M1 screw or bolt dimensions and sizes are essential for watchmaking, miniature medical devices, and high-precision micro-electronics. This size has a 1.00mm nominal major diameter and is available in M1 x 0.25 for the coarse series and M1 x 0.2 for the fine series, where 0.25 and 0.2 represents the thread pitch in millimeters. This reference chart follows DIN 86/ISO 1207 and DIN 963/2009 standards for the head size table and DIN 13-1 (coarse series), DIN 13-21 (fine series), and ISO 68-1 standards for the thread dimensions table to ensure compatibility across metric fastening applications.
Disclaimer: Actual dimensions value and tolerances may vary slightly depending on head style, manufacturer, or material — always verify with the official product datasheet before use.
M1 x 0.25 Screw & Bolt – DIN 13-1/ISO 68-1
Dimension
Size (mm)
Min
Max
Major Diameter
0.915
0.982
Pitch Diameter
0.767
0.82
Minor Diameter
0.613
0.711
Thread Pitch
0.25
Major Diameter
0.915
0.982
Pitch Diameter
0.787
0.82
Minor Diameter
0.633
0.711
Thread Pitch
0.25
M1 x 0.2 Screw & Bolt – DIN 13-21/ISO 68-1
Dimension
Size (mm)
Min
Max
Major Diameter
0.927
0.983
Pitch Diameter
0.805
0.853
Minor Diameter
0.682
0.766
Thread Pitch
0.2
Major Diameter
0.927
0.983
Pitch Diameter
0.823
0.853
Minor Diameter
0.7
0.766
Thread Pitch
0.2
Major Diameter –
The largest diameter of the external thread, measured crest to crest.
This defines the nominal size (e.g., M12 which is 12 mm of nominal major diameter).
Pitch Diameter –
The diameter of an imaginary cylinder where the thread thickness equals
the space between threads. This is the critical dimension for thread fit
(Tolerance classes 2A/3A for Imperial; 6g/4g6g for Metric).
Minor Diameter –
The smallest diameter of the external thread, measured root to root.
This represents the core strength of the fastener and is the theoretical
maximum diameter of the tap drill.
Thread Pitch –
The distance from a point on one thread to the corresponding point on the next.
What is the tap drill size for M1 x 0.25 and M1 x 0.2 screws or bolts?
For metric fasteners, the recommended tap drill size can be calculated using this formula: Major Diameter – Thread Pitch. Therefore, for an M1 x 0.25 screw or bolt, the recommended tap drill is 0.75mm, while for an M1 x 0.2, it is 0.80mm.
What clearance hole size is needed for an M1 screw or bolt?
For a Close Fit, a 1.10mm drill bit is utilized. For a Normal Fit, a 1.20mm bit is used, and for a Loose Fit, a 1.30mm bit is recommended to allow the fastener body to pass through the assembly without interference.
What is the difference between a bolt and a screw?
The difference is based on the intent of the fastener’s use; If the primary intent is for the fastener to pass through an unthreaded hole and be assembled with a nut, it is a Bolt. In this application, you usually hold the head and turn the nut to apply tension. But if the primary intent is for the fastener to be installed into a threaded (tapped) hole, it is a Screw. In this application, the connection is tightened by turning the head of the fastener itself.
