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Thread Data
On this page we have
listed dimensions for sizes of various thread forms which may help you identify
those more awkward screws etc.
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Sending us a sample for
identification
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.
Please make sure that samples are very well wrapped
- if they are sent in a plain paper envelope with
no additional packing they almost certainly will not reach us intact as the post
office sorting machinery
will push the sample through the side of the envelope.
Please also make sure you stamp your package using the appropriate postage rate,
taking note that any envelopes posted in the UK over 5mm in thickness must be
stamped at 'large letter' rate, and over 25m thick at 'packet' rate.
If you need the sample returned, please include a stamps to the appropriate
value. If you order items following our advice regarding your sample, the
stamp value will be deducted from our shipping cost.
You must also include an e mail address so
we can contact you.
Further information on UK postage rates are
available
here |
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. 25.4 divided by the pitch in millimetres figure will give the TPI
figure. |
| '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 |
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Metric Fine Pitch |
| 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 |
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M2 |
2.0 |
0.45* |
1.55 |
| M1.6 |
1.6 |
0.35 |
1.25 |
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M2.3 |
2.3 |
0.4 |
1.9 |
| M2 |
2.0 |
0.4 |
1.6 |
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M2.6 |
2.6 |
0.45 |
2.15 |
| M2.5 |
2.5 |
0.45 |
2.05 |
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M3 |
3.0 |
0.35 |
2.65 |
| M3 |
3.0 |
0.5 |
2.5 |
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M3 |
3.0 |
0.6* |
2.4 |
| M3.5 |
3.5 |
0.6 |
2.9 |
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M4 |
4.0 |
0.5 |
3.5 |
| M4 |
4.0 |
0.7 |
3.3 |
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M4 |
4.0 |
0.75* |
3.25 |
| M5 |
5.0 |
0.8 |
4.2 |
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M5 |
5.0 |
0.5 |
4.5 |
| M6 |
6.0 |
1.0 |
5.0 |
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M5 |
5.0 |
0.75 |
4.25 |
| M8 |
8.0 |
1.25 |
6.8 |
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M6 |
6.0 |
0.75 |
5.25 |
| M10 |
10.0 |
1.5 |
8.5 |
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M8 |
8.0 |
0.75 |
7.25 |
| M12 |
12.0 |
1.75 |
10.2 |
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M10 |
10.0 |
1.25 |
8.75 |
| M16 |
16.0 |
2.0 |
14.0 |
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M12 |
12.0 |
1.5 |
10.5 |
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Please note that
this is not an exhaustive list and other pitches are available
for some diameters.
Pitches marked with a * are actually coarser
than the metric coarse equivalent
size - this is not an error! |
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| Unified
Coarse (UNC) |
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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 |
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2-64 |
2.184 |
0.397 |
2.0 |
| 4-40 |
2.845 |
0.635 |
2.3 |
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3-56 |
2.515 |
0.454 |
2.3 |
| 5-40 |
3.175 |
0.635 |
2.65 |
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4-48 |
2.845 |
0.529 |
2.6 |
| 6-32 |
3.505 |
0.794 |
2.8 |
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5-44 |
3.175 |
0.577 |
2.9 |
| 8-32 |
4.166 |
0.794 |
3.5 |
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6-40 |
3.505 |
0.635 |
3.0 |
| 10-24 |
4.826 |
1.058 |
3.9 |
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8-36 |
4.166 |
0.706 |
3.5 |
| 12-24 |
5.486 |
1.058 |
4.5 |
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10-32 |
4.826 |
0.794 |
4.1 |
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1/4-20 |
6.35 |
1.27 |
5.1 |
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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 |
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* Dia and
pitch converted from inches to 3dp, 1" = 25.4mm |
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British Standard Whitworth (BSW) |
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British Standard Fine (BSF) |
| Size |
Nom |
Pitch |
Tap
Drill |
|
Size |
Nom |
Pitch |
Tap
Drill |
| ref |
Dia
(mm)* |
(mm)* |
Dia
(mm) |
|
ref |
Dia
(mm)* |
(mm)* |
Dia
(mm) |
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1/16" |
1.588 |
0.423 |
1.2 |
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3/16" |
4.763 |
0.794 |
4.0 |
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3/32" |
2.381 |
0.529 |
1.9 |
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7/32" |
5.556 |
0.907 |
4.6 |
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1/8" |
3.175 |
0.635 |
2.55 |
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1/4" |
6.350 |
0.977 |
5.3 |
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5/32" |
3.969 |
0.794 |
3.2 |
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9/32" |
7.144 |
0.977 |
6.0 |
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3/16" |
4.763 |
1.058 |
3.7 |
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5/16" |
7.938 |
1.155 |
6.8 |
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7/32" |
5.556 |
1.058 |
4.5 |
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3/8" |
9.525 |
1.27 |
8.3 |
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1/4" |
6.350 |
1.270 |
5.1 |
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7/16" |
11.113 |
1.411 |
9.7 |
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9/32" |
7.144 |
1.27 |
5.8 |
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1/2" |
12.70 |
1.588 |
11.1 |
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5/16" |
7.938 |
1.411 |
6.5 |
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9/16" |
14.288 |
1.588 |
12.7 |
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3/8" |
9.525 |
1.588 |
7.9 |
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7/16" |
11.113 |
1.814 |
9.3 |
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1/2" |
12.70 |
2.117 |
10.5 |
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9/16" |
14.288 |
2.117 |
12.1 |
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British Association (BA) |
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Metric Spark Plug Threads |
| Size |
Nom |
Pitch |
Tap Drill |
|
Size |
Nom |
Pitch |
Tap
Drill |
| ref |
Dia
(mm) |
(mm) |
Dia (mm) |
|
ref |
Dia
(mm)* |
(mm)* |
Dia
(mm) |
| 12 |
1.3 |
0.28 |
1.05 |
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M10SP |
10.0 |
1.0 |
9.0 |
| 11 |
1.5 |
0.31 |
1.2 |
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M12SP |
12.0 |
1.25 |
10.75 |
| 10 |
1.7 |
0.35 |
1.4 |
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M14SP |
14.0 |
1.25 |
12.75 |
| 9 |
1.9 |
0.39 |
1.55 |
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M18SP |
18.0 |
1.5 |
16.5 |
| 8 |
2.2 |
0.43 |
1.8 |
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| 7 |
2.5 |
0.48 |
2.05 |
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Metric Conduit Threads |
| 6 |
2.8 |
0.53 |
2.3 |
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Size |
Nom |
Pitch |
Tap
Drill |
| 5 |
3.2 |
0.59 |
2.64 |
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M16C |
16.0 |
1.5 |
14.5 |
| 4 |
3.6 |
0.66 |
3.0 |
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M20 |
20.0 |
1.5 |
18.5 |
| 3 |
4.1 |
0.73 |
3.4 |
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M25C |
25.0 |
1.5 |
23.5 |
| 2 |
4.7 |
0.81 |
4.0 |
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M32C |
32.0 |
1.5 |
30.5 |
| 1 |
5.3 |
0.9 |
4.4 |
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| 0 |
6.0 |
1.0 |
5.1 |
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This page was last modified on :
December 23, 2012
