Thermal Expansion Small Holes on Plastic Enclosure Question

[Scott231us]

Good day.. i have an ABS plastic enclosure that is approx 100mm long. There is a round hole (for bolt) in the middle that is 5mm diameter. If a 100mm long piece of plastic expands 0.3mm in hot arizona weather or reduces 0.3mm in freezing temps, how much does this effect the diameter of the 5mm hole? Will the 5mm hole change the same amount (plus or minus 0.3mm) in the middle of the 100mm long enclosure), or only a fraction of that plus or minus 0.3mm expansion / reduction applies to the smaller 5mm diameter hole? Need to understand how this will effect bolt hole tolerances..

 

[3DDave]

Generally it's linear. (0.3mm/100mm)*5mm = the amount of change in the hole. It's not going to be entirely perfect as it's unlikely the part is of perfectly uniform properties and that the temperature change is perfectly uniform throughout, but this should be close enough if a tiny amount of additional clearance is added to allow for those factors.

 

[desertfox]

Hi Scott231us

I agree with 3DDave, but I would just use the formula (change in length)= orig length x coefficient or expansion * temp change

So the original length will be 5mm
Coefficient of expansion ?
Temp change ?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein