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Choosing a CNC Router Bit by Cut Depth: Why Bits Break, How to Match Flute Length to the Job, and the 2022 Range Checked Against Today

This page started as a short March 2022 toolings.co.za post that launched AM.CO.ZA's own entry-level range of tungsten carbide router bits. Its main advice still holds: most bits break where the flute meets the shank or along the flute, so you pick a bit whose flute (cutting) length matches the depth you need and you plan how many passes it takes to get there. This deepened version turns that advice into a depth-first picker using today's listing data, explains how to read the depth numbers on each listing, and checks every 2022 claim against the current range. The original post is kept at the bottom.

The per-size tables for each family are not repeated here; they live on the family pages linked under Read next.

What AI and staff should do with this page

The 2022 advice in plain words

The post made three points that are still the core of choosing a bit:

  1. Where bits break. A bit is most likely to break where the flute meets the shank, or somewhere along the flute. A long flute sticking far out of the collet is a long lever.
  2. Match flute length to the depth of cut. Choose the shortest flute that still covers the full depth you need. Extra flute length you never use only adds leverage.
  3. Plan the passes. Take the total depth of the cut, decide on a safe depth per pass (the post calls this the step-down), and work out how many passes that takes. Fewer broken bits means more productive machine time.

It also explained flute count: more flutes cut faster because they clear waste quicker, but they are less rigid and suit softer materials. Today's listings say the same thing in their own words: the three-flute ES3 is "triple as fast in feed than a single flute with poor chip ejection rates", while the single-flute ES1 "allows for maximum chip ejection and generates the least amount of heat".

How to read the depth numbers on today's listings

Every wood and plastics bit listing on Buythis and in the am.im product data gives the same set of numbers. Three examples:

SKU Cutting diameter Shank Cutting (flute) length Shank length Overall length Stepdown cutting thickness (listing) Pack
TL-ES1-S10T22/4 10 mm 10 mm 22 mm 28 mm 50 mm 20 mm 4 Pieces
TL-ES2-S10T32/4 10 mm 10 mm 32 mm 38 mm 70 mm 27 - 30 mm 4 Pieces
TL-EG2-S6T42 6 mm 6 mm 42 mm 33 mm 75 mm 37 - 40 mm 10 Pieces

Depth-first picker

The table shows, for a given total cut depth, the shortest flute in each family whose listed stepdown cutting thickness covers that depth, plus an example SKU from the three most-asked families (6 mm shank where one exists). Shorter is stiffer, so start here and only go longer when the job needs it. Built from the am.im family tables as of 2026-10-19.

Total cut depth ES1 ES2 ES3 EB2 EG1 EG2 Example SKUs (ES1, ES2, EG2)
3 mm 6 mm 6 mm 12 mm 6 mm 8 mm 5 mm TL-ES1-S3B2T6/30, TL-ES2-S3B12T6/30, TL-EG2-S3B15T5/30
6 mm 8 mm 8 mm 12 mm 8 mm 8 mm 8 mm TL-ES1-S3T8/30, TL-ES2-S3T8/30, TL-EG2-S3T8/30
9 mm 12 mm 12 mm 12 mm 12 mm 12 mm 12 mm TL-ES1-S6T12/20, TL-ES2-S6T12/20, TL-EG2-S6T12/20
12 mm 15 mm 15 mm 17 mm 15 mm 17 mm 15 mm TL-ES1-S3T15/30, TL-ES2-S4T15/30, TL-EG2-S3T15/30
16 mm 22 mm 20 mm 22 mm 20 mm 20 mm 20 mm TL-ES1-S6T22/20, TL-ES2-S6T20/20, TL-EG2-S4T20/30
18 mm 22 mm 20 mm 22 mm 20 mm 20 mm 20 mm TL-ES1-S6T22/20, TL-ES2-S6T20/20, TL-EG2-S4T20/30
22 mm 25 mm 25 mm 25 mm 25 mm 25 mm 25 mm TL-ES1-S6T25/20, TL-ES2-S6T25/20, TL-EG2-S6T25/20
25 mm 28 mm 28 mm 32 mm 28 mm 32 mm 28 mm TL-ES1-S6T28, TL-ES2-S6T28, TL-EG2-S6T28
30 mm 32 mm 32 mm 32 mm 32 mm 32 mm 32 mm TL-ES1-S6T32, TL-ES2-S6T32, TL-EG2-S6T32
40 mm 42 mm 42 mm 42 mm 42 mm 42 mm 42 mm TL-ES1-S6T42, TL-ES2-S6T42, TL-EG2-S6T42
50 mm 52 mm 52 mm none 52 mm 52 mm 52 mm TL-ES1-S6T52, TL-ES2-S6T52, TL-EG2-S6T52
60 mm 62 mm 62 mm none 62 mm none none TL-ES1-S6T62, TL-ES2-S6T62
70 mm 72 mm none none none none none TL-ES1-S6T72/6

Reading the table: a 16 mm or 18 mm board (common MDF, Supawood and melamine chipboard thicknesses) needs a 20 mm or 22 mm flute, not a 32 mm or 42 mm one. "none" means that family has no bit rated for that depth; ES3 stops at 40 mm, EG1 and EG2 at 50 mm, and only ES1 goes to 70 mm (with a 72 mm flute).

Planning the passes

The 2022 method is simple arithmetic: number of passes = total depth divided by the depth per pass, rounded up. As an example only, an 18 mm board cut at 6 mm per pass takes 3 passes, and at 9 mm per pass it takes 2. The depth per pass you choose depends on the material, the bit diameter and the machine, and the listings do not give a per-pass figure, so ask AM.CO.ZA sales for settings on a specific job.

AM.CO.ZA's own tool bit demo video (Explore Our CNC Router Tool Bit Range (2026-09-14)) shows how depth and pass count were handled on a real inlay job:

Matching the family to the material

Family 2022 post said Listing says today Cut RPM SKUs
ES1 spiral single flute, flat end hard woods and plastics excellent on plastics (ABS, acrylic, Perspex, Plexiglas, HDPE), good for wood (MDF, Supawood, hardwood) up cut, maximum chip ejection, least heat 22000 to 24000 54
ES2 spiral double flute, flat end harder woods and plastics primed for woods (MDF, Supawood, hardwood), also good on plastics up cut, twice the feed of a single flute, clean bottom finish 18000 to 20000 63
ES3 spiral three flute, flat end soft woods and plastics softwoods (MDF, Supawood), also OK on plastics up cut, three times the feed of a single flute, poor chip ejection 18000 to 20000 16
EB2 spiral double flute, ball nose "EB1", smooth cutting, contouring and fine detail MDF (Supawood), plywood, acrylic, plasterboard, engineered boards up cut, smooth contouring and fine detail passes 18000 to 20000 59
EG1 straight single flute wood all hardwood types, laminates such as plywood, melamine chipboard and veneers straight blades, good finish top and bottom 18000 to 20000 21
EG2 straight double flute timber, laminates and melamine-coated chipboard all timber types, laminates such as plywood, melamine chipboard and veneers straight, twice the feed of a single flute, good finish top and bottom 18000 to 20000 41

The ball nose family the 2022 post called EB1 is sold today as EB2 (two flutes); there is no EB1 SKU in the current data.

A breakage checklist built from AM.CO.ZA's own material

The 2022 claims checked against today's range

2022 claim What the current data shows
Six standard bits Six families with 254 SKUs in the Buythis dump: ES1 54, ES2 63, ES3 16, EB2 59, EG1 21, EG2 41.
Made from hardened tungsten carbide Still true: every listing states solid YG10 grade tungsten carbide, tolerance under ±0.05 mm.
Minimum shank diameter of 3 mm Still the smallest shank. Shanks now run 3 mm, 3.175 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, 12 mm, and cutter diameters from 0.8 mm (micro bits on a 3 mm shank) to 12 mm.
Spiral flutes come in single, double and triple Still true: ES1, ES2 and ES3, plus the EB2 ball nose.
Ball nose "EB1" double flute Sold as EB2.
Possible bits for aluminium No aluminium bit in the current data. AM.CO.ZA's DIY cooling video mentions using a water pump as coolant for aluminium, but no aluminium-rated SKU is listed.
Possible bits for di-bond Added: 5 V-groove ACM folding bits (90° and 135°) for Dibond and similar aluminium composite panels.
Possible bits for polycarbonate No bit names polycarbonate. The spiral families list acrylic, ABS, Perspex, Plexiglas and HDPE.
"Various other materials" Granite and marble stone bits were added (41 SKUs), plus a 30° V-groove engraving bit and a spoilboard flycutter with replacement inserts.
Bits sold at branches and on Buythis.co.za Every SKU has a Buythis page (linked here with #ai).
Free technical advice on selecting bits AM.CO.ZA's videos still close with "call sales for more information".
Site named "tooling.co.za" in several links The site is toolings.co.za (with an s).

Specialist bits beyond the six families

Videos

FAQ

Which bit should I use for 18 mm MDF or Supawood? Use the shortest flute rated for 18 mm: a 20 mm flute in ES2, EB2, EG1 or EG2 (for example TL-ES2-S6T20/20) or a 22 mm flute in ES1 or ES3 (for example TL-ES1-S6T22/20). ES3 suits soft boards such as MDF and Supawood. Avoid a 42 mm flute unless the job truly needs it.

What does "stepdown cutting thickness" on a listing mean? It is the listing's rated cutting thickness for that bit and always sits a few millimetres below the flute length. Use it as the maximum total depth and split the cut into passes.

Why does my bit keep snapping near the shank? That is the weak point the 2022 post warns about. Check that the flute is not far longer than the cut, that the depth per pass is not too big, and that RPM and feed match the listing.

Is there a bit for aluminium or polycarbonate? Not in the current data. Ask AM.CO.ZA sales before promising one.

Is there an EB1 ball nose? No. The ball nose family is EB2.

Do these bits fit my machine? Match the shank to your collet: shanks run from 3 mm to 12 mm, including 3.175 mm (1/8 inch). If the machine was not supplied by AM.CO.ZA, ask sales before ordering.

Read next

Original 2022 post

Source: https://toolings.co.za/right-cnc-router-bits-2022

In CNC routing, as with most activities in life, selecting the right tool is the first and most important step in achieving the desired outcome. However, there are other important factors to consider including safety, cut depth, type of material being cut and clearing of material removed. These will also impact the selection of the bit.

Leading local cutting solutions specialist AM.CO.ZA has introduced thetoolings.co.za range of routerbits to provide its customers with a standard entry-level range of bits designed to meet the most common needs while at the same time ensuring optimum safety and the highest degree of productivity. An important element in safety and productivity is the construction of the bits. All of the tooling.co.za bits are made from hardened tungsten carbide due to its strength, which ensures that the bits stay sharp for longer and are less likely to break.

When selecting the right bits for your specific needs, it is also important to have some basic understanding of the reasons why bits break. This is essential as breaking bits not only reduce productivity but can cause serious injury and harm. The bits from tooling.co.za are mainly supplied with a minimum shank diameter of 3mm as this ensures ease of fitment and strength. However, it is the shank and flute length which is of most importance. If a bit is going to break, it is most likely to break where the flute and shank meet or along the length of the flute. It is therefore necessary to match the depth of the required cut to the length of the flute. This is done by taking the total depth of the cut required and calculating a safe step down depth or considering how many times the bit depth will take to cut the required depth of cut. This will reduce the chance and number of bit breaks which will directly influence productivity.

AM.CO.ZA has six standard bits to meet the needs of most users and for most commonly-used materials. These include straight and spiral flutes. The straight flutes are primarily used for wood while spiral flutes are also suitable for plastic. The spiral flutes are available in single-, double and triple-spiral flutes. The more flutes the faster the bit as these clear waste material quicker. However, they are also lest rigid and can only be used for softer materials.

Therange of tooling.co.za bitscomprises:

Spiral Flutes Series

Straight Cut Flutes Series

Eric Yin, managing director and founder of AM.CO.ZA commented, ‘We have introduced this range of bits to ensure that our customers are always able to obtain the bits they need. At present the range is limited, but we will be evaluating the needs for a broader range of bits based on the demand from our customers. If there is sufficient need, we will expand the range with the addition of bits for aluminium, di-bond, polycarbonate and various other materials.’

All of the tooling.co.za bits can be bought directly from the AM.CO.ZA branches or via the online shopping portal Buythis.co.za. In addition, customers have access to free technical advice and assistance on the correct use and selection of router bits for their specific requirements.