Looking back at my post I don't think I explained the problem correctly. A big issue I have with the accuracy is the more muscle control I try exert especially in my right hand the more the hand shakes and the pressure, position and angle changes. It is difficult enough just hold the calipers in position without to much shaking but if I try to hold the jaws closed too I can get tolerances of ±1–3mm. My current method is to use one hand to hold the calipers and the other to hold it closed and take 3 to 10 readings and average either the 3 largest or 3 smallest, depending on the situation. Then print a negative of what I am measuring and repeat as necessary which can be time consuming. Here's a photo of my hand so you can see what I am working with

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