When cutting through an object do you need to make "room" for the cutting tool diameter?


(Louis ) #1

So I have this very tiny gear being cut with a #122 .031 end mill. Now the cutter is smaller than the tool diameter.

So when i do my toolpaths do i compensate for this? This isnt something that just happens automatically I assume?

This is the gear, about 1.5 inch in dia, :


(William Adams) #2

Where the cutter will be placed in relation to the path is a function of two things:

  • the diameter of the cutter — this will determine how much the offset (if any) will be — note that you may want to do a test cut in a scrap of material and measure that first: http://www.shapeoko.com/wiki/index.php/Calibration_and_Squaring_the_Machine#Runout

  • the toolpath selected, which will determine whether there is:

  • Contour | Pocket or Inside / Left — the toolpath will come no closer than 1/2 endmill diameter to the geometry from the inside

  • Contour | Outside / Right — the toolpath will come no closer than 1/2 endmill diameter to the geometry from the outside

  • Contour | No Offset — the toolpath will follow the geometry as precisely as machine motion allows

Play around with assigning toolpaths — you’ll get a preview image of the toolpath after assigning it which will help to show that.

There’s some discussion of this in:


(Louis ) #3

Okay so what you are saying is that despite the smaller tool and my lack of understanding, the preview will hold true?

I see the tool is tapered, I am just not really seeing how it works (yet) and dont want to damage the machine. Because as you see its not an inlay but a cut through.


(William Adams) #4

If the tool is tapered, then you will need to input the taper angle as part of the tool definition.

This is shown at the beginning of: http://www.shapeoko.com/wiki/index.php/Carbide_Create_V-carving_(advanced) (for a Carbide 3D #301)

Do you need the taper angle for a working gear? Are you planning on cutting two of each gear, and fastening the pairs together so that the resultant gear will have a V shape, mating with the other (which would have opposing surfaces glued together so as to create the opposite V shape)?


(Louis ) #5

Sorry I didnt mean tapered like that, see the cutter here: https://shop.carbide3d.com/collections/cutters/products/122-0312-flat-cutter-qty-3?variant=3603855363

Basically im concerned that because the cutting part is so tiny, when it goes deeper the thickness of the shaft will hit the stock. Seeing the preview pictures and this tool am i in the clear here?


(William Adams) #6

Enter the cutting length: Cutting Length: .0625" and never use it on material which is thicker than that, or on a given layer which is thicker than that. If cutting thicker material, leave steps, none of which is thicker than 0.0625" and ensure that each edge is sufficiently distant from the next up to clear the taper angle (which it looks as if you’ll have to measure).

MeshCAM may have some facility for this, but I doubt Carbide Create does.


(Louis ) #7

Okay, what exactly is cutting length? I am using Carbide Create because it was much more simple than Meshcam. And Steps make steps leading up to the part or something of that nature?


(William Adams) #8

Cutting Length is one of the characteristics of an endmill. Please see: http://carbide3d.com/docs/tooling_guide/ and http://www.shapeoko.com/wiki/index.php/Endmills — it should be entered as “Flute length” in Carbide Create.

We also have a Glossary: http://www.shapeoko.com/wiki/index.php/Glossary (to which I’ve just added the cutting length as a q.v.)

Draw up the geometry of the endmill as viewed from the side, then draw a side view of the cuts which you wish to make — this should show the relief cut steps which you will need. Another alternative would be to do this as a two-sided flip-cut.