End mills overview and usage

Quick links:

• Overview of end mill characteristics
• For 2D routing
  • Plywood
  • Hardwood
  • Plastics
  • Foams
• For 3D milling
• For detailing and engraving
• Where to buy

Overview of end mill characteristics

Characteristic	Options
Flutes	Single, 2, 3 and more
Flute type	Straight, spiral and O
Nose profile	Flat, ball, bull, tapered/conical, V
Cutting length	The usable length of the tool, excluding shank.
Mill diameter	1/8" to 1/2" is common for this size of machine, but can be much smaller or a little bit larger.
Shank diameter	Varies quite a bit, but limited by spindle collet. Our spindle has an ER20 collet, with a maximum shank diameter of 1/2"
Direction	Up, down, and compression cut
Composition	HSS, carbide, exotic coatings

For 2D routing

In general, stick with flat nose end mills in order to cut all the way through material with minimal spoilboard penetration.

Plywood

Recommendation(s)

For cleaner, slower cuts: 1/2" or 1/4", flat nose, 2-flute (spiral). See notes about direction. For rougher, faster cuts: 1/2" or 1/4", flat nose, single or 2-flute, straight flute. Otherwise known as conventional router bits.

Notes

Plywoods can be surprisingly tough on end mills due to the resins used. MDF in particular is very rough on end mills, as the fine dust can function as gritty abrasive. Use something that is cheap enough that you won't be frustrated by dulling, but good enough quality that things aren't harder than they have to be. Direction Up cut can lift workpiece and/or cause ugly tearout on top surface. Down cut won't lift workpiece, but can cause ugly tearout on bottom surface. Compression cut is ideal, but more expensive. A cost effective compromise is to use down cut on first pass(es), then up cut on final pass. Composition Use carbide end mills. Avoid HSS. Save yourself money by not springing for exotic coatings.

Hardwoods

Anybody have some experience and tips for hardwoods?

• Hardwood seems like it may be easier than plywood, since it doesn't have resins.
• Conventional router bits (1/2 flute, straight profile, flat nose) might be best.

Plastics

Recommendation(s)	For soft plastics: 1/4" or 1/8" single flute, up cut, "O" profile
Notes	Softer plastics tend to produce long curls rather than chips. Single flute "O" profile tends to keep these curls nice and long, while the up cut direction moves them away from the workpiece, preventing them from welding back onto the workpiece.

Foams

• Low density foams like pink/blue insulation foam are super forgiving. What bits wouldn't work??
• Higher density and specialty foams like RenShape are still very forgiving, but may benefit from slightly more tuned speeds and feeds. Refer to manufacturer recommendations.

For 3D milling

In general, stick with ball nose end mills.

Recommendation(s)	1/8", 2 flute, ball nose for coarse details. 1/16-1/64", 2 flute, ball nose, tapered end mill for fine details.
Notes	On larger jobs it can be smart to use multiple passes with different tools. For example: Roughing pass with largest available end mill. Coarse detail pass with a 1/8" end mill. Fine detail / finishing pass with a 1/16-1/64" tapered ball nose end mill.

For detailing and engraving

• V bits are popular for classical signage, but also impose a strict (though sometimes desirable) aesthetic.
• Small diameter means finer features.
• Look into PCB isolation / micromachining bits
• Flat nose probably preferable to ball nose.
• Flutes probably don't matter as much.

Where to buy

• McMaster-Carr = moderate selection of high quality, moderately priced end mills
• ToolsToday = large selection of good quality, reasonably priced end mills
• Discount-Tools = large selection of varying quality, low-priced end mills. Good deals, but can be hard to locate appropriate end mills across multiple sections.
• MSC Direct
• Carbide3D = small selection of high quality, low and high-priced end mills. Focused on delivering fewer, but well-researched options for amateur/DIY users.
• Inventables = same idea as Carbide3D.
• Amazon = large selection of pretty much every level of quality and price. Can be hard to find what you need, but good deals are out there. Looks for end mills with lots of ratings/reviews!
• Menards and Home Depot both sell some low-cost, moderate quality straight router bits