# Dimensioning of hole from tolerances

I have two parts that should be bolted together with four M6 bolts. The tolerances of the bottom part are quite big and the holes for this part are fixed to Ø6. The tolerances of both parts are fixed due to manufacturing and lowering of costs. I need to determine the size of the holes of the top part in order for them to fit together. I have attached a photo showing the tolerances of both parts.

I am in doubt how to calculate the size of the holes. For instance for the left side, is this the correct way? \begin{align} \text{Diameter} &= \text{Delta}_{dim} + \text{Tol}_{dist} + D_{shaft} \\ &= (211.5-210)+3.5 + 6 = 1.5 + 3.5 + 6 \\ &= Ø11 \end{align}

• I'm highly skeptical that any type of manufacturing other than "squint at it and whack it with a hammer" will have such huge dimensional tolerances. What is going on here? Jul 13, 2016 at 11:51
• Make a scale drawing if the lower part with all the areas tha may be hole marked, draw a margin (tolerance of upper part) around these areas. Scale the drawing 1:1 so you can put proper nuts and washers on the paper and see how it fits.
– mart
Aug 12, 2016 at 10:07