Super precision angular bearings are very expensive. If you say $50 each that doesn't sound like a super precision bearing. So here you go:

http://bearingsdirect.com/

http://www.vxb.com/

http://arceurotrade.co.uk/Catalogue/Bearings/Angular-Contact-Ball-Bearings   (in the UK and doesn't have your size, but otherwise good pricing)

Dan

Katoh,

If you ask me, 20mm is definitely overkill for this machine. Keep in mind that the ball nut will be huge - the mounting flange being some 50mm in diameter. A 16mm diameter will have plenty strength for this machine. Even a 10mm one will cope well with those loads, but a 16mm one will not even "feel" the them

Dan

Not quite so. Lead screws can be very accurate. Not sure what are the numbers you measured. It is common to speak of a ball screw in terms of accuracy over a given length. Thus, for instance, a C5 accuracy grade would mean about 0.03mm acceptable error in travel over 300mm. Accuracy grade definition varies from one manufacturer to another, so the above example is not dictated by a standard.

Lead screws can easily hold those accuracies. So, when using ball screws it's not really an accuracy demand. Ball screws allow you to have minimal backlash (practical zero), which is often desired in a CNC application. Also, ball screws run quieter and higher speeds can be achieved without the risk of heating the nut and wearing it. Of course they wear slower. Theoretically you can have a lead screw set up to have zero backlash, but it will hardly last.

Dan

EDIT:

Forgot your lathe was Chinese, so the original screws may have been poor quality and not as accurate

Isn't it so much rewarding to finally see it in action

I like the G251 - it almost makes steppers sound like servos. Still not on all speeds though.

Dan

Thank you, Klaus!

Dan

Great!!

Dan

Hi Klaus,

We have just found with Hood that there is something that can be very useful which can be done in Screen4 but not in MachScreen. In Screen4 one can force leading zeros by using a formatting string something like this %04.0f. MachScreen on the other hand, doesn't output leading zeros with the same formatting string.

Also, using a formatting string like T%04.0f is allowed in Screen4 and and will output the T in front of the number. This is useful in some cases, like the one demonstrated by Hood, here:

http://www.machsupport.com/forum/index.php/topic,17093.msg127574.html#msg127574

Please consider adding these capabilities to MachScreen.

Thank you for your efforts and a great software!

Dan

Hi Peter,

That looks neat! Thanks for posting it.

Dan

Amazing!

Dan

If you're measuring at the PP output it would be around 0V in its low state and around 5V (or 3.3V depending on your PP card) in its high state.

Dan