My Fadal mill showed me by the cuts it was making that the spindle
needed to be trammed. I have a lot of good machine shop inspection
equipment. I can easily, repeatably, and accurately measure down to 50
millioniths of an inch. Not so easily but accurately and reapatably
down to 20 millionths. I have several standards for lengths. My best
set are the ceramic gauge blocks. The maximum deviation from nominal
size of any of the blocks is +3 millionths of an inch except the 4
inch block which is +4 millionths. Most are only + 2 or less
millionths. I have indirectly seen temperature changes by measuring
lengths. Anyway, back to the Fadal. After leveling the mill according
to the Fadal manual instructions with a precision level to better than
..0005 per foot I checked the table flatness in the six spots
corresponding to the spindle retaining bolt locations, again following
the Fadal instructions. Then, using a tool that Fadal recommends, I
set about to tramming the spindle. The Fadal manual says to tram to
better than .001 in 12 inches and that Fadal Techs usually tram the
spindles to .0005. So I figured I would make mine better. Finally,
after fussing with the damn thing for hours and hours I got the
spindle tram to just slightly better than .0004 in 12. The problem is
that the error is so magnified by the measuring tools that .0004 looks
like a huge amount. And barely touching anything moves the indicator.
I checked and re-checked and so on for the next day just to make sure
the machine wasn't going to settle and change the tram. Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change. And I have the tools and knowhow to measure the tram
error. So I have to resist the temptation to check the tram because I
know it will never end. It's the same with parts I make. I check 'em,
see an error, change an offset, see another error, change another
offset, and all the while the parts are within .001 and the tolerance
is + or - .005. It's like a disease. It also affects me when I start
to optimize programs to shave of smaller and smaller increments of
time. At least now that the spindle is in proper tram the cuts look
much better. I am milling some brass door furniture that has large
flat surfaces inside pockets. These surfaces will be polished to a
high shine so the cutter marks must be able to be removed easily. So
it's a purely cosmetic thing but since the pockets can't be sanded on
a surface plate to remove cutter marks the cutter marks must be
removable with only tripoli or E5 emery on a buffing wheel or point.
After tramming the head the parts are now coming out the way I want.
Eric

On Tue, 05 Apr 2016 11:04:20 -0700, wrote:

My Fadal mill showed me by the cuts it was making that the spindle
needed to be trammed. I have a lot of good machine shop inspection
equipment. I can easily, repeatably, and accurately measure down to 50
millioniths of an inch. Not so easily but accurately and reapatably
down to 20 millionths. I have several standards for lengths. My best
set are the ceramic gauge blocks. The maximum deviation from nominal
size of any of the blocks is +3 millionths of an inch except the 4
inch block which is +4 millionths. Most are only + 2 or less
millionths. I have indirectly seen temperature changes by measuring
lengths. Anyway, back to the Fadal. After leveling the mill according
to the Fadal manual instructions with a precision level to better than
.0005 per foot I checked the table flatness in the six spots
corresponding to the spindle retaining bolt locations, again following
the Fadal instructions. Then, using a tool that Fadal recommends, I
set about to tramming the spindle. The Fadal manual says to tram to
better than .001 in 12 inches and that Fadal Techs usually tram the
spindles to .0005. So I figured I would make mine better. Finally,
after fussing with the damn thing for hours and hours I got the
spindle tram to just slightly better than .0004 in 12. The problem is
that the error is so magnified by the measuring tools that .0004 looks
like a huge amount. And barely touching anything moves the indicator.
I checked and re-checked and so on for the next day just to make sure
the machine wasn't going to settle and change the tram. Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change. And I have the tools and knowhow to measure the tram
error. So I have to resist the temptation to check the tram because I
know it will never end. It's the same with parts I make. I check 'em,
see an error, change an offset, see another error, change another
offset, and all the while the parts are within .001 and the tolerance
is + or - .005. It's like a disease. It also affects me when I start
to optimize programs to shave of smaller and smaller increments of
time. At least now that the spindle is in proper tram the cuts look
much better. I am milling some brass door furniture that has large
flat surfaces inside pockets. These surfaces will be polished to a
high shine so the cutter marks must be able to be removed easily. So
it's a purely cosmetic thing but since the pockets can't be sanded on
a surface plate to remove cutter marks the cutter marks must be
removable with only tripoli or E5 emery on a buffing wheel or point.
After tramming the head the parts are now coming out the way I want.
Eric

Hmm. You're looking for Mikron or Kugler accuracy from a Fadal. I'm
surprised you're getting it that close. Don't sneeze! g

--
Ed Huntress

On Tue, 05 Apr 2016 14:23:59 -0400, Ed Huntress
wrote:

On Tue, 05 Apr 2016 11:04:20 -0700, wrote:

My Fadal mill showed me by the cuts it was making that the spindle
needed to be trammed. I have a lot of good machine shop inspection
equipment. I can easily, repeatably, and accurately measure down to 50
millioniths of an inch. Not so easily but accurately and reapatably
down to 20 millionths. I have several standards for lengths. My best
set are the ceramic gauge blocks. The maximum deviation from nominal
size of any of the blocks is +3 millionths of an inch except the 4
inch block which is +4 millionths. Most are only + 2 or less
millionths. I have indirectly seen temperature changes by measuring
lengths. Anyway, back to the Fadal. After leveling the mill according
to the Fadal manual instructions with a precision level to better than
.0005 per foot I checked the table flatness in the six spots
corresponding to the spindle retaining bolt locations, again following
the Fadal instructions. Then, using a tool that Fadal recommends, I
set about to tramming the spindle. The Fadal manual says to tram to
better than .001 in 12 inches and that Fadal Techs usually tram the
spindles to .0005. So I figured I would make mine better. Finally,
after fussing with the damn thing for hours and hours I got the
spindle tram to just slightly better than .0004 in 12. The problem is
that the error is so magnified by the measuring tools that .0004 looks
like a huge amount. And barely touching anything moves the indicator.
I checked and re-checked and so on for the next day just to make sure
the machine wasn't going to settle and change the tram. Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change. And I have the tools and knowhow to measure the tram
error. So I have to resist the temptation to check the tram because I
know it will never end. It's the same with parts I make. I check 'em,
see an error, change an offset, see another error, change another
offset, and all the while the parts are within .001 and the tolerance
is + or - .005. It's like a disease. It also affects me when I start
to optimize programs to shave of smaller and smaller increments of
time. At least now that the spindle is in proper tram the cuts look
much better. I am milling some brass door furniture that has large
flat surfaces inside pockets. These surfaces will be polished to a
high shine so the cutter marks must be able to be removed easily. So
it's a purely cosmetic thing but since the pockets can't be sanded on
a surface plate to remove cutter marks the cutter marks must be
removable with only tripoli or E5 emery on a buffing wheel or point.
After tramming the head the parts are now coming out the way I want.
Eric

Hmm. You're looking for Mikron or Kugler accuracy from a Fadal. I'm
surprised you're getting it that close. Don't sneeze! g

The model I have has the linear ways. Though not as heavy duty as box
ways they don't wear the way box ways do. Since the mill is back in
pruduction it has probably changed already and I am going to resist
checking it again unless I see another problem. Unbelievably the 4th
axis that came with the machine is out of square. This is the stock
Fadal 4th axis. I bought the machine used so I expected some error
somewhere but the amount of out of squareness in the 4th axis is huge
for this kind of machine. When used with the rotary table surface
parallel to the Z axis I have to put .006" shims under one edge of the
thing in order for the table to be square to the mill table. The back
surface is parallel to the table surface. I thought that maybe the
table spindle is adjustable in the casting that holds it but there is
no adjustment. The holes machined in the casting for the spindle are
off. Too bad the rotary axis spindle can't be trammed like the main
machine spindle can. One of these days I am going to set the 4th axis
on the surface grinder and square it up after I rough it in on the
mill.
Eric

On Tue, 05 Apr 2016 11:04:20 -0700, wrote:

My Fadal mill showed me by the cuts it was making that the spindle
needed to be trammed. I have a lot of good machine shop inspection
equipment. I can easily, repeatably, and accurately measure down to 50
millioniths of an inch. Not so easily but accurately and reapatably
down to 20 millionths. I have several standards for lengths. My best
set are the ceramic gauge blocks. The maximum deviation from nominal
size of any of the blocks is +3 millionths of an inch except the 4
inch block which is +4 millionths. Most are only + 2 or less
millionths. I have indirectly seen temperature changes by measuring
lengths. Anyway, back to the Fadal. After leveling the mill according
to the Fadal manual instructions with a precision level to better than
.0005 per foot I checked the table flatness in the six spots
corresponding to the spindle retaining bolt locations, again following
the Fadal instructions. Then, using a tool that Fadal recommends, I
set about to tramming the spindle. The Fadal manual says to tram to
better than .001 in 12 inches and that Fadal Techs usually tram the
spindles to .0005. So I figured I would make mine better. Finally,
after fussing with the damn thing for hours and hours I got the
spindle tram to just slightly better than .0004 in 12. The problem is
that the error is so magnified by the measuring tools that .0004 looks
like a huge amount. And barely touching anything moves the indicator.
I checked and re-checked and so on for the next day just to make sure
the machine wasn't going to settle and change the tram. Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change. And I have the tools and knowhow to measure the tram
error. So I have to resist the temptation to check the tram because I
know it will never end. It's the same with parts I make. I check 'em,
see an error, change an offset, see another error, change another
offset, and all the while the parts are within .001 and the tolerance
is + or - .005. It's like a disease. It also affects me when I start
to optimize programs to shave of smaller and smaller increments of
time. At least now that the spindle is in proper tram the cuts look
much better. I am milling some brass door furniture that has large
flat surfaces inside pockets. These surfaces will be polished to a
high shine so the cutter marks must be able to be removed easily. So
it's a purely cosmetic thing but since the pockets can't be sanded on
a surface plate to remove cutter marks the cutter marks must be
removable with only tripoli or E5 emery on a buffing wheel or point.
After tramming the head the parts are now coming out the way I want.

Repeat after me:

Measure with digital calipers.

Mark with chalk.

And cut with an axe.


All better now?

--
If you want to make your dreams come true,
the first thing you have to do is wake up!
--anon

On Tue, 05 Apr 2016 12:15:48 -0700, wrote:

On Tue, 05 Apr 2016 14:23:59 -0400, Ed Huntress
wrote:

On Tue, 05 Apr 2016 11:04:20 -0700, wrote:

My Fadal mill showed me by the cuts it was making that the spindle
needed to be trammed. I have a lot of good machine shop inspection
equipment. I can easily, repeatably, and accurately measure down to 50
millioniths of an inch. Not so easily but accurately and reapatably
down to 20 millionths. I have several standards for lengths. My best
set are the ceramic gauge blocks. The maximum deviation from nominal
size of any of the blocks is +3 millionths of an inch except the 4
inch block which is +4 millionths. Most are only + 2 or less
millionths. I have indirectly seen temperature changes by measuring
lengths. Anyway, back to the Fadal. After leveling the mill according
to the Fadal manual instructions with a precision level to better than
.0005 per foot I checked the table flatness in the six spots
corresponding to the spindle retaining bolt locations, again following
the Fadal instructions. Then, using a tool that Fadal recommends, I
set about to tramming the spindle. The Fadal manual says to tram to
better than .001 in 12 inches and that Fadal Techs usually tram the
spindles to .0005. So I figured I would make mine better. Finally,
after fussing with the damn thing for hours and hours I got the
spindle tram to just slightly better than .0004 in 12. The problem is
that the error is so magnified by the measuring tools that .0004 looks
like a huge amount. And barely touching anything moves the indicator.
I checked and re-checked and so on for the next day just to make sure
the machine wasn't going to settle and change the tram. Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change. And I have the tools and knowhow to measure the tram
error. So I have to resist the temptation to check the tram because I
know it will never end. It's the same with parts I make. I check 'em,
see an error, change an offset, see another error, change another
offset, and all the while the parts are within .001 and the tolerance
is + or - .005. It's like a disease. It also affects me when I start
to optimize programs to shave of smaller and smaller increments of
time. At least now that the spindle is in proper tram the cuts look
much better. I am milling some brass door furniture that has large
flat surfaces inside pockets. These surfaces will be polished to a
high shine so the cutter marks must be able to be removed easily. So
it's a purely cosmetic thing but since the pockets can't be sanded on
a surface plate to remove cutter marks the cutter marks must be
removable with only tripoli or E5 emery on a buffing wheel or point.
After tramming the head the parts are now coming out the way I want.
Eric

Hmm. You're looking for Mikron or Kugler accuracy from a Fadal. I'm
surprised you're getting it that close. Don't sneeze! g

The model I have has the linear ways. Though not as heavy duty as box
ways they don't wear the way box ways do. Since the mill is back in
pruduction it has probably changed already and I am going to resist
checking it again unless I see another problem. Unbelievably the 4th
axis that came with the machine is out of square. This is the stock
Fadal 4th axis. I bought the machine used so I expected some error
somewhere but the amount of out of squareness in the 4th axis is huge
for this kind of machine. When used with the rotary table surface
parallel to the Z axis I have to put .006" shims under one edge of the
thing in order for the table to be square to the mill table. The back
surface is parallel to the table surface. I thought that maybe the
table spindle is adjustable in the casting that holds it but there is
no adjustment. The holes machined in the casting for the spindle are
off. Too bad the rotary axis spindle can't be trammed like the main
machine spindle can. One of these days I am going to set the 4th axis
on the surface grinder and square it up after I rough it in on the
mill.
Eric

Well, don't tell them I told you this, but Fadals typically are pretty
rough-and-ready machines, and are not known for accuracy. A guy I knew
who used three of them to machine EDM electrodes, when asked why he
used Fadals, told me "because the graphite dust is going to wear out
any mill, and I can scrap my Fadals every two years without feeling
bad about it." I sold him a Roku-Roku with and enclosed air-blast plus
vacuum, and it solved that problem. It also gave him about five times
the accuracy. g

So, what are your ceramic gage blocks, Mitutoyo?

--
Ed Huntress

On Tue, 05 Apr 2016 11:04:20 -0700, wrote:

My Fadal mill showed me by the cuts it was making that the spindle
needed to be trammed. I have a lot of good machine shop inspection
equipment. I can easily, repeatably, and accurately measure down to 50
millioniths of an inch. Not so easily but accurately and reapatably
down to 20 millionths. I have several standards for lengths. My best
set are the ceramic gauge blocks. The maximum deviation from nominal
size of any of the blocks is +3 millionths of an inch except the 4
inch block which is +4 millionths. Most are only + 2 or less
millionths. I have indirectly seen temperature changes by measuring
lengths. Anyway, back to the Fadal. After leveling the mill according
to the Fadal manual instructions with a precision level to better than
.0005 per foot I checked the table flatness in the six spots
corresponding to the spindle retaining bolt locations, again following
the Fadal instructions. Then, using a tool that Fadal recommends, I
set about to tramming the spindle. The Fadal manual says to tram to
better than .001 in 12 inches and that Fadal Techs usually tram the
spindles to .0005. So I figured I would make mine better. Finally,
after fussing with the damn thing for hours and hours I got the
spindle tram to just slightly better than .0004 in 12. The problem is
that the error is so magnified by the measuring tools that .0004 looks
like a huge amount. And barely touching anything moves the indicator.
I checked and re-checked and so on for the next day just to make sure
the machine wasn't going to settle and change the tram. Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change. And I have the tools and knowhow to measure the tram
error. So I have to resist the temptation to check the tram because I
know it will never end. It's the same with parts I make. I check 'em,
see an error, change an offset, see another error, change another
offset, and all the while the parts are within .001 and the tolerance
is + or - .005. It's like a disease. It also affects me when I start
to optimize programs to shave of smaller and smaller increments of
time. At least now that the spindle is in proper tram the cuts look
much better. I am milling some brass door furniture that has large
flat surfaces inside pockets. These surfaces will be polished to a
high shine so the cutter marks must be able to be removed easily. So
it's a purely cosmetic thing but since the pockets can't be sanded on
a surface plate to remove cutter marks the cutter marks must be
removable with only tripoli or E5 emery on a buffing wheel or point.
After tramming the head the parts are now coming out the way I want.
Eric

In most older machine shops..and I say older meaning more than 3 yrs
old....they will tram to .001 and call it good. By the time the part
is finished, polished, handled, bead blasted, tossed in boxes and
moved around...points and surfaces are going to be farther off than
..001. Yeah..if you need mirror surfaces...a grand is still good
enough, because you are going to polish them anyways and you will be
removing more than .001 by doing just that.

ONLY in aerospace shops or some..some medical parts houses will you
find tolerences closer than that...and then only on a very few
assemblies. I know of parts that go into the F-22...that have
tolerances of .01 and others at .00005. But all those zeros come with
a very..very hefty price tag.

Gunner

On Tue, 05 Apr 2016 12:15:48 -0700, wrote:

On Tue, 05 Apr 2016 14:23:59 -0400, Ed Huntress
wrote:

On Tue, 05 Apr 2016 11:04:20 -0700, wrote:

My Fadal mill showed me by the cuts it was making that the spindle
needed to be trammed. I have a lot of good machine shop inspection
equipment. I can easily, repeatably, and accurately measure down to 50
millioniths of an inch. Not so easily but accurately and reapatably
down to 20 millionths. I have several standards for lengths. My best
set are the ceramic gauge blocks. The maximum deviation from nominal
size of any of the blocks is +3 millionths of an inch except the 4
inch block which is +4 millionths. Most are only + 2 or less
millionths. I have indirectly seen temperature changes by measuring
lengths. Anyway, back to the Fadal. After leveling the mill according
to the Fadal manual instructions with a precision level to better than
.0005 per foot I checked the table flatness in the six spots
corresponding to the spindle retaining bolt locations, again following
the Fadal instructions. Then, using a tool that Fadal recommends, I
set about to tramming the spindle. The Fadal manual says to tram to
better than .001 in 12 inches and that Fadal Techs usually tram the
spindles to .0005. So I figured I would make mine better. Finally,
after fussing with the damn thing for hours and hours I got the
spindle tram to just slightly better than .0004 in 12. The problem is
that the error is so magnified by the measuring tools that .0004 looks
like a huge amount. And barely touching anything moves the indicator.
I checked and re-checked and so on for the next day just to make sure
the machine wasn't going to settle and change the tram. Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change. And I have the tools and knowhow to measure the tram
error. So I have to resist the temptation to check the tram because I
know it will never end. It's the same with parts I make. I check 'em,
see an error, change an offset, see another error, change another
offset, and all the while the parts are within .001 and the tolerance
is + or - .005. It's like a disease. It also affects me when I start
to optimize programs to shave of smaller and smaller increments of
time. At least now that the spindle is in proper tram the cuts look
much better. I am milling some brass door furniture that has large
flat surfaces inside pockets. These surfaces will be polished to a
high shine so the cutter marks must be able to be removed easily. So
it's a purely cosmetic thing but since the pockets can't be sanded on
a surface plate to remove cutter marks the cutter marks must be
removable with only tripoli or E5 emery on a buffing wheel or point.
After tramming the head the parts are now coming out the way I want.
Eric

Hmm. You're looking for Mikron or Kugler accuracy from a Fadal. I'm
surprised you're getting it that close. Don't sneeze! g

The model I have has the linear ways. Though not as heavy duty as box
ways they don't wear the way box ways do. Since the mill is back in
pruduction it has probably changed already and I am going to resist
checking it again unless I see another problem. Unbelievably the 4th
axis that came with the machine is out of square. This is the stock
Fadal 4th axis. I bought the machine used so I expected some error
somewhere but the amount of out of squareness in the 4th axis is huge
for this kind of machine. When used with the rotary table surface
parallel to the Z axis I have to put .006" shims under one edge of the
thing in order for the table to be square to the mill table. The back
surface is parallel to the table surface. I thought that maybe the
table spindle is adjustable in the casting that holds it but there is
no adjustment. The holes machined in the casting for the spindle are
off. Too bad the rotary axis spindle can't be trammed like the main
machine spindle can. One of these days I am going to set the 4th axis
on the surface grinder and square it up after I rough it in on the
mill.
Eric

Thats ALL you can do. And its surprisingly common. There is a reason
Fadal went out of business. They had too many bad days amongst all
their good days.

Gunner

Well, don't tell them I told you this, but Fadals typically are pretty
rough-and-ready machines, and are not known for accuracy. A guy I knew
who used three of them to machine EDM electrodes, when asked why he
used Fadals, told me "because the graphite dust is going to wear out
any mill, and I can scrap my Fadals every two years without feeling
bad about it." I sold him a Roku-Roku with and enclosed air-blast plus
vacuum, and it solved that problem. It also gave him about five times
the accuracy. g

So, what are your ceramic gage blocks, Mitutoyo?
I know that Fadals are not the most accurate or fastest or beefiest.
My 16 x 30 inch travel mill weighs about 5500 or 6000 lbs. and has a
10 HP. spindle while my Miyano lathe with 13.5 inches of Z axis travel
and 5.75 of X axis travel has a 15 HP. spindle and weighs 8000 lbs.
But I still make good parts with it, to tight tolerances, and it has 4
axes. It also has the best control of any machine I have ever used. It
is the most intuitive. And tool setting is fast and easy. And the
gauge blocks are Mitutoyo. The ceramic ones. My shop set is an 81
piece that I got from SPI. I think. I've had them for something like
30 years.
Eric

On Tue, 05 Apr 2016 14:22:46 -0700, wrote:



Well, don't tell them I told you this, but Fadals typically are pretty
rough-and-ready machines, and are not known for accuracy. A guy I knew
who used three of them to machine EDM electrodes, when asked why he
used Fadals, told me "because the graphite dust is going to wear out
any mill, and I can scrap my Fadals every two years without feeling
bad about it." I sold him a Roku-Roku with and enclosed air-blast plus
vacuum, and it solved that problem. It also gave him about five times
the accuracy. g

So, what are your ceramic gage blocks, Mitutoyo?
I know that Fadals are not the most accurate or fastest or beefiest.
My 16 x 30 inch travel mill weighs about 5500 or 6000 lbs. and has a
10 HP. spindle while my Miyano lathe with 13.5 inches of Z axis travel
and 5.75 of X axis travel has a 15 HP. spindle and weighs 8000 lbs.
But I still make good parts with it, to tight tolerances, and it has 4
axes. It also has the best control of any machine I have ever used. It
is the most intuitive. And tool setting is fast and easy. And the
gauge blocks are Mitutoyo. The ceramic ones. My shop set is an 81
piece that I got from SPI. I think. I've had them for something like
30 years.
Eric

Yeah, they're great. I have a miscellaneous assortment of them, not a
set, that I a...acquired when I was doing photography for them. They'd
give me a digital mike or a surface plate to photograph, and then
they'd tell me not to bring it back, because they'd already written it
off as advertising expense. g

I wrote a whole string of publicity articles and other material for
them about the Cera Blocks when they came out. They were my
second-biggest client, after Makino.

--
Ed Huntress

wrote:

Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change.

The system I use is I put a wide chunk of thick aluminum sheet on the table,
and set up a CNC program to mill a circular groove it it, with an end mill.
So, the table orbits around, making an over 6" diameter circle. Then, it
moves to the center of that circle. I can mount a dial test indicator in
the spindle and sweep it around the groove. This allows me to detect tram
errors relative to the ACTUAL PLANE of X-Y motion, not the top of the table,
which might not be the same.

Why do you think the tram will change. Once I got mine set up, it hasn't
changed measurably in years. My table does not actually have a "plane" of
motion, as all the ways are a bit worn, and that circular ring is actually a
sort of saddle shaped.

Jon

On Tue, 05 Apr 2016 17:20:46 -0500, Jon Elson
wrote:

wrote:

Since I can
see tiny changes it makes me want to get the machine even closer. But
it's not practical. I am sure that after making some cuts the spindle
tram will change.

The system I use is I put a wide chunk of thick aluminum sheet on the table,
and set up a CNC program to mill a circular groove it it, with an end mill.
So, the table orbits around, making an over 6" diameter circle. Then, it
moves to the center of that circle. I can mount a dial test indicator in
the spindle and sweep it around the groove. This allows me to detect tram
errors relative to the ACTUAL PLANE of X-Y motion, not the top of the table,
which might not be the same.

Why do you think the tram will change. Once I got mine set up, it hasn't
changed measurably in years. My table does not actually have a "plane" of
motion, as all the ways are a bit worn, and that circular ring is actually a
sort of saddle shaped.

Jon
To tram the head the first thing to do is check the flatness of the
table in six spots corresponding to the spindle bolts. Then you take
into account the flatness measurements when you tram the head. I was
being a little facetious when I said the spindle would probably move.
I spent a long time with the torque wrench and shims getting the
spindle just as close as I could. On the other hand, when I bought the
machine the spindle tram was good. After setting it up in my shop I
leveled the mill and the tram was still good. But after a couple years
or so the level changed and so did the tram.
Eric