adhesive-backed measuring tape inaccuracies

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I just installed one of Kreg's precision track systems on a shop chop saw. It's a pair of extruded aluminum tracks which you mount on shop-built 3/4" thick fences, which then get fastened down to the counter tops on each side of the chop saw, in line with the chop saw's own built-in fence. An adhesive-backed measuring tape fits in a shallow recess along each track, and a pair of aluminum stops with hairline cursors allow you to quickly set the cut length for a board.
After installing the tracks I went through a painstaking process of aligning the tapes so that they would be accurate to a fraction of a gnat's ass on one specific measurement. Then I took an accurate 24-inch ruler and laid it along the tapes, checking for inaccuracies. To my dismay, I found that the tapes varied from the ruler's gradations by various small amounts, both high and low at different points, up to as high as a little over 1/32".
Now this is kind of depressing. It means that I can't depend on the cursor, but will have to treat it as an approximation and make a test cut for each new measurement. I've gotten used to trusting the 52" tape and cursor on the table saw (after initially checking it, of course), and I was hoping for the same kind of accuracy from this system.
Any of you faced and solved this problem? I've put in a support email to Kreg to see what they have to say. Maybe it's just a limitation of that kind of tape, but I'd like to hope that I could get a measurement system that I could trust to 1/64". If it was a plastic tape I'd say ok, try a metal one, but it looks like the Kreg tapes are metal. And searching on the web turns up a ton of adhesive-backed tapes, but hasn't shown me anyone who makes any specific claims about the accuracy of their product.
Comments? Thoughts?
Tom
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On 4/15/2014 4:20 PM, tdacon wrote:

See if Starret has adhesive backed tapes. Do you need adhesive though? Don't the Kreg have a sliding slot to stick the tape in... That allows you to adjust it?
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Jeff

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"woodchucker" wrote in message

Kreg has other tracks with sliding slots, I think, but this track just has a shallow depression a little wider than 1/2" into which you press the tape.
When I installed the tape I peeled back the paper and laid the tape gently into the depression and pressed it down with my thumb, three or four inches at a time, being careful not to put any stress on it to either stretch or compress it. I wasn't actually thinking about precision at the time, just trying to keep it from wandering out of the slot or putting it down with a "bubble" in it.
Tom
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On 4/15/2014 3:20 PM, tdacon wrote:

> To my

> Any of you faced and solved this problem?
> Comments? Thoughts?
LOL!
Don't mean to laugh at you, but the following is a truism every woodworker figures out sooner or later:
_It is extremely rare that any two measuring devices will read precisely the same at any point, and imprecision generally increases proportionately with length_
It why most of us learn that best way to insure parts that fit as intended is to ALWAYS "mark", NOT "measure"!
And also why perfecting the practice of using "story sticks" is so much more effective than measuring.
If you must measure, and most of us have to quite often, you can mitigate this truism to some extent by using ONLY one measuring device throughout the entire project.
Nirvana to a woodworker is when two measuring devices coincide throughout their usable length. So try to check out two measuring devices by brand and model before you buy, and if you, by some happy accident of fate, find two or more that coincided with precision, buy the whole damned box! :)
I have an old Stanley tape measure that I protect as if were the Crown Jewels simply because it coincides _precisely_ with the adhesive backed tape on my Unisaw fence rail, all the way out to 54".
What I measure with that tape measure, then set that reading to fence, is exactly the dimension that gets cut.
That is indeed a bit of woodworker's heaven. ;)
Good luck ....
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On 4/15/2014 5:44 PM, Swingman wrote:

I have a few that agree. My TS agrees with my 12' Komelon, my 12' Stanley Lever Lock, and my 2 Lufkin folding rulers...
I was amazed that they all agreed... it is rare, but someone was paying attention to details way back when, and with the more modern Komelon.
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On 4/15/14, 4:44 PM, Swingman wrote:

Print & frame that and hand it out to every newbie woodworker.
I now take my two favorite rules with me to the store any time I need to purchase another measuring device, after learning the hard way.
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Not unusual at all and chances are the rule has no name on it either. I had similar problems and finally found and used a Starrett adhesive backed tape. No issues with a name branded tape.
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Here's Kreg's response to my query:
Hi Tom! Usually, when the Precision Trak and Stop System is set up according to the directions, we have had much success with our customers in regards to the accuracy of the product. I am not saying that you set it up incorrectly, but it doesn't hurt to double check. While it is possible that the measuring tape could be defective, for the most part our experience has been if there are any discrepancies, it occurred during installation. Thanks, and please let me know!
So, no substantive response here. I don't think I could have been more gentle or consistent in laying that tape down, so I'm having trouble blaming myself.
Two recommendations for Starrett, so far - thanks to Woodchucker and Leon - so I'm going to look in that direction. I sent an email to Starrett customer support asking if they offer any specific representations about the accuracy of the graduations. They must have been manufactured under some sort of accuracy specification, so I'll see if they have anything to say. If I don't hear from them within a reasonable time I'll just buy a pair of Starrett tapes anyway and put them on the system and see how they do. And that'll be the end of it; I'm not going to make a career out of this. Woodworking tools aren't machine shop tools, after all, and they're made for the mass market.
Swingman went on at some length about story sticks and the general inaccuracy of woodworking measuring tools. Fair enough. If you're building a stand-alone piece of furniture like a table, for instance, and you want 32-inch legs, you probably don't care much if they're a 32nd over or under, as long as they're all the same length. After more than forty years of wooden boat restoration and repair, I'm no stranger to story sticks and the concept of marking rather than measuring. There's rarely even a straight line in a boat's structure or furnishings, and over time I've probably used up half a log from a door-skin tree making patterns for irregularly-shaped spaces with a pointed stick and a #2 pencil. But I come from an engineering background, where if our measuring systems aren't consistent, we fix our measuring systems rather than picking one of them and going with it, so that's what I'm trying to do here.
Along about now, someone's probably going to throw that joke I left here quite a while ago back at me, so I'll get it in first:
A cabinet maker works to the nearest sixty-fourth of an inch; a house builder works to the nearest eighth; a boat builder works to the nearest boat :-)
Thanks for your comments, Tom
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On 4/16/2014 10:34 AM, tdacon wrote:

http://www.mscdirect.com/browse/tn/Measuring-Inspecting/Dimensional-Measuring-Tools/Linear-Distance-Measuring-Tools/Tape-Measures-Blades/Adhesive-Tape-Measures?navid 107866
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On 4/16/2014 10:34 AM, tdacon wrote:

Personally, I've never been impressed with Kreg's accuracy/precision on any of their devices.
> Swingman went on at some length about story sticks and the general > inaccuracy of woodworking measuring tools.
> Fair enough. But I come from > an engineering background, where if our measuring systems aren't > consistent, we fix our measuring systems rather than picking one of > them and going with it, so that's what I'm trying to do here.
Surprising someone with an Engineering background would have not understood that a measurement, or measuring device, can be accurate not precise, precise but not accurate, both, or neither ... to paraphrase an old professor of mine. :)
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"Swingman" wrote in message

Oh yeah, I've got that. I may have inadvertently used the term precision when I meant accuracy but believe me I know the difference. But if you need to feel that you won something in the exchange, I'll be glad to give you a point or two. I have nothing to prove.
Tom
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On 4/16/2014 1:31 PM, tdacon wrote:

LOL You asked the question, and you asked for what someone had done to "solve" it, "thoughts:, and "comments", and it turned out you knew it ALL already?
Go figure ... sorry to bother you with all three of what you asked for.
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"Swingman" wrote in message

Oh no, Swingman - I learned a lot from the comments, including yours. I got good comments and suggestions from everybody who participated. Leon and Woodchucker in particular sent me off to Starrett to find out what would be the best accuracy I could expect to get. And in fact I fully agree with your comments about story sticks and marking vs. measuring, as I said. In the final analysis it turned out that I couldn't realistically expect better than what I was getting out of this setup, so that's the end of it as far as I'm concerned. Except that Leon in fact did say that he solved the problem to his satisfaction - as I hoped someone might have done - with Starrett tapes, so I may just go ahead and roll the dice with Starrett one more time myself to see if I get lucky. You never know. But if not, then I'll go with what I have.
So I appreciate all the comments in the thread and feel like it's been very useful. It was a civil exchange, a rarity on the internet. Rec.woodworking is just about the only newsgroup that I ever post to these days, just because of the generally good-natured behavior of its denizens and the likelihood of getting useful information.
Regards, Tom
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And here's the response from Starrett:
ACCURACY- SHORT LINE TAPES: +/- 1/32" (.03") OR +/- .80mm THE FIRST 12 FEET OR 4 METERS +/- 1/16" (.06") OR +/- 1.50mm FOR THE REMAINDER
So that's as good as it gets. Kreg's tapes are within that spec.
So that's the end of it.
Tom
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On 4/16/2014 12:02 PM, tdacon wrote:

hmmm. knowing Starret, I would have thought much tighter.
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On 4/16/2014 11:41 AM, woodchucker wrote:

That might be an allowance for the resolution of the actual markings.
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I pretty much always use a tape measure from the fence to a tooth tip at both the front and back of the blade for any "precision" cuts. If it's a good new tape measure that gets me within a few hundredths I imagine. (I have a good imagination. LOL)
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You know I was thinking about this, and there is no real good reason for that degree of inconsistency other than price. I cut parts all the time to within a few thousandths and consider consider them just ... ok. I would be no big deal for me to put a chunk of metal in the mill and cut hash marks in it to the length of travel. I could even use index marks and shift the piece only losing a extra couple thousandths accuracy ever 2 feet or so, by using a pin in the index mark to advance the piece before retightening the vises. I don't see why a company like Stanley or Lufkin (Lufkin used to be my preferred brand of tape) couldn't stay within a couple hundredths or better over the length of a 25' tape measure. Even then the consistency between marks could easily be 5 thousandths or better.
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"Bob La Londe" wrote in message
You know I was thinking about this, and there is no real good reason for that degree of inconsistency other than price. I cut parts all the time to within a few thousandths and consider consider them just ... ok. I would be no big deal for me to put a chunk of metal in the mill and cut hash marks in it to the length of travel. I could even use index marks and shift the piece only losing a extra couple thousandths accuracy ever 2 feet or so, by using a pin in the index mark to advance the piece before retightening the vises. I don't see why a company like Stanley or Lufkin (Lufkin used to be my preferred brand of tape) couldn't stay within a couple hundredths or better over the length of a 25' tape measure. Even then the consistency between marks could easily be 5 thousandths or better.
Bob, the one part of Starrett's response that I didn't include in my post was a sentence that said something like "If you want 1/64" accuracy then we suggest that you use a precision metal rule." So off I went to the Starrett site only to discover that a six-foot precision rule (the size I'd need for each side of the chop saw) was priced at about $800. So yeah, it's a price issue.
Tom
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On 4/19/2014 10:54 AM, tdacon wrote:

I have similar quality precision rules, Bridge City. Consider stacking rules, side by side on those odd times that you need a longer length.
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