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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:Thumb Screw
Materials:Steel
Surface treatment:Eco Black Zinc Plated
Head Type:Knurled thumb head
Drive:Knurled rim, hand driven
Thread:Machine thread
Point:Plain, chamfered
Forming:CNC turning; knurl rolled
Size:M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
We make thumb screws in steel with an eco black zinc plate, a knurled head and a machine thread, quoted with the head and knurl that set the hand torque. A thumb screw is specified by what fingers can apply, so the head diameter, the knurl and the thread pitch are agreed against the joint.
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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 thumb screw has a head made to be turned between finger and thumb, usually knurled, on a machine thread. The part recorded here is steel with an eco black zinc plate, quoted in metric sizes from M1 upward with the length made to the drawing.
Knurled head. A head with a grip pattern on its rim, sized to the fingers rather than to a driver.
No recess. There is no slot or socket on top, so the head is the only drive.
Machine thread. A thread that engages a tapped hole or a nut over a defined length.
They are used where a joint is adjusted or removed by hand, and where carrying a tool to it would be impractical. A thumb screw is therefore chosen for access and frequency of adjustment rather than for strength, and the joint is designed to work at hand torque, and the head has to stay reachable through the life of the equipment.
A thumb screw is specified by a torque no one measures. The joint has to work at the torque a thumb and forefinger can apply to a head of that diameter, and that figure is both small and variable. Designing the joint around a normal torque value, and then fitting a thumb head to it, is the most common way a hand-tightened joint fails: the screw never reaches the clamp the joint needs, and it looks tight because it cannot be turned further.
That is why the head diameter and the knurl are functional dimensions. A larger head gives more grip because the hand is further from the axis, and a coarser knurl gives more grip per unit of force. Reducing the head for appearance, or replacing the knurl with a smooth head, takes the torque away even though the thread is unchanged.
The thread has to suit the hand as well. A coarse pitch gives a given clamp in fewer turns, which matters when the screw is turned by fingers rather than by a tool that can spin. A fine pitch on a thumb screw means many turns for the same travel, and in practice the joint is left part-way.
Accessibility is the other half of the specification. A thumb screw is turned by a hand, so the hand has to get to it, and the head has to be clear of the parts around it. On a recessed or crowded fixing, a thumb screw becomes a part that is turned by gripping the head edge with fingertips, which removes most of the available torque.
The result is that a thumb screw is a joint designed around the user’s hand. The screw’s strength is almost never the limit; the grip, the access and the number of turns are.
The part is quoted to the drawing with the head, the knurl and the thread stated separately. Custom lengths up to 2,000 mm, subject to DFM review after drawing submission. The quotation for a thumb screw carries the head diameter and height, the knurl pattern, the thread and length, and the clearance around the head.
| Item | How it is defined | What we control |
|---|---|---|
| Head | Knurled thumb head | Diameter, height and edge |
| Knurl | Straight or diamond | Pattern and depth |
| Thread | Machine thread | Size, pitch and length |
| Torque | Hand torque available | Head size and knurl agreed |
| Clearance | Around the head | Access for fingers |
| Plate | Eco black zinc | Thickness and coverage |
The head diameter is what converts a hand force into torque, so it is chosen against the clamp the joint needs rather than against the space available. On a part that has to be turned often, a larger head is the cheaper answer than a stronger thread.
The knurl pattern is written on the drawing by type and depth. A straight knurl grips for turning but lets fingers slide along the axis; a diamond knurl grips in both directions. On a part that is pulled as well as turned, the choice matters.
The thread and the clearance are agreed together with the customer’s part, since a thumb screw with no access is a thumb screw that cannot be used.
Four properties decide thumb screws, and each one carries a cost:
| Property | What it gives | What it costs |
|---|---|---|
| Knurled head | Adjustment without tools | Torque limited by the hand |
| Coarse thread | A clamp in few turns | Less holding per turn |
| No recess | Nothing to wear out at the drive | No way to add torque with a tool |
| Eco black zinc | Dark finish, mild protection | Soft plate marks in the knurl |
The value of a thumb screw is a fixing that a user can adjust or remove without a tool, on equipment that is set up in the field. That is worth more than the strength a socket head would give.
On a thumb screw the cost is that the joint has to be designed for the hand. Where the clamp required is higher than fingers can give, a thumb screw is the wrong part, however convenient it is.
The recorded finish is eco black zinc, a trivalent black passivation over a zinc layer. On a thumb screw it gives a dark finish and sacrificial protection, and it suits visible adjustment hardware on dark equipment.
| Option | How it protects | Effect on knurl and thread | Typical use |
|---|---|---|---|
| Eco black zinc | Trivalent zinc, black | Build in the knurl valleys; re-checked | Dark equipment |
| Clear zinc | Sacrificial zinc | Build; knurl feel checked | General assemblies |
| Nickel plated | Hard bright barrier | Thin build; knurl kept | Visible adjustment parts |
| Stainless, passivated | Passive film, no coating | No build; knurl as cut | Wet and food areas |
| Anodised aluminium | Oxide film | No measurable build | Lightweight knobs |
On a thumb screw the plate can fill the knurl valleys, and that is a grip change rather than a cosmetic one. A heavy layer that rounds the ridges makes the head harder to turn, so the knurl feel is checked after plating on a sample.
The thread is the other place the plate matters. A layer inside a coarse thread is usually tolerable, but the nut or tapped hole has to be checked with the plated part rather than assumed from the white one.
Three assemblies where the fixing is adjusted by hand:
| Where it sits | The screw sets a stop or a clamp that is adjusted during commissioning and occasionally afterwards. |
| When it goes wrong | The setting drifts, or the screw cannot be turned by hand at all. |
| Why it happens | The head is too small for the clamp, and the thread pitch is too fine for fingers. |
| What we control | Head and knurl checked; first article adjusted by hand through its range. |
| Where it sits | The screw holds a panel that is removed for service without tools. |
| When it goes wrong | The panel is hard to remove, or the joint loosens in service. |
| Why it happens | The head is recessed and cannot be gripped, and there is no locking feature. |
| What we control | Clearance and knurl checked; first article removed and refitted by hand. |
| Where it sits | The screw is a small adjustment point where the setting is fine and the head is visible. |
| When it goes wrong | The setting is not repeatable, or the head is damaged by handling. |
| Why it happens | The knurl is too fine, and the head has been gripped with pliers. |
| What we control | Knurl and head checked; first article adjusted as the user would. |
Four reasons that matter on thumb screws, whose drive is a hand, each tied to something the drawing or the first article proves. All four show in the sample.
|
Head and knurl stated
The drawing states the head diameter and the knurl pattern, because together they set how much torque a hand can apply. Basis: Head and knurl dimensioned. |
Knurl rolled, edge deburred
The knurl is rolled and the edge is deburred, because the rim is what the fingers meet every time the part is used. Basis: Knurl edge deburred. |
|
Turned by hand in the check
The first article is turned by hand in the customer assembly, because grip is a property of the joint. Basis: Grip proved by hand. |
Same feel on repeat runs
Head, knurl and plate are recorded with the drawing revision, so a repeat batch feels the same. Basis: Same grip across orders. |
These screws are turned from steel bar, with the head formed, the knurl rolled, the edge deburred and the thread cut; the parts are then black zinc plated. The first piece of every run is measured on head diameter and height, knurl pattern and depth, thread and length.
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The knurl is the operation that decides how the part feels. A rolled knurl displaces material into clean ridges; a cut knurl can leave a burr at the end where the tool runs out, and that burr is what a finger meets first. On a part that is handled every time it is adjusted, the deburring is a functional step.
The head is formed before the knurl, so the ridges run on a finished diameter. The thread is cut behind the head, and its pitch is chosen with the customer, because a thumb screw that needs many turns is a thumb screw that is left part-way.
The parts are plated last. Because the knurl is the grip, the plate is checked in the valleys and on the ridges: a layer that fills the valleys makes the head harder to turn, and that shows up in the hand rather than on a drawing.
What decides whether a thumb screw passes is the knurl, the head and the thread. The inspection agreement covers those, and the criteria come from the drawing.
Knurl and head on the projector |
Thread gauged |
Core hardness checked |
Salt-spray testing of the black zinc |
The knurl is checked for pattern and depth and turned by hand on a sample from each batch. A knurl that looks right but slips is usually too shallow, and one that cuts the fingers is usually a burr rather than a depth problem.
The head is measured for diameter and height, and the edge is checked by touch. On a part that may be handled with bare fingers, a sharp edge is a defect.
The thread is gauged and a sample is turned into the customer part by hand to confirm it runs down without binding. That test is the one that matches how the part is used, and it is the one that catches a plate that is too heavy for the thread.
Every batch of thumb screws is traceable to the bar 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 report carries the layer thickness and the lot number.
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 knurl and head, and the plating report. The records carry the drawing revision and the batch number, so a repeat order of thumb screws feels the same in the hand.
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 hand-driven part the first article is turned by hand in the customer assembly. Buyers visit during the process to review samples.
|
8,678+
customers served
|
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 knurling setup 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 |
Only what fingers can apply to the head. The joint has to work at that level, or the screw is the wrong part.
It is the torque. A larger head puts the fingers further from the axis, and a coarser knurl gives more grip.
So a given clamp comes in fewer turns. A fine pitch leaves the joint part-way because the hand will not keep turning.
Then only the fingertips reach it, and most of the available torque is lost. Access is part of the specification.
It can fill the knurl valleys and round the ridges, so the knurl feel is checked after plating.
Head diameter and height, knurl pattern and depth, thread and length, finish, and the clearance around the head.
How a thumb screw project runs from drawing to repeat delivery:
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1
Send the drawing and the assembly
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→ |
2
Head, knurl and thread agreed
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→ |
3
First article turned by hand
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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, knurl pattern and depth, thread and length, finish, and the clearance around the head.
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Head diameter
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Head height
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Knurl
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Thread
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Length
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Clearance
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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
