Subject: Re: bridgeport spindle preload ?

From: [email-masked]
Date: Wed, 05 Jun 96 19:15:50 PDT

> If anyone knows what the procedure is to remove the spindle and
> bearings, I'd sure appreciate it.  Thanks,
>                                             Jon
> 
  I run my Bridgeport for extended periods at high speeds, so bearing 
replacement is needed about twice per year.  We also do surface milling with 
index cutters on this machine, and the worn bearings will leave waves in the 
surface of a machined part, so we change them a lot, despite the high cost.  
Aftermarket bearings are about $200 for the set, and not as good as 
Bridgeports.  Last set for my 2J head were just over $400.
   The spindle is removed by removing the drawbar, collet, and nose ring and 
dropping the inner spindle out of the quill.  You do not have to remove the 
quill.  This is a splined setup, since the normal quill travel never uses the 
top of the spline, sometimes you have to inset a brass rod in the drawbar 
hole, and give it a slight tap.  Mine will fall out when the nose is removed, 
as I have had it apart about 10 times.  Bearings are installed in opposition 
to each other.  They are marked, and come with instructions.  Use the propper 
bearingsand orientation.  Don't replace the bottom two with ordinary bearings. 
 These are a loaded bearing.  Any questions, feel free to E-Mail me.

Thomas

[email-masked]
http://www.pulsar.net/~tabco/

---

From: Chip Olson <[email-masked]>
Date: Sun, 09 Jun 1996 15:42:56 -0700

Jonathan M. Elson wrote:
> 
> I am just finishing rebuilding a VERY used bridgeport 1-HP J-head.
> Somebody replaced the spindle bearing set and then stopped work.  It
> appears that the brand-new bearings have never been run.  After some
> substantial work on other areas, I got a collet set and discovered
> about .005" radial play in the spindle, at the collet end.

Some rebuilders as well as OEM use grade 5 ABEC bearings instead of the 
industry standard grade 7 ABEC. With the lower quality bearings intalled, 
an internal grinding set-up is used to true the spindle taper to the 
bearings to assure axial as well as radial concentricity.While this will 
provide .0001 TIR runout when complete, this process must be repeated if 
the bearings are ever replaced.
	
		Chip Olson