M18 Metric Thread
M18 Metric Thread Dimensions and Pitch
Below are the key dimensions for M18 metric threads: pitch, tap drill and clearance drill according to ISO 724:2023.
M18 Coarse (standard)
Step onto our M18 Metric Thread Page, your comprehensive reference for swift metrics on M18 metric threads. We've compiled a broad database for all common metric threads used in your parts, emphasising critical measurements such as thread pitch, tap drill, and clearance drill. This page serves as an all-in-one destination for engineers, machinists, and hobbyists seeking precise and dependable details.
M18 Coarse Pitch Dimensions
Nominal Size
d=D
p
r
d2=D2
d3
D1
h3
H1
Tap Drill
M18
18
2.5
0.361
16.376
14.933
15.394
1.534
1.353
15.5
All dimensions stated in are mm (millimetre)
M18 Fine Pitch Dimensions
All dimensions stated in are mm (millimetre)
ISO Metric Thread profile
d=D: Major Diameter
p: Pitch
r: Root Radius
d2=D2: Pitch Diameter
d3: Minor Diameter Male Thread
D1: Minor Diameter Female Thread
h3: Thread Height Male
H1: Thread Height Female
Major Diameter
The Major Diameter is the largest diameter on the thread and is measured from the thread crest to crest (peak of the thread).
Pitch
This is the distance (mm) from one thread to the next, this can be measured from tip to tip or groove to groove. Pitch can also be defined as TPI, which stands for threads per inch.
Minor Diameter
Minor Diameter is the smallest diameter on the thread and is measured from the thread root to root (Bottom of the thread).
Thread Angle
The angle between the thread faces. 60 degrees in the example above.
Right-Hand Thread
The thread will assemble when rotated clockwise. "righty tighty lefty loosely"
Left-Hand Thread
The thread will assemble when rotated counter-clockwise.
Frequently Asked Questions
What is the pitch of an M18 thread?
The pitch for an M18 thread is 2.5 mm.
What is the tap drill for an M18 thread?
The tap drill for an M18 thread is 15.5 mm.
What size is a clearance hole for an M18 thread?
The clearance drill for an M18 thread is 20 mm.
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