Atlas 618 Leadscrew/half Nut Issues

[CarlosA]

Are there any adjustments to dial in or tighten up the leadscrew & half nuts on these lathes? My original leadscrew does show the typical wear close to the headstock, but even after buying a near NEW lead screw with nice consistent threads from end to end, it still does not feed in the center section where the leadscrew can "flex" during engagement.

If I reach under there and push against the bottom halfnut with my finger I can get the carriage moving and cant even stop it by pushing against it.

I have also ordered new half nuts ... but don`t want to put them on and have them wear out excessively if there is some other issue. This is my second atlas 618 and both have had these problems.

Any suggestions? If I can get it dialed in i`m going to make a couple sets of half nuts and maybe a new lead screw from scratch for the future.

Also, anyone find it odd that the CRS lead screw wears out faster than the Zamak half nuts?

 

[CarlosA]

I milled .005" off the mounting surface of the half nut retainer, and its holding for now ... seems to be preventing the half nuts from rocking back and forth when clamped down. Now that its feeding i`ll make the new half nuts and spares...

 

[RJSakowski]

Are there any adjustments to dial in or tighten up the leadscrew & half nuts on these lathes? My original leadscrew does show the typical wear close to the headstock, but even after buying a near NEW lead screw with nice consistent threads from end to end, it still does not feed in the center section where the leadscrew can "flex" during engagement.

If I reach under there and push against the bottom halfnut with my finger I can get the carriage moving and cant even stop it by pushing against it.

I have also ordered new half nuts ... but don`t want to put them on and have them wear out excessively if there is some other issue. This is my second atlas 618 and both have had these problems.

Any suggestions? If I can get it dialed in i`m going to make a couple sets of half nuts and maybe a new lead screw from scratch for the future.

Also, anyone find it odd that the CRS lead screw wears out faster than the Zamak half nuts?

The two half nuts should engage the lead screw from both sides, capturing it. The nuts may be worn or the linkage may have been sheared. It is also possible that there is grease/filings gunk in the threads of the half nuts. You can remove the half nuts fairly easily. Remove the two screws that hold the right hand lead screw bearing and remove the bearing block. Disengage the thread indicator. Remove the tailstock. slide the carriage to the right until the half nuts clear the lead screw shaft. Remove the two screws on either side of the engagement lever.
The two half nuts and guide plate are now free. Examine the half nuts for gunge, and wear and make sure that the two pins on the back side of the half nuts are intact. Reverse the procedure to assemble.

 

[Kernbigo]

you still can purchase a new half nut from clausing

 

[mws]

Also, anyone find it odd that the CRS lead screw wears out faster than the Zamak half nuts?

The softer material can become embedded with grit, like a lap, and wear the harder steel in short order. That's one of the reasons I hate grinding around my machine tools.

 

[CarlosA]

The softer material can become embedded with grit, like a lap, and wear the harder steel in short order. That's one of the reasons I hate grinding around my machine tools.

Yeah that makes sense. Wondering if it`d be a feature for the small atlas leadscrew to have a notch milled through its entire length like some of the bigger lathes - maybe this would serve to scrape off some of that build up and keep the half nuts in nicer condition.

 

[stupoty]

Yeah that makes sense. Wondering if it`d be a feature for the small atlas leadscrew to have a notch milled through its entire length like some of the bigger lathes - maybe this would serve to scrape off some of that build up and keep the half nuts in nicer condition.

I think your talking about the notch to drive power feed on dual drive systems with a single power bar. The slot on my drive bar just colects chips for me(small brush clean clean clean)

I'm sure i've seen some brush arangement for lead screws that acts as a wiper but cant think where.

Stuart

 

[mattthemuppet2]

also wouldn't hurt to check for leadscrew alignment with the half nuts. On mine I needed to tweaks the slots in the leadscrew supports to be able to raise the leadscrew slightly so that it didn't bind at either end of the bed.