Repair of Gyroscopic Instruments

If they are not 3/8"OD then I think there is a strong chance that my alternative part number is wrong and/or your Mid-Continent number is wrong.

There are not that many manufacturers of small precision bearings. Could well be Japanese.

Peter wrote:

There must be a hundred bearing manufacturers in the USA. I wonder if @Silvaire knows?

Sorry Peter, I don’t know. I’ll be back in the US next week and could do a bit of research.

I would get me a ballbearing with the exact i.d. and fabricate an adapter bush with slide fit of one or two hundredths mm clearance for the mini bearing. Add a little low strenght Loctite and fit the bearing into the bush. That way you could exchange later easily for minimal cost when you find you a handful of standard 2 Z bearings now. There are even ceramic bearings for 3/16 i.d. : ceramic bearing Vic

What is the advantage of a ceramic bearing? IMHO the only requirements for this bearing is that it is low friction (all ball bearings should meet that unless they have rubber seals ) and a long life at a high rpm. I have just remembered that I have the entire KI256 MM – photographed from a mouldy paper one sitting on the shelf at an old avionics shop

and the hole is 4.73-4.75 (I don’t have an accurate way to measure it).

allright, that was not an easy one: Problem is the width of just 2,76 mm , the type is called R 156. It is mostly 1/8" wide with seals, but also available with 2,76mm open . Bore is 4,76 but only 7,94 mm outer dia. , so that leaves an adapter for 1/2" o.d. to be made up. You may try there:

mini bearing

or here, see the PDF:
mini ball bearings

Vic

I know only one ball bearing manufacturer, and that’s SKF. http://www.skf.com/group/products/bearings-units-housings/ball-bearings/deep-groove-ball-bearings/deep-groove-ball-bearings/index.html

Brilliant work vic!

Now… how does one select a bearing for this application?

That’s a good page LeSving but I can’t see any which meet the requirements. These two are ok but not on the diameter, so as per Vic’s suggestion one would have to make a sleeve

90k rpm is surely enough?

For avoidance of doubt my shelf-spare KI256 has been overhauled by a 145 facility… this thread is just for fun, and of course to help others should the overhaul options go the way HBK want them to go i.e. evaporate

The other thing that is peculiar about the bearing, and which I hadn’t appreciated when I made my initial comments is that it is of odd proportions – that is a large OD given the size of the ID. The technical term is that it is a “modified dimension” bearing (really!) The alternative part number I quoted does appear now to be good:

SSRI-6632ZA0205MCRA7P24LB15P

The basic bearing is SSRI-6632ZA0205, which you will find here:

The decode for the rest of the part number MCRA7P24LB15P you will find here

In case you are wondering why I have this apparently unhealthy interest in bearings, I did a big project early in my consulting career in the 80s around ultra high precision encoders.

I reckon you must have found it, Alan. Brilliant work. I ought to buy some and see what they actually look like. It’s hilarious that they get charged out at something like $500.

No such thing as an unhealthy interest in anything to do with engineering… just don’t put it in your Tinder profile