If it is truly a thrust bearing then it must have grub screws or a
collar above with grub screws. For the former the ID - OD mismatch
could be large and still be ok. For the latter you could get a collar
machined with an 0.030" extension, but I would think that is overkill.
If it is a radial bearing then 1/16" really won't matter. I machine
plastic radial bearings with 0.030" clearance. I think that is the ID of
the "2" inch tube on larger UST crankups.
While all masts are not equal, those of real DOM (drawn over mandrel)
alloy (4130, A513, etc) are usually pretty round and very close on ID/OD
diameters. If you are using pipe then all bets are off re round and
generous diameter tolerances. (plus not a good idea unless of a known
quality source). (specs are published for both). Galvanizing adds a bit,
on the order of 0.008 to 0.015" diameter plus some droplets etc to file off.
Grant KZ1W
On 7/28/2019 2:02 PM, Mac wrote:
This measurement is near insignificant, it needs or should comport with
the mast size O.D. not all mast are equal in size by a long shot.
By its self is not enuff answer.?? The mast and thrust bearing are near
symbiotic in their relationship.
best:?? mac/mc?? w5mc
On 7/28/2019 1:06 PM, W3OA wrote:
A buddy and I are doing some work on a US Tower crank-up with an
unknown history.?? He measured the inside diameter of the thrust
bearing as 2 1/16 inches.?? Does this sound right or is it possible the
bearing has been replaced with one that is not the same size as the
original?
73 - Dick, W3OA
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