80mm mount upper Z limit

Just installed the 80mm mount for a spindle, following the 1F video instructions. I haven’t installed the spindle yet, because I notice that even with the 80mm mount’s “bearings up” orientation, it’s not the bearings that will stall home against the top of the carriage, it will be the bronze keeper hitting the bottom of the housing for the link between z stepper motor and the ball screw. Is this correct?

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Hey John,

you mean Ball Screw Nut hits Ball Screw coupler on stall homing?

The optional Onefinity 80 mm mount is 2″ (51 mm) high high and Z linear bearing should be 2.75″ (70 mm) long. I assume you have the same measurements on your machine ?

Yet I haven’t seen that someone was able to attach these useful bump-stops on Z axis, only on X and Y:

Also Stops for Homing

The reason to mount these bump stops were preventing stalling the linear bushings against the machined parts because there is a oil-wooddust mix building up with time on the chrome-plated hollow shafts which affects stall homing repeatability.

Did you have problems to loose the two set screws as mentioned here: Swapping the Spindle Mount?

Did you reuse the same set screws when reassembling and was this difficult?

It may be that this is the normal for Z stall homing, I never paid any attention before with my 65mm mount.

Ball screw coupler contacts ball screw nut before linear bearings contact the carriage frame because the length of the ball screw coupler is greater than the distance between top of ball screw nut and top of linear bearings. I do note that the linear bearings on the 80mm mount are shorter by ~3/16 than those on the 65mm mount.

I’ll shoot a short message to support team to find out if this is normal.

This is normal and by design.

Aha, the answer from support team:

[Yes, this is normal and different than the 65mm mount. It is by design.]

Hey John, hey @OnefinityCNC,

That is a little bit surprising. Is this related to 80 mm mount or do they always have some tolerance?

Why are they shorter?