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Fitting small diameter ball bearing races.

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Trevorc:
Hello
In building my previous engines i have been able to use machined bronze bushes. Now I am building the Y model Anzani I have to fit several ball bearing races with diameter below 1 inch.
I would like some advice on how to fit these in a model engine.
Do I stick with the “ correct” way by using an interferrence fit inside the housing and onto the shaft or do i go down the “ loctite “ route and effectively glue the bearings in place.
My concern is that i may be faced with having to take the engine apart several times, more difficult if interferrence fit.
What do other do?
Thanks in advance for any advice.
Trevorc

steamer:
For small bearings I try to stick with reamer sizes.   If the bore is blind, ill bore it to size.    A push fit is what im after.
Dave

Tennessee Whiskey:
I’d say that Locktite has spent billions on being able to safely call it “bearing and sleeve retainer” . If you know you are going to have several “fittings” , then I wouldn’t hesitate to machine where you can assemble and disassemble, and then rely on the product to do it’s job. I mean, most of their business is serious retention values in comparison to what we need. Just follow their guidelines. My 2 pesos worth.

Cletus

Ramon Wilson:
Trevorc,

Having built several engines now I would firmly recommend you adopt the interference fit as opposed to using Loctite.

The main reason for that you have answered yourself in that to remove and replace the bearings will be easily accomplished with a degree of heat to expand the housing slightly but no where near the heat that will be required to break the bond of Loctite.

If good measuring kit is not available I find that boring the housing to a plug gauge carefully turned and polished to just under the bearing size (0.003-5mm) until it just fits will give a good indication of fit to the bearing.

Loctite Bearing fit is ideal for bearings that will sit in situ for long periods - and yes it doe ease tolerance values but it's a rather semi permanent solution and especially so in a small engine.

Hope that helps - Tug

Mcgyver:

--- Quote from: Trevorc on January 15, 2019, 07:11:31 PM ---
I would like some advice on how to fit these in a model engine.
Do I stick with the “ correct” way by using an interferrence fit inside the housing and onto the shaft or do i go down the “ loctite “ route and effectively glue the bearings in place.

--- End quote ---

Generally you don't want to have a press on the shaft and housing.  The starting point would be the basics of rolling element bearing installations which are covered in most bearings makers catalogues, although I grant they must employ scores of highly intelligent folks focused on making said catalogues as unreadable as possible.  However it will tell you the fit required.

Basically the usual set up is the bearing is pressed to the moving part (most often the shaft) and a tight slip fit in the stationary part (tolerance you get from the maker).  Think of an electric motor, you can manually pull the bell ends off but not the bearings off the shaft.   You can also can only press on the race that is in interference, i.e. never apply force through the rolling elements.   If the press fit being on the shaft, you can only press on the inner race to install (if installing via pressing vs shrink)

So.....even if installed the proper way, well machined fits to tolerance, the bearing is not removable from 1/2 of the assembly without damaging them.  Its extremely difficult to pull off a bearing pressed on a shaft off without putting the force through the rolling elements.

Just saying that you should understand where the interference (or loctite) joint is is suppose to be and where the slip is suppose to be, and you'll have a heck of time removing the interference fit without hurting the bearing.   The interference fit also prevents any sort of eccentricity and is imo the way to go

Machining those interference and slip fits within tolerance is a  great challenge, at least in my case, probably the most demanding work done in the home shop.  For precision bearing sets you have to hold tenths, and the smaller the bearing the smaller the tolerances.  That challenge is probably why people go with loctite.  Get a tenths indicator mounted on the cross slide and it helps to hold the tongue just so.

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