PM1440GT Cross slide movement

[BCwoods]

Hi So I have an issue where the cross slide moves a little when turning to a size (this is seen on the dro ). Yes I can lock the slide but that seems excessive when taking only a .030 cut. The cross slide is loose to the point the handle itself can almost turn the wheel. I have about .005 backlash as stated in the manual. SO the gib? My understanding is the gib is more for keeping left and right movements to a min, like when I push on it there is little deflection less then .001

 

[Beckerkumm]

Have you adjusted the backlash nuts? I don't know the PM design but my Smart Brown has cap screws on the cross slide and tightening one nut and a wedge between two nuts, takes out the backlash. My old screw is worn so I do it depending on where in the travel I am. If your problem is worse in the middle of the travel and more tight on the ends, it may be wear on the screw. If consistently sloppy, it might be the nut has loosened up. Dave

 

[BCwoods]

HI Ok yea worth a look. 2 things I looked at was the end float on the wheel which I dont have any, and of course the back lash. Ill try and tighten it up a little and see what comes of it. As far as wear, the machine is new, thanks

 

[erikmannie]

I would tighten the gibs a little more.

 

[BladesIIB]

I agree with @erikmannie try tightening the gib a little more to give some friction if it is that easy to move. As long as you are removing the backlash before a cut it should not be an issue. Sounds like just the weight of your handle is enough to adjust the cross slide. If you only have .001” movement and your cross slide moves that easy then congrats! Sounds like a nice gib fit and alignment. Just give it a little more for a nice smooth feel.

 

[mksj]

Per what Dave and other's mentioned, there is some wear of the cross slide nut over time. I just adjusted my cross slide nut since I had about 0.007" play. On top of the cross slide in the center, there are four allen cap screws that retain thee cross not, lightly loosen them, then use an allen key in the center adjustment which splits the nut. You want to very lightly adjust it, you should have around 0.001-0.002" of slack in the hand wheel. Do not over tighten it, and may take a few tries to get it dialed in. The gibs will also wear, so may require a bit of adjustment but they should not make the movement too stiff. I do quite a bit of turning where I need to maintain the diameter better than 0.001" and added a cross slide lock on the headstock side (my DRO scale is on the other side), I use it all the time. Do not need to fumble for wrenches or allen keys.
https://www.hobby-machinist.com/threads/erl-1340-cross-slide-lock-for-dro-equipped-lathes.78854/

 

[Rifleman1384]

Not as nice as other have made but this is what I made for my 1440GT. I made the base from steel for rigidity that's likely not needed. I did cheat and look at the one Mark and Jbolt made before I decided on mine.

Steve

 

[Beckerkumm]

I made one that is similar with Aluminum that ended up being .4 thick with two 5/16 cap screws holding it and the bracket does bend outward a little when screwing in the lock enough to affect the slide. Dave

 

[jbolt]

Because the lead screw is an ACME thread there will always be some backlash otherwise the screw would not turn, bee too stiff and/or there can be premature wear on the nut.

Are you setting your cut depth by moving the tool toward the material to be turned? Setting your cut depth this way removes the backlash between the lead screw and the nut. When taking a cut the pressure on the tool is, in most cases, pushing away from the material.

If you go past the cut depth setting and then back the tool away from the material to set the cut depth you can get deflection of the cross slide. In this situation the lead screw is not pushing against the side of the nut where the pressure will be transferred. The tool pressure can push the cross slide into the backlash space.

The opposite can be true when taking deep cuts with high rake tools where to tool is being pulled into the material. This is typically a roughing pass and doesn't matter if the cross slide moves a few thou.