My tubes are slightly tighter than the WIX/NAPA filter. They’re 46mm/1.811in spec, calculated from the ID + wall thickness. These are foundry nominal numbers, and tolerance applies. Tubes are never perfectly round. That’s why the suggestions I constantly get on YouTube from wannabe machinists to use the calipers to measure the ID are silly (1: tubes aren’t round. 2: the threads go deeper than the caliper ears can reach. 3: arc deflection; not super important at this size, but it’s still there.).
This is why plug gauges exist. Plug gauges were invented by people who are much smarter than the people who say “Just measure it with your caliper!” These people I group, along with the “just use teflon tape” people as “people who are a danger to themselves and everyone around them.” People from whom I take no advise because I like not exploding. The kind of people who would make a zip gun out of pipes and not understand that they’re setting off a bomb in their hands… The kind of people that say “stand back and hold my beer, you ain’t gonna believe this shit!” There are a lot of know-it-alls who don’t.
There are laymen who give advice on topics they know nothing about. There are people who are authorities on these topics who try to prevent these laymen from getting people killed. Both have to use language relate-able to the person they’re trying to help. The nerds who know, often fail to do this and their points are missed. The nerds who do, often get lumped in as “just another know-it-all” simply because of the non-technical language used to relate to non-technically educated people. Cue, salesmen and Internet trolls…
Some people fully turn the ID and OD to get true numbers (there is still deflection in deep holes), but what we’re working with here is such a crude instrument, all the fancy stuff is polishing a turd. All it really does is make people who don’t know any better think that it’s special… It serves no practical functional use and adds expense.
While there are technical reasons why turning ID/OD matters in many applications, those circumstances do not exist here. Sometimes, engineering nerds get carried away…
…unless the material is badly out of spec. In which case, you have bigger problems and that material shouldn’t be used to begin with due to problems introduced in the imbalanced extrusion process that caused the deformation. It’s completely pointless to argue about it. But, salespeople often know what you don’t, and keep it to themselves as they blow smoke up your ass.
I prefer spending the money where it counts, rather than brag about how much time and money I spent polishing a turd. My products are intended for persons of a similar mindset. If you;d like to imagine that turning the ID and OD matter under these circumstances, it’s a free country. You can believe whatever the fancy nerds tell you. I’m every bit as much of a fancy nerd. The difference is; I’m not a bullshitter.