Threaded Holes Guidelines
Believe it or not, we can use a few different types of threaded holes to produce parts. While it might seem like a complex procedure, with the use of specialist CNC tools, we can apply them quickly and easily during manufacturing, meaning you can get your parts to market as soon as you need them. Continue reading to learn more about threaded holes.
Threaded Parts in 5 Easy Steps:
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Understanding thread depth: All of our threads are CNC cut using a thread mill and manually gauged during final inspection. Thread milling is more reliable than manual tapping, but for the best results thread depth is regulated to about 2.5 times the thread diameter (refer to maximum depth in the table below). Don’t worry if your hole is longer or shorter, here’s how our software will design your thread: |
QUICK THREADS: |
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Blind hole <Ø×2.5Threaded to the end (the last thread will stop about 0.25 mm from the end or drill tip). |
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Blind hole >Ø×2.5The first portion of the hole will be threaded (to a depth of about Ø×2.5 ) or refer to MAX THREAD DEPTH in the table below). |
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Through hole <Ø×2.5Completely threaded. |
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Through hole >Ø×2.5If both sides are accessible, either/or both sides can be selected:
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Through hole >Ø×5For longer holes the threads will be cut to the maximum depth possible (about Ø×2.5). |
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Tip for increasing overall thread depthAdding a counter bore will enable the thread tool to reach further. A counter bore, or countersink, is also a great Design for Assembly (DfA) feature. |
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Coil and key inserts
Coil inserts (HELICOIL®) and key inserts can provide a more durable thread in softer materials. We can machine insert ready threads, these can be selected using our interactive quote.
We will also supply and fit a range of standard metric HELICOIL® inserts, with a thread length of 1 × thread diameter (D), 1.5D and 2D. If you require fitted inserts, let us know by using the special instructions button on your quote; please include insert length and location information.
Other considerations:
Occasionally part features or fixturing will obstruct the thread tools, if a hole cannot be threaded we show this by omitting the thread on the interactive quotation.
For threading on turned parts simply model the nominal diameter; there is no need to model the threads.
Our standardised toolset enables incredibly quick CNC manufacturing (as quick as same day) however it also means we can only provide the threads listed, left handed threads, diameters or pitches not listed are not currently possible.
We can only support modelled threads larger than M12 or UNC ½”-13 (½” Unified Course by 13 Thread Per Inch (TPI)) or greater – they will be milled using a ball cutter.
We are unable to support .SLT file formats
What is the minimum thread depth? Our software will recognise threadable holes that have a depth of at least 1.5 x thread pitch.
What is the recommended minimum thread depth? The recommended minimum depth for a strong thread is 1 x diameter for steels and hard metals, 2 x diameter for aluminium alloys and soft metals and as deep as possible for plastics: 2.5 x Ø (a Helicoil® insert is recommended to further increase thread strength and durability in soft materials).
Internal Metric
Thread Pitch
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Process | Max Thread depth | CAD Ø * | Eligible Ø | Clearance Ø | ||
---|---|---|---|---|---|---|---|
MILLING | TURNING | MIN | MAX | ||||
Internal metric: standard or coarse - all dimensions in mm |
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M1.6 x 0.35** | Soft** | 3.00 | 1.25 | 1.22 | 1.32 | 1.65 | |
M2 x0.4 |
✓ | 5.08 | 1.60 | 1.57 | 1.68 | 2.05 | |
M2.5 x 0.45 |
✓ | 5.08 | 2.05 | 2.01 | 2.14 | 2.60 | |
M3 x 0.5 |
✓ | ✓ | 7.62 | 2.50 | 2.46 | 2.60 | 3.10 |
M3.5 x 0.6 |
✓ | ✓ | 10.16 | 2.90 | 2.85 | 3.01 | 3.60 |
M4 x 0.7 |
✓ | ✓ | 10.16 | 3.30 | 3.24 | 3.42 | 4.10 |
M5 x 0.8 |
✓ | ✓ | 15.24 / 10.16T* | 4.20 | 4.14 | 4.33 | 5.10 |
M6 x 1.0 |
✓ | on-axis only | 16.51 / 12.27T* | 5.00 | 4.92 | 5.15 | 6.10 |
M8 x 1.25 |
✓ | on-axis only | 16.51 / 12.27T* | 6.80 | 6.65 | 6.91 | 8.20 |
M10 x 1.5 |
✓ | 25.40 | 8.50 | 8.38 | 8.68 | 10.20 | |
M12 x 1.75 |
✓ | 25.40 | 10.20 | 10.00 | 10.44 | 12.20 | |
Internal metric: fine or special - all dimensions in mm |
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M8 x 1.0 FINE |
Metal*** | on-axis only | 16.51 | 7.00 | 6.91 | 7.16 | 8.20 |
M10 x 1.25 FINE |
Metal*** | on-axis only | 25.40 | 8.75 | 8.65 | 8.91 | 10.20 |
M12 x 1.25 FINE |
Metal*** | 25.40 | 10.75 | 10.65 | 10.91 | 12.20 |
Obstruction by other features of your part, lead-in treatments, or fixturing requirements may reduce the maximum depth of threads.
* also known as - Pilot Hole Drill Ø
Soft** Only available in soft metals
Metal *** -Only available in metal materials (both hard and soft)
T* - Turned
The Minimum Ø and Maximum Ø are the limits our software uses to recognise holes that can be threaded
The maximum thread depth is the limit of our thread cutting tools, starting from the hole face selected, excluding any chamfers of counter bores. Your hole should be deeper than this depth to allow for swarf. Even if you model a deeper hole, only the first portion will be threaded.
Coil insert metric
Coil inserts are not supplied, as standard.
We can supply and fit helicoils to all threads marked #, please request when quoting using the special instructions textbox.
Thread Pitch
|
Process | Max Thread depth | CAD Ø | Eligible Ø | Clearance Ø | ||
---|---|---|---|---|---|---|---|
MILLING | TURNING | MIN | MAX | ||||
Internal metric: standard or coarse - all dimensions in mm |
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M2 x 0.4 | ✓# | 5.08 | 2.14 | 2.09 | 2.14 | 2.05 | |
M2.5 x 0.45 | ✓# | ✓# | 7.62 | 2.6 | 2.55 | 2.65 | 2.60 |
M3 x 0.5 | ✓# | ✓# | 10.16 | 3.18 | 3.11 | 3.25 | 3.10 |
M3.5 x 0.6 | ✓ | ✓ | 15.24 / 10.16T* | 3.7 | 3.68 | 3.79 | 3.60 |
M4 x 0.7 | ✓# | ✓# | 15.24 / 10.16T* | 4.24 | 4.15 | 4.33 | 4.10 |
M5 x 0.8 | ✓# | ✓# | 16.51 / 10.16T* | 5.27 | 5.17 | 5.37 | 5.10 |
M6 x 1.0 | ✓# | on-axis only # | 16.51 / 12.7T* | 6.31 | 6.22 | 6.41 | 6.10 |
M8 x 1.25 | ✓# | on-axis only # | 25.4 / 12.7T* | 8.38 | 8.27 | 8.48 | 8.20 |
M10 x 1.5 | ✓# | 30.48 | 10.56 | 10.33 | 10.56 | 10.20 | |
M12 x 1.75 | ✓# | 30.48 | 12.51 | 12.38 | 12.64 | 12.20 |
* also known as Pilot Hole Drill Ø
T* - Turning
✓ = Threads are available: Outside diameter (on-axis), inside diameter: on axis, axial and radial.
# = Helicoil® thread inserts can be fitted on request, and are available with a thread length of 1 × thread diameter (D), 1.5D and 2D.
Outside diameter metric
Thread Pitch
|
Process | Max Thread depth | CAD Ø | Eligible Ø | Clearance Ø | ||
---|---|---|---|---|---|---|---|
MILLING | TURNING | MIN | MAX | ||||
Metric outside diameter: standard or coarse - all dimensions in mm |
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M3.5 x 0.6 |
✓ | 7 | 3.5 | 3.35 | 3.53 | 3.60 | |
M4 x 0.7 |
✓ | 8 | 4 | 3.84 | 4.03 | 4.10 | |
M5 x 0.8 |
✓ | 10 | 5 | 4.83 | 5.03 | 5.10 | |
M6 x 1.0 |
✓ | 12 | 6 | 5.79 | 6.02 | 6.10 | |
M8 x 1.25 |
✓ | 16 | 8 | 7.76 | 8.03 | 8.20 | |
M10 x 1.5 |
✓ | 20 | 10 | 9.73 | 10.03 | 10.20 | |
M12 x 1.75 |
M* | ✓ | 24 | 12 | 11.7 | 12.02 | 12.20 |
M14 x 2.0 |
M* | ✓ | 28 | 14 | 13.68 | 14.03 | 14.25 |
M16 x 2.0 |
M* | ✓ | 32 | 16 | 15.68 | 16.02 | 16.25 |
M20 x 2.5 |
M* | ✓ | 40 | 20 | 19.62 | 20.03 | 20.25 |
Metric outside diameter: fine or special - all dimensions in mm |
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M8 x 1.0 FINE |
✓ | 16 | 8 | 7.8 | 8.03 | 8.20 | |
M10 x 0.75 SP |
✓ | 20 | 10 | 9.84 | 10.03 | 10.20 | |
M10 x 1.25 FINE |
✓ | 20 | 10 | 9.76 | 10.03 | 10.20 | |
M12 x 1.25 FINE |
✓ | 24 | 12 | 11.76 | 12.02 | 12.20 | |
M12 x 1.0 SP |
✓ | 24 | 12 | 11.79 | 12.02 | 12.20 | |
M12 x 1.5 SP |
M* | ✓ | 24 | 12 | 11.73 | 12.02 | 12.20 |
M14 x 1.5 FINE |
M* | ✓ | 28 | 14 | 13.73 | 14.03 | 14.25 |
M15 x 1.0 SP |
M* | ✓ | 30 | 15 | 14.79 | 15.03 | 15.25 |
M16 x 1.5 FINE |
M* | ✓ | 32 | 16 | 15.73 | 16.02 | 16.25 |
M17 x 1.0 SP |
M* | ✓ | 34 | 17 | 16.79 | 17.03 | 17.25 |
M18 x 1.5 FINE |
M* | ✓ | 36 | 18 | 17.73 | 18.03 | 18.25 |
M20 x 1.5 FINE |
M* | ✓ | 40 | 20 | 19.73 | 20.03 | 20.25 |
*also known as - Pilot Hole Drill Ø
M* On a 3 or 5-axis mill larger external threads can be cut with a ball nose cutter… refer to Special threads.
Internal Inch
Thread Pitch
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Process | Max Thread depth | CAD Ø | Eligible Ø | Clearance Ø | ||
---|---|---|---|---|---|---|---|
MILLING | TURNING | MIN | MAX | ||||
Internal inch: unified fine UNF - all dimensions in inches |
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#2-64 | ✓ | 0.20 | 0.072 | 0.069 | 0.075 | 0.09 | |
#3-56 | ✓ | 0.20 | 0.083 | 0.080 | 0.084 | 0.10 | |
#4-48 | ✓ | ✓ | 0.30 | 0.093 | 0.087 | 0.099 | 0.12 |
#5-44 | ✓ | ✓ | 0.30 | 0.104 | 0.100 | 0.104 | 0.13 |
#6-40 | ✓ | ✓ | 0.40 | 0.115 | 0.111 | 0.119 | 0.14 |
#8-36 | ✓ | ✓ | 0.40 | 0.138 | 0.134 | 0.142 | 0.17 |
#10-32 | ✓ | ✓ | 0.60 | 0.160 | 0.156 | 0.164 | 0.19 |
#12-28 | ✓ | on-axis only | 0.6 / 0.5T* | 0.182 | 0.177 | 0.186 | 0.22 |
1/4-28 | ✓ | on-axis only | 0.65 | 0.216 | 0.211 | 0.220 | 0.26 |
5/16-24 | ✓ | on-axis only | 0.65 /0.5T* | 0.272 | 0.267 | 0.277 | 0.32 |
3/8-24 | ✓ | on-axis only | 1 / 0.5T* | 0.335 | 0.330 | 0.340 | 0.38 |
7/16-20 | ✓ | on-axis only | 1 / 0.5T* | 0.389 | 0.383 | 0.395 | 0.44 |
1/2-20 | ✓ | on-axis only | 1.2 / 0.5T* | 0.452 | 0.446 | 0.457 | 0.51 |
Internal inch: unified coarse UNC - all dimensions in inches |
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#2-56 | ✓ | 0.20 | 0.070 | 0.067 | 0.074 | 0.09 | |
#3-48 | ✓ | 0.20 | 0.082 | 0.076 | 0.084 | 0.10 | |
#4-40 | ✓ | ✓ | 0.30 | 0.089 | 0.085 | 0.094 | 0.12 |
#5-40 | ✓ | ✓ | 0.30 | 0.102 | 0.098 | 0.104 | 0.13 |
#6-32 | ✓ | ✓ | 0.40 | 0.109 | 0.105 | 0.114 | 0.14 |
#8-32 | ✓ | ✓ | 0.40 | 0.135 | 0.130 | 0.139 | 0.17 |
#10-24 | ✓ | 0.60 | 0.151 | 0.145 | 0.156 | 0.19 | |
#12-24 | ✓ | on-axis only | 0.6 / 0.5T* | 0.176 | 0.171 | 0.181 | 0.22 |
1/4-20 | ✓ | on-axis only | 0.65 / 0.5T* | 0.202 | 0.196 | 0.207 | 0.26 |
5/16-18 | ✓ | 0.65 | 0.259 | 0.252 | 0.265 | 0.32 | |
3/8-16 | ✓ | 1.00 | 0.314 | 0.307 | 0.321 | 0.38 | |
7/16-14 | ✓ | 1.00 | 0.372 | 0.360 | 0.376 | 0.44 | |
1/2-13 | ✓ | 1.00 | 0.426 | 0.417 | 0.434 | 0.51 |
* also known as Pilot Hole Drill Ø
T* - Turning
Coil Insert Inch
Coil inserts are not supplied
Thread Pitch
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Process | Max Thread depth | CAD Ø | Eligible Ø | Clearance Ø | ||
---|---|---|---|---|---|---|---|
MILLING | TURNING | MIN | MAX | ||||
Inch coil insert: unified fine UNF - all dimensions in inches |
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#2-64 |
✓ | ✓ | 0.30 | 0.093 | 0.089 | 0.095 | N/A |
#3-56 |
✓ | ✓ | 0.30 | 0.104 | 0.102 | 0.104 | N/A |
#4-48 |
✓ | ✓ | 0.40 | 0.120 | 0.116 | 0.123 | N/A |
#6-40 |
✓ | ✓ | 0.60 | 0.147 | 0.144 | 0.150 | N/A |
#8-36 |
✓ | ✓ | 0.60 | 0.173 | 0.170 | 0.177 | N/A |
#10-32 |
✓ | ✓ | 0.65 | 0.201 | 0.196 | 0.204 | N/A |
1/4-28 |
✓ | on-axis only | 0.65 | 0.261 | 0.257 | 0.265 | N/A |
5/16-24 |
✓ | on-axis only | 1.00 | 0.325 | 0.321 | 0.329 | N/A |
3/8-24 |
✓ | on-axis only | 1.00 | 0.388 | 0.384 | 0.391 | N/A |
#7/16-20 |
✓ | on-axis only | 1.00 | 0.452 | 0.448 | 0.456 | N/A |
1/2-13 |
✓ | on-axis only | 1.00 | 0.426 | 0.417 | 0.434 | N/A |
Inch coil insert: unified coarse UNC - all dimensions in inches |
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#2-56 |
✓ | ✓ | 0.30 | 0.091 | 0.090 | 0.096 | N/A |
#3-48 |
✓ | ✓ | 0.40 | 0.107 | 0.105 | 0.110 | N/A |
#4-40 |
✓ | ✓ | 0.40 | 0.119 | 0.117 | 0.125 | N/A |
#5-40 |
✓ | ✓ | 0.40 | 0.132 |
0.131 |
0.137 | N/A |
#6-32 |
✓ | ✓ | 0.60 | 0.147 | 0.145 | 0.153 | N/A |
#8-32 |
✓ | ✓ | 0.60 | 0.173 | 0.171 | 0.178 | N/A |
#10-24 |
✓ | on-axis only | 0.65 | 0.201 | 0.199 | 0.208 | N/A |
#12-24 |
✓ | on-axis only | 0.65 | 0.227 | 0.225 | 0.234 | N/A |
1/4-20 |
✓ | on-axis only | 0.65 | 0.266 | 0.261 | 0.270 | N/A |
5/16-18 |
✓ | 1.00 | 0.332 | 0.324 | 0.334 | N/A | |
3/8-16 |
✓ | 1.20 | 0.397 | 0.389 | 0.399 | N/A | |
7/16-14 |
✓ | 1.20 | 0.453 | 0.453 | 0.464 | N/A | |
1/2-13 |
✓ | 1.20 | 0.531 | 0.515 | 0.531 | N/A |
* * also known as - Pilot Hole Drill Ø
Key Insert Inch
Key inserts are not supplied
Thread Pitch
|
Process | Max Thread depth | CAD Ø | Eligible Ø | Clearance Ø | ||
---|---|---|---|---|---|---|---|
MILLING | TURNING | MIN | MAX | ||||
Inch key insert: Unified fine UNF - all dimensions in inches |
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#10-32 |
✓ | 0.600 | 0.162 | 0.160 | 0.164 | N/A | |
#12-28 |
✓ | 0.600 | 0.189 | 0.186 | 0.191 | N/A | |
1/4-28 |
✓ | 0.650 | 0.229 | 0.227 | 0.231 | N/A | |
Inch key insert: Unified coarse UNC - all dimensions in inches |
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#8-32 |
✓ | 0.400 | 0.135 | 0.133 | 0.137 | N/A | |
5/16-18 |
✓ | 0.650 | 0.274 | 0.271 | 0.276 | N/A | |
3/8-16 |
✓ | 1.000 | 0.334 | 0.331 | 0.336 | N/A | |
7/16-14 |
✓ | 1.000 | 0.399 | 0.396 | 0.401 | N/A | |
1/2-13 |
✓ | 1.000 | 0.455 | 0.452 | 0.457 | N/A |
* * also known as - Pilot Hole Drill Ø
Outside diameter inch
Thread Pitch
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Process | Max Thread depth | CAD Ø | Eligible Ø | Clearance Ø | ||
---|---|---|---|---|---|---|---|
MILLING | TURNING | MIN | MAX | ||||
Inch outside diameter: unified fine UNF - all dimensions in inches |
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#5-44 |
✓ | 0.250 | 0.125 | 0.12 | 0.126 | 0.13 | |
#6-40 |
✓ | 0.280 | 0.138 | 0.132 | 0.139 | 0.14 | |
#8-36 |
✓ | 0.330 | 0.164 | 0.158 | 0.165 | 0.17 | |
#10-32 |
✓ | 0.380 | 0.190 | 0.183 | 0.191 | 0.19 | |
#12-28 |
✓ | 0.430 | 0.216 | 0.209 | 0.217 | 0.22 | |
1/4-28 |
✓ | 0.500 | 0.250 | 0.243 | 0.251 | 0.26 | |
5/16-24 |
✓ | 0.630 | 0.313 | 0.304 | 0.314 | 0.32 | |
3/8-24 |
✓ | 0.750 | 0.375 | 0.367 | 0.376 | 0.38 | |
7/16-20 |
✓ | 0.880 | 0.438 | 0.428 | 0.439 | 0.44 | |
1/2-20 |
M* | ✓ | 1.000 | 0.500 | 0.491 | 0.501 | 0.51 |
5/8-18 |
M* | ✓ | 1.250 | 0.625 | 0.615 | 0.626 | 0.64 |
3/4-16 |
M* | ✓ | 1.500 | 0.750 | 0.739 | 0.751 | 0.76 |
Inch outside diameter: fine or special UNC - all dimensions in inches |
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#4-40 |
✓ | 0.22 | 0.112 | 0.106 | 0.113 | 0.12 | |
#5-40 |
✓ | 0.25 | 0.125 | 0.119 | 0.126 | 0.13 | |
#6-32 |
✓ | 0.28 | 0.138 | 0.131 | 0.139 | 0.14 | |
#8-32 |
✓ | 0.33 | 0.164 | 0.157 | 0.165 | 0.17 | |
#10-24 |
✓ | 0.38 | 0.190 | 0.182 | 0.191 | 0.19 | |
#12-24 |
✓ | 0.43 | 0.216 | 0.208 | 0.217 | 0.22 | |
1/4-20 |
✓ | 0.50 | 0.250 | 0.241 | 0.251 | 0.26 | |
5/16-18 |
✓ | 0.63 | 0.313 | 0.303 | 0.314 | 0.32 | |
3/8-16 |
✓ | 0.75 | 0.375 | 0.364 | 0.376 | 0.38 | |
7/16-14 |
✓ | 0.88 | 0.438 | 0.426 | 0.439 | 0.44 | |
1/2-13 |
M* | ✓ | 1.00 | 0.500 | 0.488 | 0.501 | 0.51 |
5/8-11 |
M* | ✓ | 1.25 | 0.625 | 0.611 | 0.626 | 0.64 |
3/4-10 |
M* | ✓ | 1.50 | 0.750 | 0.735 | 0.751 | 0.76 |
*also known as - Pilot Hole Drill Ø
M* On a 3 or 5-axis mill larger external threads can be cut with a ball nose cutter… refer to Special threads.
Outside diameter special threads
External threads can be milled, this normally only works well for larger threads, as these will be milled using a ball end cutter (M4 is the absolute minimum, but ideally M12 and above). Your thread will have radii in the root, so might need cleaning up with a die. We can mill most custom threads or helical forms that you can model – on the lathe, 5-axis mill or 3-axis. External 3-axis milled threads are produced on the half diameter. The part is then rotated 180 degrees, re-referenced, and the other half milled.
On parts that require externally milled threads, you must design the threads on your part. We manufacture your design using flat and ball end mills. It is not the preferred method for producing threads, but can be useful for producing ¼ turn fasteners or helical and camming features.
The CAD file should then be submitted in a 3D file format other than STL; we accept most native CAD formats or a standard file formats such as IGES or STEP are also great.
Note: for standard threads only model the drill or outside diameter, we are unable to manufacture standard threads that have been modelled.