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:Oval Head Machine Screw
Materials:Carbon Steel
Surface treatment:Black Zinc Plated
Head Type:Raised Counteresunk Head
Drive:Phillips
Thread:Machine Thread with Locking Patch
Point:Blunt
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:425-1
We make oval head machine screws from carbon steel with a raised countersunk head, a cross recess and a pre-applied locking patch, black zinc plated and quoted from M1 to M14. Cone angle, dome height, thread and patch torque come from your drawing, and the first article is seated and re-driven.
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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.
An oval head machine screw is a machine screw with a raised countersunk head: a cone that seats in the part and a shallow dome that stands above it, driven with a cross recess. The recorded item on this page is black zinc plated carbon steel with a raised countersunk head, a machine thread and a pre-applied locking patch, quoted from M1 to M14 with Number 425-1.
Raised countersunk head. An oval, in the older vocabulary: the underside is a countersunk cone that centres the screw in the hole, and the top is a low dome that sits proud of the surface. It is the only common head that is both countersunk and visible.
Cross recess. A Phillips cross in the dome. The dome gives enough height for a full-depth recess, which a flat countersunk head does not always have.
Locking patch. A pre-applied strip of nylon or adhesive on the thread, sized to interfere with the internal thread as the screw is driven. It holds the screw against vibration without a washer and without a chemical applied at assembly.
Black zinc. Electroplated zinc with a dark passivation, applied before the patch. It is sacrificial, and the dark tone is what makes the head disappear into black trim instead of reading as a bright dot.
On an oval head machine screw the head has two surfaces doing two jobs. The countersunk cone carries the clamp load and centres the screw in the hole; the dome above it is what the customer sees and what carries the recess. Because the cone is the bearing surface, the seat is decided by the angle of the countersink in the part, and a mismatch of a degree loads the head on a line rather than on a surface.
The dome is what separates an oval head from a flat countersunk head, and it is not decoration only. It gives height for a recess deep enough to drive, and it leaves a rounded profile that takes a ding without showing it the way a flush top does. On a head that is tightened with a driver, that extra height is the difference between a recess that survives and one that cams out.
The failure mode of this head is collapse. Over-tighten it and the cone presses into the countersink, the sheet or the insert deforms, and the dome sinks toward the surface. On a soft panel the head then sits in a shallow crater and cannot be re-torqued, because the bearing surface it needs no longer exists.
The locking patch sits on the thread, on the side that will meet the internal thread first. It is applied after plating, so the coating underneath is intact, and it is sized by the thread and by the prevailing torque the customer wants. A patch that is too thin does nothing; one that is too thick makes the first turn heavy and can cross a thread in aluminium.
Black zinc goes on before the patch. The plating is a few microns and it is judged on the dome, which is the most visible part of the screw; the patch then covers part of the thread, so the thread is gauged before the patch is applied as well as after.
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 an oval head machine screw the head height and the cone angle are quoted with the thread, because both decide how the head seats.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Raised countersunk, oval | Cone angle, head height and diameter |
| Recess | Phillips cross | Depth and width, bit tried on the part |
| Thread | Machine thread | Pitch and length, gauged per batch |
| Patch | Pre-applied locking strip | Position, coverage and prevailing torque |
| End | Blunt, chamfered | Chamfer cut, not deburred |
| Length | From the top of the head to the end | Measured on the shop plate |
Length is quoted from the top of the head on this form, because the head stands above the surface and the exposed height is what the customer sees. Where the joint is dimensioned from the seating cone instead, the drawing says so, and the two readings differ by the dome height.
The cone angle must match the countersink. Ninety degrees is the common case, but on thin sheet or on a part with a formed countersink the angle is whatever the tooling produces, and an oval head machine screw quoted at the wrong angle seats on a line and rocks, which on a raised head is visible from across a room.
Three features define this part: the raised countersunk head, the cross recess and the locking patch. The first two are about how the head looks and seats; the third is about how the joint behaves after it has been tightened.
| Feature | What it gives | What it costs |
|---|---|---|
| Raised countersunk head | Centring plus a visible, rounded finish | Stands proud; can collapse if over-driven |
| Cross recess in the dome | Full-depth recess for a standard bit | Less torque than a socket |
| Locking patch | Holds against vibration, reusable | Adds prevailing torque; not a seal |
| Black zinc | Dark, sacrificial, hides in trim | Thin film; wears at the dome edge |
| Blunt end | Re-enters an existing thread | Needs a tapped hole or a nut |
The raised form solves a specific problem that a flat countersunk head cannot. Where a countersink sits in a soft or thin material, a flush head can break through the cone or leave a bare chamfer showing at the rim of the hole; an oval head covers that rim with its dome and still centres on the cone. That is why the form survives on decorative panels, marine trim and instrument faces.
The patch solves a different problem: a machine screw in a joint that vibrates comes loose unless something resists it. A lock washer adds a part and does not work on a countersunk head; a liquid threadlocker has to be applied at assembly and needs a cure. The patch is pre-applied, works the moment the screw is driven, and can be re-used a few times before the prevailing torque drops off.
Oval head machine screws are finished in black zinc with a dark passivation. It is a sacrificial coating, so a scratch at the dome or a worn edge still has zinc around it, and the dark tone is what makes the fixing read as part of a black trim rather than as hardware.
| Finish | How it protects | Effect on head and patch | Typical use |
|---|---|---|---|
| Black zinc | Sacrificial zinc, dark passivation | Patch applied over the plating | Dark trim and equipment |
| White zinc | Sacrificial zinc | Patch applied over the plating | General indoor work |
| Black nickel | Hard dark deposit | Patch applied over the deposit | Visible dark instrument faces |
| Dacromet | Zinc-aluminium flake layer | Thicker; patch adhesion checked | Outdoor and damp trim |
| Stainless, plain | Passive chromium oxide film | Patch adhesion checked | Marine trim and fittings |
The patch has to stick, and that is the interaction worth watching. A flake coating with a rough surface holds a patch better than a bright smooth deposit, but a coating that is too thick can lift under the patch on the first turn. Patches are applied after the finish is cured, and the first article is checked for both coverage and adhesion.
Three assemblies where a raised countersunk head with a locking patch is the right fixing:
| Where it sits | The screw closes a face plate or a bezel where the head sits in a countersink and stands a little proud, and the joint vibrates in service. |
| When it goes wrong | A flush head leaves a bare chamfer showing, and a screw without locking works loose until the plate rattles. |
| Why it happens | The face is visible, the panel is thin, and the equipment runs with vibration. |
| What we control | Cone angle and dome height checked, recess driven with the production bit, patch torque measured. |
| Where it sits | The screw holds a trim strip, a fitting or a hatch where the head is visible above a teak or composite surface and the joint is exposed. |
| When it goes wrong | A flush head disappears into a soft core, and an unlocked screw backs out with the movement of the boat. |
| Why it happens | The material is soft, the joint moves, and the fixing is seen. |
| What we control | Patch coverage checked, plating thickness held, cone matched to the countersink. |
| Where it sits | The screw fixes a trim panel or an accessory where the head is seen, the joint sees vibration, and the fixing may be opened for service. |
| When it goes wrong | A loose screw in a trim panel is felt as a rattle long before it is found, and a flat head cannot cover the panel edge. |
| Why it happens | The panel is thin, the joint vibrates, and the screw is re-used. |
| What we control | Prevailing torque checked after a few cycles, patch position and coverage inspected. |
Four reasons that matter on a raised countersunk head with a patch, each tied to what the drawing has to prove:
|
Cone, dome and patch reviewed together
The cone angle, the dome height and the patch torque are reviewed as one set, so a head that would rock in its countersink or a patch that would cross a soft thread is raised before the tool is set. Basis: Cone, dome and patch reviewed as one set. |
Heading, rolling, plating and patch in one route
The raised head and the cross are formed in one stroke, the thread is rolled, the parts are black zinc plated and the patch is applied after the finish cures. Basis: One route from wire to patched screw. |
|
Patch measured, not assumed
The patch is checked for position and coverage, and the prevailing torque is measured on the first article rather than judged by hand. Basis: Patch torque measured on the first article. |
First article fixes the setting
The first article fixes the wire heat, die set, roll, plating barrel and patch batch; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these oval head machine screws from carbon steel wire on single-die headers that upset the raised countersunk head and form the cross in one stroke, rolls the machine thread to a blunt point, black zinc plates the parts and applies the locking patch after the finish has cured. The first part of every run is measured on the cone and dome, driven with the production bit and checked for patch coverage and prevailing torque.
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The cone is cut by the die, and the die sets the angle for the life of the tool. A worn die leaves a cone that is slightly barrel-shaped: the head looks right, the angle is half a degree out, and the screw seats on a line. On a raised head that shows as a shadow under one side of the dome, which is why the cone is gauged rather than eyeballed.
What decides whether oval head machine screws pass is the cone, the dome, the recess, the thread and the patch. The inspection agreement covers those, and the criteria come from the drawing.
Cone angle and dome on the projector |
Thread gauged before and after the patch |
Hardness testing against the property class |
Salt-spray testing of the black zinc plate |
The head is checked for cone angle, diameter and dome height on the projector, and the recess for depth and width. The cone is the dimension that decides whether the screw seats; the dome is the dimension that decides whether it looks right, and both are on the drawing.
The patch is checked for position, coverage and adhesion, and the prevailing torque is measured by running a nut or a gauge on and recording the torque needed. That number is what the joint designer used, so it is a measurement rather than an impression.
The thread is gauged before the patch is applied, because a patch hides the thread it sits on, and again with the patch to confirm the fit. On a black zinc part the plating is also read on the dome: an uneven deposit shows on a raised head as a dull band above the cone.
Every shipment of oval head machine screws is traceable to the wire it was made from, to the plating batch and to the patch 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 material or the plating. 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 patched screw the first article is also driven and re-driven, so the prevailing torque is confirmed over the cycles the joint will actually see. Buyers visit during the process to review samples and to see how the heads are formed and the patches applied.
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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, the plating line and the patching station 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 |
An oval head keeps a shallow dome above the cone. The cone seats and centres, the dome covers the rim of the countersink and leaves a rounded top instead of a flush one.
Because the joint needs both: the countersink centres the screw in a thin or soft panel, and the head still sits low. A pan head would sit on the surface and need a flat panel.
It resists vibration. A pre-applied nylon or adhesive strip on the thread creates a prevailing torque, so the screw does not back out without a washer or a liquid threadlocker.
A few cycles before the patch wears and the prevailing torque drops. Where a joint is opened often, the patch is specified for that number of cycles.
It can if it is over-driven into a soft countersink. The cone then presses in, the dome sinks and the bearing surface is gone. Torque is set from the panel.
Cone angle, head diameter and dome height, recess size, thread size and length, the patch and its torque, length from the top of the head, and the material and plating.
How an oval head machine screw project runs from drawing to repeat delivery:
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1
Send the drawing and the countersink detail
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→ |
2
Cone, dome and patch review
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→ |
3
First article seated and re-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, the head diameter and dome height, the recess size, the thread size and length, the patch requirement and its torque, the material and plating.
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Cone angle
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Head diameter
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Dome height
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Recess size
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Thread and length
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Patch and plating
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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
