Woodworker's Central Woodworker's Gazette Gazette Archive 11/19/97

Measuring Strategies - Part I: by Jim Mattson What is it about tape measures which inspire so little confidence? Why is it that whenever we're faced with critical measuring and cutting, it's easy (and usual) to cut the piece oversized and whittle it down from there? Why do we make so many trips to the table saw so we can nudge ever closer to that optimum length or width? Is it because we're afraid we'll cut our wood too short or too narrow? You bet! How we get to this point is variable for each woodworker. Some of us don't take the time and care needed for accurate measuring. Like learning to cut dovetails by hand, measure twice and cut once is a pain. For others of us, it seems no matter how meticulously we measure, we still occasionally make mistakes... so we give up. Whenever we're faced with one piece left to finish the job and one piece left on the woodpile, we become stricken with the paralysis of indecision. Our confidence in our measuring and cutting abilities gets exhausted through the blast gates of our minds. This has been one of my problems for some time. Although I've known that much of my lack of confidence lies in the measuring tool itself, somehow whenever I make a mistake I take the blame. It's never the tool but the craftsperson using it who has failed ... or is it? Not all tapes are created equal. To illustrate a potential problem, the picture above shows two Stanley 25' Powerlock IIs stretched side-by-side. They match up nicely at 21" and 25" but in between they wander off as much as 1/64". Which tape is right? The implications of this are plain: four 24" wide cabinets might not add up to 8'. Luckily we almost always don't have to meet this level of accuracy, but it explains why it can be so difficult to cut parts accurately without a lot of trial and error. To find some answers to this problem my research led me to the Sears, Stanley, Lufkin and Starrett websites. To each company I posed the same six questions and after several weeks, Lufkin, a division of Cooper Tools, was the only company to respond. If you'd like to read the questions and Lufkin's response, click here. To delve into this issue further, a question arose about which are the most accurate tape measures on the market? Is there one available we can use to restore our sagging confidence in the measuring procedure? Operator error notwithstanding, is there one tape measure which can consistently return accurate measurements? I then took off to Sears and Home Depot to purchase five tape measures, just as you would most likely do. The tools chosen were three 16' tapes and two 25' tapes with a strange newcomer to the fray, the Starrett Digitape which electronically displays it's readings. I used 16' tapes exclusively for years but lately I've grown accustomed to the 25'ers for the large projects which come my way. I like the stiffness of the blades for measuring inside diagonals and as quickie straight-edges during rough layout. Though they're bulkier to use and hang from a belt, my shop, toolboxes and trucks are littered with them.

The Candidates

On the testing board, from left to right ,with price paid. Craftsman 25', #39397 Lufkin 25', #HV1425 Starrett 16' Digitape, #D34-16 Stanley 16' Powerlock II, #33-116 Ohio Forge 16', #32819 $9.99 $8.43 $24.99 $9.96 $3.97 Also compared was my Stanley 25' Leverlock and a couple of 25' Powerlocks laying around the shop. With the exception of the Ohio Forge, which is made in Taiwan, all the tapes were made in the USA.

The First Test

The first thing many woodworkers do after buying a new tape is check the hook front and back for sliding accuracy; does the tape read the same when butted to a surface as when it's hooked over an edge. The Lufkin, Craftsman and Stanley 16' were the best. The Starrett Digitape was worst showing nearly 1/64" difference between the stretched and compressed measurement.

The next test was to measure the accuracy of each tape at 12". To make this test I needed an actual benchmark. I have several stamped or etched steel rules and comparing them to each other revealed no discernible variation between them. Using a Fowler 12" machinist rule, I placed a square line 12" from the hook edge of the testing board and looked at the tapes again to see how they matched up to the ruler.

The Second Test

The Stanley 16' Powerlock II showed the best accuracy at 12". Further sliding of the machinist rule along this tape and checking it at various spots indicated it had consistently the most accurately spaced delineations.

The 16' Ohio Forge was printed out of square from one edge to the other. It is 1/64" off along the upper edge but is nearly 1/32" off along the lower edge. This discrepancy is generally repeated along the whole length of the tape Also note how much closer in length the 16th and 32nd markings are in comparison to the Stanley. Under 12", the Ohio Forge is much more difficult to read.

The $25 Starrett Digitape was the worst indicating the machinist rule was a full 1/32" off. This inaccuracy was generally repeated along the entire tape's length leading me to believe the hook was riveted in the wrong place. The black rectangles are used by the tape's optical sensors to provide readouts to the the electronic display panel. (I think :-)

The Starrett suffered from two other shortcomings: If you pulled the tape out too fast, it would return a wild reading as pictured at left. Nudging the tape a couple inches either way returned it to normal. It also wouldn't give a reading finer than 1/16" and could have a discrepancy of 1/16" between the measurement on the readout and what was shown on the tape where it exited the case.

The Third Test

I wanted to see how the tapes fared when measuring inside distances. At 45" a block was clamped to the testing board and the tape cases were butted against the stop clamped in my tail vise. All the tapes recorded the 45" accurately with the exception of the Starrett which recorded 45 1/16". The Leverlock had the most awkward fit in the corners, yet still returned a good reading. The Ohio Forge asks the user to add 2 29/32" for the case to get an inside measurement. Yeah....right.

Test Four involved stretching all eight tapes full length across the floor, aligning them at the 1" mark. After much crawling around, the Stanley, Lufkin, Craftsman and Starrett tapes all remained within 1/32" of each other, wandering apart and then back together without reason. By 170", the Ohio Forge was a full 1/16" shorter than the rest. Test Five determined how far the tape could be extended from the case before collapsing: 25' Lufkin 25' Craftsman (with 11% thicker blade) 25' Leverlock 16' Stanley Powerlock II 16' Ohio Forge 16' Starrett Digitape 91" 89" 87" 68" 68" 48"

Test Six

I removed the fence from the Biesemeyer rig on my tablesaw and aligned each tape at 1" to the scale glued to the slide rail. The Stanley 16' (at left) which I thought was so accurate started wandering off at 5" and didn't get re-aligned until 26". Dropping the machinist rule on the Biesemeyer scale found similar irregularities as found on all the tape measures. Oddly, and surely by chance, the 25' Stanley Leverlock, which I've been using for the last year, matched the Biesemeyer almost exactly.

Recommendations: It's obvious, after spending hours with these tape measures, trying to get one that's truly accurate is a gamble. The strangest thing was how the USA tapes would wander off of alignment and then mysteriously back on - even over long distances! The email from Lufkin attempted to explain why this can be, but I suspect no one really understands it fully or else it would be corrected. It's fortunate that all single measurements are relative. We take a measurement, mark the board and cut the piece where we mark it. No problem. The trouble lies when we try to get several carefully measured parts to add up to an accurate accumulated measurement. Using a tape measure becomes even more tedious when the tape we use for measuring doesn't dovetail with the scales mounted to our power tools. I feel very fortunate to have found one tape out of eight which closely matched the scale on my tablesaw. Within the pure context of accuracy, the Stanley 16' Powerlock II edged out the other Stanleys, the Craftsman and Lufkin. However, it's safe to say this could have been a fluke. Within this small test sample, hair-splitting accuracy was scarce. The Starrett Digitape and Ohio Forge would be acceptable for rough carpentry or paint grade trim, but I would hesitate to recommend them for anything else. Starrett has a wide reputation for delivering some of the most accurate and expensive measuring instruments in the world. With their Digitape, at least one of your expectations is fulfilled. As I stumbled upon it's many weaknesses, I often found myself wondering about their corporate ethic and why they would bring such a tool forward. The technology has promise, but it's unrealized with the Digitape. Concerning the Ohio Forge - you get what you pay for. When considering the rest for purchase, perhaps it's best to examine each tape individually considering ergonomics, auxiliary features, etc. Stanley 16' PowerlockII In the 16' category, the Stanley won hands down. It was the most accurate (as far as I could tell) and did everything well except match up to the Biesemeyer tape. I probably should've tested it against a 16' Lufkin or Craftsman but the former wasn't available locally and I have some problems I'm working on with my therapist about spending too much money at Sears (:-) Another feature which sets the Stanley apart is a bevy of tables printed on the back of the tape for easy reference. I always forget to use them but they're there for those less forgetful than me. You can track down Stanley's warranty policy by clicking on this link to their site. Sears Craftsman 25' Heavy Duty/High Impact This tape measure has a lot going for it, particularly it's girth. It was the heaviest, bulkiest tape measure of the lot. On the other side of the coin, the hook is nicely reinforced, the blade is as accurate as the big Stanleys and Lufkin, and with the Craftsman name on it and it's lifetime guarantee, this could be the last tape measure you ever buy. Another nice thing was it's bright yellow case; it's easily spotted on a crowded jobsite or workbench. The really worst feature of this model was the blade lock. Although it grabbed enough to prevent the tape from rewinding, sometimes it released when you least expected it; often just from picking it up the wrong way. Lufkin 25' Of all the big tapes, this one had the best ergonomics. It's rounded rear end fit the hand almost as well as the 16'ers. The Lufkin was the only tape sporting a satin finish on the blade, a possible plus for cutting glare in bright sunlight. The Lufkin also has the best blade lock of all the tapes I looked at, really locking the blade in position. While using a tape measure as a "quickie" trammel for drawing arcs and circles, the Lufkin excelled. Additional features include four rivets to secure the hook where all the others had two or three, and the big Lufkin, other than the Ohio Forge, had the only hard rubber shock absorber inlaid in the case behind where the hook comes to rest. It's safe to say the Lufkin would survive more uncontrolled rewinds better than all the others. The only drawback I could see in the Lufkin was how crudely the delineations were imprinted on the blade. According to an advertisement on their website, this might be addressed with their newer models. Other than this one small point, the Lufkin was easily my favorite. Would this have anything to do with their being the only company to take me and this article seriously??? I'll let you be the judge. Part II continues this my exploration with tape measures. If you have any questions or comments about what you've just read, feel free to email me direct at The WWA. Jim Mattson