A machine screw is defined by four things: the thread, the head shape, the drive recess and the length. The standards fix the first three in combinations; the catalogue stocks the common ones from M1 to M10 and a few to M20. A pan head with a Torx drive is on the shelf; a cheese head with a Torx drive in M2.5 fine is not, and neither is a head diameter chosen for a slot rather than a table.
EKINSUN LTD is a custom parts manufacturer that turns machine screws to drawing when the head, drive, thread or length is not a stock combination: a head diameter for a particular hole, a drive the line does not run in that size, a fine or left-hand thread, a length between the steps, a material outside the catalogue. The two charts below name every head and every drive with its standard; the code table decodes the shorthand on stock lists; the negative-space table marks where the catalogue ends.
"Pan head, Torx T10, M2.5 x 0.35, 4.2 mm long, A4, and I need the head no wider than 4.5 mm. Four conditions and the catalogue meets two."
Most custom machine screws are that shape: each attribute is ordinary, the combination is not.
| Head | Shape | Standard (machine thread) | Stock code | Stock range | Use |
|---|---|---|---|---|---|
| Pan head | flat top, rounded edge, low | ISO 7045 / DIN 7985 (Phillips, Pozi); ISO 1580 / DIN 85 (slotted); ISO 14583 (Torx) | PM | M1–M10; Torx M2–M20 | the general-purpose machine screw |
| Cheese head | cylindrical, flat top, tall | ISO 1207 / DIN 84 (slotted); ISO 14580 (Torx) | — | M2.5–M8 | deep counterbores, instruments, electrical |
| Countersunk (flat) head | conical 90°, flush | ISO 7046 / DIN 965 (Phillips); ISO 2009 / DIN 963 (slotted); ISO 14581 (Torx) | KM | M1–M10; Torx M2–M8 | flush faces, hinges, covers |
| Raised countersunk (oval) head | conical with a domed top | ISO 7047 / DIN 966; ISO 2010 / DIN 964 (slotted) | OM | M2–M6 | flush and decorative |
| Small countersunk, thin | conical, small diameter | maker series | FM | M2–M6 | thin panels, electronics |
| Truss (mushroom) head | wide, low dome | maker series (ASME B18.6.3 in inch) | TM | M2–M8 | large bearing area on thin or slotted sheet |
| Large pan (binding / bugle) head | wide pan | maker series | BM | M2–M5 | wire terminals, thin covers |
| Thin (wafer) head | very low, wide | maker series | CM | M1.2–M8 | laptops, phones, flush covers |
| Pan head with captive washer | pan plus a captive flat washer | maker series | PWM | M1.4–M6 | electronics assembly |
| Hex washer head | hex with a flange, Phillips recess | DIN 6921 form | — | M3–M8 | sheet-metal boxes, chassis |
| Socket cap, button, countersunk socket | cylindrical, domed, conical with hex socket | ISO 4762, ISO 7380, ISO 10642 | HM | M1.4–M24 | see socket head cap screws |
| Drive | What it is | Typical size | Strong | Weak |
|---|---|---|---|---|
| Slotted | one straight slot | slot width grows with the head | any flat blade fits; cheapest | cam-out and slipping; not for power tools |
| Phillips (PH) | cross recess, tapered walls | PH1 for M2–M3, PH2 for M3.5–M5, PH3 for M6–M8 | self-centering; universal bits | designed to cam out at high torque |
| Pozidriv (PZ) | cross with four extra ribs | PZ1 / PZ2 / PZ3 as Phillips | less cam-out than Phillips | a Phillips bit in a Pozi screw strips it |
| Torx (T) | six-lobe star | T10 for M3, T20 for M4, T25 for M5, T30 for M6, T45 for M8, T50 for M10 (ISO 14583 pan) | highest torque transfer, long bit life | needs the right bit; no substitute |
| Hex socket (Allen) | hexagonal recess | 2 mm for M2.5 – 19 mm for M24 (cap screws) | high torque, compact head | rounds if the key is worn or short |
| Square (Robertson) | square recess | #1–#3 | no cam-out; one-handed driving | rare outside North America |
| Hex external | hex head | across-flats per DIN 933 / 6921 | spanner or socket; highest torque | needs clearance around the head |
| Security drives | pin-Torx, pin-hex, tri-head, one-way | as the parent drive | tamper resistance | see security screws |
| Combination (Phillips + slot) | cross and slot | PH1 / PH2 | either driver works | weaker than either alone |
A patch screw is a machine screw with a nylon patch fused onto part of the thread: 180° patches cover half the circumference and 360° patches the full circumference. The patch deforms into the mating thread and gives prevailing torque without liquid adhesive, so the screw can be reused a few times and never needs curing. Stock covers socket cap M2–M25, button, countersunk and pan heads M2–M8, SEMS M2–M8 and set screws M2.5–M3 in A2 and black steel. A patch on a screw the catalogue does not carry — a fine pitch, a custom head, a brass screw — is applied to the turned screw as a finishing step.
Read the pitch before you order the machine 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, buy the stock part. If any of the three is off the shelf, that is the one we make. The full measuring routine, including the inch traps →
| What you need | In the catalogue? | What we make |
|---|---|---|
| Pan, countersunk or cheese head M1–M10 in Phillips, slotted or Torx, A2 or zinc steel, stock length | Yes | Buy it from stock. No one-off competes with a cold-headed machine screw. |
| Truss, thin, binding, oval and washer heads in the stock ranges | Yes | Stocked; buy it. |
| A head diameter or height for a specific hole, slot or counterbore | No | Turned from bar with the head to your dimensions and any stock drive; from 1 piece. |
| A drive the line does not run in that head and size — Torx on a cheese head, hex socket on a truss head, Pozi in M1.6 | No | Recess machined on the turned screw. |
| A fine, left-hand or inch thread; a length between the stock steps | No | Single-pointed or rolled to your reading; length to the drawing. |
| A machine screw above M10 in a head the stock only carries to M10 | No | Turned; pan, cheese and countersunk heads to M36. |
| A machine screw in 316L, brass above M12, titanium, or aluminium 6061 / 7075 | No | Same geometry, your material; 7075 for light, low-preload screws, 6061 only where the screw is decorative. |
| A patch, a drilled head or a sealing washer on any of the above | No | Applied or machined as a finishing step. |
| Material | Designation | Where it fits here |
|---|---|---|
| Stainless 304 | 1.4301 / A2-70 | the stock machine screw in every head and drive |
| Stainless 316L | 1.4404 / A4-80 | stock in the common heads; turned above |
| Free-machining stainless | 303 / 1.4305 | custom turned screws with milled recesses |
| Carbon steel | zinc (white, blue, yellow, black), nickel, black oxide | stock steel machine screws M1–M8 |
| Brass | CW614N / C36000; CuZn37 cold-headed | stock M2–M12; turned above |
| Aluminium 6061 | AlMg1SiCu | decorative turned screws only |
| Aluminium 7075 | AlZn5.5MgCu | turned light screws, anodised |
| Titanium | Grade 2 / Grade 5 | stock hex and cap screws M3–M12; turned machine screws |
| Nylon 66, PC, PEEK | PA66, PC, PEEK | insulating machine screws M1.4–M12 — see plastic fasteners |
Pan, cheese, countersunk, raised countersunk, truss, binding, thin wafer and fillister for machine screws, plus socket cap, button and countersunk socket for hex-socket screws. Pan is the general-purpose head; countersunk sits flush; cheese is tall for deep counterbores; truss spreads load on thin sheet; thin heads hide under covers.
T30 for an ISO 14583 pan head; T10 for M3, T20 for M4, T25 for M5, T45 for M8, T50 for M10. Countersunk and cheese heads in the ISO 14581 / 14580 series use the same sizes for the same threads.
Catalogue shorthand: the first letter is the head (P pan, K countersunk, C thin flat, T truss, B large pan, F small countersunk, O oval), the second the thread end (M machine thread, A pointed tapping, B flat-end tapping, T cutting-end tapping). PM is a pan head machine screw, KA a countersunk self-tapping screw.
Both are cross recesses, but Pozidriv adds four small ribs between the arms, which lets the bit transmit more torque without camming out. The two are not interchangeable: a Phillips bit in a Pozi screw, or the reverse, strips the recess.
EKINSUN LTD is a custom parts manufacturer that turns machine screws with any head diameter, height and drive, in any pitch from M1.6 to M36, in 304 and 316L stainless, steel, brass, titanium and aluminium, from 1 piece, with a quote within 12 hours.
No list price; the drivers are material, head and recess machining, thread and quantity. A batch of A2 pan screws in an odd length is a short lathe job; a single M2.5 fine-pitch Torx screw in A4 with a custom head is a small precision part and priced as one. The quote states which.
Thread and pitch, length, head type or head dimensions, drive, material, finish, quantity. A photo of the old screw beside a rule is enough. From 1 piece, quote within 12 hours.
Machine screws turned to head, drive, pitch, length and material — from 1 piece, quote in 12 hours.