[tauntdesigns]

Finished slide nut plate, cut the boss around the threads for the ballnut, cut the counterbores for the bolts, and test fitted the polycarbonate tubing for the chip guard.

Couple of pics:

[tauntdesigns]

I finally got around to re-doing the ballscrews and cut them to length.

I ran into a problem, a problem I knew someday I'd have. I didn't know it was going to be now.......... I took the cross slide off the lathe and took it over to the mill to drill and tap the mounting holes for the ballnut plate. I put a angle plate on the mill, clamped the slide to the angle plate. Ok, there's not enough room to use a drill chuck and I don't have the collet size for the tap drill........(wedge) So I put the lathe back together and made a bushing (od to fit collet, id to fit drill) and took a hacksaw and cut a slot thru center hole half way up the bushing. Collet clamps against the bushing and bushing clamps against the drill..... worked rather well. Took the slide back off and drilled and tapped it, done.

After looking everything over.... I noticed:
I need to counterbore 2 cap screw holes or loose 1/4" travel.
I need to round the corners of the z-axis ballnut holder to fit in the screw chip guard.
I need to cut the polycarbonate tubing for the chip guard and flange the ends of the one for the z-axis.
Waiting on the G540(chair)

Later,
Jack

[tauntdesigns]

I decided to test fit everything.... WOW, everything bolted up perfectly, which is good because, I didn't slot any of the bolt holes. I drilled every hole the normal clearance size.

I asked a question in the linear motion group: Should I use a set screw to lock down the ball nut or use removable lock-tite thread locking compound? No answer but, I found a few other threads/post where they used set-screws. I drilled and tapped the 2 nut holders for set screws.

Found another problem... I couldn't get a wrench on the locking nut that pre-loads the ballscrew in the bearings. I need to bore the hole out .075" so the socket will fit.

Here's some pics:

Later,
Jack
P.S. I may not be able to wait for the G540 to test the movement of the axis. I may un-hook my X and Y motors from my mill and bolt them up to the lathe and jog everything around.

[ViperTX]

Jack are you milling on an X3?

Thanks,
Paul

[tauntdesigns]

Jack are you milling on an X3?

Thanks,
Paul

Howdy Paul,

Yes, everything was done on my X3, except for the work done on the ballscrews (which was done on the 8x14).

Later,
Jack

[tauntdesigns]

I couldn't wait......... I soldered some 4-pin mic connectors to my motors and unplugged the mill motors and hooked up the lathe. I got all the settings done and started moving the x and z axis around. I noticed a little bow in the screws (eye ball), but everything moved easily.
I put an indicator on the cross slide and started testing the z-axis( distances were dead on, but the backlash was .005"). I did the same on the x-axis and got the same readings.
What are the chances that I got the screw preloaded on the bearing the same amount? I tried moving the cross slide by hand and got the same .005". I tightened up the gibs on the cross slide and then tested the movement and got .008". I'll try adjusting the locknut on the screws and see if I can get the backlash out.
The nuts seemed loose when I loaded them onto the screw.

I ordered the ballscrew stock and nuts from Aaron at IH store a few years ago. It was listed as "premium ballscrew". Could it be........ that is the best I can get with those screws without changing the balls out for bigger ones or adding a second ballnut to each axis?
Maybe it's the cheap ac bearings I got.... more testing.

Anybody,
Jack

[blackbeard52]

Jack
What type of angular contact bearings are you using? Is it possible that you have them flipped? I did this once on a build and like to never figured it out. In my case, if all else fails read the directions.....

Bob

[tauntdesigns]

Hi Bob,

I got them(AC bearings) at VBX bearings. I'm pretty sure I got them in right, but I'll check to make sure.

I read some posts last night that talked about changing out the ball with larger balls in the ballnut. Others talked about adding a second ballnut on each screw.

Thanks,
Jack

[blackbeard52]

One thing to check also is the end play on the screw...You can slip a washer behind the nut to make sure you are not bottoming out in the threads...however if its the same on both this is not likely the issue. it sounds like play in bearings... and I would flip them just to see if that cures it. I have also stacked two bearings with a washer in between that clears the center hub this will preload the set and will ordinarily eliminate the need for the motor end bearing, at least in some cases. the reasoning behind this is the distance between the bearing like you have them mounted now is great and will allow whip even the slightest will cause that much slop. especially if the screw is small.

[tauntdesigns]

I tightened the locknut on the bearings until things started getting harder to turn. I put an indicator on the end of the shaft and pushed and pulled the cross slide with no movement on the dial. I couldn't stop myself from taking some test cuts and the .004" backlash is still there.

I made a part (adapter for my swivel indicator holder) on the lathe to see how it would do. All of the cut moves were in the same direction and the part came out DEAD ON/NUTS.

THINKING OUT LOUD:
I think I remember reading about others using double ballnuts to get rid of the backlash.
Bigger balls, double ballnuts, or better quality ballscrews?
If I program everything with moves that are in the same direction...... or edit the programs to account for the backlash........ or save my money for ground screws.

A couple of pics: I don't know which pics is the worst, cell phone or camera?
Cheers,
Jack

[blackbeard52]

looks like you have it... the ballscrew ... Although you can set Mach for backlash compensation... or here is the post you refered to earlier I think...http://www.cnczone.com/forums/showthread.php?t=46579.. and some guy is selling plans for one here http://www.homecnc.info/ballnuts.htm..but I havent seen them..picture looks like he took two nuts inserted a spacer.

[tauntdesigns]

Thanks for the links,

The 1st link looks like it would work on my z-axis set-up without any changes and the 2nd link looks like it would work on the x-axis.

The 2nd link with the extra ..but on the end should be:
http://www.homecnc.info/ballnuts.htm

I wish I new where to get the ballscrews that CNCFusion uses on their deluxe x3 kit. Backlash was under .001"..... maybe if I BEG

Thanks again,
Jack

[tauntdesigns]

It's been a long time since I've visited this thread....... and it's been a hit and miss for visiting the ZONE...... shame on me(nuts).

I've been using the lathe for little home projects and a few things for friends.

Peace:rainfro:

[Teyber12]

glad to see you back ive never seen this thread before and enjoyed reading it. love your work.

[tauntdesigns]

glad to see you back ive never seen this thread before and enjoyed reading it. love your work.

Thanks for the nice comments.

[rwskinner]

I hadn't seen the thread either. Nice job, and nice machining !
What did you ever end up doing about your backlash, leave it alone or double nut? Again, NICE job.

Richard

[tauntdesigns]

I hadn't seen the thread either. Nice job, and nice machining !
What did you ever end up doing about your backlash, leave it alone or double nut? Again, NICE job.

Richard

Thanks,

Almost everything I've cut so far has been in one direction on both axis and the backlash hasn't affected it.

Replacing the balls with bigger balls would be the easiest fix, but still probably would not remove all the backlash. I'd really like to add a 2nd ballnut to each axis. Adding a 2nd ballnut on the z-axis would be easy, but I'm not sure if I have enough ballscrew sticking out the back for the 2nd nut on the x-axis.

I'd like to buy what ever brand nuts and screws my X3 mill has on it. It has less then .001 backlash on it.

Thanks again for the nice comments,
Jack

[rwskinner]

On the lathe, I didn't feel it would be a big deal as long as it wasn't too bad. Some of the older, manual lathes I ran when I was younger had tons of backlash and it was never a problem, as long as you sneak up on it the same direction each time.

Now when I convert my mill, that will be a different story. Zero Backllash nuts will go on it for sure. I don't like holes coming out like a smashed egg!

I'm debating over home switches and limit switches on the lathe as well. I can see needed one or the other, like home switches and soft limits, or no home and hard limits.

If I do home switches, I guess they both need to be near the end of the axis travel, away from the spindle, but before the hard limits right?

Richard

[rwskinner]

Jack,
Did you ever finish your cover for the Z Screw? Curious how it turned out.
I got mine up and running today but I have a lot of little nitknacks to do. Screw covers being a priority. I inquired about some conical spring covers but I don't know if they'll ever respond.

Richard

[tauntdesigns]

I'm debating over home switches and limit switches on the lathe as well. I can see needed one or the other, like home switches and soft limits, or no home and hard limits.

If I do home switches, I guess they both need to be near the end of the axis travel, away from the spindle, but before the hard limits right?

Richard

I had planned on putting home/limit switch on the lathe mainly for homing the machine in both axis and to keep the X-axis from backing up against the motor mount.

The switches are on the backlash side of the screws..........errrr! Anyway, I never got around to it.