EKINSUN is a custom parts manufacturer that turns captive screws to drawing: a shoulder length for your panel, a thread reach for your boss, a knurled or lobed head for hands, a hex or Torx for tools, a 316L or brass body, a spring-loaded version with a retaining ring. The size ranges are those a distributor stocked in 2026.
A typical request: M5 captive screws for a 6 mm aluminium door, where the stock shoulder is 3 mm and the screw either binds in the door or rattles.
The shoulder must be a little longer than the panel; the series gives one shoulder per size and the panel decides the rest.
Captive screw types and size ranges
| Type | Head and drive | Size range | Common materials | Notes |
|---|---|---|---|---|
| Shoulder-retained captive screw | Phillips pan | M2–M8 | A2; zinc steel | the standard panel screw; reduced shank behind the thread |
| Shoulder-retained, hex head | hex | M4–M12 | A2 | spanner-driven covers |
| Shoulder-retained, slotted pan | slotted | M2.5–M8 | A2 | instruments |
| Shoulder-retained, countersunk | socket or Phillips countersunk | M2–M8 | A2 | flush panels |
| Shoulder-retained, socket cap | hex socket, knurled or plain head | M2–M6 / M3–M10 | A2 | machine covers |
| Shoulder-retained, button | hex socket button | M2–M8 | A2 | low domed head |
| Knurled-head captive screw | slotted knurled | M3–M8 | A2; brass | hand-tightened; slot for a coin or a blade |
| Chassis thumb screw | knurled round, Phillips or slot | M3–M4 | nickel and zinc steel; A2 | computer chassis and rack panels |
| Spring-loaded captive screw | any, with a spring and retaining ring | to order | A2; steel | the screw lifts clear of the thread when released |
| Self-clinching captive screw (PF-type) | Phillips, Torx or knurled | to order | A2; steel | clinches into the panel like a self-clinching nut |
| Captive screw with retaining washer | any | to order | A2; steel | a pressed-on washer instead of a shoulder |
Need captive screws in a size, thread or material no catalogue lists? EKINSUN is a custom parts manufacturer: we make captive screws to your drawing, sketch or sample, steel, 304 stainless steel or brass, from 1 piece, quoted in 12 hours and shipped duties paid. Already a catalogue size? Ask us too, we may have it in stock, and larger quantities cost less per piece. All custom fasteners
Shank, hole and panel: how a captive screw is sized
| Dimension | Rule | What goes wrong |
|---|---|---|
| Reduced shank diameter | smaller than the thread's minor diameter, so the thread passes through the panel hole and the shank turns freely in it | a shank equal to the minor diameter binds; too thin and the screw bends |
| Panel hole | a clearance hole for the thread (the thread must pass), then the shank runs in it | a hole sized to the shank will not let the thread through |
| Shoulder (shank) length | panel thickness plus a little, so the head seats and the thread is clear of the panel when unscrewed | shorter than the panel: the screw binds; much longer: the screw rattles and the reach into the boss is lost |
| Thread reach | long enough to engage the boss or nut fully with the panel in place | a captive screw is often ordered by total length and the reach is forgotten |
| Retention | shoulder, pressed-on washer, retaining ring or clinch; the shoulder is the simplest and the one standard uses | — |
Read the pitch before you order the captive screw. Lay a steel rule along ten thread crests and divide by ten: 10 mm over ten pitches is a 1 mm pitch (M6 coarse), 12.5 mm is M8 coarse, 15 mm is M10 coarse, 17.5 mm is M12 coarse. A reading that is not a round number of millimetres is an inch thread, and a reading that is shorter than the coarse pitch for that diameter is a fine thread. If diameter, pitch and the size range in the table all agree, the part is a standard size: buy it off the shelf, or have it made to order from 1 piece. If any of the three falls outside the table, we make it to your reading. The full measuring routine, including the inch traps
Where the captive screw catalogue stops
| What you need | In the catalogue? | What we make |
|---|---|---|
| Shoulder-retained Phillips, slotted, hex, countersunk or socket captive screw M2–M12 in A2 or zinc steel, standard shoulder | Yes | Buy it from stock, or have it made to order from 1 piece. No one-off competes with a series panel screw when the shoulder fits your panel. Standard parts: ask us too, we may have them in stock. |
| Knurled-head captive screw M3–M8, chassis thumb screw M3–M4 | Yes | Standard sizes: buy them off the shelf, or have them made to order from 1 piece. Standard parts: ask us too, we may have them in stock. |
| A shoulder length for a panel thicker or thinner than the series assumes | No | Turned from bar with the shank and shoulder to your panel, from 1 piece. |
| A thread reach longer than standard, or a plain dog point that finds the boss | No | Turned to the reach; point to the drawing. |
| A head for hands, knurled, lobed, wing, a slot for a coin, on a size or thread the series skips | No | Turned and knurled; see also thumb screws and clamping knobs. |
| A captive screw in 316L, brass above M8, titanium or PEEK | No | Same geometry, your material. |
| A spring-loaded captive screw, or one with a retaining ring or a pressed washer instead of a shoulder | No | Assembled with the spring and ring to your panel. |
| A captive screw in aluminium 6061 or 7075 | Partly | 7075 on request for light panels, anodised; not for a screw that is torqued hard, and we say so. |
Materials
| Material | Designation | Where it fits here |
|---|---|---|
| Stainless 304 | 1.4301 / A2 | the standard captive screw in every head |
| Stainless 316L | 1.4404 / A4 | turned to order for marine and washdown panels |
| Free-machining stainless | 303 / 1.4305 | custom turned captive screws with knurls |
| Carbon steel | zinc, nickel | standard chassis and panel screws |
| Brass | CW614N / C36000 | knurled-head captive screws for instruments |
| Aluminium 6061 | AlMg1SiCu | the door or panel the screw goes through; not the screw |
| Aluminium 7075 | AlZn5.5MgCu | anodised light captive screws on request |
| Titanium, PEEK | Grade 5; PEEK | turned for weight-critical and insulating panels |
Related pages
- fastener types chart, all families with standard and size range
- Thumb screws, hand-tightened screws
- security screws, tamper-resistant drives on the same panel
- clamping knobs and levers, larger hand-operated heads
- press-in nuts, studs and standoffs, the clinch principle
- Shoulder bolts, shouldered screws for pivots
- machine screws, head and drive types
- Rack-mount enclosure standoffs, the standoffs behind a rack panel
Frequently asked questions
The shank behind the thread is turned down to less than the thread's minor diameter. The thread is screwed through a clearance hole in the panel; once it is through, the thin shank turns freely in the hole and the thread is too big to come back out. Spring-loaded and clinch-in versions do the same job with a ring or a clinch.
Shoulder length equals panel thickness plus a small clearance; thread reach equals the engagement the boss or nut needs with the panel in place; panel hole is a clearance hole for the thread. The series pairs one shoulder with each size, so a panel of another thickness needs the shoulder turned to it.
Yes. Knurled and lobed heads, coin slots, hex sockets and Torx recesses are machined on the turned screw in any size, in 303 / 316L stainless or brass, from 1 piece.
Standard captive screws are A2 in M2–M12 and chassis thumb screws in nickel steel or A2. 316L, brass above M8 and titanium are turned to order.
EKINSUN is a custom parts manufacturer that turns captive and panel screws with the shoulder, reach, head and thread the panel needs, in 304 and 316L stainless, steel, brass, titanium and PEEK, from 1 piece, with a quote within 12 hours.
No list price; the drivers are material, the turned shoulder, the head (knurled heads take longer), and quantity. A batch of A2 captive screws with a longer shoulder is a short lathe job; a single spring-loaded 316L screw with a lobed head is priced as the assembly it is. The quote states which.
Send the panel thickness and the reach
Thread and pitch, panel thickness and hole, thread reach into the boss, head and drive, material, quantity. A sketch of the panel section works. From 1 piece, quote within 12 hours.