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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:Low Profile Machine Screws
Materials:Carbon Steel
Surface treatment:Black Zinc Plated
Head Type:Low Profile Head
Drive:Phillips Cross
Thread:Partial Machine Thread
Point:Blunt
Forming:Single Die Heading + Turned Shank
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M14
Number:557
We make low profile machine screws in black zinc plated carbon steel, with a shallow head, a plain shank and a partial machine thread, quoting them from M1 to M14. Head height, shank diameter and threaded length come from your drawing, and the first article is assembled into your own stack.
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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.
Low profile machine screws are machine screws with a head shallower than a standard pan, so the fixing stays close to the surface, combined here with a partly threaded shank: a plain length under the head and a thread below it. They are used where neither the head nor the thread may intrude into a working zone. This family is made in black zinc plated carbon steel, quoted from M1 to M14 with Number 557.
Low head. A shallow head with a flat top, for joints where the head cannot be buried and cannot stand proud either.
Plain shank. A turned plain length under the head that can locate, bear or slide without engaging anything.
Partial thread. The thread starts below the shank, so it engages only the part of the joint it was meant for.
Black zinc. A dark sacrificial zinc deposit, applied over the finished screw.
In practice low profile machine screws are specified from a drawing rather than from a table, because the head height and the point where the thread begins are both joint dimensions and neither is fixed by the thread size.
A low profile machine screw is usually described as a screw with a small head. In practice it is a screw with two boundaries: the top of the head, which must not rise above the surface it sits on, and the start of the thread, which must not reach into the part of the joint that has to stay free. On the recorded item both boundaries are set by the design, and both are the reason the part exists.
The head boundary is spatial. Where a joint sits inside a moving assembly, under a cover, or in a stack of modules, there is no room for a pan head and no countersink to hide one. A low head solves that without machining the panel — it does not disappear, but it stays out of the way, and it gives a bearing face that is still wider than the head of a countersunk screw at the same thread.
The thread boundary is functional. A plain shank under the head keeps the thread out of whatever the screw passes through: a bush, a bearing, a slot, a link. If thread were present there, it would cut, wear or clamp the component the screw is meant to guide. That is why the threaded length on this part is a dimension in its own right, and why it should never be inferred from the overall length.
Low profile machine screws pay for the low head in two places. The recess is shallower, because the head has little height to give it, and the bearing ring is narrower, because the head diameter is usually reduced with the height. Both are fine in a metal joint with a machined seat; both are a problem on a soft panel or with a worn bit.
Black zinc suits this family because the joints it goes into are usually inside equipment where a bright fastener would catch the eye. The coating is thin, so it does not close up the recess, and it is sacrificial, so a scratch at the head does not start corrosion the way it would on a nickel part. Where the equipment is washed or sits outdoors, a different finish and usually a different material are the answer.
The recorded range is M1 to M14, covering M1, M2, M3, M4, M5, M6, M7, M8, M9, M10 and M14. Custom lengths up to 2,000 mm are subject to DFM review after drawing submission. For low profile machine screws the quotation carries head diameter, head height, shank diameter, threaded length and overall length, because the two boundaries and the shank between them are what the joint depends on.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Low profile, flat top | Head diameter and height |
| Recess | Phillips cross | Recess size and depth after plating |
| Shank | Plain, as turned | Shank diameter and length |
| Thread | Partial machine thread | Threaded length and position |
| End | Blunt, chamfered | Chamfer cut, not deburred |
| Finish | Black zinc | Deposit thickness and adhesion |
Threaded length is the number that gets left off drawings, and it is the one that matters most here. A drawing that gives only an overall length leaves the split between shank and thread to the maker, and two batches can then both be correct and different — the first one locating on the shank, the second one threading into the bush.
Head height is the other number worth arguing about. A lower head fits more situations and carries a shallower recess; a slightly taller head drives better and still reads as low profile. Where the joint is assembled by hand with a worn bit, the taller of the two options is the better specification even if it costs a fraction of a millimetre of clearance.
Three features define this part: the low head, the plain shank and the partial thread. The first keeps the screw out of the space above the joint, the second and third keep the thread out of the space inside it.
| Feature | What it gives | What it costs |
|---|---|---|
| Low head | Clearance without a countersink | Shallow recess, narrow bearing ring |
| Plain shank | Locating or bearing without thread contact | A turned operation; tolerance to specify |
| Partial thread | Thread only where it is wanted | Threaded length must be on the drawing |
| Phillips recess | Common driver in a small head | Cam-out damages a shallow recess |
| Black zinc | Dark finish, thin deposit | Wears at the head and in the recess |
The shank is the feature that is most often misunderstood. On a screw with a plain shank, the shank is not simply the part that has not been threaded yet; it is a working diameter, and a component may slide or pivot on it. Treating it as a manufacturing leftover is how a joint ends up clamped on a bearing surface that was supposed to stay free.
The low head and the partial thread work together on assemblies that are built in layers. The head stays under the layer above, the shank passes through the middle layer, and the thread engages the last one. Everything about that arrangement is decided by the two lengths, not by the thread size, which is why this family is quoted from a drawing rather than from a table.
The recorded finish is black zinc over carbon steel. On a low head the deposit lands on a small area: it narrows the recess and thickens the thread crest, and it rounds the top edge that gives the screw its low profile. All three are checked on the plated part, because the condition the customer receives is the plated one.
| Option | How it protects | Effect on head and recess | Typical use |
|---|---|---|---|
| Black zinc | Sacrificial zinc, dark | A few microns; recess re-checked | Dark equipment interiors |
| White zinc | Sacrificial zinc, trivalent | A few microns; recess re-checked | Indoor, RoHS-driven work |
| Nickel plated | Barrier deposit, bright | Thin; decorative | Visible silver hardware |
| Black oxide | Conversion film, oiled | No measurable build | Internal machine parts |
| Stainless, plain | Passive chromium oxide film | None; recess as cut | Damp and washdown equipment |
Where the joint is inside a sealed product, black zinc is enough and it is cheap. Where the equipment is opened in a damp room, the same screw in stainless is the right part: the geometry does not change, and the low head with a plain shank is just as available in stainless as in steel. The finish decision is made by the environment, not by the head form.
The one thing to avoid on this part is a thick coating. A heavy zinc or a flake coating can fill the shallow recess on a low head, and then the driver has less to bite on than the design intended. If a thicker coating is required by the environment, the recess has to be re-checked and possibly re-cut.
Three assemblies where low profile machine screws are the fixing:
| Where it sits | The screw clamps the last layer of a stack while its shank passes through the middle one and its head stays under the layer above. |
| When it goes wrong | A thread that reaches into the middle layer clamps or scores it, and a head that is too tall lifts the top layer. |
| Why it happens | The joint is built in layers, the middle layer must stay free, and the space above is tight. |
| What we control | Head height and threaded length checked, first article assembled as a stack. |
| Where it sits | The screw acts as a shoulder for a link, a roller or a lever, with the thread taking the clamp and the shank taking the movement. |
| When it goes wrong | A threaded shank wears the moving part, and a low head gives less material to hold the recess. |
| Why it happens | The part moves on the shank, the head is buried in a pocket, and the joint is assembled once. |
| What we control | Shank diameter checked, thread start position verified on the projector. |
| Where it sits | The screw fixes a bracket or a board in a dark housing where a bright head would show through a vent or a transparent panel. |
| When it goes wrong | A zinc head that rusts inside a housing is found late, and a damaged recess is hard to reach. |
| Why it happens | The interior is dark, the access is narrow, and the joint is closed once. |
| What we control | Finish inspected, recess driven with the production bit. |
Four reasons that matter on a screw with two boundaries, each tied to what the drawing has to prove:
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Threaded length specified separately
The threaded length and the overall length are quoted as two dimensions, because the split between shank and thread is what the joint depends on. Basis: Threaded length agreed in writing. |
Head, shank and thread in one route
The low head and the recess are formed in the heading stroke, the shank is turned and the thread is rolled, with plating as the last step. Basis: One route from wire to plated screw. |
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Shank and thread measured after plating
The shank diameter and the thread start are measured on the plated part, because the deposit changes both and the customer receives the plated screw. Basis: First article checked after plating. |
First article fixes the setting
The first article fixes the wire, the head die and the second operation; repeat orders are compared against that record. Basis: First article signed off before the batch is released. |
Shi Shi Tong forms these low profile machine screws from carbon steel wire on single-die headers that form the low head and the Phillips recess in one stroke, turns the plain shank, rolls the machine thread on the remaining length and plates the finished screws in black zinc. The first part of every run is measured on the head, the shank and the thread and driven with the production bit before the batch continues.
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The shank is where a low profile machine screw is most easily made wrong. It has to come out of the second operation round, to size and concentric with the thread, and it has to stop where the drawing says the thread starts. A thread that begins a millimetre early is invisible in a tray and is a rejected part in a stack of modules.
What decides whether low profile machine screws pass is the head, the shank, the thread and the plate. The inspection agreement covers those, and the criteria come from the drawing.
Head and shank on the projector |
Thread gauged per batch |
Hardness checked on the wire |
Salt-spray testing of the plate |
The head is checked for diameter, height and face flatness, the shank for diameter and for where the thread begins, and the thread is gauged per batch. The thread start is measured rather than assumed: on this part it is a functional dimension, and a batch that starts the thread early will pass every other check.
The plate is checked for thickness and adhesion after plating, with attention to the recess and the shank. A shank that is a few microns thick will still enter a clearance hole and will not enter a close one, so the shank is measured on the finished part.
Every shipment of low profile machine 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 plating record is kept with the inspection file.
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 plating. The documents carry the drawing revision and the batch number, so a repeat order is made to the same thread-start position that was approved.
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 part with a defined shank the first article is assembled into the customer’s stack, because the fit of the shank is the function. Buyers visit during the process to review samples and to see how the parts are formed and finished.
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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 second-operation cells 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 |
Clearance where the head cannot be buried. There is no countersink to hide it, so the head is made shallow and stays under the layer above.
It is a working diameter, not a leftover. Components may slide or pivot on it, so a thread that reaches into it clamps or scores what should stay free.
From under the head. The threaded length is a separate dimension and should be on the drawing, not inferred from the overall length.
It can, with a worn bit. The recess has less material around it than on a standard pan head, so the driver matters more at assembly.
For occasional indoor exposure. The deposit is thin and the head is the first place it wears; for damp or outdoor work use stainless.
Head diameter and height, recess type, shank diameter, threaded length, overall length and the finish.
How a low profile machine screw project runs from drawing to repeat delivery:
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1
Send the drawing and the stack it passes through
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→ |
2
Head height, threaded length and shank agreed
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→ |
3
First article assembled in your stack
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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 recess type, the shank diameter, the threaded length, the overall length and the finish.
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Head height
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Head diameter
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Shank diameter
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Threaded length
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Overall length
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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
