Hi Eddy,

Yes, Jonathan used 200N but my scales were only up to 5kg so I could only apply 50N. The response will be linear anyway at these loads, and as the load is divided by the deflection it works out the same (4 times load gives 4 times deflection). The stiffness values will be the same in both cases. We also both used 50mm Z extension so the machine condition is the same and results are all therefore broadly comparible.

Jonathan has not published figures to my knowledge, just this info in the 'sufficiently strong machine' thread:
'. . . .By applying a force of 200N and measuring the deflection I found the stiffness in X and Y with the Z-axis at 50mm extension. I did the same test on my milling machine (Clarke CMD1225C column mill) and hence found that this machine is a similar stiffness to my milling machine, although a bit weaker in Y . . . '

Would love to see some figures if you have them Jonathan ! . . .and anyone else if you've measured at 50mm Z extension.

Going back to the freeplay in the FK bearings, if you only tested in one direction and took a few readings (as I did) then the freeplay would all be used up in the first test and should not be a factor in the repeat tests. It would only matter if you went back and forth. I wanted to seperate free play from actual machine stiffness so measured in one direction only.

I've currently got my AC bearings out of the housings ready to shim up as they have quite a bit of freeplay even when loaded.