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Sliding Gauges and Calipers

by Judy Larson
One of the tools that I do not know how long I have had is a brass sliding gauge. It has never been shoved in a drawer but has been on my work surface in some container or other for years because it is an often-used tool. Why would you need this inexpensive tool that takes up little space? If all you ever use it for is to measure beads or cabochons to make sure of their size, it is worth having.
How is the little brass sliding gauge used? All those numbers and lines seem to be so confusing......until you realize they aren't!

You can't reinvent the wheel. Julia Lowther of littlemetalfoxes.com published the BEST set of directions I have ever seen on how to use a brass sliding gauge to make the same precise measurements that one would obtain when using a digital caliper. She graciously gave me permission to share the link to her page. I printed the whole article out and refer to it when I need to, which takes a lot less time than going to the internet, looking up videos, and then watching several before you find the information you were looking for.

https://www.shoeboxstudio.com/2014/04/19/the-secret-power-of-the-sliding-gauge/
I did not really need digital calipers as I don't need accurate measurements down to the hundredth of a millimeter for most of what I do but thought they would be so much easier to use and be more accurate. Well, they are not necessarily easier, and accuracy may be questionable at times. I can measure the same metal sheet on a factory cut edge three times and end up with three slightly different measurements. Notice how much room it will take to store the digital caliper compared to the sliding gauge. The caliper must be stored in the case because if the power button is accidentally pushed and not caught right away, the batteries will be drained. I was on my second package of batteries before I learned my lesson. As Julia says, they can chew through watch batteries. The size means it is not on my desktop so I have to go to the cupboard it is stored in if I want to use it.
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
For this article I decided to do an experiment with both tools.

First, I measured a calibrated 10mm round carnelian cabochon the WRONG way. There is no way to know you are measuring the exact center when using the tips of the tool from above the cabochon. The sliding gauge measured 9.6mm, which I thought was way off for a calibrated stone, meaning I probably did not measure the center diameter with the tool. According to the 9.92mm measurement, I did better finding the center with the digital calipers.
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
With this method, the measurements taken will be the much more accurate. Place the cabochon flat side down on a flat surface. Place the tool on the cabochon as shown and close it. Pick the tool and cabochon up to check the back side. Make sure the flat back of the cabochon is flush with the back surface of the tool. Put the tool back down on the flat surface. Check the measurement. My measurement is still the same with the sliding gauge at 9.6mm but different with the digital calipers at 9.88mm which is withing the margin of error. So which tool measured the cabochon correctly? Both, but the question is which one is right?
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
I decided to try the same thing with beads. Beads are difficult to measure accurately because finding the exact center can be close to impossible. I purchased two 10mm sodalite beads strands from the same supplier at the same time. The beads did not look the same size, so I decided to measure them with the sliding gauge and the digital calipers.
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
I first measured the smaller of the two beads with the sliding gauge, and then with the digital caliper. The sliding gauge measured the bead at 10.1mm and the digital calipers at 10.33mm. I took the beads out of the tools and remeasured, obtaining the same results with the sliding gauge and a 10.31 reading with the digital calipers.
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Then on to the larger of the two beads. The sliding gauge measured the bead at 10.3mm and the digital calipers at 10.53.
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
At this point, I was starting to wonder what was going on and why the measurements were so different. Yes, digital calipers can be a bit fussy to work with, but this just did not seem right. I pulled out the calipers, turned them on, and it hit me. Tightly closed, the starting number was not 0. It kept fluctuating between .03 and .04. It even went to .02 once. This made measurements a few hundredths millimeters off. Did that mean that the measurements I took of the cabochon and bead were not accurate? It seems my digital calipers measure everything about 0.2mm larger than the sliding gauge. I can live with that now that I know, but I do trust my sliding scale a bit more than the digital one.
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
I will still use the digital calipers when I need approximated measurements. When coming up with link measurements for my paperclip chain tutorial, I measured the length and width of at least 5 different links, then averaged the measurements. It was quicker to use the digital calipers than the sliding gauge because there was a little less thinking involved (maybe not for you, but for me I did not have to look for where the markings lined up on the sliding gauge and then think of the number I would write down - lol).
Judy Larson's Sliding Gauges and Calipers - , Tools For Wire Jewelry, Tools, sliding gauge calipers
Conclusion: Knowing that I need to subtract 0.2mm from shorter measurements does not mean that needs to be done for longer ones. I measured a different calibrated cabochon several times, turning the tool off and on between measurements. The measurements were the same each time. Leaving it on, I opened and closed the jaws and remeasured. The measurements were slightly different each time. Yes, the tool measurements are fritzy. When I want accuracy down to a tenth of a millimeter, my sliding gauge is fine. Any finer measurements than that, I will have to rely on the digital calipers, with some reservations. They will not be the first measuring tool I reach for.

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Tools

Brass Caliper - Gemstone And Bead Measuring Tool
G7-9
  • G7-9
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 each
  • Price: $8.97
  • Gold Club Price: $6.73
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Digital Calipers With Stone Holder by Euro Tool
GAU-179.00
  • GAU-179.00
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 each
  • Price: $39.97
  • Gold Club Price: $29.98
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