Re: [TowerTalk] Which Thrust Bearing to Use

["Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>]

Except when tho OD is constrained from expanding by a metal with less 
expansion
73

Roger (K8RI).


On 12/9/2016 11:10 PM, Grant Saviers wrote:
> Sure. But since most machining isn't done at -40 deg C, the hole does 
> get smaller when the temperature is lower than when the hole was 
> bored.  I think my calc was correct from a 65 deg F machining 
> temperature.  And the CTE of steel is 20 times less than UHMW so it 
> doesn't matter much in the tolerances.
> On 12/9/2016 18:45 PM, Thomas Noel wrote:
> > Absolutely. The circumferential expansion far exceeds the tiny inward 
> > radial expansion.
> > Thomas W Noel
> > KF7RSF
> >
> > > On Dec 9, 2016, at 6:23 PM, charlie@thegallos.com wrote:
> > >
> > > <anip>
> > > > I don't agree.  If the hole is large enough to just clear at -40C, 
> > > > when
> > > > heated the entire mass will increase in volume.  The OD will get 
> > > > larger
> > > > and
> > > > the hole will get smaller and become tighter against the mast.
> > > >
> > > >
> > > > 73 de
> > > > Gene Smar  AD3F
> > > I guess your science teacher "Back when" didn't do what mine did.  
> > > He had
> > > a steel ball (on a handle, and a steel ring (ditto).  At room temp, the
> > > ball would NOT fit through the ring - maybe 1/32 of interference.  You
> > > then took the ring, put it in a bunsen burner, and hot it hot 
> > > (didn't even
> > > need to be red) - the ball fit though perfectly
> > >
> > > Yep, the way materials expand the hole gets bigger.  We do it in the 
> > > shop
> > > ALL the time, heat a gear etc to make the hole bigger to drop over a 
> > > shaft
> > >
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--

73

Roger (K8RI)


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