I just read another magazine article complaining about the error induced
if you don't look straight down on a cursor that isn't close to the
scale. They recommended shimming the cursor down to bring it closer to
the scale, (they were discussing a Powermatic Accu-fence).
The better solution is to scribe the opposite surface and fill in the
scribe line with a magic marker, and then remove the excess marker with
a white vinyl eraser. Then you just line up the two marks, and you
can't induce a parallax error. (FYI, the white vinyl eraser will take
all sorts of marks off of most impervious surfaces, i.e. magic marker
and stamp pad ink off formica).
Another old trick to eliminate parallax error is real simple. Close one eye
Of course, for those that have tested their laser embellished chop saws and
now only have one good eye - they already knew this....
Short answer - Just try it before you doubt that it works or not.
Longer Answer - Close left eye, place head over cursor and reasonably
perpendicular to it. Move the fence to the alignment mark that you want
while keeping head above the cursor and perpendicular. If you consistently
do this the same way each time you make an adjustment you will minimize the
parallax error and your measurements will be within a few thousandths of the
measurement. If you align your fence to your blade and zero the cursor
using the same method, you will just about eliminate any noticeable parallax
One other item is the width of the cursor mark. From what I've seen on the
market, the lines on the cursor have become wider and introducing even
greater error. My Jet cabinet saw came with a fine line cursor but the
newer ones have a cursor line that must be at least 1/16" wide. I align the
cursor using the above method and split the line on the attached ruler
mounted on the saw.
If you need more of a scientific answer than that, someone else will have to
provide it. This has worked for me for years and I learned it from someone
else long ago. If it doesn't work for you - find another way.
Your description of how to align things will work fine, but that
requires that you keep your eye perpendicular to the scale. If
you don't do that, even with only one eye open, you still get
parallax. Closing one eye doesn't eliminate the problem. However,
your description involves a lot more than just closing one eye.
The absolute way to eliminate parallax is to scribe a second line on the
opposite side of the current cursor. Then when you are correctly aligned
you will only see 1 line. If you see to lines you are not reading
Perhaps it's just me, but I don't use any cursor to set up cuts.
Generally, I use a cabinetmaker's rule with the zero end held tight to
the fence, and line it up with the tip of the blade on the corner that
is nearest the cut. Look at the blade with both eyes open, and make
sure that you can only see the kerf. If you can see any part of the
side of the blade, you're not aligned correctly. Move your head, and
then check the measurement again. Never have to worry about the silly
gauges on the fence system that way, and wonder if they've gotten
bumped or bent or otherwise distorted. Once the fence is locked down,
it should be good to go. I run a saw for a living and it works for
me, generally with a tolerance of 1/64" or less.
The same process applies when cutting miters on the edge of stock, but
you must bring your eyes to a level that allows you to look straight
at the blade from angle that is close to parallel to the table- if you
look from above, it will also introduce error.
I did it that way before getting a good fence. Good advise if you have a
less than desirable fence, A good fence is going to give you repeatable set
ups using its silly gauge. ;~) Using my Jet fence I get repeatable setups
using the cursor way better than you are getting. Personally I cannot see
how parallax would throw a set up off much more than 1/128" given a worst
case scenario. But if you dont have a great fence, you do with what you
There is that. I do have a less-than perfect fence with my little
TS200. But I got in the habit of hand measuring at work, where we cut
bar ends on a vertical bandsaw by lining up the final cut manually
(the rest of the cuts are power fed), and parallax problems really
come into play. It's tough to see how it could be a signifigant
problem for someone who does have a good fence, so I figured I'd toss
out the method for us bums. :)
That, and FWIW, I was was checking out a $600 Delta contractor's saw
this weekend (didn't note the model no.), and the one problem I could
find with it during my impromptu inspection was that the measurement
gauge was off by at least 1/4". Not a problem if you know it, but it
can drive a guy who likes to trust the scale nuts!
I use exactly the same procedure, and I don't do it fo a living. it
jus makes sense ot measure directly. Besides, I have a feeling it was
a troll [one of those that comes close enough to reality, but not
wuite.] The reason I say that is that is that although it can not be
denied that some parallax exists, it means about as much as those
arguments that measure to the nearest ten thou or thereabouts, as if
they were building jet engines instead of crunching wood.
Well, parallax can become a big problem quickly, but not too terribly
often on the table saw. Where I've run into problems with it is when
you take 5 or 6 2.5" round tubes, and try to line up a 45 degree angle
on them using a vertical bandsaw (where the blade tilts, not the
table) If your eyes aren't in the right spot, it can throw off the
measurement by a quarter inch or better. Of course, that's not using
the OPs concern about the minimal gap between the indicator and the
scale, it's using a rule and the blade as references. You're right
though, in the case of a 1/16" or 1/32" gap between the cursor and the
fence rail, it's a fairly trivial thing to worry about.
My Bies is as accurate (and mucho faster) as using a hand held tape
measure. My previous TS had a scale you wouldn't want to rely on. so
what fence is on your TS that you don't trust it?
That won't work with a Biesemeyer fence. You line up the cursor, lock the
handle, and the fence may move slightly as it lock in place exactly where
set, as it should. Your method is good for my old Craftsman, or to double
check on the Bies cursor, but one in place, the Bies is exactly where set.
It's certainly no Biesmeyer! It's just the little tube fence that
comes on the nicest version of the Delta benchtops. It's not a bad
saw overall, but it's still a benchtop- and the table is too small to
upgrade the fence with any of the aftermarket fences I've seen.
But, the fence is straight and it is parallel to the blade, and that's
really all you need!
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