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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:Machine Screw
Materials:Carbon Steel
Surface treatment:Eco Blue Zinc plated
Head Type:Countersunk flat head
Drive:Phillips cross recess
Thread:Machine thread
Point:Plain, chamfered
Forming:Cold heading and thread rolling
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
We make flat head machine screws in carbon steel with an eco blue zinc plate, a countersunk cone, a Phillips recess and a machine thread, quoted to the drawing. The bit pressure that keeps the cross engaged is also what seats the cone, so the countersink and the assembly method are agreed with the part.
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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 machine screw is a screw with a uniform machine thread that goes into a tapped hole or a nut, and on this page it is the flat head Phillips form. The part recorded here is carbon steel with an eco blue zinc plate, quoted from M1 upward with the length made to the drawing.
Flat head. A countersunk cone that seats in a matching countersink, so the head finishes level with the surface.
Phillips recess. A cross recess that self-centres and slips at a defined torque.
Machine thread. A thread of constant form that engages a tapped hole over a defined length.
They are used on panels, enclosures and assemblies where the fixing must be flush and the hole can be tapped. A machine screw of this form is the default choice for that joint, which is why the assembly method has to be written down rather than left to the operator.
On a flat head machine screw the driver does two things at once. The bit has to be pressed into the cross to keep engagement, and that same downward force is what seats the cone in the countersink. Both jobs are carried by one force, and that is the property that makes this joint different from a pan head with a cross or a countersunk head with a socket.
Too little pressure and the bit rides out. The cross is self-centring only while the bit is held in it; once the pressure drops, cam-out starts early, the head is not fully seated, and the recess takes the damage. Too much pressure and the cone is driven past its seat, the countersink in the customer part deforms, and the head sits below the surface.
The correct assembly is therefore a sequence rather than a setting: press, drive until the cone seats, then stop. On a power driver that means a clutch setting low enough to stop at contact, plus enough axial pressure from the operator or the nose piece to keep the bit engaged. Both parts of that are process, not product, which is why the drawing states the torque and the assembly method together.
The cone itself behaves the same way as on any countersunk screw. Its angle has to match the countersink; a mismatch contacts on a line and the head rocks, and on a flush joint the result is a ring around the head that no amount of torque removes.
The material and finish add the last variables. Blue zinc is a soft sacrificial plate, so it is the first thing damaged when the bit slips, and the cross is checked in the plated state. Carbon steel in a soft countersink is the combination that shows an over-driven head most clearly.
The part is quoted to the drawing with the head, the recess and the thread stated separately. Custom lengths up to 2,000 mm, subject to DFM review after drawing submission. The quotation for a machine screw carries the cone angle and head diameter, the recess, the thread, the length and the countersink in the customer part.
| Item | How it is defined | What we control |
|---|---|---|
| Cone | Flat head | Diameter, angle and edge |
| Recess | Phillips | Depth and width |
| Thread | Machine thread | Size, pitch and length |
| Countersink | In the customer part | Angle and depth agreed |
| Length | Under the head | Length and cut end |
| Plate | Eco blue zinc | Thickness and recess fit |
The cone angle is written as a pair with the customer’s countersink. On a flush joint this is the most common source of a proud head or a ring, and it is a drawing item on both parts.
The recess depth is limited by the head, and the head on a countersunk screw is a cone. A cross cut too deep breaks into the cone from below and leaves a head that collapses under the bit.
The length is measured under the head, which on a countersunk screw means from the cone rather than from the top. In a blind hole the cone depth is part of the stack, so the two parts have to be read together.
Four properties decide machine screws of this form, and each one carries a cost:
| Property | What it gives | What it costs |
|---|---|---|
| Flat head | A flush joint | Cone must match the countersink |
| Phillips recess | A standard bit and a torque limit | Slips early if pressure drops |
| Machine thread | A repeatable joint | Needs a tapped hole or a nut |
| Eco blue zinc | Protection at low cost | Soft plate marks at the first slip |
The value is a flush joint driven with a standard tool, in a part that can be tapped. On an enclosure or a panel that is the simplest joint that still looks finished.
On a machine screw of this form the cost is the balance between pressure and torque. The joint depends on the driver as much as on the screw, which is why an assembly method belongs with the part rather than in a work instruction alone.
The recorded finish is eco blue zinc, a trivalent zinc plate with a blue-white passivation. On a flat head it gives a bright finish and sacrificial protection, and it is the usual finish on indoor panels and enclosures.
| Option | How it protects | Effect on cone and recess | Typical use |
|---|---|---|---|
| Eco blue zinc | Trivalent zinc, blue-white | Build on cone; recess re-checked | Indoor panels and enclosures |
| Clear zinc | Sacrificial zinc, thinner | Less build; recess closer to size | Electronics assemblies |
| Nickel plated | Hard bright barrier | Thin build; recess kept | Visible hardware |
| Black oxide | Conversion film, oiled | No measurable build | Dark mechanisms |
| Stainless, passivated | Passive film, no coating | No build; different material | Wet and food areas |
A soft plate matters more on a Phillips than on other drives, because the first slip happens at the recess rather than at a socket. A plate that wears at the cross turns a single cam-out into a rounded recess, so the finish is judged there as well as on the cone.
The cone is the other surface. A film on it changes how the head seats, and on a flush joint the difference shows as a head that stands a few hundredths high.
Three assemblies where a flush joint is driven with a standard bit:
| Where it sits | The screw closes a cover or holds a plate in a countersunk hole where the surface has to stay flush. |
| When it goes wrong | The head stands proud, or the cone deforms and the head sinks. |
| Why it happens | The pressure and the clutch setting work against each other. |
| What we control | Cone angle and countersink checked; first article assembled on the panel. |
| Where it sits | The screw fixes a board or a bracket where nothing may stand above the surface. |
| When it goes wrong | The recess rounds out, or the frame distorts around the hole. |
| Why it happens | The bit is worn, and the panel is thin for the clamp. |
| What we control | Recess proved with the bit; first article tightened to the stated torque. |
| Where it sits | The screw holds a plate where the joint is small, visible and serviced occasionally. |
| When it goes wrong | The head marks the finish, or the joint loosens after reassembly. |
| Why it happens | The plate is soft, and the recess has been reused. |
| What we control | Head and recess checked; first article opened and refitted. |
Four reasons that matter when the drive and the seat share one force, each tied to something the drawing or the first article proves. All four show in the sample.
|
Cone and countersink agreed
The drawing states the cone angle together with the customer countersink, because a mismatch seats the head on a line rather than on a face. Basis: Angle agreed on both parts. |
Recess cut in a finished cone
The recess is cut after the head is formed, so its depth is taken from the surface the bit meets and the cone keeps its seat. Basis: Recess depth controlled. |
|
Bit and panel used
The first article is driven with the customer bit and assembled on the panel, because the pressure and the seat only exist in the joint. Basis: Bit and seat proved. |
Same limits on repeat runs
Cone, recess and plate are recorded with the drawing revision, so a repeat batch seats the same way. Basis: Same limits across orders. |
These screws are cold headed from carbon steel wire, with the flat head formed to its cone angle, the cross recess cut and the thread rolled; the parts are then blue zinc plated. The first piece of every run is measured on head diameter and cone angle, recess depth and width, thread and length.
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The cone comes from the heading die, so its angle is a property of the tool rather than of a later operation. That keeps the cone concentric with the thread, and on a flat head a cone that is off-axis shows as a head sitting at an angle with one side bearing.
The recess is cut after the cone is formed, so the cross stays inside the thickest part of the head. On a countersunk head the section under the cross is thin, and a recess cut a fraction deep leaves a head that deforms when the bit is pressed in.
The thread is rolled, and the parts are plated last. The recess is checked with the matching bit in the plated state, and the cone is checked for a burr at its edge, since a burr there keeps the head from seating.
What decides whether a machine screw passes is the cone, 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 |
Core hardness checked |
Salt-spray testing of the blue zinc |
The cone is measured for angle and diameter, and its edge is checked for a burr. A burr there is the difference between a head that seats and one that stands a few hundredths high.
The recess is measured for depth and width and checked with the matching bit. On a flat head there is little material under the cross, so a recess that is too deep shows as a soft feel rather than as a visible defect.
The thread is gauged, and a sample is seated in a countersink of the specified angle and driven with the customer bit. That test is the only one that shows whether the pressure and the seat work together.
Every batch of machine screws is traceable to the wire it was made from and to the plating lot that finished it. The grade and heat number appear on the material certificate supplied with the parts, and the plating report carries the layer thickness and the lot number.
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 and recess, and the plating report. The records carry the drawing revision and the batch number, so a repeat order of machine screws 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 countersunk part the first article is seated in the customer countersink and driven with the customer bit. 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 heading cell and the plating 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 |
Because the cross needs downward pressure to stay engaged, and that pressure is also what seats the cone. When it drops, cam-out starts early.
The cone is driven past its seat and the countersink deforms, so the head sinks below the surface.
Press, drive until the cone seats, then stop. On a power driver that means a clutch setting plus enough axial pressure to keep the bit in.
It has to match the countersink. A mismatch contacts on a line and leaves a ring around the head.
Blue zinc is soft and sits inside the cross, so a layer that is too heavy changes which bit enters.
Cone angle and head diameter, recess, thread, length, finish, and the countersink in the customer part.
How a flat head machine 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, recess and thread 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 cone angle and head diameter, recess, thread, length, finish, and the countersink in the customer part.
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Cone angle
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Head diameter
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Recess
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Thread
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Length
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Countersink
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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
