Engineering Tools · Machine Screw Reference
M1.6 Screw Size Chart: Head Dimensions and Drive Size
M1.6 machine screw: nominal diameter d = 1.6 mm, coarse pitch P = 0.35 mm. Head dimensions across five head types - cross recessed pan head (GB/T 818) dk = 3.2 mm, k = 1.3 mm, recess No.0 (PH0); socket head cap (GB/T 70.1) dk = 3 mm, k = 1.6 mm, hexagon socket s = 1.5 mm; slotted pan head (GB/T 67) dk = 3.2 mm, k = 1 mm, slot width n = 0.4 mm. All figures are nominal (= max) values.
M1.6 machine screw at a glance: thread diameter d = 1.6 mm, coarse pitch P = 0.35 mm; cross recessed pan head (GB/T 818) dk = 3.2 mm / k = 1.3 mm / recess No.0 = PH0; socket head cap (GB/T 70.1) dk = 3 mm / k = 1.6 mm / hexagon socket s = 1.5 mm, which takes a 1.5 mm hex key. Head figures are nominal (= max) values, not the nominal screw size.
Head figures are the standard's nominal (= max) values. Head height depends on the head type, so an M5 screw is 3.7 mm high as a cross recessed pan head and 5.0 mm as a socket head cap. Tolerances, property classes and surface finish are agreed on order.
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Machine screw size chart, M1.6–M10 (mm)
Pick a head type. dk is the head diameter and k the head height, both on the standard's nominal (= max) basis. "Recess No." is the cross recess size No.0 to No.4, which is the same as a PH0 to PH4 bit; a slotted head has a slot width n instead, and a socket head has a hexagon socket s.
Head type
Cross recessed pan head (GB/T 818) · GB/T 818-2016
| Size d (mm) | Coarse pitch P (mm) | Head dia. dk (mm) | Head height k (mm) | Recess No. |
|---|---|---|---|---|
| M1.6 | 0.35 | 3.2 | 1.3 | 0 |
| M2 | 0.4 | 4 | 1.6 | 0 |
| M2.5 | 0.45 | 5 | 2.1 | 1 |
| M3 | 0.5 | 5.6 | 2.4 | 1 |
| M4 | 0.7 | 8 | 3.1 | 2 |
| M5 | 0.8 | 9.5 | 3.7 | 2 |
| M6 | 1 | 12 | 4.6 | 3 |
| M8 | 1.25 | 16 | 6 | 4 |
| M10 | 1.5 | 20 | 7.5 | 4 |
The recess No. is the bit: No.0 to No.4 is a PH0 to PH4 bit. Recess numbering is per head type, so the same thread size can take a different recess number in two head types.
References
- GB/T 67-2016 Slotted pan head screws - table 1 (head diameter dk, head height k, slot width n)
- GB/T 818-2016 Cross recessed pan head screws - table 1 (dk, k, recess No.)
- GB/T 819.1-2016 Cross recessed countersunk head screws, part 1: class 4.8 - table 1 (dk, theoretical dk max, kc, recess No., 90° head)
- GB/T 822-2016 Cross recessed cheese head screws - table 1 (dk, k, recess No.; sizes M2.5 to M8)
- GB/T 70.1-2008 Socket head cap screws - table 1 (head diameter dk for the plain head, head height k, hexagon socket s)
- Table values are the nominal (= max) figures of the standard editions above, checked row by row against the official text. No table values are reproduced from third-party dimension tables, and each row is labelled with the standard it comes from.
M1.6 in every head type (mm)
One row per head type at the same thread size. dk and k are nominal (= max) values from the standard named in each row.
| Head type | Standard | Head dia. dk (mm) | Head height k (mm) | Coarse pitch P (mm) | Drive size |
|---|---|---|---|---|---|
| Slotted pan head (GB/T 67) | GB/T 67-2016 | 3.2 | 1 | 0.35 | Slot width n = 0.4 mm |
| Cross recessed pan head (GB/T 818) | GB/T 818-2016 | 3.2 | 1.3 | 0.35 | No.0 (PH0) |
| Cross recessed countersunk head 90° (GB/T 819.1) | GB/T 819.1-2016 | 3 | 1 | 0.35 | No.0 (PH0) |
| Cross recessed cheese head (GB/T 822) | GB/T 822-2016 | — | — | — | — |
| Socket head cap (GB/T 70.1) | GB/T 70.1-2008 | 3 | 1.6 | 0.35 | Hex socket s = 1.5 mm |
One row per head type at the same thread size. dk and k are nominal (= max) values from the standard named in each row.
GB/T 822 covers M2.5 to M8, so the cheese head row is blank at M1.6, M2 and M10. Use the pan head or socket head column for those sizes.
M1.6 beside the next sizes
In this range the nominal diameter steps by 0.5 mm or 1 mm. Measure d across the thread with a caliper and compare with the rows below before ordering.
Left four columns: cross recessed pan head (GB/T 818). Right four columns: socket head cap (GB/T 70.1). Values in mm, nominal (= max).
| Size d (mm) | Coarse pitch P (mm) | Head dia. dk (mm) | Head height k (mm) | Recess No. | Head dia. dk (mm) | Head height k (mm) | Hex socket s (mm) |
|---|---|---|---|---|---|---|---|
| M1.6d = 1.6 | 0.35 | 3.2 | 1.3 | 0 | 3 | 1.6 | 1.5 |
| M2d = 2 | 0.4 | 4 | 1.6 | 0 | 3.8 | 2 | 1.5 |
Which dimension do you need? d, dk, k and the drive size
A machine screw carries four different numbers that all get called "the size". Buyers order by the first one and measure the others, which is where most wrong orders start.
d - nominal thread diameter
The number after M: M5 is d = 5 mm, a 5 mm thread. It is what the order is placed on, and it is not the head size.
P - pitch
Distance between two thread crests. M5 in the coarse series is 0.8 mm. Coarse pitch covers almost all machine screws; fine pitch is agreed on order against the drawing.
dk - head diameter
Outside diameter of the head, measured across it with a caliper. It sets the clearance hole and the counterbore: 3.2 mm for an M5 cross recessed pan head, — mm for an M5 cheese head, 3 mm for an M5 countersunk head.
k - head height
Height of the head above the bearing surface (on a countersunk head this is kc, the depth that has to be sunk). It sets counterbore depth and how far the head stands proud: 1.3 mm for an M5 pan head, 1.6 mm for an M5 socket head, 1 mm for an M5 countersunk head.
Drive size - recess No., slot width n or hexagon socket s
The recess that takes the tool: No.0 (PH0) at M5 in the cross recessed pan head series, slot width n = 0.4 mm at M5 in the slotted series, hexagon socket s = 1.5 mm at M5 for a socket head cap screw. Take the drive size from the head type, not from the thread size.
Metric to inch machine screw sizes (approximate, not interchangeable)
Cross-reference by nominal diameter only. The inch column is a straight millimetre-to-inch conversion of d; the last column is the inch machine screw whose nominal diameter is closest to it.
| Metric size | Nominal d (mm) | Nominal d (in) | Closest inch machine screw |
|---|---|---|---|
| M1.6 | 1.6 | 0.063 | #0 (1.524 mm) |
matched by nominal diameter only
Do not substitute. Metric and inch machine screws both use a 60° thread form, but the diameters and thread counts differ, so a near-diameter inch screw starts and then jams and damages the thread. Use these rows to read which callout a drawing means, not to interchange parts.
FAQ
What head dimensions does an M1.6 machine screw have?
Cross recessed pan head (GB/T 818): head diameter dk = 3.2 mm, head height k = 1.3 mm. Slotted pan head (GB/T 67): dk = 3.2 mm, k = 1 mm. Socket head cap (GB/T 70.1): dk = 3 mm, k = 1.6 mm with a hexagon socket s = 1.5 mm. Cross recessed cheese head (GB/T 822) adds dk = — mm, k = — mm where that standard covers the size (M2.5 to M8). All of them are nominal (= max) values.
Which screwdriver bit or key fits an M1.6 machine screw?
Cross recess: No.0, which is a PH0 bit (GB/T 818). Slotted: slot width n = 0.4 mm, so a blade of that width (GB/T 67). Socket head cap: a 1.5 mm hex key (GB/T 70.1). Take the drive size from the head type rather than the thread size - the same M-size can take a different bit in another head type, and the recess numbers of the cheese head series do not match the pan head series.
Is the M number the head size on an M1.6 machine screw?
No. The number after M is the nominal thread diameter d: an M1.6 screw is d = 1.6 mm across the thread, while the head is wider - dk = 3.2 mm on a cross recessed pan head and 3 mm on a socket head cap screw. Order by the M number, and confirm dk and k against the drawing or the counterbore.
What is the pitch of an M1.6 machine screw?
0.35 mm in the coarse series, which is the pitch almost all M1.6 machine screws are supplied with. Fine pitch versions are agreed on order and quoted against the drawing. If you measure, take the distance over several thread crests and divide by the number of gaps rather than measuring one gap, and use the thread diameter to confirm you have the size right.
Countersunk or pan head M1.6 - which do I need?
Countersunk sits flush and needs a machined 90° seat: the M1.6 countersunk head is dk = 3 mm, with a theoretical dk max of 3.6 mm for the seat and kc = 1 mm of head to sink. Pan head sits on the surface and needs no seat: the M1.6 pan head is dk = 3.2 mm and stands k = 1.3 mm proud. Use countersunk where the head must not protrude, and pan head where a bearing surface or easy removal matters.
Can I replace an M1.6 metric screw with an inch screw?
No, not as a substitute. The M1.6 thread is d = 1.6 mm with a 0.35 mm pitch, and the nearest inch machine screw only matches the diameter to within a few tenths of a millimetre while carrying a different thread count - so it will not run true in the same nut or tapped hole and will damage it. Both series are 60° threads, so the two look close on a drawing; cross-reference them to read callouts, and order the thread the joint is made for.
Related References
Hex Key Size Chart
Socket head cap screws the other way round: the hexagon socket s of each size and the matching key arm lengths, M3-M24.
Bolt Weight Calculator
Unit weight and order total weight once the size and length are known - machine screws, bolts, nuts, washers and threaded rod, metric and inch.
Cross Recessed Pan Head Machine Screws (GB/T 818)
Sizes, property classes and finishes we quote to GB/T 818, with the technical package for that standard.
Cross Recessed Countersunk Machine Screws (GB/T 819.1)
The 90° countersunk machine screw range quoted to GB/T 819.1, class 4.8, with the technical package for that standard.
Socket Head Cap Screws (GB/T 70.1 / DIN 912)
Socket head cap screws to GB/T 70.1, which is the same form as DIN 912 and ISO 4762, with class and finish options.
Machine Screw Category
Head types and standard numbers in the catalog; sizes and lengths made to drawing.
Disclaimer: this table is a selection and quotation reference built from the standard editions named on this page, not a design basis or an acceptance standard.