Thread: Measuring for ball screws

Hi
Found when doing mine was to CAD the relevant bits of the mill up. If you are not across your cad program this will help you to be.
What are you going to us as software on the mill and CAD?

Russell

Originally Posted by rusel

Hi
Found when doing mine was to CAD the relevant bits of the mill up. If you are not across your cad program this will help you to be.
What are you going to us as software on the mill and CAD?

Russell

I am running Alibre.

At this stage I am not keen on putting the mill into my CAD program. I would rather measure up the leadscrews and figure it out from there. That must be how people are doing it right?

Not that I know anything about this mill, but why can't you use the existing screw and just attach a motor in place of the handle?

Originally Posted by Bob Willson

Not that I know anything about this mill, but why can't you use the existing screw and just attach a motor in place of the handle?

backlash and accuracy Bob these mills are not the most ridged and if your going to mill steel taking out the backlash in the threads is very important and the original threads will have about 10 thou of back lash in them

variant
are you going to use the existing screw mounts or make new ones, what part are you having trouble with, where are you getting your screws from

cheers
Harty

Originally Posted by variant22

Ball screws are expensive so the last thing I want to e doing is "buy and see", and then have to buy again.

Amen to that.
I just bought one that is too big for my screw

Originally Posted by harty69

are you going to use the existing screw mounts or make new ones, what part are you having trouble with, where are you getting your screws from

Harty, I was thinking of going with "Linearmotionbearings" out of China. I am not sure if I will use the existing mounts. I would think, probably not. I have not had a good look yet as I have been avoiding tearing the machine apart. I seem to be using it constantly, and would really like to avoid extended downtime. I might however have to remove the table and at least measure the X axis screws to see how they measure and take some photos so I can work on mount ideas. I have some good ideas on how to mount the servos etc, I am more stuck on the ball screws. Every discussion I have read about them becomes quite convoluted and ends up in a fair amount of ranting about things that are generally not related to the question at hand.

My strategy as of today is to take the table off, measure the existing screw lengths, then look at the mounting points. I will order the ball screws and go from there.

I am not 100% on grades, or thickness. I have in my head "C7" and "20mm", although I really do not know if that is what I will settle on.

LinearMotionBearings from Chai is a good bet. Chai has supplied many of us here with good service.

Forget about the C7 part, what you get is what you get. One grade fits all.

20mm sounds good, as long as you have the space to mount the bearing supports and also the nut for the screw. You won't be using huge speed on this mill, so whiplashing of the screw will not be a problem for you. ... just space constraints.

Read this thread from Peter Homann for some ideas on what problems you may face.

Hi variant
i converted a round column mill a long time ago the base is similar i think
there are some pics of what i did in the link below. I would not drive it this way now but like you it was my only mill at the time and i needed to get it going so it never got finnished of properly . i still use it today though
harty Gallery - My Photo Gallery
the last machine i converted in 2008 was a beaver mill a bit bigger than a bridge port and you can see the picks here
Projects Gallery
on the beaver i got the c7 ball screws from "Linearmotionbearings" out of China fantastic to deal with machined the ends for 5 bucks extra back then. if i did it again i would get 2 nuts and preload them i thought the c7s would be accurate enough but the double nut would be that little bit better

pm me and i can send you my phone number if you need any more info

cheers
Harty

Hi variant
We got our screws from LinearMotionBearings good service from Chai.
We used two nuts per screw to remove the back lash works well. Just remember that you have to run a extra oil line, that my preference though a separate oil line per screw or bearing set No tee joints.
I made my own bearing blocks up as this allowed my to get maximum travel.... used the same mounting holes. pic of x axis
I did these on the mill after pulling it down taking lots of measurement put the mill back together. Then made the bearing block, motor mount and ballnut mounts for x and y.
Hope these are helpful and give you some ideas.

Russell

Thanks for all the tips. I have a few ideas on how to measure it all up. I also have some good mounting ideas. I hope to post back when I make some progress. I intend on mounting the servos in a bit of a different manner to the usual.

harty69: Thanks for the offer of some phone support. I am not at the point where I have any concrete questions, but if/when I get stuck I will send you a PM.

Be careful with ballscrews.
I took it off the screw to put it on my old screw that has already been machined and the balls just fell out
When everything else fails, read the instructions:
Don't remove the nut from the screw, the balls could fall out

Originally Posted by SAISAY

:
Don't remove the nut from the screw, the balls could fall out

will fall out not could
but you can roll them off onto a appropriately sized piece of pvc pipe or tube even a dowel its a bit fiddly but can be done. defiantly easier than repacking the nut especially if there small ones

cheers
Harty

A bit of fiddling and I got the balls back in, wonder why there isn't a clip to hold them in like in the linear ones?

They can sell more ball screw nuts this way.