Every metrologist loves a bore gage. Ok, maybe love is a strong word here, but every metrologist can certainly appreciate the bore gage for its important uses. Bores, more commonly known as holes, present a common conundrum for many standardized measurement tools. Different than the typical surface structure, bores are encountered frequently in the world of metrology in the shape of holes, pipes, cylindrical parts, and more. Specifically designed to be used when measuring a hole, the bore gage solves the problem of trying to collect any required dimensional data. A dial bore gage in particular is used for the specific task of measuring the inside diameter of a hole. Once it is set, using a bore gage is a pretty straightforward endeavor. However, the process of setting a bore gage must be well understood and never skipped in order to allow for precise measurement. Today, we will describe the three main methods used to set a bore gage and explain the advantages and disadvantages of each. The process of setting a bore gage Understanding the process of how to set a bore gage is important for any metrologist to know. Whether working in manufacturing, machining, data collection, or any other job that requires high level measurement, you will likely encounter a bore and need to know how to properly measure it. The first step in proper bore measurement is proper bore setting. Knowing how to set a bore gage generally as well as why this process is important will ensure that you can take accurate and precise bore measurements whenever necessary. The how of setting a bore gage The general concept of how to set a bore gage is reasonably straightforward. You begin by setting up the tool you will use as a reference to the size of the bore you plan to measure. Then, you set up the bore gage with any needed extensions required for the diameter of the bore you are measuring. You then place the bore gage against the reference tool and adjust it such that it is properly fit to the tool. Eventually, you want to use the reference tool in order to set the zero point. What differs between the different methods of setting a bore gage is the tool being used as a reference point. Additionally, the specifics of pairing the bore gage with the reference tool vary slightly as different reference tools have varying structures. What remains the same is that the reference tool is used in order to set the zero point on the bore gage based on the specific size of the bore being measured. The why of setting a bore gage Setting a bore gage is pivotal to maintaining accuracy when taking bore measurements. This is because setting the bore gage ensures a true reference point of zero. On a bore gage, the reference point is used as the nominal size. It is the distance from the nominal size that becomes the measurement, therefore the nominal size must be accurately set in order to gather accurate data. Additionally, each bore is different. Taking precise measurements of a bore requires the process of setting the bore gage so that it is matched to the particular bore being measured. Therefore, understanding this process is important to be able to complete it each time you are working with a new bore. Overall, the reason why setting a bore gage is important is that the accuracy of the entire measurement rests on it being set properly. While this takes practice to perfect, knowing how to set a bore gage is an important skill for anyone working in machining or metrology. General tips for setting a bore gage Whenever you are setting a bore gage, there are some core ideas that remain important no matter what method you decide to use. All of your tools must be cleaned in order to eliminate any dust or debris. While some measurements are larger and therefore less impacted by contents on your tools, precision can be greatly impacted by even a little dust, especially when working with more minute dimensions. Cleanliness of your tools will impact your ability to properly set the reference zero point on your bore gage. When choosing a method of setting a bore gage, you will need to consider what tools you have available and your own skill set or ability to use those tools. Remember that having a partner to help with the setting process or to double-check your work can be helpful, especially when you are first learning how to properly set a bore gage. All of your measurements using a bore gage stem from the initial accuracy of the setting process, so the more safeguards you have to check your work, the better. Multiple methods for setting a bore gage When researching setting a bore gage, the most common instructions will be regarding the process when using a micrometer. However, there are three ways to set a bore gage and they each come with pros and cons. You can set a bore gage using a micrometer, using a ring set, or using a bore gage setting kit. What method you choose depends on the tools you have available and can vary depending on the circumstances as well. Having a handle on all three is important to figure out the best method to use and to be able to manage different challenges that may arise in the context of measuring a bore with a bore gage. Using a micrometer to set a bore gage Using a micrometer to set a bore gage is the fastest and most convenient method available. However, setting a bore gage with a micrometer is also the least accurate way to do so. The reason using a micrometer may be the most convenient method is that most workspaces have the tools required readily available. There may be times when this method is necessary, when you are in a pinch and need to set a bore gage quickly with lack the specific tools made for this process. However, using a micrometer to set a bore gage is not the most recommended method because you risk the accuracy of resulting measurements. One of the reasons that measurement errors can result is the condition of your micrometer itself. It is challenging to avoid measurement inaccuracies caused by the misaligning of the spherical measuring points of the bore gage to the micrometer. If you are simply a hobbyist or only have a micrometer available, a micrometer can be used to set a bore gage. Other methods are preferred for higher levels of precision. The steps to using a micrometer to set a bore gage are as follows: Set the micrometer to the size of the bore you are going to measure Set up the bore gage with any needed extensions for the specific bore diameter Place the bore gage between the spindle and the anvil of the micrometer Settle the bore gage into the micrometer by using a gentle rocking motion Zero the indicator on the bore gage to the minimum reading to have your nominal size Using a setting ring to set a bore gage Using a setting ring to set a bore gage is the most accurate method available. When using setting rings to set a bore gage, the actual measurement goal is duplicated by the setting ring, resulting in a precise match between the bore being measured and the bore gage doing the measuring. This creates a very easy way to match the size of the part. The greatest disadvantage of using a setting ring to set a bore gage is the expense of the method. Essentially, you will need a setting ring that matches each size of the different bores you measure. This limits your flexibility unless you invest in a large set of setting rings to use for different measurements. These can be expensive tools and so acquiring numerous setting rings for each potential bore size can add up. However, if measuring bores is a regular part of your work, using setting rings to set a bore gage has proven time and again to be the most accurate method. Therefore, having a range of setting rings may be your best option if you rely on precision for bore measurements. The steps to using a setting ring to set a bore gage are as follows: Lay your master ring on a smooth, hard surface (such as a granite surface plate) Set your bore gage in the ring, thus providing support to the bore gage Adjust the sensitive contact point of your bore gage until the indicator reads zero to have your nominal size Using a bore gage setting kit to set a bore gage A final method of setting a bore gage involves using a bore gage setting kit. While it may seem obvious, a bore gage setting kit is specifically made for this very purpose. What a bore gage setting kit offers is the flexibility of being able to measure a range of different sized bores without the cost of buying individual setting rings to do so. A bore gage setting kit utilizes a gage block assembly in order to create a reference master. The availability of gage blocks is a major advantage of this method and using these in a bore gage setting kit will be cheaper than the alternative of buying different setting rings without sacrificing the resulting accuracy. The biggest disadvantage of using a bore setting kit to set a bore gage is the time it takes to assemble the gage blocks that will accurately match the needed nominal size. You also may have some measurement error result from wringing that occurs between gage blocks. However, if you are looking for a more accurate way to set a bore gage than using a micrometer, but are unable to procure numerous setting rings, than a bore gage setting kit is a great method. The steps to using a setting kit to set a bore gage are as follows: Set up the required gage blocks into a clamp with jaws at both ends of the blocks During set up, wring the blocks together by sliding their faces against each other in order to create a light bond Lay the bore gage against the correctly sized gage block and set the indicator to zero to have your nominal size Conclusion Knowing how to set a bore gage is an important skill in manufacturing, machining, data collection, or any other job that requires high level measurement. When it comes to ways to set a bore gage, you have options. You can use a micrometer, a setting ring, or a bore gage setting kit. Which method you choose wi
