In article , Ned Simmons
says...

In the HLVH though (for example) the preload depends critically
on the separation between the bottoms of the bearing recesses in
the casting, and the length of the 'preload cylinder' which is
nothing more than a precision spacer that separates the two
inner races.

I'd expect to find there's both an inner and outer spacer, match ground,
though the outer spacer may be fixed in the spindle cartridge.

Gunner will no doubt correct me if I'm wrong, but my understanding
(based on his overhaul instructions) is that the outer races
are separated only by the headstock casting. These machines do not
have a 'cartridge' per se. The rear bearing comes out the back,
the front one comes out the front.

Maybe the engineers realized that the differential
thermal expansion wasn't that much of a killer, and they could
hire guys who liked cats and give 'em lots of Mt. Dew so they
could do the tricky job of assembling the bearing stack through
the headstock on the machines.

I hear those guys work cheap, too. I wonder if the 3000RPM top speed of
the HLVH is a consequence of the the bearing spacing. I often wish my
Feeler would turn faster. Likely the permanent grease lube is a limiting
factor as well.


Because the spindle is constrained axially and radially by two
bearings almost a foot apart that probably does make for a fair
degree of rigidity. As opposed to having the backside only
constrained by a radial bearing floating axially in a bore.


As long as the angular contact pair is carrying the thrust loads, the
fact that the radial bearing is floating axially has no effect on its
ability to carry a radial load. A bigger issue is the fact that a single
bearing will inevitably have some small amount of radial clearance, so
it's likely that light loads at the nose may not load the rear bearing
until its clearance is taken up. This is likely one reason it's common
to see a preloaded axially floating pair at the back end of a spindle in
place of the single bearing.

My real concern is that for the rear radial bearing to float, it must
have some non-zero clearance in the headstock bore. Even if small it
is present and will serve to reduce the rigidity of the *rear* of the
spindle. The BB headstock machine I overhauled had the rear bearing
fitted snugly but I was able to extract it without resorting to heroic
measures.

I am not certain but the instructions that Jim Schwitters sent me
for the more modern "R" type headstock imply that there is a sort
of preload spring for the rear bearing. I did not disassemble the
machine far enough to see that, I was only trying to verify the
state of the lube inside the three bearings.

Jim


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