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:Binding Head Machine Screws
Materials:Carbon Steel
Surface treatment:Black Oxide
Head Type:Pan(Binding) 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:228
We make binding head machine screws from carbon steel with a wide bearing face, an undercut neck and a cross recess, black oxide finished and quoted from M1 to M14. Head diameter, undercut, thread and finish come from your drawing, and the first article is seated on your own punched material.
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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.
Binding head machine screws are machine screws with a broad, rounded head and a turned relief directly under it, driven through a cross recess and threaded for a tapped hole or a nut. The recorded item on this page is carbon steel with a black oxide finish, a binding head and a machine thread, quoted from M1 to M14 with Number 228.
Binding head. A dome that is wider than a pan head of the same size, sitting on a narrow neck that has been undercut. The wider face spreads the clamp load without a washer, and the undercut is what lets the head come down onto an uneven surface instead of rocking on it.
Undercut neck. A relief turned under the head, so the head does not run straight into the shank. It gives the head a small clearance step that clears a burr, a radius or a rolled edge around the hole — the reason this head turns up on bound work, where the hole is punched and never quite clean.
Cross recess. Four tapered wings around a pointed centre, driven with a Phillips bit. The bit centres itself, and the wings cam out before the head is destroyed.
Machine thread. A rolled thread with a blunt end, made to engage an existing thread in a tapped hole or a nut. It does not form its own thread, so the joint can be opened without damaging the part.
Black oxide. A conversion coating on the steel, oiled after it is formed. It adds no measurable thickness, which is why the recess and the thread are exactly as machined, and it protects only while the oil film holds.
The head is formed in one stroke and the neck is undercut afterwards, and the two together are what make a binding head. A pan head runs its radius straight into the shank; a binding head stops the head at a smaller diameter and steps down, so the bearing face is a full annulus rather than a dome that curves away from the part.
The wider face is the practical difference at the bench. On a thin or soft panel, or on a stack of sheets held by one fixing, the same torque spread over a larger annulus leaves less mark and holds flatter. That is why a binding head machine screw is used where a pan head would pull in, and why it is common on bound and stitched assemblies where the material is not flat to begin with.
The undercut is the second half of that idea. Holes punched in thin sheet have a raised edge on one side and a burr on the other; a head that runs straight into the shank sits on that edge and leaves a gap under the rest of the face. With the neck relieved, the head comes down until the face touches the sheet, and the burr sits inside the relief instead of under the head.
The thread is rolled below the neck and finished with a blunt chamfer. On a machine thread the chamfer is a guide rather than a cutter: the screw enters a thread that already exists, and the blunt end stops it going past the last useful turn. A pointed end on a machine screw is a sign that a self-tapping drawing has been reused.
Black oxide goes on after the thread is rolled. The process converts the surface of the steel rather than adding a layer over it, so the screw measures the same before and after; the oil that follows fills the conversion layer and is what actually keeps the rust off, which is why a black oxide part that has been degreased rusts within days.
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 binding head the head diameter to quote is the wide face, not the pan head size that would be used on a neighbouring part.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Binding head, wide domed face | Diameter, height and face flatness |
| Neck | Undercut relief under the head | Diameter and depth on the first-article section |
| Recess | Phillips cross | Depth and width, driven with the production bit |
| Thread | Metric machine thread | Pitch and length, gauged per batch |
| Finish | Black oxide, oiled | Conversion depth and oil film |
| Length | From under the head to the end | Measured on the shop plate |
Head diameter is the dimension that decides whether the part does its job. Go smaller and the head pulls into soft material; go larger and it fouls a border, a neighbouring fixing or a cover. On a binding head machine screw the diameter is usually chosen from the hole spacing and the material, and the height follows from it.
Length is measured from under the head, because that is the face that bears. On a head with an undercut the measurement starts at the bearing face rather than at the neck, which is a difference of the relief depth — small, but exactly the kind of small that gets absorbed into a tolerance and then argued about.
Three features define a binding head machine screw: the wide face, the undercut neck and the cross recess. The first two work as a pair, and the third is what makes the pair usable at volume.
| Feature | What it gives | What it costs |
|---|---|---|
| Wide head face | Clamp load spread without a washer | Wider footprint; needs clearance around it |
| Undercut neck | Head seats over a burr or a rolled edge | Removes material at the neck |
| Cross recess | Standard bit, cams out before damage | Fits inside the head height |
| Machine thread | Re-opened without damaging the part | Needs a tapped hole or a nut |
| Black oxide | No thickness added; dark, non-reflective | Protection depends on the oil film |
The comparison that matters is with a pan head. A pan head is cheaper to make and lower, and on a clean flat surface it holds perfectly well. A binding head machine screw is chosen when the surface is not clean and flat — punched sheet, a stack of boards, a bound edge — or when a wider bearing area is needed and a washer would be a second part to handle.
The undercut also changes how the head behaves when it is over-tightened. A pan head with a continuous radius digs into soft material at the rim; a binding head, with its face flat out to a wider diameter, tends to dish at the centre if the torque is too high. The visible sign is a bright ring of contact and a head that has gone slightly concave, and the fix is a torque set from the material rather than from the thread size.
The recorded finish is black oxide, oiled. It is a conversion coating: the surface of the steel is turned into a dark oxide that is a fraction of a micron thick, and the oil applied after it fills that layer and provides what little barrier there is. Nothing is added to the dimensions, so the recess is gauged as formed and the thread is the thread the die rolled.
| Finish | How it protects | Effect on head and thread | Typical use |
|---|---|---|---|
| Black oxide | Conversion film plus oil | No measurable build | Dry indoor, machine internals |
| Black zinc | Sacrificial zinc, dark passivation | A few microns; re-checked | Dark visible assemblies |
| White zinc | Sacrificial zinc | A few microns; re-checked | General indoor work |
| Nickel plate | Hard barrier deposit | A few microns; recess re-checked | Visible, handled parts |
| Dacromet | Zinc-aluminium flake layer | Film builds; thread re-checked | Outdoor and wet assemblies |
The honest limit of black oxide is water. It is not a barrier and it is not sacrificial: once the film is broken or the oil is washed off, the steel is bare and rusts as bare steel does. A finger mark on a degreased part is enough to start a rust bloom, which is why black oxide parts are handled with gloves and packed oiled.
The advantage is tolerance. Because nothing is added, a black oxide part can be specified where a plated part would change the fit of the recess or the thread — small screws with tight cross recesses, fine threads, and parts that have to assemble to a dimension taken from the bare metal.
Three assemblies where a binding head machine screw is chosen for its wide, flat bearing face:
| Where it sits | The screw clamps a terminal, a plate or a lead where the bearing area has to be broad and the surface under the head is not perfectly flat. |
| When it goes wrong | A narrow head marks the terminal and a head with a continuous radius sits on the burr rather than on the plate. |
| Why it happens | The joint carries current or a signal, the plate is punched, and the fixing is opened for service. |
| What we control | Head flatness and diameter checked, recess driven with the production bit. |
| Where it sits | The screw holds a bound edge, a clamp bar or a cover where the material is stacked, punched and not flat, and the head has to sit down onto it. |
| When it goes wrong | A pan head rides on the punched edge, the stack loosens, and the head marks the cover. |
| Why it happens | The material is layered, the holes are punched, and the fixing is visible. |
| What we control | Undercut depth checked on the section, head face checked flat. |
| Where it sits | The screw fixes a cover, a plate or a bracket inside a machine where the finish only has to keep rust off in a dry enclosure. |
| When it goes wrong | A plated screw sheds its coating into a gearbox, and a bright head is visible through a window. |
| Why it happens | The environment is dry, the part is inside, and the finish must not flake. |
| What we control | Finish confirmed as black oxide, head and thread gauged to the drawing. |
Four reasons that matter on a wide undercut head, each tied to what the drawing has to prove:
|
Head, neck and stack reviewed together
The head diameter, the undercut depth and the material it bears on are reviewed as one set, so a head that would rock on a punched edge is raised before the die is cut. Basis: Head, neck and stack reviewed as one set. |
Forming, undercut and rolling in one route
The wide head and the cross are formed in one stroke, the neck is undercut and the thread is rolled in the same route. Basis: One route from wire to finished screw. |
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Seat checked on the first article
The head face and the undercut are checked on the first article, and the recess is driven with the production bit, because a head that rocks is invisible on a flat plate. Basis: First article seated on a punched sample. |
First article fixes the setting
The first article fixes the wire heat, die set, undercut tool and thread roll; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these binding head machine screws from carbon steel wire on single-die headers that upset the wide head and form the cross recess in one stroke, undercuts the neck, rolls the machine thread to a blunt chamfered end and black oxides the parts before packing. The first part of every run is measured on the head and neck, seated on a punched sample and entered into a thread gauge before the batch continues.
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The undercut is the operation that is easy to leave half done. It is a small amount of metal removed in a place nobody looks at, and a tool that is dull smears the relief instead of cutting it, so the head still has a step but the step is filled with a burr. The screw then seats on the burr exactly as it would have seated on the fillet, and the customer sees the gap the design was supposed to remove.
What decides whether binding head machine screws pass is the head, the undercut, the recess, the thread and the finish. The inspection agreement covers those, and the criteria come from the drawing.
Head and recess on the projector |
Thread gauged per batch |
Hardness testing against the property class |
Salt-spray testing where a coating is specified |
The head is checked on the projector for diameter, height, face flatness and the concentricity of the recess. Flatness is checked on the section as well as on the face, because a head that is flat on the bench can still dish under the driver if the material under the recess is thin.
The undercut is checked on the section of the first article: its diameter and its depth, and the condition of the surface inside it. A burr in the relief is the defect that matters, because it is the one that puts the head back onto the point it was meant to clear.
The thread is gauged per batch and the finish is checked for colour and oil. On a black oxide part the oil is part of the finish, so a batch that is dry is a batch that will rust in the bag, and that is read at packing rather than at inspection.
Every shipment of binding head machine screws is traceable to the wire it was made from. 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 finish. 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 head that has to seat on a punched edge the first article is also tried on the customer’s own material, because the undercut either clears the burr or it does not. Buyers visit during the process to review samples and to see how the heads and necks are formed.
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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 finishing 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 wider bearing face and an undercut neck. The wider face spreads the load; the undercut lets the head seat over a burr or a rolled edge instead of rocking on it.
So the head face can come down onto the part. Without the relief, the radius between head and shank lands on the edge of the hole and holds the head proud.
No. It converts the surface of the steel and adds no measurable thickness. The oil applied after it is what provides most of the protection.
In a dry interior, no. Once the oil is washed off or the film is broken they rust like bare steel, so they are not a finish for wet or damp service.
It spreads the load over a larger area, which helps on soft material, but the head is not stronger. Over-tightening dishes the face rather than digging in at the rim.
Head diameter and height, undercut diameter and depth, recess size, thread size and length, length and datum, material and finish.
How a binding head machine screw project runs from drawing to repeat delivery:
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1
Send the drawing or the punched sample
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2
Head, neck and thread review
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→ |
3
First article seated on your material
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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 and height, the undercut diameter and depth, the recess size, the thread size and length, and the material and finish.
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Head diameter
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Head height
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Undercut
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Recess size
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Thread and length
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Material and finish
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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
