NG3 pilot bearing in TC bellhousing

[Blitzen]

Does anyone have the specs for machining TC bellhousing for the NG3 bearing?  Machinist is asking how tight the pressure fit should be.  Also the the bearing has an o-ring below the flange, does there need to be a groove so the flange of the bearing will sit flush on the bellhousing?

[BDA]

Maybe this (http://www.greytower.com/jon/lotus/europa/gearbox/gearbox.html) will help.

[SwiftDB4]

I recall the fit is light pressure. Only moderate tapping is necessary to seat the bearing sleeve. I think I took the o ring off as the press fit seals things.

[Blitzen]

Maybe this (http://www.greytower.com/jon/lotus/europa/gearbox/gearbox.html) will help.

He only says should should be tight press fit. A very subjective term.

I recall the fit is light pressure. Only moderate tapping is necessary to seat the bearing sleeve. I think I took the o ring off as the press fit seals things.

Thanks, I’m still uncertain whether the bore should exactly the same as the bearing or slightly under.  But this info helps.

[BDA]

I think you're overthinking this.

I'm not a machinist so I looked up the term "tight press fit" and as you say, it isn't a formal machinist term. This is what I found out: A press fit is a type or name for the "lightest" of interference fits. It requires "cold pressing" or in other words, it does not require heating or cooling to assemble. This means the joint is provided by the friction between the piece and the hole so the hole has to be slightly smaller than the piece (bearing in your case) and as SwiftDB4 says, it requires moderate tapping to seat the sleevea. I think the main idea is that the joint created by the friction between the two pieces is pretty strong. I don't think it requires any more specificity than that. I would think that a competent machinist would would be able to translate "tight press fit" to the appropriate hole size for your bearing.

This site might help: https://www.rapiddirect.com/blog/types-of-fits/

[Blitzen]

yep, that's me! Overthinking minutiae and glossing over important things.   Thanks, I probably needed that reminder.   The link was quite informative.

[BDA]

I'm glad that helped. One thing to keep in mind is that if a dimension is critical, it will be called out. If it is just described, then it's more of a "functional" spec rather than an "absolute" spec. Hopefully that make sense.