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Re: [TowerTalk] Which Thrust Bearing to Use

To: Thomas Noel <tnoel@mac.com>, charlie@thegallos.com
Subject: Re: [TowerTalk] Which Thrust Bearing to Use
From: Grant Saviers <grants2@pacbell.net>
Date: Fri, 9 Dec 2016 20:10:52 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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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