I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made
from Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

i

On Wed, 28 Jul 2010 23:15:26 -0500, Ignoramus6705
wrote:

I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made
from Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

i

The bottom bearing may..may be a bit dry. What provisions are there on
your machine for bearing lubrication? Every Bridgeport Ive seen has
luber for the bearings.

And no..its not bad at all. Im rather surprised that it was that low,
from a 20-30 yr old machine.

My Gorton, run at 5000 rpm, wide open, will increase temps to 80' above
ambient. This of course doesnt include..as yours doesnt..the cooling
effects of coolant on the spindle as well as the cutter and work piece.

I rebuilt the spindle in mine about 6 yrs ago,...somewhere less than 30
hours of actual run time. Probably closer to 5 hours actually.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On 2010-07-29, Gunner Asch wrote:
On Wed, 28 Jul 2010 23:15:26 -0500, Ignoramus6705
wrote:

I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made
from Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

i

The bottom bearing may..may be a bit dry. What provisions are there on
your machine for bearing lubrication? Every Bridgeport Ive seen has
luber for the bearings.

bearings are permanently lubed.

And no..its not bad at all. Im rather surprised that it was that low,
from a 20-30 yr old machine.

Good to hear.

My Gorton, run at 5000 rpm, wide open, will increase temps to 80' above
ambient. This of course doesnt include..as yours doesnt..the cooling
effects of coolant on the spindle as well as the cutter and work piece.

Well, the coolant does not really get to cool what really matters,
which is the bearings.

I rebuilt the spindle in mine about 6 yrs ago,...somewhere less than 30
hours of actual run time. Probably closer to 5 hours actually.

What sort of bearings did you use?

i

On Wed, 28 Jul 2010 23:52:06 -0500, Ignoramus6705
wrote:

On 2010-07-29, Gunner Asch wrote:
On Wed, 28 Jul 2010 23:15:26 -0500, Ignoramus6705
wrote:

I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made
from Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

i

The bottom bearing may..may be a bit dry. What provisions are there on
your machine for bearing lubrication? Every Bridgeport Ive seen has
luber for the bearings.

bearings are permanently lubed.

And no..its not bad at all. Im rather surprised that it was that low,
from a 20-30 yr old machine.

Good to hear.

My Gorton, run at 5000 rpm, wide open, will increase temps to 80' above
ambient. This of course doesnt include..as yours doesnt..the cooling
effects of coolant on the spindle as well as the cutter and work piece.

Well, the coolant does not really get to cool what really matters,
which is the bearings.

You would be greatly surprised at how well heat transfer works .....


I rebuilt the spindle in mine about 6 yrs ago,...somewhere less than 30
hours of actual run time. Probably closer to 5 hours actually.

What sort of bearings did you use?

i
The same type that came out.

I dont recall what the number was. Shrug.

"A conservative who doesn't believe? in God simply doesn't pray;
a godless liberal wants no one to pray. A conservative who doesn't
like guns doesn't buy one; a liberal gun-hater wants to disarm us all.
A gay conservative has sex his own way; a gay liberal requires us all
to watch and accept his perversion and have it taught to children.
A conservative who is offended by a radio show changes the station;
an offended liberal wants it banned, prosecuted and persecuted."
Bobby XD9

Ignoramus6705 wrote:
I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made
from Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees

The varispeed runs hot, because the belts rub. That is normal, that's
why they have air vents in the housing.
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

Yes. This temp rise in only 16 minutes at 3000 RPM does sound
excessive. But, this is a series 2 machine, with 3 HP motor?
(I'm trying to remember.) They usually have sealed, grease-packed
bearings, which run a lot hotter at
high speed than the oil-drip bearings used in many of the Series-I
machines. This kind of heating is going to cause
spindle growth, for instance, making it hard to hold fine tolerances on Z.

(I see in your reply to Gunner that it is a sealed-bearing unit.) One
possible problem is somebody repacked the bearings with too much or the
wrong kind of grease, or that coolant and swarf has gotten up in there.
The oil-lubed Bridgeports depend on oil dripping down to flush
contaminants out of the bearings. If your bearing seals are shot,
contaminants could easily work up into the bearings (gulp). I think it
is fairly easy to drop the spindle cartridge out of the quill. There is
a setscrew that locks the bearing cap. You remove the setscrew and
unscrew the cap. The entire bearing/spindle assembly may just drop out
the bottom from its own weight, so be ready to support it. This should
allow you to examine the seals, at the least, and the cleanliness of the
inside of the bearing region. If filled with crap, you know you need to
flush and relube, at the least. The bearings need to be filled with a
known quantity of lube to avoid overfilling. If you have to replace the
bearings, they may be a bit expensive. I know the bearing sets for the
Series-I are quite expensive.

When reassembling, you use the dimple made for the setscrew to put the
bearing cover back in the rght position, and then GENTLY tighen the
setscrew to avoid warping the quill.

If you decide to take the bearing assembly apart, ask for advice, it is
a bit tricky, and I don't know the sealed bearing version. The bearings
need to be aligned a certain way and fitted with matched spacers. I
know there are couple guys on here that know the procedures well.

Jon

Ignoramus6705 wrote:

I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made

Oh, the other thing to know is, how far does this progress? If the
temperature just keeps
climbing at this ~ 2 degree F per minute rate, you have a SERIOUS
problem, and the bearings are going to blow shortly.
If it levels off at 130 F and stays there, I'd still be a little
concerned, but it isn't going to melt down right away.

What concerns me is the rate of rise, which is some measure of the heat
output. My spindle gets hot, too, but it
takes at least a half hour or more to get near this temp.

Jon

Jon Elson fired this volley in
news

What concerns me is the rate of rise, which is some measure of the heat
output. My spindle gets hot, too, but it
takes at least a half hour or more to get near this temp.


Iggy was gumming up in aluminum during this session, no?

Maybe it's partly heat conducted up through the cutter and tool holder.

LLoyd

On 2010-07-29, Jon Elson wrote:
Ignoramus6705 wrote:
I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made
from Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees

The varispeed runs hot, because the belts rub. That is normal, that's
why they have air vents in the housing.
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

Yes. This temp rise in only 16 minutes at 3000 RPM does sound
excessive. But, this is a series 2 machine, with 3 HP motor?

It is an Interact mill, it is not really a Series II equivalent.

It has a 2 HP motor that says "good for 3 HP for 30 minutes".

(I'm trying to remember.) They usually have sealed, grease-packed
bearings, which run a lot hotter at high speed than the oil-drip
bearings used in many of the Series-I machines.

Yes, sealed bearings.

This kind of heating is going to cause spindle growth, for instance,
making it hard to hold fine tolerances on Z.

(I see in your reply to Gunner that it is a sealed-bearing unit.)
One possible problem is somebody repacked the bearings with too much
or the wrong kind of grease, or that coolant and swarf has gotten up
in there. The oil-lubed Bridgeports depend on oil dripping down to
flush contaminants out of the bearings. If your bearing seals are
shot, contaminants could easily work up into the bearings (gulp). I
think it is fairly easy to drop the spindle cartridge out of the
quill. There is a setscrew that locks the bearing cap. You remove
the setscrew and unscrew the cap. The entire bearing/spindle
assembly may just drop out the bottom from its own weight, so be
ready to support it. This should allow you to examine the seals, at
the least, and the cleanliness of the inside of the bearing region.
If filled with crap, you know you need to flush and relube, at the
least. The bearings need to be filled with a known quantity of lube
to avoid overfilling. If you have to replace the bearings, they may
be a bit expensive. I know the bearing sets for the Series-I are
quite expensive.

When reassembling, you use the dimple made for the setscrew to put the
bearing cover back in the rght position, and then GENTLY tighen the
setscrew to avoid warping the quill.

If you decide to take the bearing assembly apart, ask for advice, it is
a bit tricky, and I don't know the sealed bearing version. The bearings
need to be aligned a certain way and fitted with matched spacers. I
know there are couple guys on here that know the procedures well.

Jon, I think that for now, I will file your advice but will refrain
from taking the head apart. It is just too risky. Just one stupid
thing and bye bye CNC mill.

i

On 2010-07-29, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Jon Elson fired this volley in
news

What concerns me is the rate of rise, which is some measure of the heat
output. My spindle gets hot, too, but it
takes at least a half hour or more to get near this temp.


Iggy was gumming up in aluminum during this session, no?

No. Wax.

Maybe it's partly heat conducted up through the cutter and tool holder.

could not be

On 2010-07-29, Jon Elson wrote:
Ignoramus6705 wrote:

I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made

Oh, the other thing to know is, how far does this progress? If the
temperature just keeps
climbing at this ~ 2 degree F per minute rate, you have a SERIOUS
problem, and the bearings are going to blow shortly.
If it levels off at 130 F and stays there, I'd still be a little
concerned, but it isn't going to melt down right away.

What concerns me is the rate of rise, which is some measure of the heat
output. My spindle gets hot, too, but it
takes at least a half hour or more to get near this temp.

I would not know, good question. I will try to check again.

i

On Thu, 29 Jul 2010 12:36:50 -0500, Jon Elson wrote:
Ignoramus6705 wrote:
I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC jobs
complete). It was machining a mold prototype for a kids toy. We will
need to cast 18 of them that in wax, and the mold will be made from
Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees
....
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

Yes. This temp rise in only 16 minutes at 3000 RPM does sound
excessive. But, [snipalot]

The rise appears to be 29 degrees F (or 16K) at the collar; is
that the figure you consider excessive?

--
jiw

Jon Elson wrote:

Ignoramus6705 wrote:
I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC
jobs complete). It was machining a mold prototype for a kids toy. We
will need to cast 18 of them that in wax, and the mold will be made
from Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees

The varispeed runs hot, because the belts rub. That is normal, that's
why they have air vents in the housing.
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

Yes. This temp rise in only 16 minutes at 3000 RPM does sound
excessive. But, this is a series 2 machine, with 3 HP motor?
(I'm trying to remember.) They usually have sealed, grease-packed
bearings, which run a lot hotter at
high speed than the oil-drip bearings used in many of the Series-I
machines. This kind of heating is going to cause
spindle growth, for instance, making it hard to hold fine tolerances on Z.

(I see in your reply to Gunner that it is a sealed-bearing unit.) One
possible problem is somebody repacked the bearings with too much or the
wrong kind of grease, or that coolant and swarf has gotten up in there.
The oil-lubed Bridgeports depend on oil dripping down to flush
contaminants out of the bearings. If your bearing seals are shot,
contaminants could easily work up into the bearings (gulp). I think it
is fairly easy to drop the spindle cartridge out of the quill. There is
a setscrew that locks the bearing cap. You remove the setscrew and
unscrew the cap. The entire bearing/spindle assembly may just drop out
the bottom from its own weight, so be ready to support it. This should
allow you to examine the seals, at the least, and the cleanliness of the
inside of the bearing region. If filled with crap, you know you need to
flush and relube, at the least. The bearings need to be filled with a
known quantity of lube to avoid overfilling. If you have to replace the
bearings, they may be a bit expensive. I know the bearing sets for the
Series-I are quite expensive.

When reassembling, you use the dimple made for the setscrew to put the
bearing cover back in the rght position, and then GENTLY tighen the
setscrew to avoid warping the quill.

If you decide to take the bearing assembly apart, ask for advice, it is
a bit tricky, and I don't know the sealed bearing version. The bearings
need to be aligned a certain way and fitted with matched spacers. I
know there are couple guys on here that know the procedures well.

Jon

Another possibility is that the machine sat unused for a fair amount of
time and the grease in the bearings hardened. The grease should
reliquify ok, but certainly he should keep an eye on spindle temp for a
while.

Ignoramus5687 wrote:


It is an Interact mill, it is not really a Series II equivalent.

It has a 2 HP motor that says "good for 3 HP for 30 minutes".

Yes, but it is a standard Bridgeport Ser-II BOSS head.

Jon, I think that for now, I will file your advice but will refrain
from taking the head apart. It is just too risky. Just one stupid
thing and bye bye CNC mill.

Yes, years ago, I was the same way, horrified at the thought of horribly
messing something up.
There ARE things that shouldn't be taken apart because the "springs will
all fly out", but I am a lot
bolder now. Of course, after doing a complete strip-down and rebuild on
a 3500 Lb toolroom lathe,
maybe I have earned the confidence.

Anyway, if the spindle temp levels off after a longer run, then I agree,
it probably isn't a big problem.
If the temp keeps going up, then you are going to have to investigate.
You can get plenty of advice
here from people who know these machines better than me.


Jon

Pete C. wrote:

Another possibility is that the machine sat unused for a fair amount of
time and the grease in the bearings hardened. The grease should
reliquify ok, but certainly he should keep an eye on spindle temp for a
while.

I really don't trust ancient, hardened grease that may have contaminants
in it in a set of expensive spindle bearings.
I have experienced this "hardened grease" and I don't think it actually
does ever liquify after that process happens.
This machine could very well have the original 30 year-old grease in it!

Yes, Iggy should DEFINITELY watch the temp until he is satisfied that it
does level off. I have a feeling with an
~30 F rise in only 16 minutes, that the limit temperature is going to be
way up there. Now, that may be normal for
the sealed bearing Ser-II head, but it will cause spindle growth that
will be several thousandths of an inch. Especially because the ballnut
is all the way at the top end of the quill in the BOSS head, a full FOOT
above the spindle nose, the expansion can be considerable.
Now, assuming the limit temp rise is 60 F (twice as hot as it got in
only 16 minutes) and assuming the whole quill heated evenly (not
possible) then it would expand .005". Assuming the quill had a linear
drop in temp along the whole foot, the expansion would be .002". While
not hideous, that could mess up precision work.

Jon

On Thu, 29 Jul 2010 12:36:50 -0500, Jon Elson
wrote:

The bearings need to be filled with a
known quantity of lube to avoid overfilling.

1/3rd fill.

Fill them completely..and they will run very warm/hot

Gunner


"A conservative who doesn't believe? in God simply doesn't pray;
a godless liberal wants no one to pray. A conservative who doesn't
like guns doesn't buy one; a liberal gun-hater wants to disarm us all.
A gay conservative has sex his own way; a gay liberal requires us all
to watch and accept his perversion and have it taught to children.
A conservative who is offended by a radio show changes the station;
an offended liberal wants it banned, prosecuted and persecuted."
Bobby XD9

Gunner Asch wrote:
On Thu, 29 Jul 2010 12:36:50 -0500, Jon Elson
wrote:


The bearings need to be filled with a
known quantity of lube to avoid overfilling.


1/3rd fill.

Fill them completely..and they will run very warm/hot

Right, but how the HECK do you determine how much is 1/3rd?
I guess the bearing manufacturer can calculate the exact volume of the
bearing that isn't filled with steel, but I think this could be hard to
do correctly in the field. Hmm, I suppose you could weight the bearing
and then calculate the volume of the OD - ID and that would get you
pretty close.

Jon

On Sun, 01 Aug 2010 00:07:34 -0500, Jon Elson
wrote:

Gunner Asch wrote:
On Thu, 29 Jul 2010 12:36:50 -0500, Jon Elson
wrote:


The bearings need to be filled with a
known quantity of lube to avoid overfilling.


1/3rd fill.

Fill them completely..and they will run very warm/hot

Right, but how the HECK do you determine how much is 1/3rd?
I guess the bearing manufacturer can calculate the exact volume of the
bearing that isn't filled with steel, but I think this could be hard to
do correctly in the field. Hmm, I suppose you could weight the bearing
and then calculate the volume of the OD - ID and that would get you
pretty close.

Jon


Nah..fill em full with a bearing grease press, then soak em in solvent,
collect the grease, burn out the solvent with heat, and measure the
grease volume. Then divide by 3 and voila!

G

Or make an educated guess like I do when packing bearings on machine
tools.

Say!..you could use a grease gun and a needle and fill in between every
third ball! That would do it!

VBG

Gunner


"A conservative who doesn't believe? in God simply doesn't pray;
a godless liberal wants no one to pray. A conservative who doesn't
like guns doesn't buy one; a liberal gun-hater wants to disarm us all.
A gay conservative has sex his own way; a gay liberal requires us all
to watch and accept his perversion and have it taught to children.
A conservative who is offended by a radio show changes the station;
an offended liberal wants it banned, prosecuted and persecuted."
Bobby XD9

On 2010-07-29, James Waldby wrote:
On Thu, 29 Jul 2010 12:36:50 -0500, Jon Elson wrote:
Ignoramus6705 wrote:
I ran my mill for 16 minutes at 3,000 RPM (I get email when my CNC jobs
complete). It was machining a mold prototype for a kids toy. We will
need to cast 18 of them that in wax, and the mold will be made from
Aluminum. But I digress.

After I finished running for 16 minutes, I measured a few temps:

*) Inside the shop - 86 degrees
*) On the variable speed transmission on top -- 105 degrees
...
*) On the low part of spindle (at the QC-30 collar) 115 degrees. I am
not sure if I fully believe this last measurement. The bottom of the
spindle feels warm to the touch, I can hold it indefinitely, but it is
not comfortable.

Would you consider this temp rise to be excessive?

Yes. This temp rise in only 16 minutes at 3000 RPM does sound
excessive. But, [snipalot]

The rise appears to be 29 degrees F (or 16K) at the collar; is
that the figure you consider excessive?


I am just asking. I am concerned that the rise is much higher inside
the bearing.

i

On 2010-07-31, Jon Elson wrote:

Anyway, if the spindle temp levels off after a longer run, then I
agree, it probably isn't a big problem. If the temp keeps going up,
then you are going to have to investigate. You can get plenty of
advice here from people who know these machines better than me.

I ran the mill for 1/2 hour at 2400 RPM. The rise does stabilize at
some point and 115F seems to be the max.

i

So, a recap is that the the outside temp of the spindle after 15
minutes running at 3K RPM, was 115F. (30 something degree F temp
rise).

I have looked far and wide for the answer as to whetehr this is excessive.

According to someone at cnczone, he measured temp on the bearing and
outside with a non-contact thermometer, and the bearing was 10 degrees
hotter than the outside of the spindle.

So it was, say, 130F, being a little generous, or 54 degrees C.

Barden machine tool bearing catalog says that their spindle bearings
can run at 100C. http://www.bardenbearings.com/PDF%20CD/MACHINET.PDF
My bearings are not Barden, but it is a good data point.

Another guy pointed out that Timken's roller bearing calculations
assume a temp of 130 C for the service life calculations.

So, everything points to a conclusion that 115C on the outside
represents a normal bearing operating temperature and is nothing to
worry about. Since I use this mill for hobby purposes, I will back out
a litle bit and will run it at 2700 or so RPM max.

i

On Mon, 02 Aug 2010 08:44:05 -0500, Ignoramus18921
wrote:

On 2010-07-31, Jon Elson wrote:

Anyway, if the spindle temp levels off after a longer run, then I
agree, it probably isn't a big problem. If the temp keeps going up,
then you are going to have to investigate. You can get plenty of
advice here from people who know these machines better than me.

I ran the mill for 1/2 hour at 2400 RPM. The rise does stabilize at
some point and 115F seems to be the max.

i

You are golden. Dont worry about it.

Gunner


"A conservative who doesn't believe? in God simply doesn't pray;
a godless liberal wants no one to pray. A conservative who doesn't
like guns doesn't buy one; a liberal gun-hater wants to disarm us all.
A gay conservative has sex his own way; a gay liberal requires us all
to watch and accept his perversion and have it taught to children.
A conservative who is offended by a radio show changes the station;
an offended liberal wants it banned, prosecuted and persecuted."
Bobby XD9

On Mon, 02 Aug 2010 09:40:13 -0500, Ignoramus18921
wrote:

So, a recap is that the the outside temp of the spindle after 15
minutes running at 3K RPM, was 115F. (30 something degree F temp
rise).

I have looked far and wide for the answer as to whetehr this is excessive.

According to someone at cnczone, he measured temp on the bearing and
outside with a non-contact thermometer, and the bearing was 10 degrees
hotter than the outside of the spindle.

So it was, say, 130F, being a little generous, or 54 degrees C.

Barden machine tool bearing catalog says that their spindle bearings
can run at 100C. http://www.bardenbearings.com/PDF%20CD/MACHINET.PDF
My bearings are not Barden, but it is a good data point.

Another guy pointed out that Timken's roller bearing calculations
assume a temp of 130 C for the service life calculations.

So, everything points to a conclusion that 115C on the outside
represents a normal bearing operating temperature and is nothing to
worry about. Since I use this mill for hobby purposes, I will back out
a litle bit and will run it at 2700 or so RPM max.

i

Or run it at full bore for the several minutes it takes to make the
cuts.

Gunner



"A conservative who doesn't believe? in God simply doesn't pray;
a godless liberal wants no one to pray. A conservative who doesn't
like guns doesn't buy one; a liberal gun-hater wants to disarm us all.
A gay conservative has sex his own way; a gay liberal requires us all
to watch and accept his perversion and have it taught to children.
A conservative who is offended by a radio show changes the station;
an offended liberal wants it banned, prosecuted and persecuted."
Bobby XD9

On 2010-08-01, Jon Elson wrote:
Gunner Asch wrote:
On Thu, 29 Jul 2010 12:36:50 -0500, Jon Elson
wrote:


The bearings need to be filled with a
known quantity of lube to avoid overfilling.


1/3rd fill.

Fill them completely..and they will run very warm/hot

Right, but how the HECK do you determine how much is 1/3rd?
I guess the bearing manufacturer can calculate the exact volume of the
bearing that isn't filled with steel, but I think this could be hard to
do correctly in the field. Hmm, I suppose you could weight the bearing
and then calculate the volume of the OD - ID and that would get you
pretty close.

Wash it clean with solvent, and then pack the bearings for 1/3
of the circumference. Once that is done, you rotate the inner or outer
race to distribute the lube evenly.

Of course, if they have shields, you'll need to remove the
shields first. :-)

Anyway -- this (including the cleaning with solvent) lets you
examine the bearings and races for pitting.

Enjoy,
DoN.

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