Flutes in end mills

Haven't a clue. I know you should spin a two flute cutter twice as fast as a four flute cutter. I also know that a two flute cutter isn't necessarily a slot drill unless it can drill - ie it's centre cutting.

I guess you get more flutes as the cutter diameter increases. If you had a twelve inch end mill, it would look a bit sad with just four flutes.

Hello Peter, My understanding it that there are two main issues. More flutes means a higher feed rate is possible because the limit is roughly a feed/flute hence more flutes means more feed.

Secondly, if you mill a slot with an end mill, the front cutting flute gives rise to a side force on the cutter. This both deflects the cutter by bending it a little and also takes up any bearing clearances and any other play in the system all of which presses the flute at the side of the cutter into the side of the slot. Hence a 4-flute end mill will generally mill an oversize slot.

I have also never heard of a 1 flute cutter, 3 flutes are a relatively recent development I think and I assume get more feed without suffering the oversize slot problem. Obviously once you get to big eg

4" diameter shell mills the story is more a matter of making best use of the large chunk of costly material and getting a smooth cutting action rather than a fly cutter type effect.

Richard

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A lot of it is down to the compromise between finish and speed. Less flutes means more space for swarf hence higher removal rate but poorer finish.

Quality, price and speed, which two would you like?

AWEM

Quality and price, of course, but ymmv.

One other thing I have noticed on the X3 mill is that there is less vibration when using larger endmills with more flutes - pushing a 12mm two flute endmill in hard material can be a problem, while pushing a

12mm four flute endmill doesn't seem to be nearly as hard.

Hmmm, pushing ... guess I want speed too,

:)

-- Peter Fairbrother

Single flute router cutters are pretty common in the smaller sizes, so why not milling cutters too?

A single flute "endmill" is very probably really a wood working mortice cutter, I have several. They do look exactly like endmills

Rigidity I assume.

Cliff Coggin.

Was that on the J B Cutting Tools stand? I was allowed to choose one for free as I bought 4 very long carbide slot drills from them. It intrigued me and assumed it was a one flute slot drill rather than an end mill as it can be plunged in as it cuts across the centre unlike an endmill which cannot. It has the designation JT0005 5x12x60/8 (ie 5mm diameter, 12mm maximium depth of cut, 60mm total length with 8mm diameter shank).

The long reach 2-flute carbide slot drills were unusual. 3 had straight flutes and were 6x40x100/8, 5x50x100x8 and 7.5x20x60/6 and the other

8x30x75/8 had slow spiral flutes. What attracted me to them was the extremely long reach and very deep depth of cut (40, 50, 20, 30 mm respectively) and cheap price.

Alan

Yes, that's the one(s) - though whether it's a slot drill or an end mill .. I dunno, the difference is unclear to me. Like TDC in beam engines, use of terminology is not standardised.

:)

-- Peter Fairbrother

I was taught at college that in the UK milling cutters that can plunge into the work ie have at least one cutting edge across the middle should be called slot drills whereas endmills with no cutting adge across the middle must be moved in from the END of the work piece or used to open out a hole or slot that has already been roughed out with a slot drill.

Alan

Traditional cutter grinders could not sharpen a centre-cutting tool with more than two flutes, so slot drills were limited to two. But modern machines can make fancier shapes, so the limitation no longer applies. Replaceable-tip tools have only one insert in the smallest sizes, then two, three and so on as the diameter increases.