Spindle removal procedure for a Hardinge TL

First, the process involves removing the spindle which 
is involved but not terribly complicated.  There are 
several areas which take considerable care and are not 
immediately intuitive so I will highlight those and not 
describe every little detail in the process.

I would recommend downloading the excellent cross section 
of the headstock provided by Rick Ibosh and posted in the 
files section under the title "Headstock Section Final".  
It is a section of the early version of the TL headstock 
containing a brake drum and brake band around the main 
spindle.  The cross section is very accurate and to my 
knowledge, the only significant differences between the 
two headstock versions are the presence or absence of 
the brake assembly.

To start, the headstock must be separated from the gearbox.  
You have a choice of removing the gearbox and leaving the 
headstock installed on the bed or vice versa.  I have done 
it both ways.  My preference is to remove the headstock so 
it can be manipulated on a bench for spindle removal.

I posted a gearbox removal summary some years ago in message 
number 38 - refer to that for some of the tricks entailed.  
Once you have the gearbox off, the belts removed from the 
intermediate shaft and the various control linkages 
disconnected, you have the choice of sliding the headstock 
either to the left (about 2 inches) or to the right (about 
4 inches) to allow the T-bolts to disengage from the bed.

With the headstock on a bench, remove the backgear.  That 
should not need elaboration, although some care is involved 
in disconnecting the activating handle and associated detent.  
Note the location of the two fiber washers on either side 
of the backgear.  Also, mind the sleeve and dog-pointed 
setscrew which locate the outboard end of the backgear shaft.  

A general note is in order here:  Hardinge is fond of placing 
two setscrews on top of each other (to prevent loosening) so 
it is worth looking down inside any hole after setscrew 
removal to ensure there is not another one.

While working on the back of the headstock it is a good time 
to remove the spindle engagement shaft and fork.  Nothing 
complicated about it but it can be fiddly, especially to 
reinstall.

Now it is time for spindle removal.  First, remove the 
spindle clamp nut followed by the handwheel.  Then loosen 
the three socket head capscrews from the front spindle nose 
flange.  Now the spindle can be gently tapped out the front 
of the headstock.  This is a time to go very slowly and 
carefully and be mindful of cleanliness (to keep any avoidable 
contamination out of the bearings).  I would use nothing 
more harsh than a deadblow hammer or soften any blows with 
a wooden block.

The spindle should slide out leaving in place a number of 
components, including the rear bearing, drive flange/backgear 
ass'y, and pulley ass'y.  These parts will all come out the 
bottom of the headstock after the spindle is removed.

It is easy to get involved in the spindle removal and miss 
what I believe is the most important aspect of retaining 
Hardinge's original spindle accuracy.  That is to ensure 
you return the bearings to their original radial location 
with respect to their shaft or bore.  Put another way, the 
bearing races, both inside and outside must be returned to 
their same rotational location.  The reason for this is 
that the front bearing pair are carefully matched and then 
oriented so that any runout (both inside and outside races) 
is aligned together and then assembled on the spindle and 
inserted in the bore.  Then the final grinding of the collet 
bearing surfaces and spindle nose are ground in place in 
the headstock.  This way Hardinge is able to attain the low 
runout and long lived bearings they are famous for.  Orienting 
the rear bearing inner race on the spindle is not as important 
as the front bearing pair but it is worth doing.

My method for marking the bearings is to:  1) reach into the 
rear of the headstock after the handwheel is removed and mark 
the inner race of the rear bearing (I usually reference all 
my marks in relation to the 5C collet key).  2) as the spindle 
is tapped out and the outer race of the front bearing pair 
appears, mark them both in turn in relation to the headstock.  
Several marking methods would work but I prefer a sharp carbide 
scriber over felt or paint markers which can get rubbed off.

While the spindle is out, it may be tempting to remove the 
matched bearing pair but I would highly recommend against it.  
Unless they are already damaged, disassembly is almost certain 
to decrease their life unless very careful precautions are taken 
(these were originally assembled in a clean room-like environment 
so the less they are exposed to dirt and dust, the better).  Also, 
do not yield to the temptation to turn the outer races of the 
matched pair in relation to each other.  There should be should 
be a very precise preload holding those bearings together which 
should not be disturbed.

Reassembly is essentially the reverse of disassembly.  It's a bit 
fiddly but careful thought should see you through.