CNC router bit set for a 3.175 mm or 1/4 inch collet
Updated: October 2026
You run a desktop CNC in plywood or MDF, and the milling cutter set in the results is a 2–12 mm high-speed-steel box. Those shanks will not enter the collet on the spindle. A CNC router bit set for this machine is a 3.175 mm pack or a true 1/4 inch pack. Peter F. updated this on 21 October 2026 from the amazon.co.uk listings in this comparison and public notes from Trend and the Health and Safety Executive. There was no workshop test. A qualifying purchase can earn a commission at no extra cost to you. The wider ranking sits on the [milling cutter set comparison](/hub/routers/milling-cutter-set).
You run a desktop CNC in plywood or MDF, and the milling cutter set in the results is a 2–12 mm high-speed-steel box. Those shanks will not enter the collet on the spindle.
You run a desktop CNC in plywood or MDF, and the milling cutter set in the results is a 2–12 mm high-speed-steel box. Those shanks will not enter the collet on the spindle. A CNC router bit set for this machine is a 3.175 mm pack or a true 1/4 inch pack. Peter F. updated this on 21 October 2026 from the amazon.co.uk listings in this comparison and public notes from Trend and the Health and Safety Executive. There was no workshop test. A qualifying purchase can earn a commission at no extra cost to you. The wider ranking sits on the milling cutter set comparison.
Our top picks
| Badge | Product | Shank | What is in the box | Collet it needs | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  SainSmart Genmitsu MRBC08 8-piece CNC bit set, 1/4 inch | 1/4 in (6.35 mm) | Eight mixed CNC profiles | True 1/4 inch only | 9.6 | about £93.99 | View offer |
 AFUNTA AFUNTA 10-piece HSS end mill set, 2-12 mm | Steps with the cutting diameter | Ten metric end mills | Mill holder, not a 3.175 mm nut | 9.0 | about £16.99 | View offer | |
 EU_HOZLY Hozly 5-pack 1/8 inch downcut O-flute, carbide | 3.175 mm (1/8 in) | Five identical downcuts | 3.175 mm ER11-style | 8.8 | about £16.99 | View offer |
On this page
The milling set that will not fit
A 2–12 mm end-mill set belongs on a hobby mill, where you swap the holder for each shank. Many 3018-style machines state an ER11 collet of 3.175 mm, which is 1/8 inch. A 4 mm, 6 mm, or 10 mm shank from that box will not clamp, and forcing it marks the collet or lets the cutter spin.
Those high-speed-steel cutters suit a light side cut in aluminium on a slower mill-drill. A small gantry in sheet goods wants a short carbide bit on the shank it already holds. The CNC listings here are Hozly’s five identical 3.175 mm downcuts and SainSmart Genmitsu MRBC08 on a 1/4 inch shank. Other shank tables are on the milling cutter set buying guide.
3.175 mm spares versus a 1/4 inch mix
Hozly (B0BL7C4QY3) is five copies of one solid-carbide downcut at £16.99 on amazon.co.uk, rated 4.4 from 251 reviews. Shank and cutting diameter are both 3.175 mm, with one flute 22 mm long, for the collet that a 3018-style machine usually states. Two overall lengths are printed, 38 mm in a bullet and 45 mm on the size line, so measure before a deep Z.
Genmitsu MRBC08 (B0DGTKRPKC) is eight profiles on a 1/4 inch shank at £93.99. A score of 4.8 from eight reviews, with no United Kingdom review text, is too thin for a top pick. You get a taper, a ball nose, an upcut, a downcut, a 60 degree V, a 90 degree V, an O-flute, and a two-flute. Trend puts 1/4 inch at 6.35 mm, so this shank misses both a 6 mm collet and a 3.175 mm collet. Hozly fits when the nut is already 3.175 mm. Genmitsu fits when the collet really is 1/4 inch and you want several profiles. For one straight bit in ply, the £16.99 five-pack is the best value. The mill comparison of those materials is on the HSS or carbide end mills page.
Downcut means the chip stays in the slot
A downcut pushes the chip toward the spoilboard, so the plywood veneer stays pressed and the top edge looks tidy. The same spiral leaves the waste in the groove. Hozly’s bullet says the top is clean, the bottom is rougher, and you should slow the feed so chips can escape. A UK review on that listing reported smoke in maple when the spindle was fast and the slot packed.
If the groove smells of burning wood, stop, clear it, and take less depth. An upcut lifts the chips and can fuzz the top veneer. Genmitsu includes both spirals on a 1/4 inch shank. Every Hozly piece is a downcut, so that five-pack has no upcut spare. The first depth is set on the how to use a milling cutter set page.
Dust on a CNC
Plywood and MDF make a fine dust, and a downcut throws a cloud when you clear a packed slot. The Health and Safety Executive’s sheet WD5, for CNC flat-bed routers, says the head should be enclosed and the dust extracted. WD5 is a workplace note. A garage machine still makes the same dust.
Take the air off at the cutter, because a window fan misses the plume at the flute. A vacuum shoe or a small hood is the home version of WD5’s enclosure on a light gantry. At work, follow that sheet and your own assessment. Genmitsu’s bullets name aluminium beside wood and plastics, which is a seller list, while Hozly stays with wood and plastics.
Common questions
Do I need 1/8 inch or 1/4 inch bits?
Buy the shank the collet already is. 1/8 inch equals 3.175 mm, the ER11 size many 3018-style machines state, and that is Hozly at £16.99. 1/4 inch equals 6.35 mm, the Genmitsu MRBC08 shank at £93.99. The larger shank fits neither a 3.175 mm collet nor a 6 mm collet.
Is a 2–12 mm HSS set usable on a 3018?
Not with the stock collet. Those boxes are metric end mills, and the larger shanks run past 3.175 mm. A 3018-style spindle with a 3.175 mm ER11 collet cannot hold them. Another collet is a different setup from this CNC router bit set. Keep that high-speed-steel box for a hobby mill.
Should I use an upcut or a downcut in plywood?
Use a downcut when the top face must stay clean and each pass stays shallow enough for the chips to leave. Hozly is only that shape, and the listing says the bottom edge will be rougher. Use an upcut for a deeper slot, where the veneer may fuzz. Genmitsu includes both spirals on a 1/4 inch shank only.
Why did the bit smoke?
The chips stayed in the groove and the wood overheated. Hozly’s bullet says to slow the feed because a downcut packs the waste, and a UK review reported smoke in maple. Clear the slot, take less depth, and keep the stick-out short. MRBC08 prints no feed in millimetres per minute.
Is five of the same bit a CNC router bit set?
It is five spares of one cutter. Hozly is a single 3.175 mm downcut, useful when carbide snaps, and the box has no V-bit or ball nose. Genmitsu is eight profiles at £93.99 on a 1/4 inch shank. One straight bit plus spares makes the five-pack the best value of the two.
What does nano blue mean on the Genmitsu listing?
The bullets say nano blue and the finish line says TiAlN. Both names are printed, and no United Kingdom review in the file checks either coating. Read the pair as a conflict on the listing. The same bullets claim tungsten steel and 60–70 HRC. The shank remains 1/4 inch, so the pack misses a 3.175 mm collet.
Related pages
Sources
Public UK and manufacturer sources from the research digest, October 2026.
- HSE — Wood dust (retrieved 21.10.2026)
- HSE — WD5 Routers (retrieved 21.10.2026)
- HSE — WIS22 (retrieved 21.10.2026)
- HSE — High-speed router (retrieved 21.10.2026)
- BSI — BS EN 847-1:2017 (retrieved 21.10.2026)
- BSI — BS EN 847-2:2017 (retrieved 21.10.2026)
- Trend — Routing FAQ (retrieved 21.10.2026)
- Model Engineer — End mill versus slot drill (retrieved 21.10.2026)
- Machine Mart — Clarke ET163 (retrieved 21.10.2026)