Recently got a Powermatic PM2000 cabinet saw. Yesterday I set the miter
slot to blade and miter slot to fence parallel adjustments using a dial
indicator. I was able to get both to within .002". So far so good. Today,
I've place the blade at 45 deg., and the measurement from the front of the
blade to the rear is +.016". I understand this indicates the table is
sloping at the front side & needs to be shimmed. OK, I get that. HOWEVER,
if I loosen the 2 bolts on the front side of the table & lift, the error
INCREASES. If I loosen the 2 bolts on the REAR SIDE of the table & lift,
the error ALSO INCREASES. How an this be??? Any suggestions appreciated.

TIA

Dan

On Thu, 20 Sep 2007 12:23:43 -0700, "Dan" wrote:

Recently got a Powermatic PM2000 cabinet saw. Yesterday I set the miter
slot to blade and miter slot to fence parallel adjustments using a dial
indicator. I was able to get both to within .002". So far so good. Today,
I've place the blade at 45 deg., and the measurement from the front of the
blade to the rear is +.016". I understand this indicates the table is
sloping at the front side & needs to be shimmed.

Not necessarily.


OK, I get that. HOWEVER,
if I loosen the 2 bolts on the front side of the table & lift, the error
INCREASES. If I loosen the 2 bolts on the REAR SIDE of the table & lift,
the error ALSO INCREASES. How an this be??? Any suggestions appreciated.

TIA

Dan



First suggestion is that a range of .002" to .016" from 90 to 45
degrees is more than likely well within the tolerance specifications
of the machine.

Secondly, it is not only the table that can cause the change. The
machined tolerances of the trunions, trunion brackets, plane of the
cabinet flange, change in the moment arm created by the motor, the
blade if that is what you are checking off of. as well as the
flatness of the table, how parrallel the table bottom bosses are to
the top, etc.

During the assembly process the manufacturer sets the alignment at 90
to as close to zero as possible. The tolerance stack up of all the
other parts mentioned above is what determines what that becomes at
45. The manufacture then rolls it over to 45 and checks the alignment
to the slot and has a tolerance that qualifies the saw as a good unit.
Often there is nothing you can do unless you want to loose the close
setting at 90. to improve the 45.




Frank

"Frank Boettcher" wrote in message
...
On Thu, 20 Sep 2007 12:23:43 -0700, "Dan" wrote:

Recently got a Powermatic PM2000 cabinet saw. Yesterday I set the miter
slot to blade and miter slot to fence parallel adjustments using a dial
indicator. I was able to get both to within .002". So far so good.
Today,
I've place the blade at 45 deg., and the measurement from the front of the
blade to the rear is +.016". I understand this indicates the table is
sloping at the front side & needs to be shimmed.

Not necessarily.


OK, I get that. HOWEVER,
if I loosen the 2 bolts on the front side of the table & lift, the error
INCREASES. If I loosen the 2 bolts on the REAR SIDE of the table & lift,
the error ALSO INCREASES. How an this be??? Any suggestions appreciated.

TIA

Dan



First suggestion is that a range of .002" to .016" from 90 to 45
degrees is more than likely well within the tolerance specifications
of the machine.

Secondly, it is not only the table that can cause the change. The
machined tolerances of the trunions, trunion brackets, plane of the
cabinet flange, change in the moment arm created by the motor, the
blade if that is what you are checking off of. as well as the
flatness of the table, how parrallel the table bottom bosses are to
the top, etc.

During the assembly process the manufacturer sets the alignment at 90
to as close to zero as possible. The tolerance stack up of all the
other parts mentioned above is what determines what that becomes at
45. The manufacture then rolls it over to 45 and checks the alignment
to the slot and has a tolerance that qualifies the saw as a good unit.
Often there is nothing you can do unless you want to loose the close
setting at 90. to improve the 45.




Frank

Frank-thanks for the reply. I'm using a good quality blade (Forrest
woodworker II) which I have measured & which has minimal runout. Plus I am
measuring at the same point on the blade front & back (rotating the blade).
I understand what you mean about tolerances stacking up. I also understand
the issue may not be purely the top is uniformly lower in the front; could
be one corner, etc. However a .016 variation is more than 1/64 of an inch.
This amount would make it virtually impossible to make anything like a tight
edge miter of any length (say, for a speaker cabinet) with the blade tilted.
I expect more from a $2000 saw.

Dan wrote:
"Frank Boettcher" wrote in message
...
On Thu, 20 Sep 2007 12:23:43 -0700, "Dan" wrote:

Recently got a Powermatic PM2000 cabinet saw. Yesterday I set the miter
slot to blade and miter slot to fence parallel adjustments using a dial
indicator. I was able to get both to within .002". So far so good.
Today,
I've place the blade at 45 deg., and the measurement from the front of the
blade to the rear is +.016". I understand this indicates the table is
sloping at the front side & needs to be shimmed.
Not necessarily.

....
First suggestion is that a range of .002" to .016" from 90 to 45
degrees is more than likely well within the tolerance specifications
of the machine.

Secondly, it is not only the table that can cause the change. The
machined tolerances of the trunions, trunion brackets, plane of the
cabinet flange, change in the moment arm created by the motor, the
blade if that is what you are checking off of. as well as the
flatness of the table, how parrallel the table bottom bosses are to
the top, etc.

During the assembly process the manufacturer sets the alignment at 90
to as close to zero as possible. The tolerance stack up of all the
other parts mentioned above is what determines what that becomes at
45. The manufacture then rolls it over to 45 and checks the alignment
to the slot and has a tolerance that qualifies the saw as a good unit.
Often there is nothing you can do unless you want to loose the close
setting at 90. to improve the 45.

....
Frank-thanks for the reply. I'm using a good quality blade (Forrest
woodworker II) which I have measured & which has minimal runout. Plus I am
measuring at the same point on the blade front & back (rotating the blade).
I understand what you mean about tolerances stacking up. I also understand
the issue may not be purely the top is uniformly lower in the front; could
be one corner, etc. However a .016 variation is more than 1/64 of an inch.
This amount would make it virtually impossible to make anything like a tight
edge miter of any length (say, for a speaker cabinet) with the blade tilted.
I expect more from a $2000 saw.

Check w/ PM. I would expect better as well. I don't know what they've
done w/ the mounts on the PM2000 vis a vis the PM66 which I have.

--

On Thu, 20 Sep 2007 13:02:56 -0700, "Dan" wrote:

"Frank Boettcher" wrote in message
.. .
On Thu, 20 Sep 2007 12:23:43 -0700, "Dan" wrote:


snipped a bunch


However a .016 variation is more than 1/64 of an inch.
This amount would make it virtually impossible to make anything like a tight
edge miter of any length (say, for a speaker cabinet) with the blade tilted.


Once again, not necessarily. You might get a surface that is ever so
slightly more rough than perfection. Probably take a profilometer to
measure it. You might get a touch of burn, although I doubt it. But
the wood travels past the whole blade. Doesn't mean that any part of
your cut is .016" off to any other part of the same board.

However, as you might know, a plane is established by three points
only and your table and cabinet are four. You may improve by shimming
one corner, if the bulk of the "problem" is either parrallel of the
plane of the bosses to the top of the table or plane of the top plate
on the cabinet. It is all trial and error. Or if bevel cuts are a
way of life for you, you might cheat your 90 setting the other way a
little.

And you might call Powermatic to see if they have any tricks. They
will probably tell you it is within specs. but may give you some
ideas.

However, if it were mine and I were within .016" with a dead on 90,
I'd lock it down and cut wood.

Frank

Frank

"Dan" wrote in message
. ..


Frank

Frank-thanks for the reply. I'm using a good quality blade (Forrest
woodworker II) which I have measured & which has minimal runout. Plus I
am measuring at the same point on the blade front & back (rotating the
blade). I understand what you mean about tolerances stacking up. I also
understand the issue may not be purely the top is uniformly lower in the
front; could be one corner, etc. However a .016 variation is more than
1/64 of an inch. This amount would make it virtually impossible to make
anything like a tight edge miter of any length (say, for a speaker
cabinet) with the blade tilted. I expect more from a $2000 saw.


I would at this point suggest to first take Frank's advice and start cutting
some wood. While exacting tolerances are a plus, sometimes we cannot take
full advantages of these fine settings because of the quality of the
material that we cut and or out technique can be sub par to the machine
tolerances.
First see how the saw cuts at a 45 degree bevel. If you don't see any kerf
marks or burning you should be good to go.
We often get a bit too wrapped up in using a dial indicator to measure
"everything".
If you are not happy with the cutting results call Powermatic and get them
involved.

"Frank Boettcher" wrote in message

However, if it were mine and I were within .016" with a dead on 90,
I'd lock it down and cut wood.

Ditto. The proof is in the pudding ... or, as an old friend, full of
(resigned) Italian wisdom, oft stated: "What you lose on the bananas, you
make on the grapes".

One of the most time wasting tools in the hands of an anal wooddorker is an
alignment tool. How do I know? ... just finished my regularly scheduled,
once a decade, more or less, alignment of the table saw last week, so the
subject be (too) fresh on my mind.

When I start chasing my tail, I split the difference ... cuz, what you make
on the grapes, you also lose on the banana's.

Boudreaux says c'est la vie.... and make some sawdust.

--
www.e-woodshop.net
Last update: 8/08/07
KarlC@ (the obvious)

"Swingman" wrote in message
...
"Frank Boettcher" wrote in message

However, if it were mine and I were within .016" with a dead on 90,
I'd lock it down and cut wood.

Ditto. The proof is in the pudding ... or, as an old friend, full of
(resigned) Italian wisdom, oft stated: "What you lose on the bananas, you
make on the grapes".

One of the most time wasting tools in the hands of an anal wooddorker is
an alignment tool. How do I know? ... just finished my regularly
scheduled, once a decade, more or less, alignment of the table saw last
week, so the subject be (too) fresh on my mind.

When I start chasing my tail, I split the difference ... cuz, what you
make on the grapes, you also lose on the banana's.

Boudreaux says c'est la vie.... and make some sawdust.


Thanks for the replies. I guess the net result of the blade being angled
~.016, all other things being equal, would be a kerf wider by that amount.
By futzing around, I was able to get a tradeoff error of .008 on 90, .009 on
45. One reason I'm a bit obsessed with this is about a year ago I bought a
Bosch 5412 slide miter saw, specifically to execute a dining room table
design I had in mind. Hard to describe in words, but where the members
which connect to the legs attach to a center longitudinal member entailed 4
45 degree cuts. No matter how much screwing around I did with that saw, I
could not get this joint to not have gaps in the range 3/64". The pieces
kept getting shorter & shorter as I attempted to get the joint to be tight.
Made a lot of expensive sawdust (but no table) with that one.

"Dan" wrote in message
. ..
~.016, all other things being equal, would be a kerf wider by that amount.
By futzing around, I was able to get a tradeoff error of .008 on 90, .009
on 45.

After setting the saw this way, I made some test cuts on a piece of 3/4"
inch plywood, 4.5" wide by 10.5" long. The board is perfectly square and
flat. A 90 degree cut made on each end is perfect. However when I switch
to 45 & make an edge miter cut, the angle is perfect, but the trailing edge
of the cut protrudes 1 full 1/16" above the square when the leading edge is
brought flush with the square on that end. In other words, the board is now
1/16 inch longer on one edge at the miter cut than at the other. Try to
make a box with 8 such cuts & you'd produce a spiral. If anyone has further
suggestions please share them.

Dan

On Thu, 20 Sep 2007 12:23:43 -0700, Dan wrote:

Recently got a Powermatic PM2000 cabinet saw. Yesterday I set the miter
slot to blade and miter slot to fence parallel adjustments using a dial
indicator. I was able to get both to within .002". So far so good. Today,
I've place the blade at 45 deg., and the measurement from the front of the
blade to the rear is +.016".

On a contractors saw, this problem is usually caused by the two trunnions
not being parallel and the answer is to shim one side of one of the
trunnions. I don't know if the same applies to cabinet saws, but they do
have trunnions - perhaps someone else can comment.

On Sep 20, 4:48 pm, "Dan" wrote:

After setting the saw this way, I made some test cuts on a piece of 3/4"
inch plywood, 4.5" wide by 10.5" long. The board is perfectly square and
flat. A 90 degree cut made on each end is perfect. However when I switch
to 45 & make an edge miter cut, the angle is perfect, but the trailing edge
of the cut protrudes 1 full 1/16" above the square when the leading edge is
brought flush with the square on that end. In other words, the board is now
1/16 inch longer on one edge at the miter cut than at the other. Try to
make a box with 8 such cuts & you'd produce a spiral. If anyone has further
suggestions please share them.

Dan

Hi Dan,

I read through the original problem and your replies so far. Sorry I
didn't notice the thread earlier. As you have now discovered, the
situation isn't quite as tolerable as some have said. There has to be
a reason why shimming the table doesn't fix the problem but makes it
worse. It doesn't make any sense that this should happen. I'm sure
that it wouldn't take long to figure it out if I could come by to look
at it but I suspect that you are not in my neighborhood (Boise, ID).
So, you'll have to do the legwork.

If the reading at the rear of the blade is higher than the reading at
the front, then the rear side of the table needs shimming (bringing up
the table will, in effect, lower the blade). If the reading at the
front of the blade is higher than the reading at the rear, then the
front needs to be shimmed. Pay careful attention to the magnitude and
direction of the reading because it's easy to get confused. You might
think that you've made it worse, only to discover that you have over
corrected and caused larger error in the other direction. And, don't
use any paper, wood, or other fiberous material for the shimms. I'm
not a big fan of plastic either. I like using aluminum. Thicker
pieces can be cut from soda cans, thinner pieces can be had from a
roll of foil.

Give me a call on the phone if you want to go through it in real time:
1-800-333-4994

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

Subject

Remember the old saying, "A Flying Red Horse can't tell the difference
from 1,000 ft"?

It applies.

Lew

PS:

Ask the guys in metrology about the magnitude of built in errors of
single ended vs differential measurements.

Measurements under discussion are single ended.

"Dan" wrote in message

If anyone has further suggestions please share them.

Yeah ..., make some goddamn furniture and quit f*cking with the table saw!
G

If nothing else, what I did for the 30 years before I had a table saw worth
"setting up" ... a plane and a shooting board.

It is absolutely ridiculous to get bogged down in measuring, in thousandths
the tools we use, in a medium that is liable to change +/- 1/16th between
sundown and sunrise.

And ... beware of those who do nothing else but measure, and make no sawdust
whatsoever.

--
www.e-woodshop.net
Last update: 8/08/07
KarlC@ (the obvious)

"Ed Bennett" wrote in message
ups.com...
On Sep 20, 4:48 pm, "Dan" wrote:

I read through the original problem and your replies so far. Sorry I
didn't notice the thread earlier. As you have now discovered, the
situation isn't quite as tolerable as some have said. There has to be
a reason why shimming the table doesn't fix the problem but makes it
worse. It doesn't make any sense that this should happen. I'm sure
that it wouldn't take long to figure it out if I could come by to look
at it but I suspect that you are not in my neighborhood (Boise, ID).
So, you'll have to do the legwork.

Ed-Thanks for the reply. Seattle's not THAT far from Boise! ;-) Saw is
left tilt, I'm using the right miter slot. On 90, both slots measure the
same, so are parallel to one another. I reset the 90 to about .003, at
which point the 45 is about +.012. To me this says the table is HIGHER in
the rear (gauge tip is going up the left tilting blade as it moves front to
rear, and thus increasing the gap). I'll try the pop can shims. And thanks
for the offer of phone assistance, I may end up taking you up on that!

I understand the "make some sawdust" sentiment, but cutting expensive wood
before the saw is all it should be makes no sense. If you bought a brand
new sports car which pulled to one side, would the response be "just go for
a drive"? 1/16" of error across a 4.5" cut is simply not acceptable. I
could better that result cutting by eye with my circular saw.

Dan

On Sep 20, 6:57 pm, "Dan" wrote:
Ed-Thanks for the reply. Seattle's not THAT far from Boise! ;-)

Bit much for a day trip ;-)

Saw is
left tilt, I'm using the right miter slot. On 90, both slots measure the
same, so are parallel to one another. I reset the 90 to about .003, at
which point the 45 is about +.012. To me this says the table is HIGHER in
the rear (gauge tip is going up the left tilting blade as it moves front to
rear, and thus increasing the gap).

Ok, so if I understand you correctly, the reading on the indicator is
going down (counter-clockwise) as you move from the front to the
back. Correct? This would correspond to the table being higher
(blade being lower) in the rear. This means that you need to shim in
the front.

You can quickly approximate the amount of shim needed by knowing how
much the reading changes and how far apart the two readings are.
First, correct the reading for cosine errors. Then figure out the
ammount of change per inch. Finally, multiply this by the distance
between your table bolts.

So, for example, if your blade is tilted to 45 degrees, then the
correction factor is going to be 0.7071 (cos(45)). If you measure
0.012" misalignment, then the actual change is 0.0085" (0.012 *
0.7071). If it was measured over a distance of 8", then you have a
change of 0.0011" per inch (0.0085 / 8). Then, if your bolts are 20"
apart, then you should start with 0.022" (0.0011 * 20) worth of
shims. This isn't going to be exact but it's a good place to start.

I'll try the pop can shims. And thanks
for the offer of phone assistance, I may end up taking you up on that!

No problem. Glad to help.

I understand the "make some sawdust" sentiment, but cutting expensive wood
before the saw is all it should be makes no sense. If you bought a brand
new sports car which pulled to one side, would the response be "just go for
a drive"? 1/16" of error across a 4.5" cut is simply not acceptable. I
could better that result cutting by eye with my circular saw.

I understand completely. If you wanted to spend your time reworking
everything that your tablesaw should have done correctly, then you
wouldn't have spent $2000 on a new tablesaw.

Beware of the guy who spends more time making sawdust than
furniture. ;-)

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

"Ed Bennett" wrote in message
ps.com...

So, for example, if your blade is tilted to 45 degrees, then the
correction factor is going to be 0.7071 (cos(45)). If you measure
0.012" misalignment, then the actual change is 0.0085" (0.012 *
0.7071). If it was measured over a distance of 8", then you have a
change of 0.0011" per inch (0.0085 / 8). Then, if your bolts are 20"
apart, then you should start with 0.022" (0.0011 * 20) worth of


You have the scenario exactly, and I must say I'm very impressed, though I
am simultaneously saddened by the fact that at one time I actually *did
know* all that trigonometry. Now get this: After some experimenting (and
BEFORE I read your prediction) I was able to get the error of both 90 & 45
degrees down to ~.003 by inserting a .025" washer under the table at the 2
front table corner bolts. Again, very impressed you were able to predict
this so closely with calculations.

Cuts are now PERFECT!

LET'S MAKE SOME SAWDUST!!!!!!!!!

BTW if anyone is interested, I can email PDF's of several articles I have
on tablesaw tune-ups which helped me work this out, a video of one of which
can be seen at
http://www.taunton.com/finewoodworki...e.aspx?id=5313.

Thanks for your support!

Dan

Frank Boettcher wrote:

During the assembly process the manufacturer sets the alignment at 90
to as close to zero as possible. ...
The manufacture then rolls it over to 45 and checks the alignment
to the slot and has a tolerance that qualifies the saw as a good unit.
Often there is nothing you can do unless you want to loose the close
setting at 90. to improve the 45.

If the only problem is that the axis of rotation of the arbor is not
parallel to the table, then shimming the table relative to the cabinet
can fix the problem.

If there is other slop and play in the mechanism, I agree that there
isn't much that can be done.

Chris

Swingman wrote:

It is absolutely ridiculous to get bogged down in measuring, in thousandths
the tools we use, in a medium that is liable to change +/- 1/16th between
sundown and sunrise.

Good quality pieces are designed to handle wood dimension changes. It's
expected. That doesn't mean that you can cut your parts to +/- 1/16th
and have it come out anywhere close to decent right off the saw.

If the power tools aren't accurately set up it means that the hand tools
get more of a workout paring and shooting to get everything accurate.

Chris

On Sep 20, 8:40 pm, "Dan" wrote:
You have the scenario exactly, and I must say I'm very impressed, though I
am simultaneously saddened by the fact that at one time I actually *did
know* all that trigonometry. Now get this: After some experimenting (and
BEFORE I read your prediction) I was able to get the error of both 90 & 45
degrees down to ~.003 by inserting a .025" washer under the table at the 2
front table corner bolts. Again, very impressed you were able to predict
this so closely with calculations.

Cuts are now PERFECT!

LET'S MAKE SOME SAWDUST!!!!!!!!!

BTW if anyone is interested, I can email PDF's of several articles I have
on tablesaw tune-ups which helped me work this out, a video of one of which
can be seen athttp://www.taunton.com/finewoodworking/ToolGuide/ToolGuideArticle.asp....

Thanks for your support!

Dan

You're welcome! Every now and then the old gray matter comes in
handy.

I wouldn't mind seeing these articles you mention.

Thanks,
Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

On Sep 20, 3:23 pm, "Dan" wrote:
Recently got a Powermatic PM2000 cabinet saw. Yesterday I set the miter
slot to blade and miter slot to fence parallel adjustments using a dial
indicator. I was able to get both to within .002". So far so good. Today,
I've place the blade at 45 deg., and the measurement from the front of the
blade to the rear is +.016". I understand this indicates the table is
sloping at the front side & needs to be shimmed. OK, I get that. HOWEVER,
if I loosen the 2 bolts on the front side of the table & lift, the error
INCREASES. If I loosen the 2 bolts on the REAR SIDE of the table & lift,
the error ALSO INCREASES. How an this be??? Any suggestions appreciated.

TIA

Dan

It's possible that you're cranking the blade too hard against the 45
or 90 degree stops. I might try cuts at 46 and 89 degrees, just to
see if the stops are the problem.

Hard to imagine how the error can increase no matter which way you
tilt the table.

John Martin

"John Martin" wrote in message
ups.com...
On Sep 20, 3:23 pm, "Dan" wrote:
It's possible that you're cranking the blade too hard against the 45
or 90 degree stops. I might try cuts at 46 and 89 degrees, just to
see if the stops are the problem.

Hard to imagine how the error can increase no matter which way you
tilt the table.

John Martin


John-I finally worked it out with .025" shims, now I'm good to ~.003 on
each. I think the error was that prying the table on one side didn't really
replicate the effect of shims.

"Ed Bennett" wrote in message
ups.com...
On Sep 20, 8:40 pm, "Dan" wrote:
You're welcome! Every now and then the old gray matter comes in
handy.

I wouldn't mind seeing these articles you mention.

You got it, Ed.

Dan

Dan wrote:
"Ed Bennett" wrote in message
ps.com...

So, for example, if your blade is tilted to 45 degrees, then the
correction factor is going to be 0.7071 (cos(45)). If you measure
0.012" misalignment, then the actual change is 0.0085" (0.012 *
0.7071). If it was measured over a distance of 8", then you have a
change of 0.0011" per inch (0.0085 / 8). Then, if your bolts are
20" apart, then you should start with 0.022" (0.0011 * 20) worth of


You have the scenario exactly, and I must say I'm very impressed,
though I am simultaneously saddened by the fact that at one time I
actually *did know* all that trigonometry. Now get this: After
some experimenting (and BEFORE I read your prediction) I was able
to get the error of both 90 & 45 degrees down to ~.003 by inserting
a .025" washer under the table at the 2 front table corner bolts.
Again, very impressed you were able to predict this so closely with
calculations.

Dang shame you didn't have a .022 washer so the .003 error disappeared


--

dadiOH
____________________________

dadiOH's dandies v3.06...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico

"Chris Friesen" wrote in message
Swingman wrote:

It is absolutely ridiculous to get bogged down in measuring, in
thousandths the tools we use, in a medium that is liable to change +/-
1/16th between sundown and sunrise.

Good quality pieces are designed to handle wood dimension changes. It's
expected.

No ****? But apparently not without a $2000 cabinet saw set up to +/- .003,
eh?

That doesn't mean that you can cut your parts to +/- 1/16th and have it
come out anywhere close to decent right off the saw.
If the power tools aren't accurately set up it means that the hand tools
get more of a workout paring and shooting to get everything accurate.

Yessir, it a damn crying shame that the lack of a $2000 cabinet saw, set up
to .003, stopped the likes of Duncan Phyfe, and more recently old Frank and
Sam's careers, dead in their tracks.

--
www.e-woodshop.net
Last update: 8/08/07
KarlC@ (the obvious)

"Ed Bennett" wrote in message

Beware of the guy who spends more time making sawdust than
furniture. ;-)

LOL ... the key to actually "making furniture" is to make more more sawdust
than OCD measurements.

--
www.e-woodshop.net
Last update: 8/08/07
KarlC@ (the obvious)

"dadiOH" wrote in message

Dang shame you didn't have a .022 washer so the .003 error disappeared


ROTFLMAO! ... Hey, think of the commercial possibilities! "Woodmachinists"
everywhere would beat your door down.

--
www.e-woodshop.net
Last update: 8/08/07
KarlC@ (the obvious)

On Sep 20, 10:40 pm, "Dan" wrote:
"Ed Bennett" wrote in message

ps.com...

So, for example, if your blade is tilted to 45 degrees, then the
correction factor is going to be 0.7071 (cos(45)). If you measure
0.012" misalignment, then the actual change is 0.0085" (0.012 *
0.7071). If it was measured over a distance of 8", then you have a
change of 0.0011" per inch (0.0085 / 8). Then, if your bolts are 20"
apart, then you should start with 0.022" (0.0011 * 20) worth of

You have the scenario exactly, and I must say I'm very impressed, though I
am simultaneously saddened by the fact that at one time I actually *did
know* all that trigonometry. Now get this: After some experimenting (and
BEFORE I read your prediction) I was able to get the error of both 90 & 45
degrees down to ~.003 by inserting a .025" washer under the table at the 2
front table corner bolts. Again, very impressed you were able to predict
this so closely with calculations.

Cuts are now PERFECT!

LET'S MAKE SOME SAWDUST!!!!!!!!!

BTW if anyone is interested, I can email PDF's of several articles I have
on tablesaw tune-ups which helped me work this out, a video of one of which
can be seen athttp://www.taunton.com/finewoodworking/ToolGuide/ToolGuideArticle.asp....

Thanks for your support!

Dan

Dan,

I would also appreciate the PDF articles you mentioned in your post.

TIA.
Ed F.

In article , "Dan" wrote:
"Ed Bennett" wrote in message
oups.com...
On Sep 20, 4:48 pm, "Dan" wrote:

I read through the original problem and your replies so far. Sorry I
didn't notice the thread earlier. As you have now discovered, the
situation isn't quite as tolerable as some have said. There has to be
a reason why shimming the table doesn't fix the problem but makes it
worse. It doesn't make any sense that this should happen. I'm sure
that it wouldn't take long to figure it out if I could come by to look
at it but I suspect that you are not in my neighborhood (Boise, ID).
So, you'll have to do the legwork.

Ed-Thanks for the reply. Seattle's not THAT far from Boise! ;-)

Ed, it sounds like he's offering to pay your travel expenses. g

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Y'know - after many years of lurking and occasional posting in this
newsgroup and having to deal with the seasonal trolls that surface, it's
nice to be reminded of the good stuff - like someone actually helping
someone else.


OK, enough sentiment - gotta go make some noise & sawdust!

Vic


"Dan" wrote in message
. ..
"John Martin" wrote in message
ups.com...
On Sep 20, 3:23 pm, "Dan" wrote:
It's possible that you're cranking the blade too hard against the 45
or 90 degree stops. I might try cuts at 46 and 89 degrees, just to
see if the stops are the problem.

Hard to imagine how the error can increase no matter which way you
tilt the table.

John Martin


John-I finally worked it out with .025" shims, now I'm good to ~.003 on
each. I think the error was that prying the table on one side didn't
really replicate the effect of shims.

Dan,

I would also appreciate the PDF articles you mentioned in your post.

TIA.
Ed F.


Ed - They're on their way, let me know if you have any trouble receiving
them.

Dan

On Sep 20, 3:24 pm, "Dan" wrote:

...where the members
which connect to the legs attach to a center longitudinal member entailed 4
45 degree cuts. No matter how much screwing around I did with that saw, I
could not get this joint to not have gaps in the range 3/64".

45 degrees is always described (by careful persons) as 45 +/-
something-or-other.
So the typical way to get a full circle out of 45 degree wedges is to
join
four wedges for the left half, join four wedges for the right half,
and joint both
halves to make the final joints fit. Another way is to temporary-
mount the items
side-to-side with the crack, run it through the table saw to open that
crack to
a straight 1/8" void, then close the joint. Kerfing was what Roy
Underhill
called it, though his technique used a handsaw...

On Sep 21, 2:07 pm, whit3rd wrote:
45 degrees is always described (by careful persons) as 45 +/-
something-or-other.

Very true! The words "dead on" are somewhat of a misnomer.
Everything has some error if you look closely enough.

So the typical way to get a full circle out of 45 degree wedges is to
join
four wedges for the left half, join four wedges for the right half,
and joint both
halves to make the final joints fit.

I've heard of this. It's a popular technique among those who do
segmented turnings. The joints will all be tight but the circle
becomes a bit less circular. The lathe guys end up having to make the
walls of their turnings a bit thicker so that they can then turn them
round.

Another way is to temporary-
mount the items
side-to-side with the crack, run it through the table saw to open that
crack to
a straight 1/8" void, then close the joint. Kerfing was what Roy
Underhill
called it, though his technique used a handsaw...

In other words, cut both pieces at the same time. Yes, I've used this
technique (long, long ago). You pretty much want to assemble the
whole thing first. For something like a frame, where you have to
maintain equal lengths on opposite sides, you'll end up cutting
through all of the joints - gap or no.

There's a third option that you didn't mention. That is, cut the
pieces accurately enough to avoid the gap in the first place. Then
you don't have to use these or any other methods to rework the
joint(s). It takes a bit more skill and knowledge but it's much
faster and cleaner in the end. The other techniques are good for
those who are not interested in developing their machinery skills.

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner.com

"Lew Hodgett" wrote in message
...
PS:

Ask the guys in metrology about the magnitude of built in errors of
single ended vs differential measurements.

Measurements under discussion are single ended.

There's something I've never heard of before!

I've heard of "single-ended" and "differential" used to describe electrical
interfaces. In that application, the differential interface is very immune
to noise. There are many measurement instruments that take advantage of
this interface. They're not mechanical instruments.

I've heard of (and used) measurement setups where the output of two gauges
are combined by a dual channel amplifier to produce a sum or difference
reading. I wouldn't exactly call such a setup less prone to error! And
I've never heard it described as "differential". I've never heard of single
gage setups as being "single-ended".

I've been designing and manufacturing measurement instruments since 1991 and
have never heard the terms "single-ended" or "differential" used to describe
the measurement technique/process itself. Please do tell.

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

"whit3rd" wrote in message
ps.com...
Another way is to temporary-
mount the items
side-to-side with the crack, run it through the table saw to open that
crack to
a straight 1/8" void, then close the joint. Kerfing was what Roy
Underhill
called it, though his technique used a handsaw...


Thanks for the reply. An interesting technique, I'll have to keep it in
mind.

Dan

"Doug Miller" wrote in message
t...
Ed, it sounds like he's offering to pay your travel expenses. g

Doh! Blew that one big time!

Anybody in Hawaii need help with their table saw? Perhaps sometime in
January or February? ;-)

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

"Swingman" wrote in message
...
LOL ... the key to actually "making furniture" is to make more more
sawdust than OCD measurements.

I'd like to think that there's a happy medium between those two extremes.
Certainly, you can't avoid making some sawdust while woodworking. But, the
guy who spends all his time doing test cuts and reworking joints doesn't
really have much authority on the topic of machinery skills and the need for
proper alignment. Neither does the guy who can't apply his machinery skills
to solve real world woodworking problems.

Some guys, when they first get an alignment jig, are like a kid who has
never had candy before. They eat so much of it that they end up with a
tummy ache.

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

"Ed Bennett" wrote in message
...
"Swingman" wrote in message
...
LOL ... the key to actually "making furniture" is to make more more
sawdust than OCD measurements.

I'd like to think that there's a happy medium between those two extremes.
Certainly, you can't avoid making some sawdust while woodworking. But,
the guy who spends all his time doing test cuts and reworking joints
doesn't really have much authority on the topic of machinery skills and
the need for proper alignment. Neither does the guy who can't apply his
machinery skills to solve real world woodworking problems.

Some guys, when they first get an alignment jig, are like a kid who has
never had candy before. They eat so much of it that they end up with a
tummy ache.

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

Well in my case I had the applicable measuring tools from a number of engine
overhauls I had done some years ago, they were readily adapted to this task,
and using them in this way was not a special "treat".

Individuals have varying philosophies about what is important in all manner
of things; I guess woodworking is no different. But referring to someone's
attempt to simply realize the full potential of a sizable investment as
"OCD" strikes me as childish name calling and requires no further response.

Thanks again to those who made helpful replies to my post.

Dan

"Ed Bennett" wrote in message
...
"Swingman" wrote in message
...
LOL ... the key to actually "making furniture" is to make more more
sawdust than OCD measurements.

I'd like to think that there's a happy medium between those two extremes.
Certainly, you can't avoid making some sawdust while woodworking. But,
the guy who spends all his time doing test cuts and reworking joints
doesn't really have much authority on the topic of machinery skills and
the need for proper alignment. Neither does the guy who can't apply his
machinery skills to solve real world woodworking problems.


Well, ;~) spending a lot of time doing test cuts to sneak up on a setting
is certainly less than desirable.
However, ;~) If you don't make a test cut after changing a bevel or miter
angle you are making a test cut on you project wood. I stole that from the,
"test a finish on scraps rather than your project".
Almost always I make the test cut to verify that I have set the machine up
to the correct angle to start with. LOL

On Sep 21, 5:55 pm, "Leon" wrote:
Well, ;~) spending a lot of time doing test cuts to sneak up on a setting
is certainly less than desirable.
However, ;~) If you don't make a test cut after changing a bevel or miter
angle you are making a test cut on you project wood. I stole that from the,
"test a finish on scraps rather than your project".
Almost always I make the test cut to verify that I have set the machine up
to the correct angle to start with. LOL

Thanks Leon, it sounds like your medium is much happier than some
others!

Ed Bennett


http://www.ts-aligner.com
Home of the TS-Aligner

"Dan" wrote in message

of things; I guess woodworking is no different. But referring to
someone's
attempt to simply realize the full potential of a sizable investment as
"OCD" strikes me as childish name calling and requires no further
response.

Bzzzzt! ... If you'd been around a little longer, you'd realized that "OCD"
was a reference to Ed's self characterization in a recent thread on plywood
manufacture.

You apology is accepted.

--
www.e-woodshop.net
Last update: 8/8/07
KarlC@ (the obvious)