Rotating Ballnut - design ideas

[vre]

Very nice the idea of rotating nut!
I want to convert a conventional lathe to cnc and Z axis leadscrew has 1900mm length 30mm diameter.
If i use L1900mm 3210 rotating ballscrew with 2 bk25 end supports i will have 1300rpm citical speed & column strength 28477 newton
The critical speed is ok to me because i will get 10m/min rapids with 1000rpm in ballscrew i have concern about column strength because 28477 newton (2900kg / Z axis servo can give 3400kg ) isn't to big force and also i have fear about sag to 3210 ballscrew and runout at rotation that will do a lot of vibration.

In my situation would be better a rotating nut design like this to overcome these 2 problems (column strength & ballscrew sag/buckling) ?
Also with rotating nut design can i use a lower diameter ballscrew without having whipping ?

[mutzy]

Jonathan and all of the determined mad scientists and hobbyists of this forum. This is great work. I really appreciate you sharing the setbacks and successes of hard work. Keep up the great efforts...I learn so much from this. Thank you again......Mutzy

[mutzy]

Jonathan, how are you?
1. Where did you get the pulley that is associated with post 79? Was it machined out with a larger bore to fit the shaft or store bought? Where can i get one?
2. I see that there are two different shaft configurations with the pics. One the shaft where the ballnut attaches sits kind of deeper in the cupped out area, and the other sits flush with the whole face. what is the reason for this.
Thank you so much for your time.

[Jonathan]

Where did you get the pulley that is associated with post 79? Was it machined out with a larger bore to fit the shaft or store bought? Where can i get one?

I used a standard pulley and bored it out to the size of the shaft.

I see that there are two different shaft configurations with the pics. One the shaft where the ballnut attaches sits kind of deeper in the cupped out area, and the other sits flush with the whole face. what is the reason for this.

This shaft where the face is 'cupped out' leaves a surface to locate the ballnut concentric to the shaft. This works well if the ballnut is accurately machined, but I found that you can't necessarily rely on this so sometimes it's better to just go with a face and align the nut with a DTI.

[mutzy]

Thank you Jonathan. What is a DTI?

Mutzy

[Clive S]

Thank you Jonathan. What is a DTI?

Mutzy

Dial test indicator https://www.machinemart.co.uk/p/cm22...c4FBoCNljw_wcB

[Jonathan]

e.g:

[Black Forest]

Hello Jonathan, Do you not accept PM? I would like to contact you.

[reefy86]

Jonathan do you sell these to other people at all or know anyone specifically who can make the from drawings?

cheers

Ash

[mutzy]

Hello Jonathan, how are you today? Wow, you certainly created a great thread here. I can't seem to find distributors that have this size bearing to bore out. Do you have any suggestions of who might sell them? USA would be best for shipping. Once again thank you.