On 9/30/26 15:09, Stuart Stevenson wrote:
SFM is how fast the cutter edges are moving around the axis of rotation of
the cutter. The spindle of the mill is the axis of rotation of the cutting
edges. You mentioned 20K rpm for a .0625 cutter. You have 327.25 SFM.
The cutter moving through the material is the G93 (inverse time), G94
(FPM), G95 (IPM). I don't know how the control calculates (DPM) Degrees Per
Minute or (DPR) Degrees Per Revolution.
You don't want (CSS) Constant Surface Speed.
You want (CFR) Constant Feed Rate to give you a (CCL) Constant Chip Load.
For that you (or the control) would need to know the distance the cutter is
from the axis of the rotary table.
The TA (Tool Axis) statement in my CAM system allows me to tell it to
calculate the feed rate at the tool tip or some distance along the tool
axis if I want to have the feed rate calculated for some distance away from
the tool tip.
For example, if I have a 4 inch long cutter and want the feed rate
calculated 2 inches (or some other value) above the tool tip.
It can get complicated depending on the machine configuration.
regards
Stuart
And I have to admit the question was somewhat tongue-in-cheek Stuart.
Carving that huge bolt, once the stick has been rounded, I made another
jig for my G0704 that does the rounding with a .750 cemented carbide
router bit turning about 2950(max high gear) to do the rounding while
the A is turning about 200 rpms. Takes longer to mount the stick than to
round it. Once rounded, its moved to the 6040 & the threading takes
about an hour. If I don't play out, 3 a day. I print everything else
and that is boringly slow, but printers are getting faster. I have 1
that can do a meter cubed at 600 mmpm. And one hugely rebuilt Ender5
that can now do 250mmpm, running out of hot plastic so 200 is normal
speed. That printer is my goto as I've made a nozzle cleaner and
incorporated it into the startup g-code. Butt ugly sticking out the side
of the frame but cleans very well. That one can get hot, polycarb prints
like PLA.
On Wed, Sep 30, 2026 at 1:33 PM maurice e heskett <[email protected]>
wrote:
On 9/30/26 13:42, Stuart Stevenson wrote:
Surface Feed per Minute is only relevant on a turning process. On a
milling
process the SFM is determined by the spindle speed.
How is this determined if B is turning 500 rpms while Y is moving 400mm
and the radii of the B is about 1"?, carving a bolt's 4x6 buttress
thread in hard maple at a 12mm pitch? One start while going down the
stick, 2nd start while coming back to the starting point?
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