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.
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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
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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.
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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/



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