DIYbanter - View Single Post - Clausing spindle bearings-help!

In article ,
says...
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.

Yeah, I just looked in the HLVH manual. I don't know how I
got it in my head that it's a cartridge spindle, unless on
account of a Rathbone chucker I once had which was a
functional copy of an HC. The Rathbone did have a
cartridge. A functional copy in that all the HC tooling and
attachments fit - it was constructed more like the Monarch
chucker with round ways.

But there is a separate spacer that appears to be pinned in
the headstock casting that separates the bearings' outer
races.

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 don't disagree, but think the bearing's radial looseness
is a more likely culprit. Barden recommends a transition
fit, around .0002 either side of line to line, for the
housing in this situation. I'd describe the housing fit on
the 3rd bearing in the few spindles I've had apart as a
wringing fit - tighter than a slip fit, but moves with firm
hand pressure. In either case, movement due to radial
clearance in the bearing itself or radial movement of the
bearing in the bore, you'd expect to see a knee in a force
vs. deflection curve. I mentioned in an earlier post in
this thread that I was able to see the effect of the radial
bearing in a BP spindle by measuring the difference in
deflection at the nose with the top radial bearing both
removed and installed, but I don't recall checking for a
change in stiffness as the top bearing loads up. So I just
did a quick test with a spring scale and indicator on the
BP.

I mounted a 50 millionths indicator on an Indicol holder
clamped to the spindle collar and placed the probe on the
OD of the quill. A spring scale was clamped in the vise and
arranged to push on a rod held in a drill chuck. Cranking
the table allowed me to apply a controlled force while
monitoring deflection. I *may* have been able to see the
expected effect, but the deflections were much too small to
measure reliably - even with the force applied about 5"
below the spindle nose, a 60# load only moved the spindle
about .00015 relative to the quill. It *looked* like the
first .00005 occurred at about 10# load, but it'd take much
better resolution to be sure.

Ned Simmons