BuildingAfloat

[BikerAfloat]

Robin,

That is excellent, when I stop laughing and the tears have cleared, I'll see if I can find how many fat blokes can stand on the average cutter, should be an interesting Google!

Now looking at Irving's stepper motor tutorial, will then see if I can estimate the mass of my machine components and see where I go from there. Since I'm quite a bit heavier than a BS Fatbloke I keep thinking I could snap (or at least bend) most things that will fit in a Kress collet!

Do we have shear force tables for typical cutters anywhere? Is it a common figure maufacturers supply? or do we just go by Dia of the cutter and its material spec?

I'm guessing snapping during plunging is much less of an issue as the material is in compression. So am I right in thinking that as long as the shear force for a cutter is not exceeded things should be OK?

Cheers,
Geoff.

[Jonathan]

Do we have shear force tables for typical cutters anywhere? Is it a common figure maufacturers supply? or do we just go by Dia of the cutter and its material spec?

Unfortunately it's not trivial to get an accurate idea of the forces on a milling cutter since there are so many variables, some of which are hard to quantify. But if you say 20N for cutting aluminium and 50N for steel with your average size cutter (very vague statement there on purpose) you wont be far off...

I'm guessing snapping during plunging is much less of an issue as the material is in compression. So am I right in thinking that as long as the shear force for a cutter is not exceeded things should be OK?

Quite the opposite actually as the geometry of the cutter is not favourable. Plunging with a milling cutter puts a very high axial force on the spindle, so it's generally something to be avoided by instead moving the cutter in Z and X or Y at the same time to enter the material - i.e. ramping.