Clearance measurements - general advice?

[FrankV]

If wall sides are 3mm then 74 + 3 + 3=80mm (Assuming you mean the outside dia of the lid)

[DrUsual]

No, the inside diameter of the lid, because the lid fits over the edges of the box bottom. So, ID of the lid should be larger than the OD of the bottom, right? Tinkercad only measures (easily) the OD of a circle, though, so I did 74 OD of the bottom + 3 mm lid walls = 77 inside diameter of the lid, plus clearance. I was thinking that that clearance wouldn't need to be much, though, and even making the OD of the lid 78mm is leaving the ID too small to fit over the 74mm box bottom.

[FrankV]

Tinkercad only measures (easily) the OD of a circle, though, so I did 74 OD of the bottom + 3 mm lid walls = 77 inside diameter of the lid, plus clearance.

Ok, so this is the confusion. What do you mean by 3mm walls? If you mean the wall is 1.5mm then it would be 3mm total, but if the wall thickness is 3mm then the outside diameter must be the inside (74mm) plus the 2 x 3mm = 80mm outside dia for the lid (plus a bit of clearance of course).

[DrUsual]

Ok, so this is the confusion. What do you mean by 3mm walls? If you mean the wall is 1.5mm then it would be 3mm total, but if the wall thickness is 3mm then the outside diameter must be the inside (74mm) plus the 2 x 3mm = 80mm outside dia for the lid (plus a bit of clearance of course).

GAH.

I had a funny feeling that the answer would be that I'm an idiot...

You're correct, I only accounted for 3mm of wall, not 6mm.

At least I know my printer's working correctly.

Thanks!

[soofle616]

GAH.

I had a funny feeling that the answer would be that I'm an idiot...

You're correct, I only accounted for 3mm of wall, not 6mm.

At least I know my printer's working correctly.

Thanks!

Don't feel bad. I'm a mechanical engineer and I do stupid stuff like that from time to time. Actually, things like that are why I call my friend chris whenever I have a carpentry project to deal with because for some reason I can never keep it in my head that 2x4's are not actually 2x4" so I always end up cutting things wrong.

[DrUsual]

Another good lesson here...we're doing these in Tinkercad, and we started by creating the bottom of the box, then duplicating it, then scaling the duplicate/lid. My gut feel is that scaling the OD of the lid should scale proportionately the ID, so that it maintains the 2mm lip. Re-thinking, though, I'm guessing that scaling is increasing the thickness of the lip as well as the diameter of the hole and the exterior? Probably something very fundamental to an engineer, not quite as obvious to a liberal arts guy.