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• # Sunday morning quiz. What size hole is this?

Discussion in 'The main mechanical design forum' started by Outofmydepth, Nov 14, 2010.

1. ### OutofmydepthActive Member

Joined:
Oct 2010
Posts:
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0
What size hole is this?

I need to determine the size of a hole with means I have available.

An 8.5mm drill bit fits in easily

A 21/64ths drill bit fits in easily

A 9mm drill bit does not fit.

A 11/32nds seems as if it might be a perfect fit but I am afraid to push it in too hard in case I cannot easily remove it.

The hole has to be either

0.335"

OR

0.350"

Which is it?

Thanks

Outofmydepth

2.
3. ### GarethWChief ClickerStaff Member

Joined:
Jul 2009
Posts:
1,433
5
Re: Sunday morning quiz.

OK, to summarise..

21/64ths or 0.33" (8.3mm) = fits in easily
8.5mm = fits in easily
11/32nds or 0.34375" (8.73mm) = possible interference fit
(0.35") 9mm = doesn't fit

I think I've got those right - this is handy for converting units by the way

Sounds like your hole is probably 8.5mm (0.335"). 8.9mm (0.350") sounds a little on the large size if you have an interference fit potentially starting at 8.7mm.

4. ### OutofmydepthActive Member

Joined:
Oct 2010
Posts:
31
0
Thanks GarethW,

After posting this question I had a look at it myself.

Found a conversion factor cm to inches x 0.3937

21/64 = 0.328125

11/32 = 0.34375

8.5mm = 0.334645

9mm = 0.35433

Given the alternatives .335 and .350

If hole was .350 the 11/32 / 0.34375 would fit but it does not.

Hole is therefore .335

Outofmydepth