tapped hole or a nut, with the length measured over the head.
They are used on plates, covers, machine beds and instrument panels where a fixing must not stand proud of the surface and the joint has to survive moisture without a coating that wears.
A countersunk screw does not make a flush joint by itself. The head is a cone, and the panel has to carry a matching cone cut into it at the same angle and to the same depth. Get the screw perfectly and cut the seat badly, and the head sits proud or sinks below the surface; the fixing is judged by the seat.
That makes three things panel operations rather than screw features. The first is the angle: 90 degrees is the metric practice, and a seat cut at 82 degrees will leave a 90 degree head resting on its rim. The second is the depth: too shallow and the head stands proud, too deep and the head sinks and the cone bears on nothing but its edge. The third is the edge of the hole, which has to be clean, because a burr under the cone holds the head off the seat by more than the tolerance the joint allows.
A deburred hole is not a countersink and the difference catches people out. A chamfer that only breaks the edge looks like a seat, takes the head part of the way, and leaves it standing proud by a fraction that is visible in a row of fixings. The seat is a formed cone, cut with a tool of the right angle, to the diameter the head needs.
Material thickness then sets the limit. A countersink removes material around the hole, so on thin sheet there is little left to carry the cone and the seat either pulls through or distorts the panel. The rule of thumb is that the remaining material under the head has to be enough to take the clamp, and where it is not, a different head form is the honest answer rather than a deeper seat.
Stainless behaves like steel in the joint and differently at the edges. It work-hardens, so a seat cut with a dull tool leaves a hardened, ragged rim that the cone cannot bed into, and the head of a stainless countersunk screw will then show a bright ring where it has been pulled against the burr. That bright ring is the symptom; the cause is in the panel operation.
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 stainless steel machine screws countersunk carries the head diameter, the countersink angle, the head height, the PH size and recess 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 |
| Recess | Phillips, PH size per diameter | Depth and floor thickness |
| Thread | Machine thread in stainless | Pitch, length and start position |
| Seat | Panel cone, on the mating drawing | Angle, depth and hole edge |
The seat line is in the table because it is the dimension that decides the result. Where the panel drawing gives the seat, the screw becomes a known quantity; where it does not, the joint depends on whoever drills first.
Head height is measured from the top face to the top of the cone, and it is small on a countersunk part because the cone takes most of the head. The recess is cut into what remains, which is why a head that is a fraction low loses a visible part of its recess depth.
Length is measured over the head. In a seated joint the usable thread length is the overall length minus the cone depth in the panel, and that is what decides engagement in a thin plate.
Four properties decide stainless steel machine screws countersunk, and each one carries a cost:
| Property | What it gives | What it costs |
|---|---|---|
| Countersunk head | A flush surface when seated | The panel must carry the matching cone |
| Cross recess | Standard bit, self-centring | Shallow recess in a thin head |
| Stainless body | Corrosion without a coating | Work-hardens at a badly cut seat |
| Machine thread | Repeatable joint | Needs a tapped hole or a nut |
The value is a surface with nothing standing on it. Where a part slides, seals or is cleaned across the fixing, that is a requirement rather than a preference, and a countersunk head is the simplest way to meet it.
The cost is that the result is shared with the panel. A perfect screw in a poor seat looks like a poor screw, and the customer judges the fixing because that is what they can see.
The recorded finish is plain. On a countersunk screw that is the right choice, because the cone is a bearing surface: a coating there changes both the fit and the friction of seating, and the head then beds in at a different height.
| Option | How it protects | Effect on cone and recess | Typical use |
|---|---|---|---|
| Passivated, plain | Removes free iron; rebuilds oxide | No build; cone as cut | Default for stainless |
| Electropolished | Levels the surface | Cone edges rounded slightly | Food and medical equipment |
| Black oxide on stainless | Colours the surface | Thin film; seat unchanged | Dark machine beds |
| Nickel plated | Hard bright barrier | Build on the cone; seating changes | Where a bright finish is wanted |
| Zinc plated steel equivalent | Sacrificial zinc | Build on cone; friction changes | Where stainless is not needed |
Where a plated part is used in the same seat, the head seats a fraction higher and the friction that holds it there is different. On a flush joint that shows as a high spot, and on a joint that is opened often it shows as a head that comes loose at a torque that used to hold it.
Plain stainless has no such variable. The cone that leaves the heading machine is the cone that bears on the seat, which is why a flush-joint specification is easier to hold in stainless than in a plated steel part.
Three settings where the surface has to stay clear and the joint must not corrode:
| Where it sits | The screw closes a plate where the surface is machined flat and remains flat for a workpiece. |
| When it goes wrong | A seat cut too shallow leaves heads proud and the workpiece rocks on them. |
| Why it happens | The surface is machined, the fixings are numerous, and flatness is inspected. |
| What we control | Seat angle and depth on the panel drawing; first article checked for proudness. |
| 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, the surface is finished, and the fixing is covered. |
| What we control | Head height checked; first article assembled and cycled. |
| Where it sits | The screw closes a faceplate where the fixing must be invisible and must not corrode. |
| When it goes wrong | A plated screw wears at the recess and shows a different tone in the plate. |
| Why it happens | The panel is visible, the fixing is small, and the surface is inspected. |
| What we control | Passivation verified; first article fitted in the plate. |
Four reasons that matter on a joint where the result depends on two parts, each tied to something the drawing or the first article has to prove:
|
Cone angle and seat agreed together
The countersink angle and the seat are confirmed as one pair, because a 90 degree head in an 82 degree seat stands proud however well the screw is made. Basis: Cone and seat as one pair. |
Headed, recessed, threaded, passivated
The cone and head are formed in one stroke, the recess cut, the thread rolled, and the batch passivated so the cone stays as cut. Basis: One route, cone as cut. |
|
Height and recess measured
Head height and recess depth are measured together on the projector, because on a countersunk head the recess lives in the few tenths left above the cone. Basis: Height and recess measured. |
Seated in your plate first
The first article is seated in the customer plate, because proudness only appears against the real seat and the real hole edge. Basis: First article in your seat. |
These screws are headed on single-die machines that form the cone and the top face in one stroke, cut with the cross recess, thread rolled on the stainless shank and passivated as a batch. The first part of every run is measured on head diameter, cone angle, head height, recess depth, thread and length.
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Forming the cone is a flow problem. The metal is pushed out and down into the cone, and the top face is what remains; a punch set slightly deep leaves that face too thin to hold the recess, and a punch set shallow leaves the head standing taller than the drawing. Both are measurable on the first article and neither is visible in a bin of parts.
The recess is cut after the cone and is the operation with the least room on this head form. Because the cone consumes most of the height, the cross sits in a thin disc, and a punch that is a little dull leaves a floor that is high and arms that are rounded, which produces a part that takes a bit part of the way and then marks.
Passivation follows forming and reaches the cone as well as the recess. Both are cut features that hold contamination, and both are invisible once the screw is seated, which is why the batch is checked at the cone rather than only on the head face.
What decides whether stainless steel machine screws countersunk pass is the cone, the head height, the recess and the thread. The inspection agreement covers those, and the criteria come from the drawing.
Cone and recess on the projector |
Thread and start checked |
Hardness against the stainless spec |
Salt-spray testing of the cone and recess |
Cone angle, head diameter and head height are measured as one set on the projector, then the recess depth is read against the height. The four together decide whether the head will seat and whether the bit will reach the floor.
The functional check is a seat. A sample from every batch is fitted into a countersunk test plate of the agreed angle and depth, and checked for rocking and for proudness; that is the only check that reproduces what the customer does with the part.
A second sample is driven into the customer plate and removed, which shows a burr in the seat, a cone that does not match, or a recess that has started to mark. Both checks are recorded with the batch.
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 records carry the measured values for the cone and the recess.
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 cone angle, and the passivation records for the batch. The documents carry the drawing revision and the batch number, so a repeat order of stainless steel machine screws countersunk seats the same way.
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 joint the first article is seated in the customer plate, because proudness is judged against the real seat. Buyers visit during the process to review samples.
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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 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 |
Almost always the seat. A shallow countersink, a wrong angle or a burr at the hole edge holds the cone off the surface.
No. Breaking the edge is not a seat; the cone needs a formed counterangle of the right depth.
A countersink removes material around the hole, so there is less left to take the clamp. A different head form is the honest answer.
It removes the coating variable: the cone is bare metal on bare metal, so it seats consistently from batch to batch.
Yes, but check the seat quality. Aluminium cuts easily and grabs the tool, leaving burrs that hold the head off the seat.
Head diameter, countersink angle, head height, PH size and recess depth, thread pitch and overall length, plus the seat on the panel.
How a flush joint 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 seat agreed
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→ |
3
First article seated in your plate
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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, PH size, thread pitch and overall length, plus the seat on the panel.
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Head diameter
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Cone angle
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Head height
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PH 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
