Which way round to mount a FK12 bearing ?

It seems that the usual way is to mount a FK12 with the boss facing the ball screw and the nut and pulley at the flange end but this needs an approx 34mm hole in the mounting bracket and I'm struggling to make clean holes without a lot of work. I saw in a catalogue for these bearing that they can be mounted either way round which would make life so much easier, so . . . any thoughts on that ?

I think that only one end of these are machined to give a proper fit, but I could be wrong on that. If you mount it the other way round in might give you alignment problems.

Thanks for the reply, I see what you mean and it 'feels' better that way round but look at this;

Fixed Bearing FK

The only thing is the counterbores on the bearing housing indicates the bolting direction and in both A & B variants it implies the boss fits into a bracket which is what I dreaded. I think I've answered this myself ?

Edit: And I think I've thought of an easier way, for me, to make the large diameter holes.

I've used BK bearings (similar to FK but in block format) both ways around depending upon package space with other parts of the machine. Didn't notice and problems from doing this.

I assumed that angular contact bearings could take equal loads in each axial direction therefore it didn't matter. But thinking about it I guess one face of the flange/block could be more accurately machined 90 degrees to the main axis? But don't know for sure.

If both faces are 90 degrees to the main axis then I can't see a reason for not connecting it the other way around if you need to.

You could also build it the 'wrong way round' then use the CNC machine to make new bits including the clearance hole to mount it the 'right way'.

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Originally Posted by routercnc

But thinking about it I guess one face of the flange/block could be more accurately machined 90 degrees to the main axis?

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Thanks, yes that's what I thought later, anyway I likely wasn't trying hard enough before because I've done it now and quite easy.

Drill largest feasible hole in bracket, in my case about 19mm using a cone cutter (it's hard work and hardly cuts), position bearing block on bracket and clamp, drill mounting holes in bracket using bearing block as a guide, bolt bearing block to bracket with some spacers between, mount in lathe chuck, use boring bar to open hole out to final size.

Attachment 11745Attachment 11746

I think the answer to my original question is this;
The bearings can be used either way around but the face next to the boss is the one that goes up to a bracket. This allows for the fact that the mounting holes are counter bored on the flange face and it's possible that the face next to the boss is more accurately machined.

Nice solution.

By the way is the angle bracket the only part holding the bearing? There will be some flex here if that is the fixed end. Is it part of some bigger grand design involving the plate in photo2?

Good work anyway.

Your right, the floating end will have two pieces of angle and the driven end will have three, as per drawing.
Angle is 6mm thick by the way.

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