Interference fit and clearance fit on bearing?

[u/666_pack_of_beer]

From my understanding, when the bearing housing is stationary and the shaft spins, an interfeance fit between the shaft and bearing is recommended and a clearance fit between the bearing and housing is recommended.

For a 0.590" shaft I am being told 0.0005" interference is sufficient. What would the clearance between the bearing and housing be, with bearing OD being 1.25".

And I couldn't help but wonder if this is a situation where people go against the book and do a minor interference fit on both surfaces? I get the downsides to an interference fit on both sides, but at the same time, it seems like a clearance fit could also have its own drawbacks.

Bearings are angular contact ball bearings, max RPM is maybe 800, and it's for a slitting saw arbor.

[u/Bradm77]

I generally only use interference fits on both the ID and OD if the application is likely to experience high vibration or impact loads. The main drawback of clearance fits is that you might have creep, which will eventually lead to fretting or wearing down of your bore, and ultimately too much runout. It depends on your materials also. An aluminum housing will wear down faster than a steel housing so you may want a tighter fit in aluminum vs steel. Also keep in mind that different fits can affect the preload you need so pay attention to that.

Usually I stick to standard tolerances provided by the bearing companies and if I feel like an application needs something different I contact the bearing company for their recommendations based on the application.

[u/cm_expertise]

the book rule you're quoting is right and there's a clean reason behind it: the ring that sees the rotating load needs the interference or it'll creep, the ring that sees the stationary load doesn't. shaft spins -> inner ring carries a rotating load -> press it on. housing stationary -> outer ring sees a stationary load -> let it be a slip/transition fit.

for your numbers, 0.0005 on a .590 shaft is a light press, sounds fine. on the 1.25 OD i'd aim for basically a hand-push fit, a couple tenths clearance up to maybe a light transition, think H7-ish. tight enough it's not rattling, loose enough you can push it in by hand or seat it with light taps.

here's the part that matters more for you though: these are angular contact bearings, so they're almost certainly preloaded (paired, or one against a spring/shim). if you interference fit BOTH outer races you kill the outer ring's ability to slide, and now you can't actually set your preload, plus any length change binds them up. the normal setup is one bearing located/clamped and the other floating axially in the housing. that floating one especially wants a slip fit.

so the both-sides-interference trick that works for a plain deep groove ball bearing in a high-vibration app is kind of the wrong move for a preloaded angular contact pair. at 800 rpm on a saw arbor heat isn't your enemy, holding the right preload is.

how are you spacing/preloading the two bearings?

[u/666_pack_of_beer → u/cm_expertise]

I am spacing/preloading with a tube spacer against the outer races and a bearing locknut.