Millrite MVI spindle bearing repair - first report

Millrite MVI spindle bearing repair - first report

Post by Joseph Gwin » Tue, 17 Aug 2010 22:55:27



This is a continuation of the thread "Millrite MVI spindle bearings may need
replacement" first posted on 31 July 2010.

I now have the spindle out of the quill and the taper roller bearings off the
quill.  I made (from a cast iron pipe fitting) a special pusher to avoid
crushing the grease slinger, and (lacking a press) used a piece of 1/2-13
allthread passed through the drawbar hole to generate the needed force.  
Greasing the spindle just ahead of the sliding bearing race also helped.

The taper roller bearings are not in that bad condition, given that the grease
had turned into some kind of chalky cake.  However, the absence of grease had
allowed coolant to enter and corrode the bearing "cup" (the outer race) of the
lower bearing assembly in a few places.  I assume that the area weakened by
corrosion will soon fail.  The rollers are not yet clean enough to tell if they
have been compromised, but one assumes that there has been damage.

It is not obvious how one would grease these bearings without removing spindle
from quill (which isn't that hard, but still).  I have heard of people instead
using DTE24 or heavier hydraulic oil fed in through the plug in the side of the
quill, and letting it drip out of the bottom of the quill.  This may be a better
approach.  What experience do people have with this?

For the record, the two outer races ("cups") are each Timken 19268; and thetwo  
assemblies of inner races ("cones"), rollers, and cages are each Timken 19150.  
The stated ID of a 19150 cone is 1.5000".  

The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
light press fit. As others have noted , this cripples the running preload
adjustment by turning a ring nut on the spindle, and press fits are too hard to
get exactly correct.  

Is there a standard solution?  I'm tempted to polish the spindle shaft down
until the (new?) bearings are a (hand) push fit.  Has anyone done this?

Joe Gwinn

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Ned Simmon » Wed, 18 Aug 2010 08:24:44


On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

Quote:

>For the record, the two outer races ("cups") are each Timken 19268; and thetwo  
>assemblies of inner races ("cones"), rollers, and cages are each Timken 19150.  
>The stated ID of a 19150 cone is 1.5000".  

>The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
>light press fit. As others have noted , this cripples the running preload
>adjustment by turning a ring nut on the spindle, and press fits are too hard to
>get exactly correct.

>Is there a standard solution?  I'm tempted to polish the spindle shaft down
>until the (new?) bearings are a (hand) push fit.  Has anyone done this?

That's near the high end of the recommended shaft diameter, which is
.0007 to .0012 (+18 to +30 microns) over nominal. The ID of a class 0
precision cone is nominal +13/+0 microns, with a resulting 5 to 30
micron interference. Personally, I wouldn't mess with the bearing
seats. Even if you can maintain cylindricity, you're risking fretting
of the seat if the fit is not tight enough.

Be aware that the specs on standard tapered rollers are very loose
compared to inexpensive ball bearings, and precision class bearings
are quite expensive. Expect to pay around $270 for each cup/cone ass'y
in class 0 vs. $45 for a standard bearing.

BTW, the first thousand or so J-head Bridgeports used tapered rollers
on the spindle; the subsequent couple hundred thousand have angular
contact bearings.

--
Ned Simmons

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Denis G » Wed, 18 Aug 2010 10:17:40



Quote:
> This is a continuation of the thread "Millrite MVI spindle bearings may need
> replacement" first posted on 31 July 2010.

> I now have the spindle out of the quill and the taper roller bearings off the
> quill. ?I made (from a cast iron pipe fitting) a special pusher to avoid
> crushing the grease slinger, and (lacking a press) used a piece of 1/2-13
> allthread passed through the drawbar hole to generate the needed force. ?
> Greasing the spindle just ahead of the sliding bearing race also helped.

> The taper roller bearings are not in that bad condition, given that the grease
> had turned into some kind of chalky cake. ?However, the absence of grease had
> allowed coolant to enter and corrode the bearing "cup" (the outer race) of the
> lower bearing assembly in a few places. ?I assume that the area weakened by
> corrosion will soon fail. ?The rollers are not yet clean enough to tell if they
> have been compromised, but one assumes that there has been damage.

> It is not obvious how one would grease these bearings without removing spindle
> from quill (which isn't that hard, but still). ?I have heard of people instead
> using DTE24 or heavier hydraulic oil fed in through the plug in the side of the
> quill, and letting it drip out of the bottom of the quill. ?This may be a better
> approach. ?What experience do people have with this?

> For the record, the two outer races ("cups") are each Timken 19268; and thetwo ?
> assemblies of inner races ("cones"), rollers, and cages are each Timken 19150. ?
> The stated ID of a 19150 cone is 1.5000". ?

> The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
> light press fit. As others have noted , this cripples the running preload
> adjustment by turning a ring nut on the spindle, and press fits are too hard to
> get exactly correct. ?

> Is there a standard solution? ?I'm tempted to polish the spindle shaft down
> until the (new?) bearings are a (hand) push fit. ?Has anyone done this?

> Joe Gwinn

There are people probably a lot more knowledgeable on this subject,
but heres my two cents.  When youre pressing the bearing into place,
youre putting the load on the outer race.  When you tighten the ring
nut, it preloads the inner race and rollers.  The force used getting
the bearing set in the bottom of bushing shouldnt come into play.
(If the bushing was too tight, I suppose that you might crack the
bushing or outer bearing race.)

Ive put in a grease-fitting in the rod end of an old Keller power
hacksaw that Ive refurbished and it seems to have worked well.  I
think that my repair will make it last much longer, but what you
probably have to guess is the level of stresses in the area supporting
the bearing.  If you drill there to put an oil cup or grease fitting,
you could possibly cause a stress riser.  If the bearing support is
low-stressed, youre probably safe to drill & tap it to add a
lubrication fitting.

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Joseph Gwin » Wed, 18 Aug 2010 12:21:59




Quote:

> > This is a continuation of the thread "Millrite MVI spindle bearings may
> > need
> > replacement" first posted on 31 July 2010.

> > I now have the spindle out of the quill and the taper roller bearings off
> > the
> > quill. ?I made (from a cast iron pipe fitting) a special pusher to avoid
> > crushing the grease slinger, and (lacking a press) used a piece of 1/2-13
> > allthread passed through the drawbar hole to generate the needed force. ?
> > Greasing the spindle just ahead of the sliding bearing race also helped.

> > The taper roller bearings are not in that bad condition, given that the
> > grease
> > had turned into some kind of chalky cake. ?However, the absence of grease
> > had
> > allowed coolant to enter and corrode the bearing "cup" (the outer race) of
> > the
> > lower bearing assembly in a few places. ?I assume that the area weakened by
> > corrosion will soon fail. ?The rollers are not yet clean enough to tell if
> > they
> > have been compromised, but one assumes that there has been damage.

> > It is not obvious how one would grease these bearings without removing
> > spindle
> > from quill (which isn't that hard, but still). ?I have heard of people
> > instead
> > using DTE24 or heavier hydraulic oil fed in through the plug in the side of
> > the
> > quill, and letting it drip out of the bottom of the quill. ?This may be a
> > better
> > approach. ?What experience do people have with this?

> > For the record, the two outer races ("cups") are each Timken 19268; and
> > thetwo ?
> > assemblies of inner races ("cones"), rollers, and cages are each Timken
> > 19150. ?
> > The stated ID of a 19150 cone is 1.5000". ?

> > The quill shaft is about 0.0011" larger than the stated cone ID, so it was
> > a
> > light press fit. As others have noted , this cripples the running preload
> > adjustment by turning a ring nut on the spindle, and press fits are too
> > hard to
> > get exactly correct. ?

> > Is there a standard solution? ?I'm tempted to polish the spindle shaft down
> > until the (new?) bearings are a (hand) push fit. ?Has anyone done this?

> > Joe Gwinn

> There are people probably a lot more knowledgeable on this subject,
> but here1s my two cents.  When you1re pressing the bearing into place,
> you1re putting the load on the outer race.  When you tighten the ring
> nut, it preloads the inner race and rollers.  The force used getting
> the bearing set in the bottom of bushing shouldn1t come into play.
> (If the bushing was too tight, I suppose that you might crack the
> bushing or outer bearing race.)

Yep.

Quote:
> I1ve put in a grease-fitting in the rod end of an old Keller power
> hacksaw that I1ve refurbished and it seems to have worked well.  I
> think that my repair will make it last much longer, but what you
> probably have to guess is the level of stresses in the area supporting
> the bearing.  If you drill there to put an oil cup or grease fitting,
> you could possibly cause a stress riser.  If the bearing support is
> low-stressed, you1re probably safe to drill & tap it to add a
> lubrication fitting.

D.C.Morrison says that if one just puts the grease in at the quill side port, it
will work itself into the roller bearings (which are open).  No harm in trying.

Joe Gwinn

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Joseph Gwin » Wed, 18 Aug 2010 12:28:56




Quote:
> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

> >For the record, the two outer races ("cups") are each Timken 19268; and
> >thetwo  
> >assemblies of inner races ("cones"), rollers, and cages are each Timken
> >19150.  
> >The stated ID of a 19150 cone is 1.5000".  

> >The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
> >light press fit. As others have noted , this cripples the running preload
> >adjustment by turning a ring nut on the spindle, and press fits are too hard
> >to get exactly correct.

> >Is there a standard solution?  I'm tempted to polish the spindle shaft down
> >until the (new?) bearings are a (hand) push fit.  Has anyone done this?

> That's near the high end of the recommended shaft diameter, which is
> .0007 to .0012 (+18 to +30 microns) over nominal. The ID of a class 0
> precision cone is nominal +13/+0 microns, with a resulting 5 to 30
> micron interference. Personally, I wouldn't mess with the bearing
> seats. Even if you can maintain cylindricity, you're risking fretting
> of the seat if the fit is not tight enough.

D.C.Morrison says that the bearings should be a "tap fit" on the spindle, not a
press fit, and endorsed my plan to polish the quill down a bit to achieve a tap
fit.

Quote:
> Be aware that the specs on standard tapered rollers are very loose
> compared to inexpensive ball bearings, and precision class bearings
> are quite expensive. Expect to pay around $270 for each cup/cone ass'y
> in class 0 vs. $45 for a standard bearing.

What class is needed for a MVI anyway?

Quote:
> BTW, the first thousand or so J-head Bridgeports used tapered rollers
> on the spindle; the subsequent couple hundred thousand have angular
> contact bearings.

Burke used taper roller bearings for the standard R8 spindle, and ball bearings
for the high-speed spindle.  Taper roller bearings are more robust than ball
bearings under shock loads (like interrupted cuts).

Joe Gwinn

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Ned Simmon » Thu, 19 Aug 2010 12:26:09


On Mon, 16 Aug 2010 23:28:56 -0400, Joseph Gwinn

Quote:



>> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

>> >For the record, the two outer races ("cups") are each Timken 19268; and
>> >thetwo  
>> >assemblies of inner races ("cones"), rollers, and cages are each Timken
>> >19150.  
>> >The stated ID of a 19150 cone is 1.5000".  

>> >The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
>> >light press fit. As others have noted , this cripples the running preload
>> >adjustment by turning a ring nut on the spindle, and press fits are too hard
>> >to get exactly correct.

>> >Is there a standard solution?  I'm tempted to polish the spindle shaft down
>> >until the (new?) bearings are a (hand) push fit.  Has anyone done this?

>> That's near the high end of the recommended shaft diameter, which is
>> .0007 to .0012 (+18 to +30 microns) over nominal. The ID of a class 0
>> precision cone is nominal +13/+0 microns, with a resulting 5 to 30
>> micron interference. Personally, I wouldn't mess with the bearing
>> seats. Even if you can maintain cylindricity, you're risking fretting
>> of the seat if the fit is not tight enough.

>D.C.Morrison says that the bearings should be a "tap fit" on the spindle, not a
>press fit, and endorsed my plan to polish the quill down a bit to achieve a tap
>fit.

I dunno who DC Morrison is so can't decide whether their opinion
should carry more weight than that of Timken's engineers in this case.
"Tap fit" is a rather subjective way to characterize a bearing fit,
depending on who's doing the tapping and the size of the tapper, but I
assume it means a transitional fit with minimal interference. The ID
of your cones can vary by 5 tenths, so a tap fit on one bearing may
result in excessive clearance on another.

Quote:

>> Be aware that the specs on standard tapered rollers are very loose
>> compared to inexpensive ball bearings, and precision class bearings
>> are quite expensive. Expect to pay around $270 for each cup/cone ass'y
>> in class 0 vs. $45 for a standard bearing.

>What class is needed for a MVI anyway?

Class   TIR
4       .0020
2       .0015
3       .0003
0       .00015
00      .000075

The runout of Class 0 roller bearings is approximately the same as the
ABEC 7 angular contact bearings typically found in machine tool
spindles.

Quote:

>> BTW, the first thousand or so J-head Bridgeports used tapered rollers
>> on the spindle; the subsequent couple hundred thousand have angular
>> contact bearings.

>Burke used taper roller bearings for the standard R8 spindle, and ball bearings
>for the high-speed spindle.  Taper roller bearings are more robust than ball
>bearings under shock loads (like interrupted cuts).

True, but BP spindle bearings will take a lot of abuse if they're
lubricated properly and kept clean. Tapered rollers will carry a
substantially heavier load than angular contact bearings in a given
volume. But there are tradeoffs, such as added complexity, expense,
and less tolerance of contamination.

--
Ned Simmons

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Joseph Gwin » Thu, 19 Aug 2010 13:02:45




Quote:
> On Mon, 16 Aug 2010 23:28:56 -0400, Joseph Gwinn



> >> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

> >> >For the record, the two outer races ("cups") are each Timken 19268; and
> >> >the two assemblies of inner races ("cones"), rollers, and cages are each
> >> >Timken 19150.  
> >> >The stated ID of a 19150 cone is 1.5000".  

> >> >The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
> >> >light press fit. As others have noted , this cripples the running preload
> >> >adjustment by turning a ring nut on the spindle, and press fits are too
> >> >hard to get exactly correct.

By the way, the interference may be half that.  I found the the zero of the
micrometer (B&S 84) I am using is off by about 0.0005".  This will be fixed over
the weekend.

- Show quoted text -

Quote:
> >> >Is there a standard solution?  I'm tempted to polish the spindle shaft down
> >> >until the (new?) bearings are a (hand) push fit.  Has anyone done this?

> >> That's near the high end of the recommended shaft diameter, which is
> >> .0007 to .0012 (+18 to +30 microns) over nominal. The ID of a class 0
> >> precision cone is nominal +13/+0 microns, with a resulting 5 to 30
> >> micron interference. Personally, I wouldn't mess with the bearing
> >> seats. Even if you can maintain cylindricity, you're risking fretting
> >> of the seat if the fit is not tight enough.

> >D.C.Morrison says that the bearings should be a "tap fit" on the spindle, not a
> >press fit, and endorsed my plan to polish the quill down a bit to achieve a
> >tap fit.

> I dunno who DC Morrison is so can't decide whether their opinion
> should carry more weight than that of Timken's engineers in this case.

DC Morrison is the company that supports Millrites, having bought the wreakage
of Burke.  <http://www.dcmorrison.com/>  You must call for Millrite manuals and
parts.

The issue is to ensure that the preload can be set accurately enough.  This is
impossible if the bearing closest to the preload ring nut cannot move because
it's too tight a press fit.

Does Timken mention alignment of high spots and low spots to reduce runout?

Quote:
> "Tap fit" is a rather subjective way to characterize a bearing fit,
> depending on who's doing the tapping and the size of the tapper, but I
> assume it means a transitional fit with minimal interference. The ID
> of your cones can vary by 5 tenths, so a tap fit on one bearing may
> result in excessive clearance on another.

This may be what is happening.  And things may have corroded and so grown a bit
over the years.  I think I'll do most of the polishing on the bearing ID, rather
than the shaft OD, although I'll clean corrosion off the shaft.

Quote:
> >> Be aware that the specs on standard tapered rollers are very loose
> >> compared to inexpensive ball bearings, and precision class bearings
> >> are quite expensive. Expect to pay around $270 for each cup/cone ass'y
> >> in class 0 vs. $45 for a standard bearing.

Which class is a "standard bearing"?  I'd guess 4, for wheel bearings.

What are "airplane bearings", like from skygeek.com?  They are priced at the $45
level for the cup and another $45 for the cone et al.

What is a typical price for Class 3 set of one 19268 and one 19150?

Quote:
> >What class is needed for a MVI anyway?

> Class      TIR
> 4  .0020
> 2  .0015
> 3  .0003
> 0  .00015
> 00 .000075

> The runout of Class 0 roller bearings is approximately the same as the
> ABEC 7 angular contact bearings typically found in machine tool
> spindles.

DC Morrison says that Timken Class 3 are what was specified for the Millrite
spindle, and the existing bearings are in fact marked 3.

Quote:
> >> BTW, the first thousand or so J-head Bridgeports used tapered rollers
> >> on the spindle; the subsequent couple hundred thousand have angular
> >> contact bearings.

> >Burke used taper roller bearings for the standard R8 spindle, and ball bearings
> >for the high-speed spindle.  Taper roller bearings are more robust than ball
> >bearings under shock loads (like interrupted cuts).

> True, but BP spindle bearings will take a lot of abuse if they're
> lubricated properly and kept clean. Tapered rollers will carry a
> substantially heavier load than angular contact bearings in a given
> volume. But there are tradeoffs, such as added complexity, expense,
> and less tolerance of contamination.

All true, and Burke apparently valued robust more than Bridgeport.  Perhaps the
intended audiences were different.  Not that I've heard of Bridgeport spindles
being so fragile.  But I don't know why Burke didn't provide more protection
against the entry of dirt and coolants.

Joe Gwinn

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Ned Simmon » Thu, 19 Aug 2010 23:51:47


On Wed, 18 Aug 2010 00:02:45 -0400, Joseph Gwinn

Quote:



>> On Mon, 16 Aug 2010 23:28:56 -0400, Joseph Gwinn



>> >> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

>> >> >For the record, the two outer races ("cups") are each Timken 19268; and
>> >> >the two assemblies of inner races ("cones"), rollers, and cages are each
>> >> >Timken 19150.  
>> >> >The stated ID of a 19150 cone is 1.5000".  

>> >> >The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
>> >> >light press fit. As others have noted , this cripples the running preload
>> >> >adjustment by turning a ring nut on the spindle, and press fits are too
>> >> >hard to get exactly correct.

>By the way, the interference may be half that.  I found the the zero of the
>micrometer (B&S 84) I am using is off by about 0.0005".  This will be fixed over
>the weekend.

>> >> >Is there a standard solution?  I'm tempted to polish the spindle shaft down
>> >> >until the (new?) bearings are a (hand) push fit.  Has anyone done this?

>> >> That's near the high end of the recommended shaft diameter, which is
>> >> .0007 to .0012 (+18 to +30 microns) over nominal. The ID of a class 0
>> >> precision cone is nominal +13/+0 microns, with a resulting 5 to 30
>> >> micron interference. Personally, I wouldn't mess with the bearing
>> >> seats. Even if you can maintain cylindricity, you're risking fretting
>> >> of the seat if the fit is not tight enough.

>> >D.C.Morrison says that the bearings should be a "tap fit" on the spindle, not a
>> >press fit, and endorsed my plan to polish the quill down a bit to achieve a
>> >tap fit.

>> I dunno who DC Morrison is so can't decide whether their opinion
>> should carry more weight than that of Timken's engineers in this case.

>DC Morrison is the company that supports Millrites, having bought the wreakage
>of Burke.  <http://www.dcmorrison.com/>  You must call for Millrite manuals and
>parts.

>The issue is to ensure that the preload can be set accurately enough.  This is
>impossible if the bearing closest to the preload ring nut cannot move because
>it's too tight a press fit.

That's one of the complications of tapered rollers. Angular contact
bearings can use equal length ID and OD spacers to control preload,
and the same spacers will work with a new bearing pair. Not so with
roller bearings.

Quote:

>Does Timken mention alignment of high spots and low spots to reduce runout?

Not that I see in the literature I have, but "Timken Bearings for
Machine Tools" is mentioned in the section on precision bearings, and
may have more info if you can find a copy online.

Quote:

>> "Tap fit" is a rather subjective way to characterize a bearing fit,
>> depending on who's doing the tapping and the size of the tapper, but I
>> assume it means a transitional fit with minimal interference. The ID
>> of your cones can vary by 5 tenths, so a tap fit on one bearing may
>> result in excessive clearance on another.

>This may be what is happening.  And things may have corroded and so grown a bit
>over the years.  I think I'll do most of the polishing on the bearing ID, rather
>than the shaft OD, although I'll clean corrosion off the shaft.

I certainly wouldn't hesitate to cautiously remove any corrosion or
high spots you find.

Quote:

>> >> Be aware that the specs on standard tapered rollers are very loose
>> >> compared to inexpensive ball bearings, and precision class bearings
>> >> are quite expensive. Expect to pay around $270 for each cup/cone ass'y
>> >> in class 0 vs. $45 for a standard bearing.

>Which class is a "standard bearing"?  I'd guess 4, for wheel bearings.

Yes.

Quote:

>What are "airplane bearings", like from skygeek.com?  They are priced at the $45
>level for the cup and another $45 for the cone et al.

I don't know what "airplane bearings" are, but Motion Industries also
references "aircraft bearings" in their database, with no indication
of what distinguishes them from standard bearings. But they are listed
as "standard precision."

Quote:
>What is a typical price for Class 3 set of one 19268 and one 19150?

Looks like about $125 for the cone and $68 for the cup. Those are my
approx prices from Motion Industries.

- Show quoted text -

Quote:

>> >What class is needed for a MVI anyway?

>> Class  TIR
>> 4      .0020
>> 2      .0015
>> 3      .0003
>> 0      .00015
>> 00     .000075

>> The runout of Class 0 roller bearings is approximately the same as the
>> ABEC 7 angular contact bearings typically found in machine tool
>> spindles.

>DC Morrison says that Timken Class 3 are what was specified for the Millrite
>spindle, and the existing bearings are in fact marked 3.

>> >> BTW, the first thousand or so J-head Bridgeports used tapered rollers
>> >> on the spindle; the subsequent couple hundred thousand have angular
>> >> contact bearings.

>> >Burke used taper roller bearings for the standard R8 spindle, and ball bearings
>> >for the high-speed spindle.  Taper roller bearings are more robust than ball
>> >bearings under shock loads (like interrupted cuts).

>> True, but BP spindle bearings will take a lot of abuse if they're
>> lubricated properly and kept clean. Tapered rollers will carry a
>> substantially heavier load than angular contact bearings in a given
>> volume. But there are tradeoffs, such as added complexity, expense,
>> and less tolerance of contamination.

>All true, and Burke apparently valued robust more than Bridgeport.  Perhaps the
>intended audiences were different.  Not that I've heard of Bridgeport spindles
>being so fragile.  But I don't know why Burke didn't provide more protection
>against the entry of dirt and coolants.

BP spindles are not especially well protected, either. The nose pair
is protected only by a labyrinth formed by close clearances between
the various parts of the spindle and quill. Indiscriminate use of air
to clear chips can force crud up into the bearings.

--
Ned Simmons

 
 
 

Millrite MVI spindle bearing repair - first report

Post by J. Clark » Fri, 20 Aug 2010 02:24:57



Quote:
> On Wed, 18 Aug 2010 00:02:45 -0400, Joseph Gwinn



>>> On Mon, 16 Aug 2010 23:28:56 -0400, Joseph Gwinn



>>>>> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

>>>>>> For the record, the two outer races ("cups") are each Timken 19268; and
>>>>>> the two assemblies of inner races ("cones"), rollers, and cages are each
>>>>>> Timken 19150.
>>>>>> The stated ID of a 19150 cone is 1.5000".

>>>>>> The quill shaft is about 0.0011" larger than the stated cone ID, so it was a
>>>>>> light press fit. As others have noted , this cripples the running preload
>>>>>> adjustment by turning a ring nut on the spindle, and press fits are too
>>>>>> hard to get exactly correct.

>> By the way, the interference may be half that.  I found the the zero of the
>> micrometer (B&S 84) I am using is off by about 0.0005".  This will be fixed over
>> the weekend.

>>>>>> Is there a standard solution?  I'm tempted to polish the spindle shaft down
>>>>>> until the (new?) bearings are a (hand) push fit.  Has anyone done this?

>>>>> That's near the high end of the recommended shaft diameter, which is
>>>>> .0007 to .0012 (+18 to +30 microns) over nominal. The ID of a class 0
>>>>> precision cone is nominal +13/+0 microns, with a resulting 5 to 30
>>>>> micron interference. Personally, I wouldn't mess with the bearing
>>>>> seats. Even if you can maintain cylindricity, you're risking fretting
>>>>> of the seat if the fit is not tight enough.

>>>> D.C.Morrison says that the bearings should be a "tap fit" on the spindle, not a
>>>> press fit, and endorsed my plan to polish the quill down a bit to achieve a
>>>> tap fit.

>>> I dunno who DC Morrison is so can't decide whether their opinion
>>> should carry more weight than that of Timken's engineers in this case.

>> DC Morrison is the company that supports Millrites, having bought the wreakage
>> of Burke.<http://www.dcmorrison.com/>   You must call for Millrite manuals and
>> parts.

>> The issue is to ensure that the preload can be set accurately enough.  This is
>> impossible if the bearing closest to the preload ring nut cannot move because
>> it's too tight a press fit.

> That's one of the complications of tapered rollers. Angular contact
> bearings can use equal length ID and OD spacers to control preload,
> and the same spacers will work with a new bearing pair. Not so with
> roller bearings.

>> Does Timken mention alignment of high spots and low spots to reduce runout?

> Not that I see in the literature I have, but "Timken Bearings for
> Machine Tools" is mentioned in the section on precision bearings, and
> may have more info if you can find a copy online.

>>> "Tap fit" is a rather subjective way to characterize a bearing fit,
>>> depending on who's doing the tapping and the size of the tapper, but I
>>> assume it means a transitional fit with minimal interference. The ID
>>> of your cones can vary by 5 tenths, so a tap fit on one bearing may
>>> result in excessive clearance on another.

>> This may be what is happening.  And things may have corroded and so grown a bit
>> over the years.  I think I'll do most of the polishing on the bearing ID, rather
>> than the shaft OD, although I'll clean corrosion off the shaft.

> I certainly wouldn't hesitate to cautiously remove any corrosion or
> high spots you find.

>>>>> Be aware that the specs on standard tapered rollers are very loose
>>>>> compared to inexpensive ball bearings, and precision class bearings
>>>>> are quite expensive. Expect to pay around $270 for each cup/cone ass'y
>>>>> in class 0 vs. $45 for a standard bearing.

>> Which class is a "standard bearing"?  I'd guess 4, for wheel bearings.

> Yes.

>> What are "airplane bearings", like from skygeek.com?  They are priced at the $45
>> level for the cup and another $45 for the cone et al.

> I don't know what "airplane bearings" are, but Motion Industries also
> references "aircraft bearings" in their database, with no indication
> of what distinguishes them from standard bearings. But they are listed
> as "standard precision."

Generally means that they've jumped through the hoops to get the part
FAA approved for repairs of certificated aircraft.

- Show quoted text -

Quote:
>> What is a typical price for Class 3 set of one 19268 and one 19150?

> Looks like about $125 for the cone and $68 for the cup. Those are my
> approx prices from Motion Industries.

>>>> What class is needed for a MVI anyway?

>>> Class      TIR
>>> 4  .0020
>>> 2  .0015
>>> 3  .0003
>>> 0  .00015
>>> 00 .000075

>>> The runout of Class 0 roller bearings is approximately the same as the
>>> ABEC 7 angular contact bearings typically found in machine tool
>>> spindles.

>> DC Morrison says that Timken Class 3 are what was specified for the Millrite
>> spindle, and the existing bearings are in fact marked 3.

>>>>> BTW, the first thousand or so J-head Bridgeports used tapered rollers
>>>>> on the spindle; the subsequent couple hundred thousand have angular
>>>>> contact bearings.

>>>> Burke used taper roller bearings for the standard R8 spindle, and ball bearings
>>>> for the high-speed spindle.  Taper roller bearings are more robust than ball
>>>> bearings under shock loads (like interrupted cuts).

>>> True, but BP spindle bearings will take a lot of abuse if they're
>>> lubricated properly and kept clean. Tapered rollers will carry a
>>> substantially heavier load than angular contact bearings in a given
>>> volume. But there are tradeoffs, such as added complexity, expense,
>>> and less tolerance of contamination.

>> All true, and Burke apparently valued robust more than Bridgeport.  Perhaps the
>> intended audiences were different.  Not that I've heard of Bridgeport spindles
>> being so fragile.  But I don't know why Burke didn't provide more protection
>> against the entry of dirt and coolants.

> BP spindles are not especially well protected, either. The nose pair
> is protected only by a labyrinth formed by close clearances between
> the various parts of the spindle and quill. Indiscriminate use of air
> to clear chips can force crud up into the bearings.

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Joseph Gwin » Fri, 20 Aug 2010 12:27:22




Quote:
> On Wed, 18 Aug 2010 00:02:45 -0400, Joseph Gwinn



> >> On Mon, 16 Aug 2010 23:28:56 -0400, Joseph Gwinn



> >> >> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

[snip]

> >The issue is to ensure that the preload can be set accurately enough.  This
> >is impossible if the bearing closest to the preload ring nut cannot move
> >because it's too tight a press fit.

> That's one of the complications of tapered rollers. Angular contact
> bearings can use equal length ID and OD spacers to control preload,
> and the same spacers will work with a new bearing pair. Not so with
> roller bearings.

So the tap fit is the compromise.

Quote:
> >Does Timken mention alignment of high spots and low spots to reduce runout?

> Not that I see in the literature I have, but "Timken Bearings for
> Machine Tools" is mentioned in the section on precision bearings, and
> may have more info if you can find a copy online.

I'm not finding anything by this name; perhaps this was an earlier version
and/or name.  

What I did find is "Timken Super Precision Bearings for Machine Tool
Applications", file "5918_09-09-29.pdf", 259 pages.  The pages are all marked
"TIMKEN MACHINE TOOL CATALOG" at the bottom.  This is a very useful document,
from the look of it.

On page 100, they start to talk about aligning the high spots in exactly the
same terms as I have been hearing, and later there is a picture showing what the
high-spot marks look like.  I found such marks on the bearings in my mill.  
Well, I'm short one mark (on a cup), which mark seems to have been abraded off.

Quote:
> >> "Tap fit" is a rather subjective way to characterize a bearing fit,
> >> depending on who's doing the tapping and the size of the tapper, but I
> >> assume it means a transitional fit with minimal interference. The ID
> >> of your cones can vary by 5 tenths, so a tap fit on one bearing may
> >> result in excessive clearance on another.

> >This may be what is happening.  And things may have corroded and so grown a
> >bit over the years.  I think I'll do most of the polishing on the bearing ID,
> >rather than the shaft OD, although I'll clean corrosion off the shaft.

> I certainly wouldn't hesitate to cautiously remove any corrosion or
> high spots you find.

Yes.  This weekend.

- Show quoted text -

Quote:
> >> >> Be aware that the specs on standard tapered rollers are very loose
> >> >> compared to inexpensive ball bearings, and precision class bearings
> >> >> are quite expensive. Expect to pay around $270 for each cup/cone ass'y
> >> >> in class 0 vs. $45 for a standard bearing.

> >Which class is a "standard bearing"?  I'd guess 4, for wheel bearings.

> Yes.

> >What are "airplane bearings", like from skygeek.com?  They are priced at the
> >$45 level for the cup and another $45 for the cone et al.

> I don't know what "airplane bearings" are, but Motion Industries also
> references "aircraft bearings" in their database, with no indication
> of what distinguishes them from standard bearings. But they are listed
> as "standard precision."

Another poster (J.Clarke) said that it meant only that the maker had jumped the
hoops to become FAA certified for airplane repair.

Quote:
> >What is a typical price for Class 3 set of one 19268 and one 19150?

> Looks like about $125 for the cone and $68 for the cup. Those are my
> approx prices from Motion Industries.

Oof.  That's a total of 2(125+68)= 386= $400.  I was leaning towards letting it
be for now, and this is pushing me that direction.  There is only one corroded
spot, about 0.25" in diameter.

- Show quoted text -

Quote:
> >> >What class is needed for a MVI anyway?

> >> Class     TIR
> >> 4 .0020
> >> 2 .0015
> >> 3 .0003
> >> 0 .00015
> >> 00        .000075

> >> The runout of Class 0 roller bearings is approximately the same as the
> >> ABEC 7 angular contact bearings typically found in machine tool
> >> spindles.

> >DC Morrison says that Timken Class 3 are what was specified for the Millrite
> >spindle, and the existing bearings are in fact marked 3.

> >> >> BTW, the first thousand or so J-head Bridgeports used tapered rollers
> >> >> on the spindle; the subsequent couple hundred thousand have angular
> >> >> contact bearings.

> >> >Burke used taper roller bearings for the standard R8 spindle, and ball
> >> >bearings
> >> >for the high-speed spindle.  Taper roller bearings are more robust than
> >> >ball bearings under shock loads (like interrupted cuts).

> >> True, but BP spindle bearings will take a lot of abuse if they're
> >> lubricated properly and kept clean. Tapered rollers will carry a
> >> substantially heavier load than angular contact bearings in a given
> >> volume. But there are tradeoffs, such as added complexity, expense,
> >> and less tolerance of contamination.

> >All true, and Burke apparently valued robust more than Bridgeport.  Perhaps
> >the intended audiences were different.  Not that I've heard of Bridgeport
> >spindles
> >being so fragile.  But I don't know why Burke didn't provide more protection
> >against the entry of dirt and coolants.

> BP spindles are not especially well protected, either. The nose pair
> is protected only by a labyrinth formed by close clearances between
> the various parts of the spindle and quill.

The Millrite also has a labyrinth of sorts, being three ~square cross section
grooves in the quill nut through which the spindle nose protrudes.  It's a tight
fit.  Sounds like the BP approach.  The grooves were packed full of crud, now
removed.

Quote:
>   Indiscriminate use of air
> to clear chips can force crud up into the bearings.

Yet another reason for the tradition to forbid use of compressed air on machine
tools.

Joe Gwinn

 
 
 

Millrite MVI spindle bearing repair - first report

Post by pentag.. » Fri, 20 Aug 2010 18:20:48


On Wed, 18 Aug 2010 23:27:22 -0400, Joseph Gwinn

Quote:



>> On Wed, 18 Aug 2010 00:02:45 -0400, Joseph Gwinn



>> >> On Mon, 16 Aug 2010 23:28:56 -0400, Joseph Gwinn



>> >> >> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

>[snip]

>> >The issue is to ensure that the preload can be set accurately enough.  This
>> >is impossible if the bearing closest to the preload ring nut cannot move
>> >because it's too tight a press fit.

>> That's one of the complications of tapered rollers. Angular contact
>> bearings can use equal length ID and OD spacers to control preload,
>> and the same spacers will work with a new bearing pair. Not so with
>> roller bearings.

>So the tap fit is the compromise.

>> >Does Timken mention alignment of high spots and low spots to reduce runout?

>> Not that I see in the literature I have, but "Timken Bearings for
>> Machine Tools" is mentioned in the section on precision bearings, and
>> may have more info if you can find a copy online.

>I'm not finding anything by this name; perhaps this was an earlier version
>and/or name.  

>What I did find is "Timken Super Precision Bearings for Machine Tool
>Applications", file "5918_09-09-29.pdf", 259 pages.  The pages are all marked
>"TIMKEN MACHINE TOOL CATALOG" at the bottom.  This is a very useful document,
>from the look of it.

>On page 100, they start to talk about aligning the high spots in exactly the
>same terms as I have been hearing, and later there is a picture showing what the
>high-spot marks look like.  I found such marks on the bearings in my mill.  
>Well, I'm short one mark (on a cup), which mark seems to have been abraded off.

>> >> "Tap fit" is a rather subjective way to characterize a bearing fit,
>> >> depending on who's doing the tapping and the size of the tapper, but I
>> >> assume it means a transitional fit with minimal interference. The ID
>> >> of your cones can vary by 5 tenths, so a tap fit on one bearing may
>> >> result in excessive clearance on another.

>> >This may be what is happening.  And things may have corroded and so grown a
>> >bit over the years.  I think I'll do most of the polishing on the bearing ID,
>> >rather than the shaft OD, although I'll clean corrosion off the shaft.

>> I certainly wouldn't hesitate to cautiously remove any corrosion or
>> high spots you find.

>Yes.  This weekend.

>> >> >> Be aware that the specs on standard tapered rollers are very loose
>> >> >> compared to inexpensive ball bearings, and precision class bearings
>> >> >> are quite expensive. Expect to pay around $270 for each cup/cone ass'y
>> >> >> in class 0 vs. $45 for a standard bearing.

>> >Which class is a "standard bearing"?  I'd guess 4, for wheel bearings.

>> Yes.

>> >What are "airplane bearings", like from skygeek.com?  They are priced at the
>> >$45 level for the cup and another $45 for the cone et al.

>> I don't know what "airplane bearings" are, but Motion Industries also
>> references "aircraft bearings" in their database, with no indication
>> of what distinguishes them from standard bearings. But they are listed
>> as "standard precision."

>Another poster (J.Clarke) said that it meant only that the maker had jumped the
>hoops to become FAA certified for airplane repair.

>> >What is a typical price for Class 3 set of one 19268 and one 19150?

>> Looks like about $125 for the cone and $68 for the cup. Those are my
>> approx prices from Motion Industries.

>Oof.  That's a total of 2(125+68)= 386= $400.  I was leaning towards letting it
>be for now, and this is pushing me that direction.  There is only one corroded
>spot, about 0.25" in diameter.

>> >> >What class is needed for a MVI anyway?

>> >> Class TIR
>> >> 4     .0020
>> >> 2     .0015
>> >> 3     .0003
>> >> 0     .00015
>> >> 00    .000075

>> >> The runout of Class 0 roller bearings is approximately the same as the
>> >> ABEC 7 angular contact bearings typically found in machine tool
>> >> spindles.

>> >DC Morrison says that Timken Class 3 are what was specified for the Millrite
>> >spindle, and the existing bearings are in fact marked 3.

>> >> >> BTW, the first thousand or so J-head Bridgeports used tapered rollers
>> >> >> on the spindle; the subsequent couple hundred thousand have angular
>> >> >> contact bearings.

>> >> >Burke used taper roller bearings for the standard R8 spindle, and ball
>> >> >bearings
>> >> >for the high-speed spindle.  Taper roller bearings are more robust than
>> >> >ball bearings under shock loads (like interrupted cuts).

>> >> True, but BP spindle bearings will take a lot of abuse if they're
>> >> lubricated properly and kept clean. Tapered rollers will carry a
>> >> substantially heavier load than angular contact bearings in a given
>> >> volume. But there are tradeoffs, such as added complexity, expense,
>> >> and less tolerance of contamination.

>> >All true, and Burke apparently valued robust more than Bridgeport.  Perhaps
>> >the intended audiences were different.  Not that I've heard of Bridgeport
>> >spindles
>> >being so fragile.  But I don't know why Burke didn't provide more protection
>> >against the entry of dirt and coolants.

>> BP spindles are not especially well protected, either. The nose pair
>> is protected only by a labyrinth formed by close clearances between
>> the various parts of the spindle and quill.

>The Millrite also has a labyrinth of sorts, being three ~square cross section
>grooves in the quill nut through which the spindle nose protrudes.  It's a tight
>fit.  Sounds like the BP approach.  The grooves were packed full of crud, now
>removed.

>>   Indiscriminate use of air
>> to clear chips can force crud up into the bearings.

>Yet another reason for the tradition to forbid use of compressed air on machine
>tools.

>Joe Gwinn

As an interested onlooker. How much of the TIR is eccentricity
and how  much is "out of round".

For instance. If we fitted class 2 set of bearings and then
finish ground the spindle nose and bore in situ, would we have a
class 00 sytem?

Jim

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Joseph Gwin » Fri, 20 Aug 2010 22:17:15




Quote:
> On Wed, 18 Aug 2010 23:27:22 -0400, Joseph Gwinn



> >> On Wed, 18 Aug 2010 00:02:45 -0400, Joseph Gwinn



> >> >> On Mon, 16 Aug 2010 23:28:56 -0400, Joseph Gwinn



> >> >> >> On Mon, 16 Aug 2010 09:55:27 -0400, Joseph Gwinn

[snip]

> >> >Does Timken mention alignment of high spots and low spots to reduce
> >> >runout?

> >> Not that I see in the literature I have, but "Timken Bearings for
> >> Machine Tools" is mentioned in the section on precision bearings, and
> >> may have more info if you can find a copy online.

> >I'm not finding anything by this name; perhaps this was an earlier version
> >and/or name.  

> >What I did find is "Timken Super Precision Bearings for Machine Tool
> >Applications", file "5918_09-09-29.pdf", 259 pages.  The pages are all
> >marked
> >"TIMKEN MACHINE TOOL CATALOG" at the bottom.  This is a very useful
> >document,
> >from the look of it.

> >On page 100, they start to talk about aligning the high spots in exactly the
> >same terms as I have been hearing, and later there is a picture showing what
> >the high-spot marks look like.  I found such marks on the bearings in my mill.  
> >Well, I'm short one mark (on a cup), which mark seems to have been abraded
> >off.

[snip]

> >> >> >> Be aware that the specs on standard tapered rollers are very loose
> >> >> >> compared to inexpensive ball bearings, and precision class bearings
> >> >> >> are quite expensive. Expect to pay around $270 for each cup/cone
> >> >> >> ass'y in class 0 vs. $45 for a standard bearing.

[snip]

> >> >> >What class is needed for a MVI anyway?

> >> >> Class    TIR
> >> >> 4        .0020
> >> >> 2        .0015
> >> >> 3        .0003
> >> >> 0        .00015
> >> >> 00       .000075

> >> >> The runout of Class 0 roller bearings is approximately the same as the
> >> >> ABEC 7 angular contact bearings typically found in machine tool
> >> >> spindles.

> >> >DC Morrison says that Timken Class 3 are what was specified for the
> >> >Millrite spindle, and the existing bearings are in fact marked 3.

[snip]

> >Joe Gwinn

> As an interested onlooker. How much of the TIR is eccentricity
> and how  much is "out of round".

I have no way to measure out of round better than measuring the spindle diameter
in various places around the circle, and I get the same answer all around.  

The spindle appears to have been ground.   What I had thought were are
longitudinal ripples from some kind of chatter in the grinder upon cleaning,
polishing, and inspection with a 10x magnifier are scratches, apparently from
dirt caught between spindle and cup when the cups were pulled off the spindle.  
Given the design, it was difficult to clean this area before disassembly, a
Catch-22.

The inside of the quill is bored, and so is likely quite round.

Quote:
> For instance. If we fitted class 2 set of bearings and then
> finish ground the spindle nose and bore in situ, would we have a
> class 00 sytem?

If the two bearing cones (or cups respectively) can be depended on not to rotate
with respect to one another over time, it could work I would think.  

The cones (inner races) are too tight on the spindle shaft to rotate unless a
bearing completely jams.  Even then, a more likely outcome is rollers skidding.  
In any event, a repair must immediately follow.

Both cup (outer race) faces are scuffed, apparently by the spacer tube, but the
cup OD cylinder surfaces show no signs of having rotated in the quill.  So, the
cups may stay put well enough.  The movement of the spacer tube may indicate
that the preload wasn't quite enough.

At least at low rotation rates, where the resulting slight imbalance is without
effect.  Given the maximum of ~3000 rpm for a Millrite spindle, I would doubt
that a little spindle imbalance would be noticed.  After all, we are likely
talking about a few times 0.0001" of decentering, which we probably already have.

Joe Gwinn

 
 
 

Millrite MVI spindle bearing repair - first report

Post by Michael A. Terrel » Sat, 21 Aug 2010 17:10:38


Quote:

> If you prefer, when calling Thompson...tell them you are with Coyote
> Engineering, (my company) and get a price.

   Just stay away from 'Acme' brand bearings and anvils ;-)
 
 
 

Millrite MVI spindle bearing repair - first report

Post by Ned Simmon » Tue, 24 Aug 2010 22:47:16




Quote:


>>> Looks like about $125 for the cone and $68 for the cup. Those are my
>>> approx prices from Motion Industries.

>Guys..when pricing bearings....a hint and an offer Ive made before...

>Contact Alpine Bearing and Thompson Industrial Bearing

>Tell them you are with Rapid Turn..and ask for pricing. If they ask
>about John..tell them he is doing fine.

>If you prefer, when calling Thompson...tell them you are with Coyote
>Engineering, (my company) and get a price.

>Period.

>You will get FAR better pricing quotes than a cold call to Motion
>Industries.

>We do this with GREAT regularlity for our customers and its quite
>common.

>As long as they have a name with regular bearing sales..they give 3rd
>column pricing..and the differences in pricing is often staggering.

>http://www.alpinebearing.com/

>http://www.tismc.com/

I've had an OEM account with MI for about 25 years, since the ME
branches were a family owned business. I'll bet the prices I gave are
pretty close to the best you can do in small quantities, but a thrifty
man will shop around.

For curiosity's sake, I sent an RFQ on the bearings to Thompson
Industrial last Wed. They didn't reply.

--
Ned Simmons