Woodworker's Central Woodworker's Gazette Gazette Archive 1/31/98

Measuring Strategies Part II: by Jim Mattson The Hypothesis Those of you who stopped by for the first installment of this article no doubt remember the perplexity I experienced in trying to find an accurate tape measure. (Those of you who didn't see that part need to read it first or you'll understand squat about what I'm writing here in part II :-) After looking at many tapes from several different manufacturers and getting a wide variation in comparison I decided to try a new approach. It seemed to me that 'maybe' it might be possible to find accurately matching tapes if they came from the same manufacturer and were likely made at the same time on the same machine. To answer this question meant a trip back to Home Depot. Instead of taking tape measures off the display rack, I was looking for a carton - an unopened manufacturer's box of tape measures. It seemed plausible if there were any way to find some tape measures which compared alike, this was the best way to go. In the store that many people love to hate (or in my case - hate to love) my quest wasn't going to be easy. Though there seemed many boxes of tape measures, they were all stored just out of reach. I needed one of those aisle-blocking, toe-stubbing rolling staircases and unusually, there wasn't one nearby. Scanning the horizon I spotted one two aisles over in front of the portable power tools. Off I went. Getting the staircase over to the tape measures was a bit tricky and apparently my bumping around inspired the attention of a nearby customer service representative. In the middle of fumbling through the boxes looking for acceptable test samples, she surprised me with the question, 'Can I help you find something?' Immediately I realized how unusual this might seem for someone to be looking for a 'carton' of tapes with so many displayed within reach on the rack. I almost replied that, 'I have this website and I'm researching the possibility...', but instead decided to keep it simple, replying, 'I'm looking for some tape measures which all measure the same.' I've had dealings with this particular salesperson before and my impression of her always indicated she was much brighter than the average, orange-aproned Home Depot employee. Her puzzled expression showed some more explanation was necessary. I went on, 'If I can get them all from the same box, I'll have a better chance they'll be alike.' 'But how different can they be?', she asked. 'As much as a 1/32"', I responded. She digested this rather quickly and asked, 'Does that matter?' This seemed perfectly reasonable to me given that most of the customers she deals with spend their days banging 2x4s together. Perhaps I should've started out by saying, 'I have this website...' but time is money and I needed to get going. 'I'm a professional cabinetmaker', I responded. Again she did the extrapolations, nodded in understanding and decided perhaps the idea (or me) wasn't as crazy as it would initially appear. She drifted away. Fearing a similar encounter with another one of her compatriots, I grabbed a box and headed for checkout. So what did I bring back to the shop? From my earlier tests it seemed the Stanley 16' Powerlock IIs were the most accurate. The following tests showed this not to be conclusive. Read on...

The Candidates

The first thing I did was label each tape upon removing it from the bubble pack - numbers 1, 2, 3, and 4. I left the original 16' Stanley Powerlock from the earlier test unmarked. I then re-calibrated the testing board for fear the 1/2" melamine may have altered it's dimension since performing the earlier tests. I trimmed it's end and using the steel rule, scribed a new 12" mark. From there the tests went pretty much as before. All were accurate within 1/100th of an inch at the 12" mark with only numbers 1 and 4 showing any deviation at the hook where an inside measurement didn't quite match up to an outside, or hooked measurement. It seemed with these two the rivets were a little tighter than the others and that perhaps they would break in (figuratively:-).

So, by now you're probably asking, 'Do the tapes match up or not?' The short answer is yes and no. In the above photo, the original Stanley 16' Powerlock II from the previous article is compared to the number 4 tape measure from the carton. When aligned at 15" to the right, a significant deviation is present towards the left. This didn't surprise me as the original tape was purchased a month before and came off the rack, that is... out of a different box from Stanley. Comparing number 3 from the carton to number 4 reveals a near perfect match over the same distance. In fact, tapes numbered 1, 3 and 4 are nearly perfect over their whole length. Number 4 starts to wander very slightly after 30" but the deviations are minimal and short-lived. Numbers 1 and 3 are indistinguishable from each other no matter where I look or how carefully I compare them to each other. Happy Day! I have finally found two tape measures essentially the same! (What can I say, I'm easily amused :-) Number 2 is the odd tape out. It's as different from it's box mates as the original 16' tape. It also suffers a minor defect I've never seen on a tape measure before; it has little blobs of the Mylar coating stuck to the tape every 20" or so. It obviously wasn't made with numbers 1,3 and 4 but must have been re-worked into the production line at some point to get packed in the same box. I guess the question now is, 'So what?' How do we take advantage of this inexplicable phenomenon to improve our measuring? If you remember from the earlier article, a large problem comes from dissimilar readings from the tape you use to take measurements and the scale on the tablesaw you use to set your fence. If they don't match up, measuring the distance between the fence and blade is the only solution. Or is it? I had some ideas before beginning these tests but didn't give them much credence for lack of similar tape measures. Now that we have three, let's explore something called: The Calibrated Workshop To call me a pack-rat is an understatement. Like many woodworkers, any little obscure hardware item, any usable piece of material scrounged from a contractor's dumpster, or just anything I might ever use sometime finds a home in the nooks and crannies of my shop. This is true of tape measures with a broken spring or a snapped hook. For years I saved them thinking I might figure out a possible utility someday...somehow. About ten years ago I began inlaying them into wooden extension fences for my miter saw and radial arm. I could never really use them for truly accurate cutting (now I know why!) but half of all my cuts don't need to be that accurate and it saved me the time of marking boards when only a rough cut is desired.

In the photo at left, tape Number 4 is buried in the miter saw fence above the inlaid tape I've been using for the last five years. The length of the stop block and left-hand cursor match the offset of the tape's end from the miter saw blade. Unlike the lower tape which is measured directly to the saw, this setup permits Number 4 to retain it's hook should I ever want to remove it for another application. Both tapes are 'captured' in the fence by a two-step groove. The widest step is 11/16" wide and an 1/8" deep. The 3/4" wide blade presses against the sides of the groove which prevents it from shifting. A narrower, deeper groove (1/2" wide x 1/4" deep) is centered in the middle of the wider groove. By applying pressure to the center of the blade it retracts from the groove sides should it need removal.

Tape Number 1 got attached to the Biesemeyer rail on the table saw. The strip of poplar holding it (1 1/8" x 7/16") is held firmly to the fence's original scale with double-sided tape. (Scotch 'Wallsaver' Removable Poster tape from 3M)

I had to remove the stock cursor plate and replace it with a small square of plexiglass. The cursor is easily created by lightly dragging the point of a knife backwards along a straightedge three or four times. Then the scratch is blackened with a felt marking pen (Sharpie). Any of the ink which falls out of the scratch is removed with paint thinner applied to a rag wrapped tightly around a flat piece of wood. By lightly taking swipes at the acrylic, the ink comes off the surface but stays in the scratch.

As with tape Number 4, the tape case butts against the end of the fence rail where it will stay until... whenever? Tape Number 3, by virtue of it's most accurately riveted hook, has become the 'Workshop Tape' I'll hang on my belt. It's used for taking measurements for pieces which are to be cut by the miter saw or tablesaw. It will never leave the shop. (And why should it with all the other tapes I have lying around? Does anyone want the Digitape? :-)))

This system has been in place for a month now and it's impact has been significant. A large built-in which is in the finishing stage was constructed entirely without any trial and error cuts. Every once in a while, sort of like pinching myself, I'll measure a piece fresh from the tablesaw to see if it's the right size. It is. As a professional, the time savings will quickly repay the $45 spent on the tapes and the half day spent building them into my workshop. And not having to worry about being off 1/32" will free me to pursue other things to worry about. :-) Certainly, this technique might not be favorable to all woodworkers. Hobbyists might like the 'artistic unpredictability' of their woodworking and might reject this attempt to bring a small portion of machine-like precision into their shop. But those who have spent hundreds of dollars on Incra-Jigs, fancy squares, expensive rulers and precision straight-edges might want to consider this inexpensive option. Success is keyed to getting the proper number of similar tape measures. My experience with the Stanley 16's might be highly unusual and there are no guarantees you'll find another box like I did. It also might be prevalent that a carton of tapes from any manufacturer will yield several similar tapes. It could be that Starrett, Lufkin and Craftsman all work the same way. If you decide to try this method, let me know how it goes and I'll update this page to reflect the possibilities. If you aren't very lucky you can always take them back. In my mind, tape measures which don't align are defective. (Well... at least one of them is, but deciding which one is beyond the scope of my capabilities.) For the future I'd like to see the manufacturers address this problem even if it means adding a few dollars to the price of a tape. I would gladly pay $15 or even $20 for a tape measure I knew was really accurate and would match the scales on my power tools. As it stands now, I still don't know that four pieces cut 24" long will add up to 8', but I do know that whatever measurement I take off the hip will match what comes from the saw. Jim Mattson 1/31/98 If you have any questions, comments or suggestions, you can email me at: jmattson@intrepid.net Final Note: Month's ago I had a very interesting email exchange with a professional in the printing industry. We discussed some of the problems facing the tape manufacturers and their alternatives for improvement. Don Florida is his name and you can read his opinions here.