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Milling bits: From OK to GOOD

Shortly after I jumped into CNC machining I ordered some single flute mills from Aliexpress (the 5mm one on the left [1]). I’m still happy with the quality of the cuts I can get with them. :slight_smile:

Some weeks ago I ordered the two roughing mills on the right (6 and 4mm with three flutes). I started with 6mm bit [2] and got nice results and less noise during the cutting process. It struggles a bit while diving straight into the wood (ramp plunge would definitely help).

Today I took the 4mm one [3]. I was impressed how easy it cut through the material and diving did not seem to be a problem. :slight_smile:

Settings:

  • Material: Birch plywood 15mm
  • Mill: dia 4mm; 3 flutes
  • Spindle Speed 12000 RPM
  • Pass depth: 4mm (4 cycles to cut trough the sheet)

[1] 5 stücke Schaft 5mm Hohe Qualität Hartmetall CNC Fräser Eine Einzelne Flöte Schaftfräser Werkzeug 5*25mm|mill tools|single flutecnc router bits - AliExpress
[2 & 3] WeiTol freies verschiffen TCT drei flöten gerade bit 6mm ende mühle holz schneiden werkzeuge gerade router bits für feste holz|bits 6mm|straight router bitstraight bit - AliExpress

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That’s really great information. I have not worked with bits like the one on the right so I’ll have to get one of those myself.

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Great information, great post, really helpfull.

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I used to use 2 flute 1/8in bits for a while. However, for me, upon using bits with multiple flutes for long periods of time, the bits started to burn out. From my understanding, this is due to the feed rate. It is difficult to explain that concept, but basically because the Maslow is a slow moving machine the feed rate is too slow to accommodate a bit with many flutes such as those. That said, I would be cautious using those bits for long cut jobs. Signs that the bit is burning out/feed rate is too slow include: increased noise, increased vibration, and a smoky sawdust smell. In addition to that, your bit should be cutting small “chips” (almost like flakes) not sawdust.

I ran 1/4 and 1/8 inch bits (both single flutes) at 30ipm at 8 or 10K rpms and that worked well. (Ideally it would be a little bit faster but the Maslow could not do that)

–Just something that I would watch out for as I would hate to see you make the same mistakes that I had made. Note: This is really important if you plan to use your bits for long periods of time or if you plan to do long milling jobs.

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I do agree with you and that’s why I started with the one flute mill on the left.

Given values:

  • Feed rate: 600 mm/min
  • Speed: 12000 min-1

Single flute mill:
Feed per flute and revolution = Feed rate / Spindle Speed / Flutes | 12000 / 600 / 1 = 0.05mm

Roughing mill with 3 flutes:
12000 / 600 / 3 = 0.0166mm

I learnt that a feed per flute < 0.01mm is bad for the mill and when working with wood also dangerous. With the given settings I’m on the safe side. :slight_smile:

Since I upgraded my Z-axis the spindle dives into the wood and retracks instantly. So the mill is not scratching the surface a long time.

As I mentioned in the initial post I’m impressed with the qualitiy I get with these tools and settings. And to keep you updated I’ll report back when I have done a longer cut with these roughing mills. :slight_smile:

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