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

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.

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