Building Bernard Tekippe’s Precision Regulator

[John HaineParticipant @johnhaine32865]

Given the limited choice that Chris has, I refer to my answer above.

[gerry maddenParticipant @gerrymadden53711]

Thanks for the information Gerry. Can I ask what you mean when you say to watch the corner radius? You also mention, “Secondly the shaft must be accurately square with the outer rings. Therefore machine the two housing together” 

 

Hi Chris, re corner radius I mean this feature shown in the snip below. The corner radii on small bearings can be very small. Typically on a bearing with a 3mm bore size, it may be in the order of 0.1mm.

The radius on your shaft (between the abutment face and cylindrical seat) MUST be smaller than the one on the bearing. If it’s not, then when you press/tap the bearing up against the abutment it will simply sit cock-eyed. This will not be detectable without some good metrology but the bearing’s friction/smoothness will definitely be compromised.

If you can’t be confident of getting the required small radius, a small undercut will be acceptable provided it doesn’t eat in too much to the cylindrical seating area or the abutment face. Oversized radii are an easy mistake to make. Industry frequently gets it wrong!

Regarding housing alignment, this is what I’m referring to.

Obviously the permissable lateral displacement depends on how far the housing are apart and can be calculated by simple geometry.

In practical terms, Im not sure how you might achieve it because I haven’t yet studied the clock design! 🙂 I will try to do that shortly and come back you.

Finally, I keep seeing people suggesting running the bearings dry. You really don’t want to do this, especially if the bearings have pressed metal cages. These will wear and make steel dust in not a great deal of clock lifetime. If you are able to completely eradicate the initial grease charge, (which I tend to doubt :)) then relubricate the bearing with a tiny quantity of very low viscosity, long-life oil. Excess can be easily drained out if required by lying the bearing flat on some dust-free paper for a while. Oil will never give create the same kind of friction levels as grease, but will stop wear and oxidation in the following years.

Gerry

 

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