Reaming a Pressfit BB Frame Shell to Size Part 3: Exactly How Does Press-Fitting Work?

December 28, 2022

 

Part 3 of 5: Press-fitting requires something larger being pressed into a hole that's slightly smaller, but how much smaller should the hole be? The answer is simple; it needs to be just right. What this Goldilocks-zone is and how it is achieved are the questions we answer in this video, among other things. Check out:

• Part 1: Introduction
• Part 2: Preparing the Ream
• Part 3: Exactly How Does Press-Fitting Work?
• Part 4: Cutting Operation; Let The Ream Do The Work
• Part 5: Post-reaming BB Install
• Part 6: Post-reaming BB Install (Bonus Vid)

 

So we're doing something here we normally wouldn't do and that's we're using a lot of really expensive shop tools we try to avoid that as much as possible because not everybody's going to be able to afford what is basically this ends up being about a 500 rig when it's all set in time when you buy everything okay so that's really pricey for the home mechanic but for shot mechanics they need to be able to do this and for home mechanics they need to know that this can be done that's the purpose of what we're doing here now i i measured this in our last video we measured that we determined we need to ream it and we also show that this is basically a 40.98 ring all right now that's 41mm. 40.98 what's the deal well we need that little bit in there to give us the press fit. Press fitting requires a very accurate interference okay between the parts so the hole has to be a little bit smaller than what's going in for us to get what we want a little bit smaller okay once you exceed that 1000 excuse me one thousand two thousandths of fit the whole thing is going to go awry you're gonna start having degradation of performance immediately and of course if it's way too big then that you don't have enough retention and it's not a press fit at all it's a slip fit and you can't do that that will not work so we need to be in that goldilocks zone and this is what's going to get us there um so let's go ahead and uh before we start reaming which we will do in our next video i want to show you guys something very important and that is this bike has this brakes we are going to be putting oil and solvents up here very shortly if anybody gets on these pads they will be ruined so whenever you're doing something like this i recommend taking a a glove okay and putting a glove over it to protect it from all the oil and stuff that's about to get on

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Also in BBInfinite exists to elevate the bottom bracket to the high-performance, low-maintenance, reliable component it is meant to be. Rid yourself of press fit bottom bracket creaks and pops. BBInfinite is silent performance.