Daniel,
The screw is like 0.004" out over 5 feet. It's small but when mounted such that it's made parallel to the lathe bed you sometimes see it since that tolerance can be in the short section used. There is some radial loading no matter what you do and you want to minimise it. The bearing support plates are made such that they can be adjusted for parallelism between the bearing supports. I fooled for some time with the mill as the ball screw was locked in, you find the spot that just works, but need to play around some to make it just so. Using the torque measurements is a great help as it shows you that what you have done is improving the mounting.
RICH
 

This conversion may never end! But it is getting more fun now, since the bulk of the
main work is done. A third bearing was added to the X axis and whole bunch of holes were drilled into the X axis cross slide providing the ability to make adapter plates and special mounting for miscellaneous accessories to be used later on. Figure 44 shows one of the guards, and still need to make the others.
RICH

There are numerous accessories already made and to be used for this lathe. It’s one of the reasons I never wanted to part with it. Figure 45 shows two different tool holders. The one on the right can rotate and is vertically adjustable. So a number of mounting blocks will be done over time. At least the small quick change on the left is ready to go.
RICH

Here are some more accessories for the lathe. Note that both the three and four jaw
chucks have index’s. The three jaw chuck also has a vernier attachment ( not shown ) that can be used for finer indexing. The index band (magnified as shown in figure 50 ) is graduated in 1 degree steps on one side and then offset by 30 minutes on the other side. Additionally when using the vernier you can down to 5 minutes. When used with a high speed drill very small accurately placed holes can be done as shown in figure 51. The smallest holes in the piece are 0.010” in diameter. I placed a 0.010” drill in the test piece for reference. What is nice, is that you can do some fancy drilling with the finished turned piece left in the chuck and thus there is no need to do additional setups using a  sensitive drill press / mill / rotary table. Note that both radial and axial drilling is easily done. Yes, you can also then do some fancy pocketing, hole elongation, and scribing on the lathe. That is where an axis with almost zero backlash is important. If backlash is used you will snap a lot of the small end mills / tooling in a heart beat. As you can tell, the lathe will be used for small model work besides general turning functions.
RICH

That's a pretty slick project you've got going on, Rich. I have enjoyed following your progress. Do you have a mill at home that you make your parts with? You do know, that were gonna need to see a video of it making chips when your done, don't you. Is your wife as enthusiastic about your machines as Simpsons wife is with his? Good job Rich, I'm looking forward to the next update.

I trying to post a little for every one.

Have two mill's, one CNC'd which is a converted Atlas knee mill  (you can find pictures of it on the Show N Tell ) and a manual import mill drill that i beat the poop out of.
What is interesting is that you have all this CNC stuff and for the most part of this conversion you end up doing it manualy because it's a design / mill / drill, turn a piece......... work as i go kind of thing.....very little cnc work.  Now once done all ,of the machining could be optimized and CNC used more. 

You may get a video since a friend has a desire for creating one for other things to. 

My bride of 34 years has her side of the basement and i got my shop on the other side.  I stay out her Kitchen and she stays out of my shop. There are certain nuptual agreements that are made in your vow's which never should be infringed on. It's just a matter of respect. She does Tai Bow  ( can kick the poop out of you! ) and i make metal chips.
You know like, honey, when we get married you do realise that i will still go hunting for one week's vacation in the mountains, of course you are welcome to come and joint the boys, but it is not really required on your part. It's a guy thing like you getting together with the gal's once a year! 

RICH

RICH

Z AXIS BALL SCREW  PROTECTION

I looked at a number of different bellows that you can buy which encase the screw. The metal ones as shown on a piece of screw in the picture are expensive and act as a spring. Didn't care for rubber bellows ones as they just won't hold up. Telescoping tubing requires installation on the screw before the screw is mounted. I realy wanted something that can be removed and mounted very easly. Screw wipers will mounted in back of the carriage and on both ends of it and there ball nut adjusting screws i need to get to. A shower curtain rod cover can rap around the screw and i quess you can make your owne slinky type.

I decided to give the homebrew telescoping angle covers shown in the picture a go. Easy to install and remove. Don't know how they will act during a high Z rapid move. I guess we will find out.

The MPG may get mounted to the carriage or off to the side at the tailstock end of the lathe. The one shown is just for comcept. The future new one will have a smaller box, and yes, actual wheels. The most natural mounting is on the cariage but mounted near the tail wouldn't be too bad either. Usualy i use the MPG while also looking in the microscope. You want to feel comfortable and instinctively operate them just as if it were a manual lathe.

They call this thinking "conceptual design" especialy when using high tech things like  tape and clamps.

Any simple ideas out there on the covers, give a reply!
RICH

 

Just a little update on the conversion. The pictures show the X and Z axis ball screw covers done and attached. The telescoping Z ones work great and are made from Al angle while the X axis was bent and then welded. Shouldn’t have any debris getting on the screws. What is not apparent is that the carriage drilling was completed and that to install the gibs on the operator side of the carriage the Z axis needed to be removed. So all was taken apart and put back together, realigned, gibs shimmed just so for a nice slide of the carriage, etc. The Z now only takes 16 in oz ( with out motor attached ) to just start movement. That gave me an extra 40 IPM to the Z max velocity.

The X travels within 0.0005” perpendicular to the Z axis over it’s 4” travel. Remember that the carriage was re-machined where it sits on the ways. The chuck ( a set thru ) was re-checked holding a ground rod in it and centers to within 0.001” . The Z run out is within 0.0015” /  8”away from the chuck. So I will just leave the chuck as is. Just ran the spindle at different speeds (  from low to high rpm ) for about four hours since the lathe was not used since new bearings were installed a long time ago.

X axis backlash is 0.0003” and the Z is 0.001”. Trying to bring the Z backlash done just a little required
to much preload on the anchor bearing and the ball screw nut. You can’t get zero!

Still need to make a new pulley cover for the head stock and wipers for the Z axis. Also need to make and mount the index disc for threading and get the limit switches installed. The other stuff for accessories will
come over time.

Since the lathe is basically checked out and usable as is, maybe I will just try it out for kicks.
Lot of work ……but also a lot of satisfaction!

RICH

If your following this thread nothing new other than i am making chips as i test out the machine some.
So far all the conversion meets expectations and it sure is nice to not to have to deal with backlash.
Waiting for some hall sensors ( to be tried for as a threading index source ) and then willl try threading.
Will post as time goes on.
RICH

I have been playing with the converted lathe using the wizards to do basic things like cutting down shafts, ball ends etc  and she's got accuracy and repeatablity.

Figured i would rig up something quick and dirty to try some threading ( waiting for a hall sensor ). Just quickly mounted a small disc with a single slot as shown in the picture. I couldn't use any regular chucks so used a small one which has a MT to fit the lathe spinde as shown in the picture #1.

Picture #2 & 3 was my first thread, 5/16- 24 cut at 402 rpm. The rpm would  occasionialy flicker between 401 and 402 rpm. Measured rpm to displayed rpm was within 1 rpm.  One thing for sure, there is no slow down of the spindle!  What a difference as compared to using my punny Sherline lathe. The thread pitch diameter only varied 2 thousands across the length of the thread.

After cutting some finer threads, i tried a 3/8-20 as shown in picture #4. It was cut at 863 rpm / 43 ipm and .008" cuts. All was fine up until the next to last pass when the little chucks MT came loose outof the spindle. Result was a chewed up thread! No spindle slow down at all and at that speed not much time to hit the Estop! Oh well, i quess I'll just waite to test out some of the larger / deeper threads using a regular chuck.

I am using a  SS and of course i have  no need for backlash compensation now. Additionaly, believe spindle slowdown will no longer be an issue. Hey, small lathe but running with the big dogs now!  It will be interesting to see how long threads and multiple threading goes. I'll waite for the sensor to be installed first.

RICH