[andrew2085]

I received my g0704 about a week ago which I'm planning on converting to CNC. I've been having problems adjusting the gibs. Even if I adjust the Y axis gib so there is a fair amount of resistance turning the wheel, there is a significant amount of play. I had a dial indicator mounted on the column checking the flatness of the table along the whole Y travel and I noticed that I can pull up on the table and move the indicator about 0.004". I can see oil being sucked in and out of the dovetails. If I lock the Y axis with the locking handles I get 0.00025" or less movement. What does this mean? I would think that the angle of the gib isn't matching the angle ground into the cross-slide so one end is tight and the other is loose allowing for slop. Is there anything I can do about this?

The situation with the Z axis is even worse. I can tighten the gib adjustment screw all the way until it bottoms out and its just almost as easy to move as with it not tightened at all. There's also about 0.005" of slop if I lift up on the head. I'm sure some of that is from the lead screw, but I don't think I should be able to tighten it all the way without it locking the Z axis right?

Once I can get this sorted out I'll be tramming. It looks like the column is just bolted right on to the painted base, which doesn't seem like it would make a square connection even if the metal underneath is.

Thanks for any help!

[photomankc]

Just to be clear you are backing the screw at the narrow end of the gib out before you tighten down the screw on the wide end? If you don't do that then you jam the gib into the other screw and warp it so the friction goes way up but the fit still is loose. If that is not the case I would remove them and check for debris or warping and proper orientation.

I can easily adjust mine to run real smooth with under a thou of deflection detectable. I can't get much better than that though or it becomes VERY stiff on the extremes of the travel and prone to stick-slip. The Z is just a pain. Best way I was told was to remove the lower gib adjustment screw and run the head down to a wood block on the table. and rest it against that to relieve the pressure. Now adjust the tob gib screw till it is snug but the head still moves up and down without stick slip and then snug up the lower gib screw to just touch. That was as good as it was going to get and it still nods just a bit and tends to move the spindle around if the lower lock is set.

The column mating surfaces should be clean of paint. That said on my PM-25 there was some bleed through that I cleaned off after the first take-down but I don't think that was really causing a problem. Still I cleaned it off because I sure didn't want to repeat the process of squaring the column any more than I had to.

[andrew2085]

Right, I loosen the back screw a little then snug up the front one. I took the gib out and looked at it. The side that goes against the cross-slide is ground smooth. The dovetail side looks like its scraped I guess, but it looks rough. It was the same on the Z. I'm not sure if its supposed to look like that. I'm going to have at it again later, maybe I'll take some pictures.

[mrcodewiz]

Make sure the screw is actually pushing the gib in. On my Y, the gib screw hole was off center enough that the head would go right past the end of the gib.

[andrew2085]

yea the heads of the screws all push the gib like they should. I think I'm being too paranoid which I have a tendency to do. I have to exert a lot of force to get the 0.005" of movement, like 50 pounds. Its a gradual deflection like from bending not a sudden jump.

I went ahead and trammed the column. 3 layers of aluminum foil that I measured at 0.001" thick did the trick for the 0.003" forward nod I measured over a 6" square. I just used two pieces on the top of each side as far down as the top bolts. That got me within 0.0005" both ways, I didn't have to adjust side to side. I still need to make sure the head is square to the table too.