[CrossSlide]

I have the head removed and I'm trying to adjust the saddle gib. I've adjusted it to slide easily without slop but it binds 2.5" from the top. I can't push it to the top with my hands at all. But if I loosen the gib to allow the saddle to move to the top then it feels really loose on the rest of the column. What I'm I doing wrong?

Thanks

[kdoney]

I have the head removed and I'm trying to adjust the saddle gib. I've adjusted it to slide easily without slop but it binds 2.5" from the top. I can't push it to the top with my hands at all. But if I loosen the gib to allow the saddle to move to the top then it feels really loose on the rest of the column. What I'm I doing wrong?

Thanks

When you first took it out of the crate, did it work? I assume you're talking about the spindle axis. Have you made any changes to the head?

[CrossSlide]

I just bought this used. It's about a year and a half old. No real changes. Yes the spindle axis.

[zach540]

Has yours been converted to ballscrews? Regardless, I was having similar issues with mine after a conversion.

Prior to installing the ballscrew, I rolled it on a flat surface and it appeared to be straight, after installation, with the Z axis way cover removed, I noticed a lot of whip in the screw, using a heel pry bar, wrapped with several layers of electric tape, I was able to gradually pry the ballscrew into alignment, a lot less whip now, and no more issues with it binding near the top.

Zach

[CrossSlide]

No ballscrews here but I'm glad you figured yours out! In my situation the screw is not connected and it's binding moving by hand.

[zach540]

Out of curiosity, have you tried to loosen (not remove) the 2 socket head cap screws which attach the leadscrew nut to the saddle to see if it frees the movement? Could be slightly off center one way or the other.

[Stigoe]

Sounds like you have a small bow in the dovetails, with the distance between the dovetails slightly larger at the top than further down.

[CS900]

Sounds like you have a small bow in the dovetails, with the distance between the dovetails slightly larger at the top than further down.

yup, or it's been used significantly more in the lower area of the dovetail and worn it down a bit

[CrossSlide]

Thanks for the ideas!

[109jb]

This isn't all that uncommon an issue on the G0704 from what I have read. My G0704 had the same issue and it was pretty easy to fix. Some might take issue with the way I did it, but it worked for me. What I did was I simply filed the upper part of the dovetail a little to get rid of the high spots and then I lapped the ways. For the filing part I used a fine tooth file and was careful not to get into the "good" part of the dovetail. I blued the dovetail and used the slide, without the gib in, to check for the high spots at the top periodically. On mine it was only about the last inch or so of the dovetail that needed work. I really wasn't terribly concerned about screwing up the top part of the dovetail since being up that high means you aren't likely machining anyway. I just wanted to get smooth motion up there to prevent binding and stalling of the stepper motor. After filing, I then lapped using just an abrasive metal polish as that is all I had. The polish is very very fine, so a more agressive lapping compound would have been better and faster, but the polish worked and my Z axis is smooth from top to bottom.

[kdoney]

I would file as little of the gib as necessary.

[109jb]

I would file as little of the gib as necessary.

It isn't the gib that needs filing, but the dovetail on the column.