Ballscrew or leave alone?

[russell]

Delrin will have reduced friction But I found that it just acted as a damper and masked the backlash. measuring low backlash only under a no-load condition. Once the load is applied it compresses until the the other edge of the screw is in contact( ie play in the screw/nut). The amount of compression is dependant on the load so you end up with varying amounts of error on the work piece.

Agreed, this can be a problem but like everything it depends on the design. Some use springs to compress the split nut and of course these flex under load. I am just using screws to adjust it with no flexibility. My first attempt did have a flexibility problem which I traced to the flange on the nut flexing. It was cured by backing it with a substantial steel washer.

Again, horses for courses.

Russell.

[i2i]

at the end of the day, you're going to cnc a manual mill for what reason. You want an accurate computer controlled milling machine that will cut metals from ally to probably steel.

The first need is accuracy, which means ballscrews.

You don't need to go any further.

[manofgresley]

Many thanks i2i.

Yes commonsense must prevail, i am converting to CNC for greater control and accuracy, so i will go down the ball screw route, if i can find screws and nuts that will fit under my slides. My Lead screws are 14 mm diameter, what would be the smallest diameter ball screw i could use i wonder?

Regards

Ray

[ptjw7uk]

You could go down to 12mm dia ball screw.
The biggest problem will be finding enough room for the ball nut!
On my Sieg X1 conversion I used RSW ball nuts which have the smallest dia, when I did mine I thought you could not get them with wipers fitted but you can.
RSW Ballnut

Just an idea to think about
Peter

[Jonathan]

You can get 12mm (RM1204) ballscrews from linearmotionbearings2008 on eBay. The steel the ballnuts is made from is just about soft enough to mill, so if you need to make them a bit smaller that's a cheap option. It's probably easier to grind it and glean the nut thoroughly afterwards. Clearly the stiffness and critical speed of the screw are both reduced if it's smaller, however in this instance neither is significant since it's a small machine.

[Ross77]

Have you got any space between the base and end plate on the bottom axis (Y- I think on a mill)? I'm just looking to put ballscrews on my mill and want the biggest diameter possible as it is only supported on one end. The channel between the ways is too small for 20mm dia. ball nut but I have space to move it forward and mount the nut flange on the face of the base.

Any way just a thought.