I always see people laughing at mechanical drawings that have really precise dimensions.
I wanted to ask how detailed should my drawings be when I asked for quotes.
I don't want to get expensive quotes back because I carry the drawing to the 42nd decimal place. However I need to make sure that my parts will work.
Example.
I have a cylinder that is 12mm OD x 6.5mm ID x 2mm long.
I have a push rod that is 6mm that rides inside the spacer. It cannot be any bigger than 6mm.
I'll be using 1mm diameter o-rings. So I'm guessing that I need to have the o-ring groove to be ~.50mm. That will give me .25mm of compression.
Is .25mm enough clearance to provide a sliding fit on the push rod?
What should I ask for on my tolerances? Is asking for a 6.25mm hole to much?
All of these measurements are approximate. I'm only looking to keep about 300psi from blowing past the o-ring.
However I'd prefer the parts to be as precise as possible. But I don't need the parts to break the bank.
Thanks.
**Corrected the ID on the cylinder. Changed from 6.25 to 6.5MM**