Ready Steady Eddy

[Lee Roberts]

Who did you buy from ?

[EddyCurrent]

Who did you buy from ?

I bought them from Chai

[Jonathan]

Whilst we're close to the topic...for a while now I've been dismantling new ballnuts I've obtained from Chai, as it's not uncommon to find debris in them - be that just general dirt or bits of metal.

On the machines I've made to get zero backlash (lathe, mill & router), I preloaded the angular contact bearings using disc springs and shims between the bearings. That way there's less risk of damaging a bearing by over-tightening the nut as you know how much force you're applying from the spring deflection and it avoids buying matched bearing pairs. I also use bearings with a bigger outer diameter than the ones in the BK blocks - i.e. use 7201. They're less delicate...

If you want an easy option for a standard CNC router, then I don't see much wrong with just using double row angular contact bearings (52xx series), as although they have a small amount of axial play, the amount is much smaller than the single ballnut backlash so overall the effect isn't very significant. If you start pre-loading the nuts, then naturally the bearings need pre-loading too.

Also, be very careful with opening out the bearing blocks to better fit the bearings, as going too far may introduce backlash (depending on quite a few factors).