CAM Tool lengths? Flute vs Shoulder vs Body vs Overall

[Anonymous]

Anyone help me on understanding End Mill length definitions?

I'm typing in the numbers for a 1/4" (Dia.) Double Flute Straight Bit and I'm struggling to understand the defintions.

Flute Length - I assume this is the cutting blade, which in my case is 1"

Shoulder Length - I assume this is the gap between the tool holder and the cutting surface. I tried entering 1/8" but it will only take a value of 1" or the OK button greys out. The entire shank/shaft is a 2.5" length with a .25" diameter.

Body Length: I assume this is the cutter plus the exposed shaft (or shoulder length). I entered 1.125 (1" for the cutter, 1/8" for the exposed shaft)

Overall Length - I assume this is the entire piece. I entered 2.5"

Can anyone tell me what I'm doing wrong? When I select Shoulder length it is highlighting the flute.

[maker9876]

I see.

No point in being in this game if one doesn't like being sandwiched between constraints. 😉

Incidentally in the configuration of the chamfer tool (and thence perhaps the countersink tool as well) it seems strange to enter:

- diameter

- taper angle

- flute length

- AND tip size

Fusion360 sketch would say that is over-constrained.

And indeed if one has measured the two diameters & flute length with calipers (with a certain inaccuracy) it leaves one wondering whether the inadvertent gradient implied by these values is going to over-ride the definitive taper angle setting that CAM should be using as the basis for its calculations?

(In my experience tip diameter is difficult to measure: that might be the one to drop.)

[cj.abraham]

Actually, flute length is something of an independant variable. Diameter, angle, and tip diameter determine the shape, flute length is simply how far from the tool tip the material can cut before the simulation kicks an error for insufficient flute length.

Tip diameter is necessary for chamfer tools that have "flat" bottoms (like indexable chamfer tools), but tools that come to a point often do not come to a true, sharp point. Often you will find that the tip is .02" to .05" and the tip diameter field allows for this shape to be properly accounted for in toolpath generation.

[maker9876]

That makes perfect sense.

In the particular case of the chamfer, this is what I had in mind.

Case A, there's a flat tip (see photo)

Flute length = f

taper angle = Ø (don't find a Theta on my keyboard)

Diameter = 2 (fsinØ + r)

tip diameter = 2 r

Case B, it goes to a point.

Flute length = f

taper angle = Ø

Diameter = 2 (fsinØ )

tip diameter = 0

In both of these cases there's only a need for 3 variables (f, r, Ø ) to define the chamfer tip.

Since F360 has asked for 4 variables it sort of leaves me wondering how it calculates how to position the tool when you give it a "tip offset".

Does it start from the tip diameter and figure out the right displacements, downwards and inwards, of the tool using the taper angle?

Or does it calculate by creating a shape formed by the "diameter" the "tip diameter" and the "flute length" - which probably implies a slightly different gradient to the taper angle since the angle came from manufacturer's specs whereas the diameter and tip diameter may have been measured with calipers?

[maker9876]

small but important edit to above post:

wherever I've written "fsinø" it should probably be "f * tanø"

since the flute length, f, is not the hypotenuse of the triangle

i.e. it's not what it sounds like but rather, as drawn, "the length of the flute as measured along the axis of the tool" 😉

Oops

[ndevenish]

This doesn't really explain what the consequences of these settings are, especially for straight end mills.

E.g. If I set the shoulder equal to the flute length, which seems to be the most common conclusion in this thread, will the CAM module only allow cutting to that depth? Should I instead set the shoulder length equal to the body length to ensure the CAM module understands the tool reach?

And, isn't the body vs total length often a function of the holder or collett being used? Some of the smaller mills we have include a plastic "ring" to ensure they are placed at the same position, but many of the larger tools don't have that.

[cj.abraham]

The shoulder/flute length will not affect how deep the tool will reach when used in an operation. It is for simulation events (w.g. tool should collides with stock)

Body length is tool stick out from the holder

Total length is totally fictitious and does nothing of consequence in the software. It's just an item that can be printed on a setup sheet.

[stephenEJRWF]

One more thing that makes sense to me now. Thank you!

[Anonymous]

So, what about widths? It seems (perhaps an update issue, I'm on 2.0.5519) fusion is completely ignoring the situation where the shank is wider than the cutter and running my shank into things it shouldn't be milling. 3D clearing toolpath, 3D pocket, 2D clearing, they are all showing several collision events (so it knows its doing something bad) 

[johnswetz1982]

@Anonymous I'm guessing your tool does not have a 90 shoulder. You probably have to go into the second tab of the tool definition and define the angle of the shank to get it to simulate properly though you st.ill may have collisions even if it is modeled properly

[Anonymous]

Hey John,  

Well... it was showing/modeled as a 90 degree (or step function change in the diameter) on the tool manager screens and on screen during simulation. Just no matter what I clicked for "shank and holder yes" and pull away options fusion was adamant about ignoring all my requests and jamming the shank into my model. Fortunately the latest update has fixed that. Now, when I tool path a 3D adaptive using my 3mm dia 5mm flute length bit for roughing out a 25mm deep pocket it can be seem nicely stepping in as the depth gets too much for the flute length as one would expect.