Some advice from Discord members:
one and two flutes in 2mm, 3mm or 1/8", 6mm or 1/4", 4mm ball endmill, a vbit. That's the bare minimum, IMO. It allows you do to do aluminum, wood, and plastic easily
If you’re working in wood/plastics: 6mm, one flute spiral upcut and 6mm 2 flute flat. Get a handful of both. They’ll be your workhorses. If you want to go aluminum, some more of the single flute spirals :)
1 and 2 flute flat end mills: 4, 6, 8 mm in diameter.
ball end mills: r0.5, r2 -
chamfer end mill: 4 mm 2 flute 90 degree
(all end mills as short as possible depending on how thick stock you're cutting - all end mills without any coating)
Downcut and/or compression bit
V-bits for V-carving and Engraving (60° is a nice middle ground).
Some advice from Discord Members:
Buy cheap to learn your machine. Better bits will last longer but will still break if abused
cheap carbide bits are plenty good more expensive ones aren't really worth it at the beginning and also, yeah. Use 6mm as much as you can, but IMO having the smaller ones is still a necessity because they come up way too often
After getting started with your machine and having wrecked a few of your hopefully cheap endmills you might want to buy more specific bits for the task at hand. If that task is milling aluminium then here are some suggestions:
The performance of carbide endmills can be improved by coating them with a different material making them better suited for a specific application. Some coatings work really well in aluminium. They reduce the friction between your part and the endmill and will dull slower. Most notably a possible coating is DLC, which stands for “diamond like carbon”. On Aliexpress you can order these at a really reasonable price (<10$), local sellers will most likely not provide these for cheap.
Another great option when trying to get a beautiful surface finish from facing operations is using a BAP300 with PCD (Polycrystalline Diamond) inserts. You might need to shorten your BAP300 with an angle grinder if it's too long. Also, PCD is technically not a coating but rather the material of the cutting edge, but it's close enough to list it here.
Do not use any bits which have a coating that contains Aluminium itself like TiAlN.
If you use adaptive machining paths and can guarantee good chip evacuation, you can easily use a 3 flute endmill. Therefore you are able to use higher feeds. For slotting single flute endmills may be the better option.
Here are some examples you could buy: 1 flute DLC, 3 flute DLC, 3 flute DLC, BAP300, PCD insert (APKT1135)
You surely also saw videos of the PrintNC milling steel, while it's not the perfect machine for this task, occasionally milling steel still works rather well when using light cuts. When shopping for bits a good idea is to get one with 2 flutes which are as short as possible and a TiAlN coating. These should be run without any coolant.
"I recommend CarbideToolSource.com if you have inch sized tool holders (1/8" and 1/4" are are in the US. They are manufactured in the USA, have free USPS shipping, and are affordably priced since they ship direct to consumer. Here's their 3-flute, 1/4" endmill with aluminum-specific geometry. https://www.carbidetoolsource.com/aluminum-cutting-endmills/14-dia-x-12-cut-3fl-square-end-alumacut-carbide-end-mill-2-pack-f26"
https://www.kbctools.ca/products/search/InventoryClearance
Dreanique Multiple Diameter Single Flute End Mill Aluminum Carbide No Coating
Multiple Diameters 2 Flute Flat Carbide End Mill Aluminum Carbide No Coating
6.35mm 1/4" 1 Flute End Mill 25mm Aluminum Carbide No Coating
6mm End Mill 2 Flute Aluminium Carbide No Coating
6mm X 22mm 1 Flute Carbide No Coating
Multiple Diameters 2 Flute End Mill Alloy Coating Cemented Carbide
3.175mm 4mm 6mm 8mm Ball Nose Tapered End Mill Carbide No Coating
6mm 2 Flute Aluminum Carbide No Coating
Adam's Bits; based in Derrimut, Western Melbourne
https://wiki.shapeoko.com/index.php/Endmills
https://all3dp.com/2/guide-to-cnc-router-bits-all-you-need-to-know/
JJ119: MDF wrecks your good bits. Make sure to keep a couple cheap bits exclusively for mdf
Spikee: When you are starting out, there will be mistakes. Be sure to get a few extra.
Spikee: The BAP300R is an index-style facing/roughing cutter. It utilizes replaceable (commercial) inserts to cut materials. These inserts can come in various kinds of materials and finishes. The most popular being the PCD (Polycrystalline Diamond) APKT1135 insert which allows mirror-style finishes even with hobby machines such as the PrintNC
Spikee: In this article I go over the various type of endmills and a list of which ones to buy as a beginner.