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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:Flat head screw m6 tail milling flat
Materials:Carbon steel
Surface treatment:Blue zinc plated
Head Type:Countersunk head
Drive type:None (no slot; per drawing)
Tail feature:Milled flat on the large shank
Thread:Partial (half) machine thread, chamfered end
Forming:Multi-station cold heading with milled tail flat
Number:1711
We manufacture M6 flat head screws in carbon steel, blue zinc plated, with a countersunk head, no slot and a milled flat on the tail, cold headed on a multi-station machine and made to drawing. Head angle, tail flat, thread class and plating are checked in the finished condition.
Watch the factory video·Email sst@szsst88.com
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 flat head screw is a screw with a conical head that pulls into a countersink until the top sits level with the panel. The M6 part on this page is made in carbon steel, blue zinc plated, with no slot in the head and a milled flat on the tail, so the drive and the location come from the shank rather than from the head.
Countersunk head. The head underside is a cone, and the cone angle has to match the countersink in the panel. Match the angle and the head disappears into the surface; mismatch it and the head stands proud on one side, marks the panel and never sits flat however hard it is driven.
No slot in the head. There is no cross, slot or socket, so the head is a smooth cone. The part is held and turned from the tail: the milled flat gives a key face or a wrench face, and the drawing states which.
Milled flat on the large shank. The flat is milled on the large-diameter shank behind the thread. Its width, depth and position decide whether the part keys into a D-shaped bore, clears a mating part or takes a wrench, and they are checked on the first article.
Together these decide the fit: the head sits flush in the countersink, the flat locates or drives the part, and the partial thread engages the tapped hole the drawing specifies.
This flat head screw is made from carbon steel wire, cold headed on a multi-station machine, thread rolled and blue zinc plated. The grade comes from the drawing, and the wire heat number is recorded on the material certificate so the batch stays traceable to the coil.
The countersunk head is formed in the heading die, so the cone angle and the head diameter come off the same tool. The tail flat is milled after heading, before plating, because a flat cut after plating would expose bare steel and start corrosion at the very face that keys the part.
The thread is a partial machine thread with a chamfered end. It runs over the drawing length and stops short of the milled flat, leaving enough plain shank for the flat and enough thread for the joint.
Blue zinc is the finish: a zinc layer with a blue passivation on top. It adds a few microns to the thread and to the flat, so both are checked after plating, in the condition the customer assembles.
This page records an M6 flat head screw. The family is quoted in metric sizes from M4 to M10 and in lengths to suit the drawing, with the head angle and the tail flat measured on the projector and the thread gauged. Where a long version is required, custom lengths up to 2,000 mm are subject to DFM review after drawing submission.
| Item | How it is defined | What we control |
|---|---|---|
| Head diameter and angle | The cone that matches the panel countersink | Checked on the projector on the first article |
| Head height | The depth the head sinks into the countersink | Measured from the bearing cone |
| Tail flat width and depth | The key or wrench face on the large shank | Checked on the projector and with the mating key |
| Flat position | Where the flat starts from the tail | Measured from the tail end on the drawing |
| Thread size and length | Partial machine thread, chamfered end | Gauged per batch after plating |
| Total length | From the top of the flat head to the tail | Datum stated on the drawing; measured on the shop plate |
Each size is quoted against the joint it closes. The countersink angle, the panel thickness and the head height are reviewed together, because a flat head that is right for one panel stands proud in another even at the same nominal size.
The tail flat is measured from the tail end, and the total length from the top of the head. The batch is checked on the features the process can drift on: head angle, flat width and thread class, all read after plating.
The milled flat is what makes this flat head screw a special part rather than a standard countersunk screw. With no slot in the head, the shank has to provide the drive and the location, and the flat does both: it gives a wrench or key a face to hold, and it keys the part into a D-shaped bore where the joint needs it not to rotate.
Width and depth are read together. A flat that is too shallow will not key and the part spins in the bore; one that is too deep cuts into the thread wall and weakens the section that carries the clamp load. The drawing states both, and the first article is checked with the mating key.
Position matters as much as size. The flat starts at a stated distance from the tail and runs for a stated length; move it towards the head and it eats into the thread, move it towards the tip and the key no longer reaches. It is measured from the tail end, the same datum used at assembly.
Plating builds on the flat. Blue zinc adds a few microns to every surface, so the flat is checked after plating with the key that will be used on the line, not before the bath. A flat that fits before plating and not after is a fit failure, not a cosmetic one.
This flat head screw is blue zinc plated: a zinc layer deposited on the carbon steel, then a blue passivation on top. The zinc protects the steel sacrificially, so a scratch at the cone or on the flat does not start rust immediately the way a bare carbon steel surface would.
| Finish | How it protects | Effect on head and thread | Typical use |
|---|---|---|---|
| Blue zinc (trivalent) | Zinc layer with blue passivation | Build-up on thread and flat; gauged after | Indoor parts, general assemblies |
| Clear zinc | Zinc layer, clear passivation | Same build-up; checked after plating | Parts where a bright finish is wanted |
| Black oxide | Conversion coating, minimal thickness | No measurable build-up | Indoor parts where black is required |
| Dacromet flake | Zinc-aluminium flake layer | Thin film; thread checked over coating | Outdoor and wet assemblies |
| Stainless (equivalent part) | Alloy resists corrosion without coating | No coating build-up | Marine and wash-down service |
Salt-spray exposure is agreed per project and written on the drawing, and the plated parts are tested in the condition they ship in. On a countersunk head the cone and the flat are the two faces where a thin or uneven coating shows first, so both are checked on the sample.
Packing protects the cone and the flat. Parts are packed so the heads do not knock and the flats do not rub, and the label carries the batch, the wire heat and the plating lot.
Three assemblies where a flat head screw with a milled tail earns its cost, and what the screw has to do instead:
| Where it sits | The screw closes a guard or a cover into a countersink, and the milled tail keys into a D-shaped hole so the part cannot turn with the nut. |
| When it goes wrong | A flat that is too shallow lets the part spin and the guard loosens, and a head angle that does not match the countersink leaves the head proud. |
| Why it happens | The panel is thin, the joint is opened for service, and the screw is one of several along the edge. |
| What we control | Head angle matched to the countersink, flat checked with the key, and the thread gauged after plating. |
| Where it sits | The screw sits flush in a painted panel where a protruding head would catch a door or a cable tray. |
| When it goes wrong | A proud head fouls a hinged door, and a plated thread that is out of class seizes in the tapped insert. |
| Why it happens | The panel is painted after countersinking, the head is visible, and the joint is assembled once. |
| What we control | Head height and cone checked, thread gauged after zinc plating, and packing that protects the paint-side face. |
| Where it sits | The screw closes a bracket or a fitting where the head has to disappear into the surface and the joint is fixed. |
| When it goes wrong | A head that does not sit flush shows on a visible surface, and a flat that is off position stops the bracket seating. |
| Why it happens | The parts are visible, the finish is decorative, and the assembly is fixed after adjustment. |
| What we control | Cone angle and head height checked, flat position measured from the tail, and the plating checked against the sample. |
Four reasons that matter on a flat head screw with a milled tail, each tied to what the drawing has to prove:
|
Head angle and tail flat reviewed together
The countersink angle, the head height and the flat width, depth and position are reviewed before the die and the milling fixture are set, so a part that would not seat or key is raised with you first. Basis: Head angle and tail flat reviewed before tooling. |
Headed, threaded and milled in one route
The head and thread are formed on the multi-station header and the flat is milled in a fixtured step, so the flat stays parallel to the axis and the thread start does not move. Basis: One route for head, thread and tail flat. |
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Flat and thread checked after plating
The flat is checked with the mating key and the thread with GO/NO-GO gauges after blue zinc plating, so the part that passes is the part that assembles. Basis: Fit and thread measured in the plated condition. |
First article to repeat production
The first article fixes the drawing revision, wire heat, die set, milling set-up and plating lot; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these flat head screws on a multi-station header: the countersunk head is struck in the die, the partial thread is rolled, the tail flat is milled in a fixtured operation, and the parts go to blue zinc plating as a batch. The first part of every run is checked on the projector and with the key before the batch continues.
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Between runs the die insert is changed to the drawing head and the milling fixture is set to the flat position; the first parts go to the projector and the gauges before the run continues, and the setting is recorded. Plated parts are packed so the cone and the flat are not marked before they reach the assembly.
What decides whether a flat head screw passes is not the colour of the zinc: it is the head angle and height, the tail flat width, depth and position, the thread class and the plating thickness. The inspection agreement covers those, and the criteria come from the drawing.
Thread gauging after blue zinc plating |
Head angle and tail flat on the projector |
Hardness testing where the drawing requires it |
Salt-spray testing of the blue zinc finish |
Each batch is recorded against the drawing revision: head angle and flat from the first article, the flat checked with the key, and the thread gauged per batch after plating. If a gauge or the key check fails, the parts back to the last good setting are held and re-checked.
Where a third-party report is required for the material or the plating, it is listed on the drawing so the paperwork ships with the parts, and the batch number on the label matches the record used for inspection.
Every flat head screw shipment is traceable to the wire it was made from. The grade, heat number and standard 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. Parts with a milled tail are approved together with the mating key, so the flat and the bore are signed off as a pair. Buyers visit during the process to review samples and to see how the heads are formed and the flats milled.
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8,678+
customers served
|
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 header, the milling 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 |
It is a screw with a conical head that pulls into a countersink until the top sits level with the panel. This M6 part is carbon steel, blue zinc plated, with no slot in the head and a milled flat on the tail.
From the tail. The milled flat gives a key or wrench face, and the drawing states whether the part keys into a D-shaped bore or takes a wrench. The head stays smooth and flush.
The flat either locks the part against rotation in a D-shaped hole or gives a tool a face to hold. Its width, depth and position are on the drawing, and it is checked with the mating key.
This page records M6; the family is quoted in metric sizes from M4 to M10 and in lengths to suit the drawing. Where a long version is required, custom lengths up to 2,000 mm are subject to DFM review after drawing submission.
Yes. Blue zinc adds a few microns to the thread and to the flat, so the thread is gauged and the flat checked with the key after plating, in the condition the customer assembles.
Head diameter, height and countersink angle, flat width, depth, length and position, thread size and length, chamfer, total length and datum, material, plating and the mating key or bore.
How a flat head screw project runs from drawing to repeat delivery:
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1
Send the drawing or sample
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→ |
2
Head and tail review
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→ |
3
First article approval
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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, height and countersink angle, the tail flat width, depth and position, thread size and length, chamfer, total length and datum, material, plating and the mating key or bore.
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Head diameter and angle
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Head height
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Tail flat width and depth
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Flat position and length
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Thread size and length
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Material, plating and key
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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
