This is an easy modification to any steel tape measure. The length of the tape and degree of precision you want will determine how much time is spent making it.
When I first entered this instructable in the "I Can Make That" contest, I intended it to mimic a new device that hasn't been marketed yet. I started receiving comments about patent infringement issues and my patent attorney (who confirmed there were no issues) suggested I remove all reference of the product as a way to stop the well-intended, but bothersome comments... Which I did. Now, being without a product I can copy, I'm no longer in alignment with the contest rules. Therefore, I'll chose the next closest product, the Inca Rule which is far enough away from the design of my instructable to make patent infringement a non-issue.
That being said, let's get started:
Step 1: What You'll Need
Here's what you'll need: A steel measuring tape, a small" diameter hole punch, a pencil (optional), and a steady hand.
I use a Roper Whitney #5 Jr. Hand Punch, probably the second most used tool in my shop. It comes with interchangeable punches ranging from .094" (3/32") to .281" (9/32"). Mine even has a custom made square punch that Roper Whitney made for me.
I suppose a small drill would also work, but it's disturbing to think of how frustrating that would be to use.
After I completed my first tape by hand (it took forever... And there were mistakes too), I made a simple guide and hooked it up to my hand punch. The guide indexed the tape every inch, so on my second attempt, I never made a mistake, and it only took me 15 minutes to punch 10' (120 holes). The instructions for making the guide are in step 4.
Step 2: Making It
Load the smallest punch you have and depending on how many holes you want to make, take your punch and carefully align (this is where the steady hand comes in) it with the measured lines along the center of the tape. I've used a tape measured in inches, but metric would be the same, only closer.
Punch a hole every 1/2" or .5cm along the center of the tape.
That's it. Now take your pencil and try it out. If the measurement is 1/4", place a mark inˆ the inch hole AND the 1/2" hole. Then measure half the distance between the marks and you have your measurement.
Step 3: A Variation
We often need to make 1/4" and 1/8" measurements and it would be easy to punch holes every 1/4" along the tape. The difficulty is, all these holes lined up can't be too good for the strength of the tape and a single line of holes may become confusing to use.
I've taken the original idea and modified it a bit to make the tape a "little" more structurally sound, and help them stand apart from each other.
By adjusting the location guide on my punch, I've created a diagonal line of holes that quickly define it's position within the inch markers. It's a lot more work, but now, I can measure to the nearest 1/8" quickly and accurately. You can modify what I've done and locate the inch mark at the high point, making the half inch at the low point, with the 1/4" and 3/4" marks at the mid point. Since I began making the marks on my 10' rule near the centerline, the pattern ended up being what it is.
I'm going to make a complete and (hopefully) mistake-free tape for myself. Time will tell if I reach for "any tape" or look for this one specifically. I think I'll be trying different hole patterns until I hit on one I won't be able to live without.
Step 4: Making Better Holes... Maybe
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Smaller holes would be more accurate, but so far, I've found the size in my tapes are adequate. Locating the center of a small circle with my pencil is an easy chore and the hole size in my tape makes aiming for tired eyes a lot easier. Even though didn't intensionally choose it for it's size, It was simply the smallest punch I have. That doesn't mean you couldn't find smaller ones.
I've seen small punch pliers on Amazon for less than $13: "Euro Metal Hole Punch Pliers" with a 1.25mm punch, which is quite a bit smaller than the one I used.
Or, if you have a drill press to use as a ram, check on eBay for a "Shoe Punch press". I've seen them for as low as $20.
If you own a hand punch, the setup, described here, which I used to finish my 2nd prototype tape worked out well.
Using a scrap piece of aluminum, I milled a groove for the tape to slide in. In my case, the groove wasn't nearly deep enough to entrap the tape. I had to devise a clamp to keep in in the groove. It would have been better and easier if I had simply made a guide out of wood.
At one end of the guide, I drilled and tapped a hole that the Whitney receiver could thread onto. If you're using a different punch, you'll need to figure out how to secure it to the guide.Make sure the connection is rigid. If it moves, your holes won't be exact.
Exactly 1" further along the groove, I drilled and tapped a hole, a little larger than the punch size and threaded a small machine screw in from the bottom. I tapered the portion of the screw that was exposed so it slipped into the punched holes on the tape. It doesn't have to stick up very far, only enough to allow the holes in the tape to snap over it, keeping the tape from moving.
Because my guide was 4" long, I had to punch the initial 5 holes by hand. I then clamped the tape so it was trapped, but still slid in the groove and placed the last hole I punched over the protruding pin. This set up my 6th hole, exactly 1 inch away from the 5th. I continued until I'd finished 10' of the 20' tape. 10 feet took me about 15 minutes.
It would have gone much easier if I had a helper to guide the tape along. I was alone, so I had to come up with an alternate solution. I laid the tape out on the floor and using a dolly, clamped the punch and guide to it. It was a bit Rube Goldberg, but ended up working fairly well. I did have to re-calibrate the holes every 20 inches or so. My measurement between the punch and the pin were off ever so slightly and the punch would begin to drift a tiny bit off center. When that happened, I simply punched a new, centered one and picked up on the process where I left off.
After I figured out how to do it, the process was quite simple.
After the initial 1" spacing is done, it's actually pretty easy to remove the pin at this point and punch the 1/2" and 14" holes by sliding the tape through the guide, using the 1" holes as visual markers. This allowed me to finish all of the 1/2" and 1/4" holes for the first 10' in about half an hour. And I only made one mistake, close to the 10' line, when I was nearly done. :/
Look over the photos for ideas and good luck to all who make this.