A bore gage is a comparative gage that must be set to a master prior to use. Unfortunately, some people who purchase bore gages for the first time only realize once they receive the product that a setting master purchase should have occurred concurrently with the bore gage purchase. Without a setting master, the bore gage will not be properly set. With this said, setting a bore gage sometimes ends up being more expensive than the bore gage itself.
There are many different kinds of masters or gages that are capable of setting the bore gage prior to its first use. No matter what method you choose, bore gage calibration must be the completed prior to using your bore gage. When it comes to the bore micrometer or pistol grip style bore gages, setting rings are usually used to calibrate the gages. Setting rings are one of the best ways to set a bore gage, but it can be very expensive if you have to purchase multiple setting rings. A cylinder bore gage only has about 0.100” of range before you must change out the posts or washers. For example, just to cover a full inch of travel, approximately 10 setting rings must be purchased. This bore gauge calibration standard adds up in cost for the end user.
Due to the cost of setting rings, many companies also use different types of setting masters or micrometers to set the gage. A micrometer is able to be opened up to a nominal size and have the anvils locked in place. The end user can then rock the cylinder bore gage in between the two micrometer anvils to set and calibrate the gage. This practice is used for end users trying to hold an accuracy of about 0.001”. Other companies actually send a part out to a calibration house and use the part itself as the setting master for their bore gage. It really depends on whether you want to be reading the actual diameter or just a deviation away from “0.” Depending on your preferred reading, either of these bore gauge calibration procedures is a sensible choice.
Fowler supplies a Bore Gage Setting Master Kit that offers an end user a great bang for their buck. Retailing for around $250, this setting master kit allows customers to set cylinder bore gages for sizes up to 6.0”. That is an incredible range for one-stop shop bore gage calibration. Included in the kit is a 36-piece gage block set already certified to N.I.S.T. Purchasing the gage block set alone would cost hundreds of dollars, so in our opinion, Fowler is offering an end user a good deal. This kit is operator friendly and much easier to use than trying to use micrometers each time to calibrate your bore gage. The Fowler Bore Gage Setting Master Kit truly streamlines the bore gage calibration procedure.
No matter what solution you choose, keep in mind that bore gauge calibration is extremely important and will affect the accuracy of the gage. After completing each bore gauge calibration, you may utilize a removable sticker, noting the approval date as well as the date of the next required calibration. Staying on top of every bore gage calibration in your workshop, starting before first use, will help protect the quality of the parts you manufacture. When you utilize an accurate bore gauge calibration standard and implement a regular bore gauge calibration procedure, you are ensuring the highest precision of each measurement taken with that instrument.