Router bits?

[Doug]

For now, I'm mostly sticking to wood materials.    Any suggestions for the best router bits to get started?

Plastic is probably in my future (for template making), and I imagine that requires different bits to cut cleanly without getting gummed up from melted plastic.    Tips there would help too.

Thanks!

[Jeff]

For parts without a lot of detail, I'd use a 1/4" diameter ball-nose bit.  At mcmaster.com, you can search for p/n    8878A17.  These are solid carbide spiral bits.

There are also some more conventional straight-flute ball-end bits at:

mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_core.html

The spiral bits can be a bit smoother cutting, but if your work is not clamped down really firmly, the up-lift action of the cutter can cause your part to lift up and chatter - especially when cutting across the end-grain.

For small things you can get almost any diameter solid carbide bit (less than 1/8" dia) with either square end or ball end and a 1/8" dia shank.  (Just search for end-mills at mcmaster.com to find examples.)  To use these, you'll need a 1/4" to 1/8" collet adapter sleeve.  Here's a nice one:

stewmac.com/Shopping?actn=search&keyword=collet+adapter&x=-288&y=-66 

If your looking to get going with a minimal set of bits, here's what I use mostly:

1/4" round-end bit for profiling

1/8" round-end bit for detailed profiling

1/8" square-end bit for slotting, general cutout, rough inlays

1/32" square-end bit for inlay details

I'll address machining plastic in another post - that's a whole different ball of wax.

[ted.m...@gmail.com]

hey Doug,

Amazon stocks a lot of router bits too. The HSS bits from Amico are decent for rough cuts and will do finish cuts at slower speeds (like most bits).

To start I would get a 1/4" end mill (with cutting end so you can plunge). I use this one frequently. http://www.amazon.com/gp/product/B007Q92RTA/

Tune your depth of cut (doc), feed speed and spindle speed based on material. There's a few common formulas - search the tubes for 'cnc router feed formula' or similar phrases.

For plastic, it's not too different than wood. If your bit ever gets gummed up, you used a wrong setting (spindle, feed, depth). You should see chips flying from the cutter when machining plastic - not melting or dissolving around the bit. Best plastic to mess with is HDPE or delrin. It's very forgiving and relatively soft so you can use 2 flute cutters at lowish speeds. I generally machine plastics starting with 8k ~ 12k, 0.15" doc, 20 IPM. And adjust to get a a good chip load. Same thing for wood. It's all about the chips (or dust in the case of MDF .. lots of dust)

Ted

[Ted Markson]

Jeff, what settings and bits are you using to cut aluminum?  I'm striking out with the 4 fluters I've been trying. Thanks.- ted

[Jeff]

For aluminum, I use 2 -flute bits - especially for smaller diameters.  The 4-flute bits don't leave a lot of room for chip ejection, and things can gum up pretty quickly.  Also, I really like using 91% isopropyl alcohol as a cutting fluid, especially when working with softer aluminum alloys like 5052 or 3003.  I have a squeeze bottle with a hypodermic needle tip and I keep a tiny but steady stream of alcohol on the bit when cutting.  Makes a world of difference.  It also evaporates and leaves no mess.

[Ted Markson]

Cool. I was using the alcohol, not the 2 flute bits. What feed and spindle speeds have worked for you? 

[Jeff]

Spindle speeds and feedrates will depend on the tool diameter and depth of cut.  But as an example, if I'm using an 1/8" bit in aluminum, I might take a 0.040" depth cut with a spindle speed of 15,000 RPM and a feedrate of 10"/min.  I generally go by the sound of the cut and will speed up the spindle or slow down the feed rate if there is too much chatter.  

The Lobo mill is not hugely stiff like a conventional milling machine, so taking a finish pass will really clean up the finish.  I've found that for profiles, I don't need to generate separate roughing and finish path G-codes.  I always use a climbing cut which tends to push the bit away from the finished surface.  Therefore, there is always a little material left to remove when I execute the exact same path as a finish pass. 

-Jeff