Paperwheels suddenly not true anymore

[Fluehue]

I have two slow speed benchgrinders.

I got help to machine flanges to make them 100%.
I have Spherical washers to make sure that the nut is not doing anything to the wheel.

Still for some odd reason it takes a couple of days from the wheels are 100% true untill they slowsly start to untrue.
What I mean by untrue is that the knife starts to jump on the wheel since it is no longer completely round?

Does anyone have any tips on what is happening?
How can a wheel that is true change?

The room has a humidity controll and is always at 60% humidity.
The temperature is 16degrees in the room.
The machines are bolted to a heavy table.

[cbwx34]

I have two slow speed benchgrinders.

I got help to machine flanges to make them 100%.
I have Spherical washers to make sure that the nut is not doing anything to the wheel.

Still for some odd reason it takes a couple of days from the wheels are 100% true untill they slowsly start to untrue.
What I mean by untrue is that the knife starts to jump on the wheel since it is no longer completely round?

Does anyone have any tips on what is happening?
How can a wheel that is true change?

The room has a humidity controll and is always at 60% humidity.
The temperature is 16degrees in the room.
The machines are bolted to a heavy table.

I know some (many) don't agree, but I sold paper wheels at one time, and the ones I sold were designed to run at a higher speed.  Doing this "smooths out" things like what you're noticing.  I ran a set on a variable speed grinder, and they always worked better faster.  Heat was never an issue that couldn't be dealt with... like anything else... practice.

So, don't know why you're seeing this... just thought I'd throw this out there.