Gibb adjustment help

[TT350]

I was in the shop today looking at my machine
and was wondering how one would adjust the gibs
if they needing adjusting. On my manual mill I turn the
gib screw until I feel a light drag and back the screw off
about a ¼ turn.

But with no hand wheels how would you do this?
Well curiosity was getting the best of me so I grabbed
the X axes motor mount to see of I could feel any slack
in the table.

Well to my surprise there was a ton of slack!
I could pull and push on the X axes motor mount in the Y axes + - direction and see the table move!
The table looked like it was pivoting on the ball screw yoke.

It looked like the Y axes gib need to be adjusted so I made me a handle so I could move the Y axes by hand and adjust the gib.

I adjusted the gib until I felt a light drag it took about three full turns so I said that was easy and grabbed
the X axes mount again to see if the slack was gone.

The slack was no better, so I thought for a moment
and remembered reading the manual about adjusting
the Z axes gib, the manual tells you to tighten the Z
gib until it takes about 40-80 lbs of force to move the
Z with the machine powered down, I said to my self if
there using the Z gib as a “friction brake” for the Z maybe it’s ok to tighten my Y axes gib until my slack
is gone and ignore my old “feel” method.


My 14 year old son was in the shop so I give him a screwdriver and told him to apply light pressure
to the Y axes gib screw as I shook the slack, I could
see his hand move the gib screw in steps, it took about
3 full turns to get rid of the slack. I said to my self now I got it!

Now I’m curios to see how much drag is on the table
so I crank on my home made handle and there was a LOT of drag. If it’s ok for the Z it shouldn’t hurt the Y write!

I put the Y motor back on the machine and jogged the Y
and it sounded ok.

No I’m not finished hold on!

When I got my machine hooked up and running the first thing I done was check the accuracy and noticed that it
would loose a .001 on a direction change on the X an Y.

I would set my jog to .010 and it would hit dead on the mark every time I jogged in that direction. When I changed directions I would loose a .001 only moving the table back .009 but would move the table .010 dead on every time after that. I can live with that I’m not making
Shuttle parts.

Now is where it gets good!

I put my indicator on the machine hopping to find my .001 loose in direction change to be gone but now instead of .001 I have .006 in direction change!

So I put my son back on the screw driver and had him back the gib off as I jogged the machine back and forth .010 wile watching the indicator until I was back down to my .001 in direction change and found the gib adjustment to be back where I started from and all the table slack was back as well.

Is it possible that there is to much taper in the gib
and it is only touching the ways on one end and that’s
a pivot point?

If this is the case I thought about drilling a tapping the casting outside the gib and putting some set screws with jam nuts to apply the gib squarely against the ways.

How would you handle this?
Or is this normal?

[philbur]

I would talk to Tormach. I would not start drilling holes for adjusting screws. Have you tried removing the gib, cleaning and checking, then replacing. Make sure the adjusting screw does not (is not) running down the side of the gib. This happened to me on the Z axis.

Regards
Phil

Originally Posted by TT350 I was in the shop today looking at my machine and was wondering how one would adjust the gibs if they needing adjusting. On my manual mill I turn the gib screw until I feel a light drag and back the screw off about a ¼ turn. But with no hand wheels how would you do this? Well curiosity was getting the best of me so I grabbed the X axes motor mount to see of I could feel any slack in the table. Well to my surprise there was a ton of slack! I could pull and push on the X axes motor mount in the Y axes + - direction and see the table move! The table looked like it was pivoting on the ball screw yoke. It looked like the Y axes gib need to be adjusted so I made me a handle so I could move the Y axes by hand and adjust the gib. I adjusted the gib until I felt a light drag it took about three full turns so I said that was easy and grabbed the X axes mount again to see if the slack was gone. The slack was no better, so I thought for a moment and remembered reading the manual about adjusting the Z axes gib, the manual tells you to tighten the Z gib until it takes about 40-80 lbs of force to move the Z with the machine powered down, I said to my self if there using the Z gib as a “friction brake” for the Z maybe it’s ok to tighten my Y axes gib until my slack is gone and ignore my old “feel” method. My 14 year old son was in the shop so I give him a screwdriver and told him to apply light pressure to the Y axes gib screw as I shook the slack, I could see his hand move the gib screw in steps, it took about 3 full turns to get rid of the slack. I said to my self now I got it! Now I’m curios to see how much drag is on the table so I crank on my home made handle and there was a LOT of drag. If it’s ok for the Z it shouldn’t hurt the Y write! I put the Y motor back on the machine and jogged the Y and it sounded ok. No I’m not finished hold on! When I got my machine hooked up and running the first thing I done was check the accuracy and noticed that it would loose a .001 on a direction change on the X an Y. I would set my jog to .010 and it would hit dead on the mark every time I jogged in that direction. When I changed directions I would loose a .001 only moving the table back .009 but would move the table .010 dead on every time after that. I can live with that I’m not making Shuttle parts. Now is where it gets good! I put my indicator on the machine hopping to find my .001 loose in direction change to be gone but now instead of .001 I have .006 in direction change! So I put my son back on the screw driver and had him back the gib off as I jogged the machine back and forth .010 wile watching the indicator until I was back down to my .001 in direction change and found the gib adjustment to be back where I started from and all the table slack was back as well. Is it possible that there is to much taper in the gib and it is only touching the ways on one end and that’s a pivot point? If this is the case I thought about drilling a tapping the casting outside the gib and putting some set screws with jam nuts to apply the gib squarely against the ways. How would you handle this? Or is this normal?

[TT350]

The screw isn’t getting under the gib I checked that.
I ask a friend about this and he said that he’s seen this
before even on American machines. He told me to paint
the gib with layout dye put it back in and run the axes remove the gib and find the high spots and file them
a little and repeat until the gib fits write.

[philbur]

Sounds like a solid idea to me. Possibly scraping rather than filing would be more "standard practice". I would still talk with Tormach.

If you have already run the machine a bit you may already be able to see any high spots with out the dye procedure.

Let us know how you get on.

Regards
Phil

PS it takes a bit of practice to get the dye coating right. It needs to be as thin a coat as you can achieve. You should use the right dye also, it's known as prussian blue in this neck of the woods.

Originally Posted by TT350 He told me to paint the gib with layout dye put it back in and run the axes remove the gib and find the high spots and file them a little and repeat until the gib fits write.

[paulsmith632]

TT350, I've experienced this same thing, as I'm sure many many others have as well. My gibbs for some reason had a curve in them, so the middle contacted the ways first, and tightening one side caused slack on the other, and tightening both sides caused unusable drag. After removing the gibbs and filing on them lightly until the entire surface was smooth and flat, I replaced them, and have been smiling ever since. Another big problem and and easy fix to it.

good luck,
Paul

[TT350]

I have a friend that’s had to do this in the past
he’s going to help me with this.

He teals me that it can be time consuming but it’s
not rocket science.

He said the gib probably has a bow in it like your’s did.

Chris

[yantra3d]

My x3 also had some seriously bowed gibs on both the x and y. I went ahead and lapped them on my surface plate with 330/220 grit and was able to get it 80% "flat", however I'm not going to be content with that. I mean what happens when you tighten the gibs and the bow straightens out? That will surely throw off the flatness that I got from lapping right?

I think I'm going to make my own gib strips to replace the stock ones. They're just too warped!

[philbur]

If the gib is bowed why not get Tormach to send you a replacement under warrantee

Regards
Phil

Originally Posted by TT350 I have a friend that’s had to do this in the past he’s going to help me with this. He teals me that it can be time consuming but it’s not rocket science. He said the gib probably has a bow in it like your’s did. Chris

[TT350]

I'm going to take it down this weekend and see what's going on with
the gib before I call them.

[keen]

It could also be that the machined casting surface backing up the gib - or the other side of the gib - has a burr or paint or swarf etc - I removed the slides completely to get at this on my x3 and stone these surfaces. Believe it or not the supplier even reccommends you do this!

[keen]

When I had finished I adjusted the gib with a dial indicator at each end of the slide - between table and slide etc until the play with a heavy push and pull was less than 0.0003 - not counting the flex/spring of course. this is 'across' the gap - not along the screw - then the slide should still be free to slide.

[TT350]

I took the Y axes motor and motor mount off so I cound
slide the axes and hand

After putting layout die on it and checking the witness
marks it was only touching on the big end.

After a day of in and out with the gibb and layout die and a file I got the all the slack out of the Y axes.

I took a lot work but the Y axes is silky smooth moves freely and has no slack!