Monday, July 23, 2012

Blind Hole Dimensions Test

In response to a previous blog entry, someone asked me to see if the dimensions of a blind hole are similar or the same to a standard hole.  A blind hole is simply a hole that does not go all the way through an object. 

I'm here to please... and, the results are in.

Test Method

I created 3 objects with an outside diameter of 40mm and an inside diameter of 20mm.  One of the objects was exactly like the "washer" in the previous test.  It was 3mm tall.  The other two objects were 20mm tall.  One had a hole completely through the object and the other had a blind hole that went into the object about 15mm.

Here are the measurements...

3MM Washer - Hole

3mm Tall Cylinder: Hole - 18.41mm Inside Diameter

The 3mm tall washer had an inside diameter, in this test. of 18.41mm. 

20mm Tall Cylinder - Hole

20mm Tall Cylinder: Hole - 18.58mm Inside Diameter

The first 20mm tall cylinder, with the full hole through it,  had an inside diameter of 18.58mm.

20mm Tall Cylinder - Blind Hole

20mm Tall Cylinder: Blind Hole - 18.38mm Inside Diameter

The second 20mm tall cylinder, with the blind hole,  had an inside diameter of 18.38mm.


The strangest result of this test was that the 3mm washer, which one would expect would have the exact same dimensions of the first test, had an inside diameter that was more than .7mm more than the first test.  In test #1, the inside diameter was 17.71 and in this test it was 18.41!

Otherwise, the differences don't seem all that remarkable.  The distribution from smallest to largest is mildly interesting.    The greatest degree of difference is between the two objects with holes.  The blind hold object turns out to be the SMALLEST!  Is this due to the greater mass of the blind hole object, which results in more overall shrinkage?  I don't know.  But, I do find the differences to be intriguing. 

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