On 25.06.19 09:54, Chris Albertson wrote: > On Tue, Jun 25, 2019 at 7:34 AM andy pugh <bodge...@gmail.com> wrote: > > > On Tue, 25 Jun 2019 at 14:27, Gene Heskett <ghesk...@shentel.net> wrote: > > > > > Absolutely. And in the ER32's turning 3G's max in my G0704's abused > > > spindle, balance is not a prime concern, but in an ER20 where you expect > > > to hit perhaps 15k revs, or in my 6040 with its ER11 turning 24k, a few > > > milligrams can destroy the motors bearings eventually. > > > > An ER16 nut is 22mm dia. > > > > Centrifugal[1] force is MR(omega)^2. > > 24k rpm = 2513 rad/sec > > So the bearing force on a 24k rpm ER16 is 138N / g. > > > > How unbalanced are the nuts typically? 138N/g is not bad if the nuts are > balanced to 1 milligram. > > Also you calculation overstates the force because all the mass is not at > the outside shell of the nut. The mass is distributed throughout the steel
My reading of Andy's "An ER16 nut is 22mm dia." is an implicit assumption that the degree of imbalance is referred to the diameter. As force varies linearly with both mass and radius, it is only their product which affects the result. I.e. the effect of 1 mg at 11mm radius is exactly the same as 2 mg at 5.5mm radius. Any mass which is balanced is irrelevant if the bearings are perfectly round. I wasn't exposed to such overzealous physics lecturers, although colleagues back in the '80s had been. My reaction to them describing centrifugal force as a "fictitious force" was to reason that it is a resultant force, equal and opposite to the centripetal force which is continually accelerating the mass, just as gravity does with astronomical bodies. But that's just my reaction to what I heard. Erik _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
