I’ve got a Warco WM 16B, so assuming the gib details are similar ie – tapered gibs with cheese-head adjusting screws top and bottom, with the small end of the taper gib at the  bottom – it may be the other way round on your machine, I can’t find a manual on the web for the WM 12.

Make sure that the two Z axis locking screws are unlocked, lubricate the z axis both sides, crank it up and down to distribute the oil, and adjust to tighten the gib by loosening the bottom screw half a turn anti clockwise and tighten the top screw half a turn clockwise, the gib should be lightly trapped top and bottom by the screws.

Keep doing this half a turn at a time until it gets rid of the slack.

No need to have the screws mega-tight, just snug them up. After doing this crank the head up and down every time to check how much effort is needed. When you can feel more effort is needed that’s when you should have the least play, but you may find you need to slack the adjustment off slightly to reduce the effort required at the crank handle.

A quill needs some clearance to move, the lock takes the clearance out (stating the obvious.)

The same applies to the head, which will lean forward if the gib is loose.

Could this be play in the gibs on the Z axis? Simple answer, yes, but you should be locking the head as well as the quill.

Ideally gibs, especially taper gibs, should be essentially unloaded when adjusting. Fairly obviously any load makes it harder to feel what is going on as the gib is adjusted. By its very nature the loads on the Z axis gib of the WM12 are asymmetric. The weight of the head inevitably imposes a tilting force.

Given the relatively small size of the WM12 it’s not totally impractical to lay the machine down on its back, with suitable supports, to remove most of the offset loading. Which should improve the feel of whats going on although the motor still imposes an offset load. Albeit the other way.

If the machine were mine and I had similar worries about poor gib adjustment possibly contributing to the machine being less stiff than it should be I’d take the nuclear option of removing the head completely at the tilt joint and disconnecting the elevating screw after laying the machine on its back. Having thoroughly cleaned the dovetail slideways and gib I’d re-assemble with copious lubrication before carefully adjusting the gibs whilst sliding things back and forth by hand. A somewhat tedious process. It may take 30 or 40 reciprocations before you are sure that oil has gotten everywhere it should be and the gibs are evenly adjusted to the minimum clearances commensurate with sensibly free movement.

Sliding by hand gives a much better feel as to incipient tightness or attempting to adjust on the tilt. If the elevation screw mountings aren’t properly aligned its pretty easy to feel the extra stiffness when the screw is fitted and take appropriate measures.

Starting from scratch ensures you don’t wind up running down the rabbit hole of trying to correct one error with another. With a used machine of unknown history it’s impossible to be certain that any previous adjustments haven’t introduced a corrective error rather than re-set things properly. It’s possible to go quite a long way with corrective errors generating better, but still not quite right, performance before the house of cards collapses.

Correct set-ups are generally stable over relatively long periods. Corrective errors tend to need tweaking on a regular basis. Accepting that a lightweight machine like the WM12 can ultimately never be as stable as their bigger brethren I’d expect carefully and properly made adjustments to be stable for years in a home workshop. If you feel the urge to fiddle every month or six it’s likely you have corrective error rather than correct adjustment.

Or maybe unreasonable expectations as to the inherent stability limitations of a small machine.

In many ways big machines are mass stabilised! Large lumps of cast iron tend to sit still unless serious efforts to move them are made.

Clive

I to have a Warco WM12 with 3 axis DRO & I noticed that when I lock the quill that the reading on the DRO changes so I got into the habit of stopping just short of the reading I need so when I lock the quill I am at the correct reading as for the gibs I think they wear easily because I have to adjust them more on the mill than I do on the lathe.

I have done other mods on the mill apart from the DRO but that on it’s own was a game changer as far as accuracy goes but the biggest improvement for me has been changing to belt drive as it’s so much quieter & better finish to the work, I have also added power to X axis mainly because I have trouble with my hands so it makes life easier for me.

I think Dave (SOD) has got it dead right.  That and the fact that this style of mill is poorly designed.  The head is far too “massive”, unnecessarily so.  Then hung off a somewhat flimsy column.  It is not a rigid structure.

I have a mill of this style, sold by many, often called ZX7***.   Just leaning on the head will cause measurable flex.  Although not good at shifting stock, several small cuts rather than one big cut it has done some accurate work.

Dell, I have sent you a PM.

Keith.