"Number of flutes" for drills and feed rate calculation

[evugar]

Hi folks!


Is there any reason why all drills in tool library have "Number of flutes" set to 2 and not to 1? Feed rate doubles because of this. Do I miss something here?

[PAnderson]

You might have missed the fact that all drills have at least 2 flutes, some 3.

 

Paul

[Guest]

You need to figure the IPT

[evugar]

Yeah, IPT is what Mastercam cares for, but all manufacturers lists their drills in Inch per rev.

[Rick46]

We run sumitomo brand carbide drills and in order to get the correct feed rates output in mastercam we have to set them as 1 flute tools instead of 2 or thus we get doubled feed rates.

[evugar]

So, for now, I just wrote a quick SQL-command, which changed all "Number of flutes" values for drills in tool database.

[evugar]

We run sumitomo brand carbide drills and in order to get the correct feed rates output in mastercam we have to set them as 1 flute tools instead of 2 or thus we get doubled feed rates.

Yeah, exactly what I did as well.

[evugar]

Got link on reddit to Interesting discussion about number of drill flutes:

 

http://www.practicalmachinist.com/vb/cnc-machining/hss-twist-drills-118074/

[Guest MTB Technical Services]

It's the same principle as pinch turning.

For a 2 flute drill, each cutting edge is only in the cut for 180 degrees of each spindle revolution.

[Newbeeee™]

Tim - really (he says stepping in with a HUGE flame suit on)?

My mind/logic says that if each edge was only in the cut for 180degrees, then with the incut/outcut/incut/outcut rotation as you're feeding, you'd have chips that are broken.

I always thought that because of the simultaneous engagement, you're effectively getting 2x cutting edges 180degrees apart, that are joined in the middle.

Hence when cutting, you get one long continuous string/chip up each flute (yeh I know not for production so don't bash me as you all know what I mean ).

And if you used a 3 flute/core drill, you'd get the same again.

Interesting.

[Guest MTB Technical Services]

Tim - really (he says stepping in with a HUGE flame suit on)?

My mind/logic says that if each edge was only in the cut for 180degrees, then with the incut/outcut/incut/outcut rotation as you're feeding, you'd have chips that are broken.

I always thought that because of the simultaneous engagement, you're effectively getting 2x cutting edges 180degrees apart, that are joined in the middle.

Hence when cutting, you get one long continuous string/chip up each flute (yeh I know not for production so don't bash me as you all know what I mean ).

And if you used a 3 flute/core drill, you'd get the same again.

Interesting.

 

What you are not understanding is that you are cutting with the bottom of the cutter, in the axial direction, and NOT the side.

 

I have demonstrated this to people numerous times on a machine itself.

You can really see it when demonstrating pinch turning but it is the same principle.

A single edge of a 2-Flute drill is removing only HALF of the material.

 

Correct drilling feed per minute is based on a single flute/UPR calculation.

You take the UPR and DIVIDE  by the number of flutes to get the correct chip load per flute.

If you are calculating your drilling feedrates based on the number of flutes and multiplying like milling, you are doing it wrong.