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Guidelines for Threaded Holes in CNC Machining

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 the manufacturing process. This means you can get your parts to market as soon as you need them. Continue reading to learn more about threaded holes.

Standard Holes mm

/ Standard Holes in

Coil Inserts mm

/ Coil inserts in

 

Key Inserts in

 

* Milling Only

OD Threads mm

/ OD Threads in

* Turning Only

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Threaded Parts in 5 Easy Steps: Model holes in your CAD design using the pilot hole diameter (listed below) Upload your CAD quotation Our software will automatically show which threads are eligible On the interactive quote select the holes you need to thread (or select all) The thread depth is shown on the quote along with the price	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:
		Easy: Select all of your threaded holes with a single drop down Specific: Or select specific threads by clicking on the CAD model Quick: No need to 2D drawings, or text explanation Wide range: We offer a range of metric, metric fine, unified fine and coarse (UNF/UNC) Right Handed: All threads will be right handed

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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).

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Internal Metric 

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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.

 

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Outside diameter metric

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Internal Inch

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Coil Insert Inch

Coil inserts are not supplied

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Key Insert Inch

Key inserts are not supplied

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Outside diameter inch

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 indexed mill or 3-axis.

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.