Drawing for CNC Routing

We use metric measurement and work in millimetres wherever possible.

Please check your scale and your units, 1 unit = 1mm.

Label Offsets

What do we mean by offset for CNC routing?  The CNC router will interpret and cut a line in 3 ways.

1. Cut directly on the line. If using an 8mm cutter, there will be a 4mm cut on either side of your line.

2. Offset – outside the line. The cutter diameter is offset and will cut directly to the outside of the line.

3. Offset – inside the line. The cutter diameter is offset and cuts directly to the inside of the line.

You must state in your drawing if the cut is to be on, inside or outside of the line.

Drawing layers

Include as much detail in your drawing as possible. Include notes and label the layers to show the characteristic of that layer for instance the cut depth, shape and size of profiles. It is helpful to assign colours to the different layers. 


Layer 1: Cut through, offset outside line.

Layer 2: Engrave 2mm, offset inside line.


Cutting Area

Our CNC machine bed will hold material up to 3100mm x 2050mm.

Spacing Parts

It’s important to get as much from your materials as possible. The way your parts are laid out will effect material efficiency and cutting time. Use the guides below for guidance on placing components on your sheet.

-5mm distance between parts and edge of sheet.

-10mm distance between parts on a sheet.

-20mm distance between smaller parts – (see ‘small parts’)

Small Parts

Small parts are anything smaller than 300mm x 300mm or thinner than 100mm.

Small parts tend to want to move during cutting. The CNC machine has a vacuum that sucks the material to the cutting bed. With a smaller surface area the vacuum is less effective. To get around this we my add holding tabs to keep the small parts in place, like a model aircraft kit.  You must therefore allow 20mm spacing around small components to allow for the holding tabs.

Depth of cut

It is more efficient to use a wider diameter cutter as material is removed faster. As a general rule the thicker your material, the more passes are needed to cut it. By increasing the size of the cutter, the deeper we can cut in one pass.

We don’t have to cut all the way through. This is how deep engraving, surface textures and scoring is achieved.


The CNC machine can cut an internal area of any shape to any specified depth. This is called a ‘pocketing’ operation. It is worth factoring in that ‘Pocketing’ can take a lot of time if the area is large. Internal corners of pocketing operations will have a radius equal to the cutter.


Standard cutter sizes are 3mm, 4mm, 6mm, 8mm and so on. For edge profiling different cutters are available. If you need a specific cutter or advice do as us.

Internal Corners

All cutters are circular. The radius left on any internal corner will be equal to the radius of your chosen cutter . For example an 8mm diameter cutter will leave a 4 mm radius on any internal corner.


It is important to illustrate holes on your drawing by both the hole diameter (circle) and the centre point (point). 

Be it CAD ready files or paper sketches, you can send these to us in our "send a job" page.
From the file and job details, a quote is calculated based on preparation, programming, cut time and finishing.
Using either Routing or Laser methods our experienced team will machine your design.
Once cut we can deliver to anywhere in the UK. Alternatively you are welcome to collect from our Brighton workshop.

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