HD Panel Saw: How precise, and where is the source(s) of accumulated error(s)
 

When you walk up to the m/c and stop the needle pointer on the rule by
eye-balling it carefully, what is the accuracy resultant. I believe eye.
For this to be true the material, blade and rule zero positions have to be
set correctly. Lets say that it is set correctly. This is something you do
not have any control over anyways. The variable magnitude of this error if
set correctly is negligible. Cut to cut to cut. If it is not good the only
thing you could do is mentally add/move the needle approprriately after
taking a cut and comparing with a tape measure.. Lets say it is set and we
don't have to worry about it. In order to answer this I need answers from
people who know what it is like to stare down the pointer and graduations on
this machine The answers I hear, including none, may affect how I approach
the machine when I go get my material cut. Whether I get involved, and
whether I take a measurement after the first cuts V and H. I believe it is
entirely dependant on where you lay the pointer w/r/t the graduations on the
rule. I think it is easy to see the pointer on the 1/16" graduation lines.
It must be. Where is any introduced inaccuracy when you do this. It is easy
enough to divide this repetitively by aligning anywher in between these
lines, say divided by 25% increments, for example. so 1/64ths. I think you
can do this by visible inspection, no problem. But how would the machine
respond? But how repetable would it be? everytime. For here to there,
over, and back, over and over. Then there is the V cut stop block.

I love talking to any employee and determining if you'll have to reverse
engineer your project when some guy sets your cut once on the wrong line.
Hopefully if you're cutting an 8 foot long piece of ply four times
combined it's gonna be off by the thickness of the material. Remember we're
dealing with the thickness of the pointer, and the blade is already taken
care of. After a long discussion you ask, and he says no problem. So he
takes the first cut, lays out the tape measure and
exclaims PERFECT. Perfectly closer to the next closest line. Thats a buck.
Do you want the next sixty cuts?

a cut (sorry about errors):
I figured the panel saw out. For cutting horizontally there are two
platforms, and two reference rules. The rules don't move. One is to the
lower rest, the other to the upper rest, depending on the width of the sheet
and convenience. Absolute dimentions from bottom to top. No adding or
subtracting. No factoring in the blade. Because of gravity I draw all my
rips from bottom to top. The machine isn't set to measure the other way.
Maybe some employees would assume a perfect 48" and subtract if a drawing is
made that way. All dimensions should be contiguous, not combined, because
the top piece is removed after each cut. The thickness of the blade is zero
set. The rule never moves. 1/8" is set when the machine is built. That
is, with the needle pointer at 15-15/16", thats what you get. If you were
resting on the lower platform, say 30" away, use the other rule. It is
offset by 30" It would read 15-15/16", The machine cuts straight as an
arrow and perfectly normal.
With vertical cuts, the blade is slid over to a lock position and rides up
and down. The wood is slid side to side to a stop block. Accuracy of
consecutive cuts just depends on moving the wood over to lightly touch the
stop block. The rule for the stop block starts at zero and works both ways.
The blade is accounted for, the rules origins start .250" appart (two 1/8"
saw kerfs). The stop block is a steel fixture with a cam clamp that rides
on a rail. It is a bit figetty, but done firmly and right its all over.
The V and H rules are the same. and the indicating pointers are the same.
There is no paralax error to worry about. Pointer to rule is a fractions of
a millimeter. White steel rule with black graduations. Black spring steel
pointers. There is no operational errror introduced.

These are posible sources of error: (assume sharp blade, and sraight factory
material edge)
the rules themselves are not accurate or consistent throughout the full
length of blade travel (w/r/t standard at Bureau of measurements)
the rule zero position is not set correctly w/r/t material zero, or the
blade zero position
the material, blade, pointer or rule zero position is not constrained
blade or m/c runout during operation
paralax error or other visible or mechanical error in setup of indicator
pointer at position on rule
V cuts: the position, alignment and constraint of the stop block

I always remember that 1/32" is approximately 1/33". 32s or 33s, who cares.
And I know 1/33
divided by 1/33 is .99999... (1.0000...). So a 1/32" (1/33")=~ .033..." In
words, a thirty-second is thirty-three thou.

HD Panel Saw: How precise, and where is the source(s) of accumulated error(s)
 

"bent" writes:


I love talking to any employee and determining if you'll have to reverse
engineer your project when some guy sets your cut once on the wrong line.

I can only assume you're talking at a panel saw at Home Depot since you
mention HD and employees.

Home Depot guarantees no level of accuracy with their saws at all. The
local HDs have signs saying no precision cuts. The saws operate in a
harsh environemt with uncaring employees and forklifts/carts probably
knocking them out of alignment.

One store had a Jet dust collector at the saw station. I felt it and both
the bottom and top bags were completely full! If they don't even bother
to empty the dust collector, how do you think they treat the saws?

Brian Elfert

HD Panel Saw: How precise, and where is the source(s) of accumulated error(s)
 

snipe of long post.......

Bent,

Interesting but let me relate a short story to you about HD's cutting
policy - now. It's +/- 1/4" period.

A few years back they actually had someone come in and align their panel
saws and it took the tech a better part of a day to do it. I forget exactly
how much they said it cost but was several hundred dollars - if not more.

Today - the saw gets aligned if someone bangs on it in the right spot and I
can attest that the panel saws are not maintained as well as they should
be - at least not here. I had a sheet of MDF I wanted cut - precisely. So I
marked the sheet, told the operator which side the kerf was to be on,
watched him move it into the correct position and saw the saw go off at the
bottom by almost a 1/4". I complained of course and that's when they
pointed to the sign... I refused the panels.

I wish you luck but I think you would be better off having them rough cut,
leave enough waste to insure you have enough material to square up to what
your finish size needs to be. Other alternative is to cut it yourself
obviously.

Bob S.

HD Panel Saw: How precise, and where is the source(s) of accumulated error(s)
 

"bent" wrote in message

I love talking to any employee and determining if you'll have to reverse
engineer your project when some guy sets your cut once on the wrong line.


After a long discussion you ask, and he says no problem. So he
takes the first cut, lays out the tape measure and
exclaims PERFECT. Perfectly closer to the next closest line. Thats a
buck.

Wow, you've put a lot of time trying to correct the uncorrectable. I'd no
sooner rely on the HD "associate" to cut my lumber that I would have him do
brain surgery. Even if the cut happened to be on the mark, the resulting
finish is too splintered to be of any use.

HD does not guarantee the accuracy of their cuts, nor do I expect them to.
I'm not about to turn over control of my $60 sheet of plywood to a guy that
may have used a tape measure for the first time that day. Your money, do as
you wish.
--
Ed
http://pages.cthome.net/edhome/

HD Panel Saw: How precise, and where is the source(s) of accumulated error(s)
 

I am talking about the saw. The operation seems to be such that it is
repeatable enough for anybody to place the needle between the graduations
say by quarters. From anywhere to anywhere. Again and again. This must be
agreed. Then it takes no skil. Anyone with sight could do it. Many
operators don't know an inch from a parsec. That is why I ask this post.
It is a function of the saw. It is the limit of the machines
discrimination. Out of ten people, depending on what they know about an
inch, you may or may not be able to get agreement on where the saw is set.
But it is set, I'm saying +/- a quarter of a 1/16th. Anybody (everybody)
who knows anything about the inch would clearly see it, and there would be
no discussion about it. The machine itself gives you the impression that it
has sucessfully found that position again - it's repeatability. What is it
that makes it not be be tryuly as accurate as it seems to be set. Out of
ten answers the guys at the Bereau of measurements would throw out 11 of 12
jurors. Then the answer could be found. If I found out what the answer was
I would feel confident about getting my sizes cut, because I could with
authority interupt the guy with a new fascination of the inch, and look, and
place the m/c where it should be. Hey, look what I see. If he doesn't see
it, he's blind, or the inch is his enemy. Depending on the employee, you
may need to insist on looking at every setting with the intention of getting
it right. Better. Setting them all yourself. Best. Neccessary, no.
Probably in most cases. Pretty embarassing. Is it the machine or is it the
line. Words are our friends. But I don't see the sign that says "You are
responsible for paying us $1 a cut to offset the cost of us paying our
employee for deliberately ****ing up your piece"

I actually took a course in CAD/CAM called dimentional metrology, with an
oficial 350 page text. Bring me the keeper of the inch.

At the manufacturer of the saw, if they have the right engineer, they know
what you can see, and know what number it is I'm looking for, and anybody
else with any knowledge of math could analyze the data and tell me the
deviations to the statistics. One could explain the data in x consonants
and y vowels to another, who would go away wondering which suppliers parts
went into making the machine.

Now the saw itself is a pretty decent tool. I would put it against a table
saw in many places. Lots of cuts you can live with the size you get. I
don't have a helper. but I do have a table saw.

There may be abuse, and you have to be sure the wood is right, its laying
flat, etc. There is a certain amount of risk. I'd rather play in traffic,
etc. But what is likely?

HD Panel Saw: How precise, and where is the source(s) of accumulated error(s)
 

bent wrote:
I am talking about the saw. The operation seems to be such that it is
repeatable enough for anybody to place the needle between the graduations
say by quarters.

snip the incomprehensible run on paragraph

What part of "the saw isn't calibrated and is usually out of whack"
don't you understand?

HD Panel Saw: How precise, and where is the source(s) of accumulated error(s)
 

I didn't see that sign