On this page we have
listed dimensions for sizes of various thread forms which may help you identify
those more awkward screws etc.
Many customers send
us samples to identify - we provide this service free of charge, and can almost
always source matching nuts and screws. Samples should be sent to the address at
the bottom of our home page.
Some Explanation of Terms Used
These are intended to give some basic guidance to
customers that may be unfamiliar with the technical details of the many screw
thread forms available.
We could fill this page with masses of technical thread
data, but some basic definition of the terms used in the table below will
hopefully give enough guidance without putting you to sleep !
If you do require more in depth data, please do not
hesitate to
e mail us with your
questions.
Please also remember that we are happy identify samples
sent to us by post at no cost.
We now stock a range of taps and dies to match our
metric, UNC, UNF and BA fixings range (other threads also available on request) - please
click
here for details.
| 'Nom
Dia' |
This is the nominal diameter over
the thread, i.e. the approx diameter over the thread peaks. In practice if
measured very accurately, the diameter across the tips of the thread peaks
will be very slightly less than the nominal diameter |
|
'Pitch' |
The distance between the peaks of adjacent
threads. |
| 'TPI' |
A term often stated for threads = Threads per Inch. 25.4
divided by the TPI figure will give the pitch dimension in millimetres. |
| Tap
Drill |
The diameter of the drill required to give the
correct pilot hole before tapping to the specified thread size and form.
The sizes listed below are the standard size for maximum thread
engagement. Larger sizes can be used for increased tap life but
reduced thread engagement. Our drill bits page lists alternative sizes for
65% engagement for non critical applications. |
The
information below is given in good faith, however we accept no responsibility
for any consequences of its use.
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| Metric
Coarse Pitch |
|
British
Association (BA) |
| Size |
Nom |
Pitch |
Tap
Drill |
|
Size |
Nom |
Pitch |
Tap Drill |
| ref |
Dia
(mm) |
(mm) |
Dia
(mm) |
|
ref |
Dia
(mm) |
(mm) |
Dia (mm) |
| M1 |
1.0 |
0.25 |
0.75 |
|
12 |
1.3 |
0.28 |
|
| M1.6 |
1.6 |
0.35 |
1.25 |
|
11 |
1.5 |
0.31 |
|
| M2 |
2.0 |
0.4 |
1.6 |
|
10 |
1.7 |
0.35 |
1.35 |
| M2.5 |
2.5 |
0.45 |
2.05 |
|
9 |
1.9 |
0.39 |
1.5 |
| M3 |
3.0 |
0.5 |
2.5 |
|
8 |
2.2 |
0.43 |
1.8 |
| M3.5 |
3.5 |
0.6 |
2.9 |
|
7 |
2.5 |
0.48 |
2.0 |
| M4 |
4.0 |
0.7 |
3.3 |
|
6 |
2.8 |
0.53 |
2.3 |
| M5 |
5.0 |
0.8 |
4.5 |
|
5 |
3.2 |
0.59 |
2.6 |
| M6 |
6.0 |
1.0 |
5.0 |
|
4 |
3.6 |
0.66 |
3.0 |
| M8 |
8.0 |
1.25 |
6.8 |
|
3 |
4.1 |
0.73 |
3.4 |
| M10 |
10.0 |
1.5 |
8.5 |
|
2 |
4.7 |
0.81 |
4.0 |
| M12 |
12.0 |
1.75 |
10.2 |
|
1 |
5.3 |
0.9 |
4.4 |
| M16 |
16.0 |
2.0 |
14.0 |
|
0 |
6.0 |
1.0 |
5.0 |
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| Unified
Coarse (UNC) |
|
Unified
Fine (UNF) |
| Size |
Nom |
Pitch |
Tap Drill |
|
Size |
Nom |
Pitch |
Tap
Drill |
| ref |
Dia
(mm)* |
(mm)* |
Dia (mm) |
|
ref |
Dia
(mm)* |
(mm)* |
Dia
(mm) |
| 1-64 |
1.854 |
0.397 |
1.6 |
|
0-80 |
1.524 |
0.318 |
1.4 |
| 2-56 |
2.184 |
0.454 |
1.8 |
|
1-72 |
1.854 |
0.353 |
1.7 |
| 3-48 |
2.515 |
0.529 |
2.1 |
|
2-64 |
2.184 |
0.397 |
2.0 |
| 4-40 |
2.845 |
0.635 |
2.3 |
|
3-56 |
2.515 |
0.454 |
2.3 |
| 5-40 |
3.175 |
0.635 |
2.65 |
|
4-48 |
2.845 |
0.529 |
2.6 |
| 6-32 |
3.505 |
0.794 |
2.8 |
|
5-44 |
3.175 |
0.577 |
2.9 |
| 8-32 |
4.166 |
0.794 |
3.5 |
|
6-40 |
3.505 |
0.635 |
3.0 |
| 10-24 |
4.826 |
1.058 |
3.9 |
|
8-36 |
4.166 |
0.706 |
3.5 |
| 12-24 |
5.486 |
1.058 |
4.5 |
|
10-32 |
4.826 |
0.794 |
4.1 |
|
1/4-20 |
6.35 |
1.27 |
5.1 |
|
12-28 |
5.486 |
0.907 |
4.7 |
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1/4-28 |
6.35 |
0.907 |
5.5 |
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| * Dia and
pitch converted from inches to 3dp, 1" = 25.4mm |
|
* Dia and
pitch converted from inches to 3dp, 1" = 25.4mm |
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