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:M4 100mm Screw
Materials:Carbon Steel
Surface treatment:Black Zinc Plated
Head Type:Cap head (socket)
Drive:Hexagon socket (Allen)
Thread:Machine thread, partial
Point:Plain, chamfered
Forming:Single Die Heading
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
We make M4 100mm screws in carbon steel with a black zinc finish, cap head and hexagon socket, with the other sizes in the same range and lengths to the drawing. The thread length and head height are matched to the part being replaced, and the first article is compared with it side by side.
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.
An M4 100mm screw is a socket head cap screw of one specific size and length, used where a joint has to reach a hundred millimetres through a bracket or a spacer. The part recorded here is carbon steel with a black zinc finish, pan-headed in appearance but a cap head in form, in the M4 thread.
M4 thread. A metric machine thread a step up from the smallest sizes, used on brackets, covers and light structures.
100 mm length. Enough to pass through a bracket and a spacer before threading into an insert.
Cap head, socket drive. A tall head with a hexagon socket, driven with a key, not a bit.
Black zinc. A thin dark zinc passivate that keeps the fixing from reading as a bright dot on dark equipment.
They are used on equipment covers, brackets, bicycle and motorbike accessories, machine guards and audio hardware, where the fixing is dark, the reach is long and the head has to sit in a pocket.
Pages for a single size exist because most visitors are not designing; they are replacing. Someone has an assembly with an M4 100mm screw in it and needs the same part again. That changes what the page has to explain: not the range of what is possible, but which features have to match for the replacement to behave like the original.
The first thing to match on an M4 100mm screw is the thread itself. M4 is M4, but the thread length is not fixed: a 100 mm screw can be fully threaded or partially threaded, and the boundary between shank and thread changes how the joint clamps. A replacement with a different boundary will fit and will not hold the same way.
The second is the head. A cap head of M4 has a defined diameter and height, and a pocket or a counterbore was cut to that. A substitute with a taller head will not sit down; one with a shallower socket will not take the same key to the same depth.
The third is the finish. Black zinc is thin, and on a long threaded section it adds a little friction over every turn. A replacement in clear zinc feels different in the key and looks different on dark equipment, even though the thread is identical.
The fourth is the length datum. On a cap head the length is measured under the head, so a part quoted from the top of the head is a different value by the head height. On a 100 mm fixing that is the difference between reaching the insert and stopping short, and it is the most common mistake in a replacement order.
The recorded product is M4 by 100 mm, with the other sizes in the same range and lengths made to the drawing. Custom lengths up to 2,000 mm, subject to DFM review after drawing submission. The quotation for an M4 100mm screw carries the thread, the length, the threaded length, the head dimensions, the socket size and the finish.
| Item | How it is defined | What we control |
|---|---|---|
| Thread | M4 metric machine thread | Pitch, class and start |
| Length | 100 mm under the head | Length and its datum |
| Threaded length | Thread from the point upward | Where the thread ends |
| Head | Cap head with hexagon | Diameter, height and bearing face |
| Socket | Key size per diameter | Depth and wall thickness |
| Finish | Black zinc | Thickness and coverage |
The threaded length is the item most often missed in a replacement, because the part number rarely carries it. On a joint that passes through a bracket and a spacer, a fully threaded replacement puts thread in the clearance holes and the clamp is carried by ridges rather than a shank.
Head height matters where the head sits in a pocket. M4 cap heads have a defined height, and if the replacement is taller the head will bottom out in the pocket before the joint seats, which reads as a screw that will not tighten.
The socket size is fixed by the diameter, but its depth is set by the head height, so a replacement from another supplier can take the same key and still drive differently. That is worth checking on the first article rather than at the bench.
Four properties decide an M4 100mm screw, and each one carries a cost:
| Property | What it gives | What it costs |
|---|---|---|
| M4 100 mm size | Reaches through bracket and spacer | Only suits one joint thickness |
| Cap head socket | High clamp with a key | Needs a counterbore or a flat seat |
| Partial thread | Plain shank across the clearance hole | Boundary must match the original |
| Black zinc | Dark, low-reflection finish | Wears bright where the key bears |
The value of an M4 100mm screw is that the joint does not have to be redesigned to be repaired. Where an assembly already has this size, a replacement that matches in thread length, head height and finish restores it exactly.
The cost is that the size is a commitment: 100 mm fits the joint it was chosen for, and a thicker bracket or a deeper spacer needs a different length rather than more torque.
The recorded finish is black zinc, a trivalent zinc with a dark passivate. It protects by sacrificial action, keeps the fixing quiet on a dark assembly, and is thin enough that the socket and the thread keep most of their geometry.
| Option | How it protects | Effect on thread and socket | Typical use |
|---|---|---|---|
| Black zinc | Trivalent zinc, dark passivate | Thin; wears bright at the key | Dark covers and brackets |
| Clear zinc | Trivalent zinc, bright | Thin; wear less visible | General indoor work |
| Nickel plated | Hard barrier deposit | Build in socket; gauged after | Visible dry machinery |
| Black oxide | Conversion film, oiled | Almost no build | Dark, dry assemblies |
| Stainless, passivated | Passive film, no coating | No build at all | Wet and coastal joints |
Where the assembly is dark and the head is visible, black zinc is the economical answer, provided the customer accepts the bright ring that appears at the socket after a few assemblies. Where the joint is damp, the same size in stainless is the honest replacement.
Where the finish is the reason for the part, black oxide on stainless gives a dark head that keeps its seat geometry and does not wear to a bright patch, at a higher cost.
Three settings where this size is the standard fixing:
| Where it sits | The screw passes through a bracket and a spacer and threads into an insert in the frame. |
| When it goes wrong | A replacement that is shorter stops short of the insert and the bracket moves. |
| Why it happens | The reach is long, the joint is dark, and the fixing is serviced. |
| What we control | Thread length and head height matched; first article fitted in the bracket. |
| Where it sits | The screw holds a bracket where the head sits in a pocket and the finish has to match the bike. |
| When it goes wrong | A taller head will not enter the pocket, or a clear zinc replacement reads as a different part. |
| Why it happens | The part is visible, the joint is exposed, and the fixing is adjusted. |
| What we control | Head height and finish checked; first article fitted with the accessory. |
| Where it sits | The screw fixes a guard where a long reach is needed to clear a standoff. |
| When it goes wrong | A fully threaded replacement rubs in the standoff and the guard sits crooked. |
| Why it happens | The reach is long, the fixing is repeated, and the joint is inspected. |
| What we control | Boundary checked against the standoff; first article assembled. |
Four reasons that matter when the job is a replacement rather than a design, each tied to something the first article has to prove:
|
Thread length matched, not assumed
The threaded length is confirmed against the original, because a fully threaded replacement puts thread in the clearance holes and changes how the joint clamps. Basis: Thread length matched to the original. |
Headed, broached, threaded and plated
The cap head and socket are formed, the thread rolled over the agreed boundary, and the batch black zinc plated with the socket re-checked. Basis: One route, socket re-checked. |
|
Head height and socket measured
Head height and socket depth are measured on the first article, because either being off is a head that will not enter the pocket or a key that will not seat. Basis: Head and socket measured. |
Same part, same joint
The drawing revision, thread boundary and plating lot are recorded, so the next order fits the same bracket the same way. Basis: Same fit across orders. |
These screws are headed on single-die machines that form the cap head and the under-head fillet, broached with a hexagonal punch, thread rolled over the agreed length and black zinc plated. The first part of every run is measured on head diameter and height, socket size and depth, overall length, threaded length and thread.
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On an M4 100mm screw the shank is thin relative to its length, so the heading and the rolling both have to keep the part straight enough to start in a bracket. The thread boundary is set by the rolls rather than by a later operation, and a drift there is invisible in a photograph and decisive in assembly.
Plating comes last and is checked inside the socket as well as on the head. A dark finish on a socket can look complete and be thin at the floor, which is where the key bears; the recess is re-proved with the production key before packing.
Because the finish is thin, the parts are packed so they do not rub against each other. A batch of black screws that has been shaken in a bag arrives with bright marks on the heads, which is the first thing a customer sees on a replacement order.
What decides whether M4 100mm screws pass is the length, the thread boundary, the head and the socket. The inspection agreement covers those, and the criteria come from the drawing.
Boundary and socket on the projector |
Thread and start checked |
Core hardness checked |
Salt-spray testing of the black zinc layer |
Overall length is measured under the head and the threaded length separately, because a replacement that is right in one and wrong in the other is the failure this page exists to prevent. The head height and socket depth are read together, since the socket lives in the head.
The socket is proved with the production key at the torque the joint calls for, and the corners are inspected under magnification after a drive and removal. On a plated part that cycle shows whether the deposit has changed which key seats.
A sample from every batch is fitted into the customer bracket with the original part alongside. That side-by-side check is the one a replacement buyer actually makes.
Every batch 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 thickness is recorded for the batch.
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 thread boundary, and the plating and RoHS reports. The documents carry the drawing revision and the batch number, so a replacement order of M4 100mm screws matches the original.
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 replacement the first article is compared with the part it replaces, side by side and in the bracket. Buyers visit during the process to review samples.
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8,678+
customers served
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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 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 |
An M4 metric thread with an overall length of 100 mm measured under the head. The threaded length is a separate dimension and should be checked against the original.
Usually a different thread length. Fully threaded replacements put thread in the clearance holes instead of a plain shank.
No, if the head sits in a pocket. The pocket was cut to a defined head height, and a taller head bottoms out before the joint seats.
It is a thin layer and the key bears on the socket. The bright ring appears after a few assemblies and is normal for the finish.
Yes, and it is the better answer for damp or coastal joints. The size stays the same and the finish variable disappears.
A photo of the original with a rule, the threaded length, and the head height if it sits in a pocket, plus the bracket it goes into.
How a replacement order is specified and confirmed:
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1
Send the original or its dimensions
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2
Thread length and head height matched
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3
First article compared with your part
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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 or the original dimensions: thread, overall length under the head, threaded length, head height and finish.
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Thread
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Overall length
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Threaded length
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Head height
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Socket size
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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
