Backlash in X-ballscrew indicating -vs- table top to Spindle base BL- Whats up here?

Our 98 VF/4 rebuild has been doing well. The Son graduated and is going into bidding for work.
The only issue he feels he has; we measure X-axis w/ 7-8tens in backlash. He measured from the table against the spindle ( this test Ballscrew - Backlash Test - VMC)
Y is .0002 every time from the table to spindle test.

Then we pulled the X way covers (both sides) to do a Ballscrew type backlash test. New to me... but it's his machine now. (pic) I have a vid as well if it'll help.



As shown in pic; He measures from the table base side to the screw edge. He ran several different setups and ran from both sides. He never gets more than 2 or 3 tens BL on either side when switching directions.
We also did from Table edge to the X motor mount cast. Just to emulate testing to non-moving fixture like the tabletop BL test. Same few tenths. Seems solid.

Then he goes back up to the table top to spindle and still ends up w/ that 8 tens larger value... Just not sure what's going on? Same table, but measuring against the spindle base as opposed to something solid below the table or the screw gets a 2x BL value? There's some other things he did but I'm asking him to re-evaluate before I post up here on those.

I have no clue how anyone can get under the table to look at the actual Ball Nut, Ball Nut Housing and table mount-up... buried in there!
We're learning... Just not sure what to make of this X BL value. Not sure how to test the Motor 'thrust bearing?) I think Haas calls it a motor housing bearing nut? Not finding a lot of detail on what the thrust bearing actually consists of or to test accurately.

Just thought I would ask folks here. The kid is starting on bidding jobs (Graduated in June! congrats kiddo!). He just wanted to chase this X BL value during some quiet time.

thanks,
CG

Typically the way backlash is measured (at least in my experience), is by placing a dial indicator needle against a tool or toolholder shank. Then creep it in X- direction about .003 and zero it out. Use MDI to slowly jog .01 in the X+ direction and see what the indicator says. A tight machine should read exactly .01".

I have never done a comp on a Haas, but a Centroid had to have a comp value put into the control. You would put in what you measured and check it again to verify it.

And no, I wouldn't be shocked if a machine that old had 7-8 tenths.

Check! And agree for sure. It's not bad and I noted he should really do a decent warm-up on the screws and run the test. (but dads are dad and just seem to make a lot of noise when your 23 ;-p ) Y never needs any warm up and is tight. Essentially we're going at it both (many) ways. Against a shank, against the spindle.. every-which way to beat up the data. We run up a few thou- Zero, and set to .0001 moves... he hand wheels in/out and you can see the tens dial sit perfectly still till the lash moves out then the table moves and the dial moves.. Just makin'n sure I'm on your page.

ChipSplitter said:

Typically the way backlash is measured (at least in my experience), is by placing a dial indicator needle against a tool or toolholder shank. Then creep it in X- direction about .003 and zero it out. Use MDI to slowly jog .01 in the X+ direction and see what the indicator says. A tight machine should read exactly .01".

I have never done a comp on a Haas, but a Centroid had to have a comp value put into the control. You would put in what you measured and check it again to verify it.

And no, I wouldn't be shocked if a machine that old had 7-8 tenths.

Click to expand...

countryguy said:

Check! And agree for sure. It's not bad and I noted he should really do a decent warm-up on the screws and run the test. (but dads are dad and just seem to make a lot of noise when your 23 ;-p ) Y never needs any warm up and is tight. Essentially we're going at it both (many) ways. Against a shank, against the spindle.. every-which way to beat up the data. We run up a few thou- Zero, and set to .0001 moves... he hand wheels in/out and you can see the tens dial sit perfectly still till the lash moves out then the table moves and the dial moves.. Just makin'n sure I'm on your page.

Click to expand...

Yes, that sounds like you are doing it right. Now, I don't know where Haas stores their BL comp values....

Have you inspected the thrust bearings?

Hi bgl. We would love to. We simply are not sure how? I looked all over for info on how to test. Any help appreciated!

I am going to pop up a new post on this one.. how to test the Thrust bearings on the older Haas.. I looked all over and we're just not sure how to test that thing... Most posts on BL indicate this is the typical issue but we cannot locate how to confirm? Would love to know how.