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+86 13143444311
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:100 Degree Flat Head Screw
Materials:Carbon Steel
Surface treatment:Black Zinc Plated
Head Type:Flat Head
Drive:Phillips
Thread:Machine Thread
Point:Blunt
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:567
We make 100 degree flat head screws in black zinc plated carbon steel, with a flush countersunk head that seats in thin sheet without breaking through. Cone angle, head diameter, recess, thread and plating are taken from your drawing, and the first article is seated in 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 100 degree flat head screw is a countersunk machine screw whose cone is cut at 100 degrees instead of the usual 90, so the head spreads its load over a shallower cone and sits flush in thinner material. The recorded item on this page is carbon steel with a black zinc plate, a flat head and a cross recess, quoted from M1 to M14 with Number 567.
100 degree cone. Ten degrees flatter than the standard countersink. The head is shallower for a given diameter, which means less material stands above the surface for the same flush depth and more of the head width ends up bearing on the sheet.
Flat head. A countersunk cone with a flat top. It seats in a matching cone cut in the part, centres itself as it is driven, and leaves the surface unbroken behind it.
Cross recess. Four tapered wings around a pointed centre. On a flush head the recess is the only access, and its depth is limited by the head height — which on a 100 degree head is the first thing that has to be checked.
Black zinc. Electroplated zinc with a dark passivation, applied after the thread is rolled. It is sacrificial like any zinc, and the dark tone is what makes a flush fixing disappear into a black panel rather than reading as a bright dot.
The angle is the design. A 90 degree countersink puts the bearing surface at 45 degrees to the axis; a 100 degree countersink lays it back to 40, so the same head diameter produces a shallower cone with a larger flat area in contact. That is why a 100 degree flat head screw is chosen for thin sheet: there is more bearing area available before the countersink breaks through the far side.
The trade is head thickness at the rim. A shallower cone means the edge of the head is thin, and a thin edge is easy to damage and easy to distort into the countersink. On a small screw the rim is fractions of a millimetre thick, so the countersink depth in the part and the head diameter on the drawing have to be read together: deepen the countersink and the head sits lower, but the rim also reaches the point where it no longer gives.
The cone must match the countersink tool. A 100 degree head in a 90 degree hole seats on a circle at the top of the cone and leaves a gap below it; it looks flush and it is not bearing. The reverse leaves the head standing proud. Neither is visible from the top once the screw is tight, which is why the angle is gauged on the part and not only assumed from the drawing.
The recess has to fit inside a shallower head. On a 100 degree head there is less material above the cone than on a 90 degree head of the same diameter, so the cross is shallower, the bit engages less, and the cam-out torque is lower. That is not a defect; it is the consequence of the angle, and it sets the torque the joint can carry.
Black zinc goes on after the thread is rolled. It builds a few microns in the recess and across the cone, and on a head this shallow a few microns is a larger fraction of the material above the slot than it would be on a pan head. The first article is therefore driven with the production bit in the plated condition.
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 a countersunk screw the length is measured from the top face, which sits flush, rather than from a bearing face that stands above the part.
| Item | How it is defined | What we control |
|---|---|---|
| Head | 100 degree countersunk cone, flat top | Angle, diameter and concentricity |
| Recess | Phillips cross | Depth in the shallow head, bit tried after plating |
| Thread | Metric machine thread | Pitch and length, gauged per batch |
| End | Blunt, chamfered | Chamfer cut, not deburred |
| Plating | Black zinc, dark passivation | Thickness range and salt-spray sample |
| Length | From the top face to the end | Measured on the shop plate |
Head diameter and cone angle are quoted together, because one defines the other’s bearing area. A 100 degree flat head screw with a larger head carries more load but needs a wider countersink and leaves a bigger witness circle on a visible panel; a smaller head is neater and bears on less material, which in thin sheet is the wrong way round.
Length from the top face is the dimension that decides thread engagement on the far side of a thin stack. Measuring from the start of the cone gives a screw that is short by the head depth, and in a panel a few tenths thick that difference is the whole engagement.
Three features define a 100 degree flat head screw: the shallow cone, the flush top and the cross recess. The angle is the reason the part exists, and it is worth setting against the standard head it replaces.
| Feature | What it gives | What it costs |
|---|---|---|
| 100 degree cone | More bearing area in thin sheet, shallower head | Thin rim; needs a 100 degree countersink |
| Flush top | Unbroken surface, self-centring | Bears on a cone; less torque than a cap head |
| Shallow cross | Standard bit still fits | Cams out earlier than a 90 degree head |
| Black zinc | Dark, sacrificial, hides in a black panel | Thin film; not for chloride service |
| Blunt end | Re-enters an existing thread | Needs a tapped hole or a nut |
The case for the flatter angle is thin material. In a 1 mm panel a 90 degree countersink of a given head diameter has to cut deeper to reach the same bearing width, and it can reach the far surface; at 100 degrees the same bearing width sits in a shallower cone and the panel keeps its skin. That is the whole argument, and it is why the angle appears on aerospace panel drawings more often than on general sheet-metal work.
The case against is tooling and torque. The countersink tool has to be 100 degrees, the head has to be matched to it, and the driver has to be content with a shallower cross. Where those three are in place the joint is flush and serviceable; where the shop runs a 90 degree tool because that is what is on the shelf, the head seats on a line and the flush joint is an illusion.
The recorded finish is black zinc with a dark passivation, applied after the thread is rolled. The dark tone is the functional part on a visible panel: a bright zinc head in a black face reads as a spot from across a room, and a black one disappears into the surface it is flush with.
| Finish | How it protects | Effect on cone and recess | Typical use |
|---|---|---|---|
| Black zinc | Sacrificial zinc, dark passivation | A few microns; both re-checked | Dark panels and housings |
| White zinc | Sacrificial zinc, blue-white passivation | A few microns; both re-checked | General indoor work |
| Black oxide | Thin conversion film, oiled | Almost no change | Unseen joints, dark assemblies |
| Dacromet | Zinc-aluminium flake layer, cured | Film builds; cone re-checked | Outdoor and wet panels |
| Stainless, plain | Passive chromium oxide film | None; gauged as formed | Cleaned or washed assemblies |
Plating on a countersunk head has a specific risk: the cone is the bearing surface, and a coating that is thicker at one edge than the other tilts the head. Barrel plating is even enough on a small part, but the check is still made on the seat and not only on the top.
The dark passivation is also the weakest part of this finish. It is a thin film over the zinc, and on a flush head the edge of the countersink is where it wears through first, leaving a bright ring around a black head after a few assembly cycles. Where that ring is unacceptable the answer is a different finish or a different base metal, not a thicker coat.
Three assemblies where a 100 degree flat head screw solves a thickness problem that 90 degrees cannot:
| Where it sits | The screw closes a panel where the sheet is 0.8 to 1.5 mm and the countersink has to give a flush head without cutting through to the far side. |
| When it goes wrong | A 90 degree countersink of the same bearing width breaks through, and the head pulls into the hole instead of sitting on it. |
| Why it happens | The sheet is thin, the head must be flush, and the joint repeats. |
| What we control | Cone angle gauged, head diameter matched to the sheet, thread engagement checked on the flat side. |
| Where it sits | The screw fixes a trim panel, an access cover or a bracket where the head is flush and the panel is thin or composite. |
| When it goes wrong | A head that stands proud chafes the adjacent panel, and a cone mismatch loads the composite at a line instead of an area. |
| Why it happens | The panel is thin, flush is functional, and the fixings are inspected. |
| What we control | Cone angle and head concentricity checked, plating thickness held to the drawing. |
| Where it sits | The screw closes a painted or powder-coated housing where the head has to be flush and dark so that it reads as part of the case. |
| When it goes wrong | A bright head breaks the face of the housing, and a proud head snags a cable or a cover. |
| Why it happens | The housing is dark, the head is visible, and the fixing is opened for service. |
| What we control | Colour and plating thickness held to the sample, recess driven with the production bit. |
Four reasons that matter on a shallow countersunk head, each tied to what the drawing has to prove:
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Angle, head and sheet reviewed together
The cone angle, the head diameter and the sheet thickness are reviewed as one set, so a countersink that would break through or a head that would stand proud is raised before the die is cut. Basis: Angle, head and sheet reviewed as one set. |
Forming, rolling and plating in one route
The 100 degree head and the cross are formed in one stroke, the thread is rolled, and the parts are black zinc plated and baked in the same route. Basis: One route from wire to plated screw. |
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Seat and recess checked after plating
The cone is gauged for angle and concentricity, and the recess is driven with the production bit in the plated condition on the first article. Basis: First article checked after plating. |
First article fixes the setting
The first article fixes the wire heat, die set and plating barrel; repeat orders are compared against that record rather than re-read from the drawing. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these 100 degree flat head screws from carbon steel wire on single-die headers that cut the countersunk cone and the cross recess in one stroke, rolls the machine thread to a blunt chamfered end and plates the parts black zinc before packing. The first part of every run is measured for cone angle and head height, seated in a countersunk sample and driven with the production bit before the batch continues.
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The cone is cut by the die, so the die sets the angle. A die that is worn at the cone leaves a head that is slightly barrel-shaped: the top looks right, the angle is half a degree out, and the head seats on a line. That is why the angle is checked with a countersink gauge on the first article and sampled through the run, rather than judged by eye against a sample.
What decides whether 100 degree flat head screws pass is the cone, the head height, the recess, the thread and the plating. The inspection agreement covers those, and the criteria come from the drawing.
Cone angle on the projector |
Thread gauged after plating |
Hardness testing against the property class |
Salt-spray testing of the black zinc plate |
The cone is checked on the projector for angle, diameter and concentricity. Angle is the check that a general-purpose screw gauge will not make, and it is the one that matters most on this part: a 90 degree head passes every dimensional check except the one that decides whether it seats.
Seating is checked by driving the first article into a countersunk sample and looking for a gap under a light. That is the customer’s acceptance test on a flush joint, and it catches the ring of contact that a dimensional check accepts.
The recess is driven with the production bit after plating. On a 100 degree head the material above the cross is thinner than on a 90 degree head, so a worn bit cams out earlier and the first article tells you whether the bit is still good before the batch is run.
Every shipment of 100 degree flat head screws is traceable to the wire it was made from and to the plating 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 flush joint the first article is seated in the customer’s own panel, so the gap and the bearing ring are read on the real joint. Buyers visit during the process to review samples and to see how the heads are formed and the parts plated.
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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 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 |
A flatter cone gives more bearing area for the same head diameter, so a flush head can sit in thinner sheet without the countersink breaking through.
Yes. A 100 degree head in a 90 degree hole seats on a line at the top of the cone and leaves a gap below it, which looks flush and is not bearing.
Less than a 90 degree head of the same size, because there is less material above the cross. In thin sheet the sheet distorts before the screw reaches its limit.
Clearance and appearance. It sets how much of the head stands above the cone and how much material remains for the recess, so it is a functional dimension.
For dry indoor equipment it is. The dark passivation wears at the countersink edge first, and in chloride service the zinc itself is consumed quickly.
Cone angle and head diameter, head height, recess size, thread size and length, length from the top face, material, plating thickness and the panel thickness it sits in.
How a 100 degree flat head screw project runs from drawing to repeat delivery:
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1
Send the drawing or the panel sample
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2
Angle, head and sheet review
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3
First article seated in 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 cone angle and head diameter, the head height, the recess size, the thread size and length, the length from the top face, the material and the plating.
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Cone angle
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Head diameter
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Head height
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Recess size
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Thread and length
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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
