Gazette Archive 12/17/98
Subject: Tape measures!
This phenomenom can even be random in nature and can appear to make no sense whatsoever. The key to this mystery is in the process used to print the tape. Lufkin mentioned the printing process is very similar to offset printing except a rubber printing plate is used to transfer the image to the tape. Rubber..... Actually rubber is used extensively in the printing industry. The contradiction here, if there is one, is that rubber printing plates are generally associated with lower quality printing. A good example would be a mass mailing that doesn't really need litho quality. Every envelope is going to a different address and in mass mailings, 95-98% of the mailings are trashed before they are ever opened anyway. Rubber plate printing is characterized by thickened edges of the print and a slightly washed out center of the letter or character printed. This is most noticeable on letters with large vertical areas like the letter L.
The reason that rubber printing plates are used on tape measures has very little to do with cutting corners though. It is strictly for practical reasons. The printing plate on long printing requirements, dictates that the printing plate has to take the shape of a loop, simply so that it can fit on a very specialized printing press. Can you imagine the size of an impression cylinder capable of printing a 33' long image in one pass without using a belt for a printing plate?
Further, the manufacturer doesn't print one tape measure at a time. They will be gang printed in multiples of 30-40 at a time. The explanation for the measurement variations is simple really. Rubber stretches. Rubber stretches in a non-linear fashion so that you will find your measurements wandering in and out of being accurate over the entire range of the tape. Can this be corrected? Sure, but at what cost. The printer would have to change plates more often. He would have to have a standard to compare the printed work to right on site. The reject rate would be horrendous and in the end, the consumer would'nt pay the price that the manufacturer would have to charge to make a profit. We would just buy one from someone else that was cheaper and keep on making those visits to the table saw to cut it until it fit correctly.
I know this was
wordy, but I hope it makes sense. BTW I sell printing paper
and plates to commercial printers for a living. Thanks for your
wonderful articles. Keep them coming and I will keep reading
Hi Don, Thank you very much for your remarks about tape measures. Had the manufacturers responded so honestly perhaps my attitude would have been better - well...maybe not.:)
I do have a question. You mention the difficulties in printng a 33' tape. Would it be possible, given your experience, to print a more accurate 16' tape? I ask this because several months after the article uploaded I heard from Starrett rather informally. They mentioned the main reason for the 1/32" discrepencies lied more with regulation than the actual physicalities of the process. According to government standards, they're allowed 1/32" off per 16', which leads me to believe they could do better without too much additional cost if only they were required to do so.
Also, my partner, Chuck Ring, inquires as to whether we could reprint your email on a link from the article. It's certainly a better perspective than any others we've received.
Subject: Re: Tape measures!
In the paper manufacturing industry there are government standards too. All kinds of them. Everything from stiffness index, curl index, sheffield smoothness, brightness, opacity, dennison wax pick number.....you get the idea. All of these standards are written for the government by (first guess doesn't count) the industry themselves. Starrett and the companies that make tape measures write the tolerances into the regulations for themselves so that they can conform to their own standards. This is sort of like allowing the fox to manufacture the lock on the henhouse and write the specifications for the keys while he's at it.
This is actually a widespread practice in the manufacturing industry where there is any sort of government regulation. That, my friend, covers just about every type of manufacturing that goes on in this fair land.
Concerning your question about accuracy for a 16' tape measure, the length is still too long to print with a fixed plate. The largest sheet fed printing presses in common use in the US are 35"x45". That means that you could print a 45" tape on a sheet fed printing press with microscopic accuracy but it would have little practical use. The process used to print long items like tape measures and newspapers is called rotogravure. You can really make newspapers work easily because you have a long web of paper to print but each page is only a small part of the total.
Believe it or not, my professional opinion is that the tape manufacturers are doing an excellent job of providing a "reasonably" accurate product for a decent cost. I believe that more accurate tape measures are on the horizon, but they won't come from advances in the printing process. More likely, they will come from advances in the Xerographic process. These machines already feature full on-line word processing, optical character generators and the ability to continuously create the image (electronically) necessary to print an infinitely long tape measure with accuracy that would bring a tear to a German machinist's eye. Several roadblocks that are holding the application up at this point would probably include cost (these units run into the hundreds of thousands for the basic unit plus many more thousands for the skilled personnel to run them), market driven need (you and a small group of dedicated professionals would dearly love to have consistent, accurate tape measures, but there is no way that one of the striped pants financial types at a major manufacturer is going to pony up that kind of money until his potential market numbers in the hundreds of thousands of units/year.
Last but not least, these machines don't have the capability to feed anything more exotic than paper at this point but that will change rapidly as the market demands it. After reading the above drivel several times, I think that you probably solved your own problem the best way. I'm going to Home Depot tomorrow and see if I can dig up a new box of tape measures and get down to some serious comparisons.
Best to you,