This angle vise is not specifically a vise. The insertion pin size is 2.98mm and the receiver hole size is 3.22mm, so the maximum possible error is 0.24mm. This equates to degrees as the variance of 0.0026667 at 90 degrees, but much more than 15 degrees, about 0.016 of the variance. Therefore it is not an accurate instrument. You can replace the pin by taking a steel wire or bar of the correct diameter and aligning the end to accommodate the hole for the attached chain. However, the question remains as to whether the holes for the pin are drilled accurately, since holes for the receivers are supposed to be drilled every 15 degrees. The clamp can be installed anywhere from 0 degrees horizontally to 90 degrees vertically in increments of one degree or less. An electronic protractor or inclinometer will give you the exact number you are looking for in degrees, taking into account the maximum possible manufacturing error. However, the vise allows you to install it at any angle that suits you. The pre-drilled holes are for reference only and may be a failsafe in case the vise slips. Although the clamp seems very secure when properly tightened. It fits my needs very well, and at around $84, it's a reasonable price for what you're getting. As a carpenter it serves my purpose very successfully, but as a locksmith I would never rely on a set of pre-drilled holes to determine the accuracy of my operation and verify it with an electronic protractor, inclinometer or any other method. to determine the accuracy of the operation.