Saddle play in z axis

[fcs]

My lathe saddle has a lot of play in the z axis. About 0.035”. I guess this is the same as backlash in the leadscrew. (You can tell I’m new at this.) Anyway it was playing havoc with a slitting operation. Can this play be reduced?

 

[benmychree]

It is not clear what you are doing or what is moving.

 

[jwmelvin]

Maybe you could describe the slitting operation a little more. It seems like backlash in the lead screw isn't usually an issue because threading passes are always unidirectional. If you're wanting the carriage to stay motionless in the z-axis, then you'll want a carriage lock; I know nothing of your specific lathe but I seem to remember that for some of the smaller lathes, people has to add that feature.

 

[benmychree]

What do you call the Z axis?

 

[fcs]

Well I managed to solve the problem. Here is what I was seeing. If I pressed the carriage/saddle to the right (toward the headstock):


And when I pressed to the left (toward the tailstock):

It moved about 0.035.

The problem was simply that this bolt had become loose somehow:


With the bolt tightened the play dropped to 0.006 inches. The Sherline website says that the leadscrew backlash should be 0.003 to 0.005 so its close. I see that Sherline has a carriage lock: lathe leadscrew lock upgrade. I may spring for this.

Edit: An easy solution will be to position the carriage with finger pressure from the left, then “lock“ it there using the carriage stop rod thru the headstock. Now it can’t move left or right while I do the slitting operation.

I'm making ferrules for bamboo fly rods, and the ends have to get 6 slits around the circumference. I've got a jig that lets me remove and rotate the piece 60 degrees for each slot. But the carriage moving during the process made it easy to cut a slot in the wrong place. After spending a couple hours making one ferrule its no fun to screw it up on the last step.

Thanks for looking

 

[EricB]

I've learned that those screws that hold the saddle lead screw nuts are the weakest connections on Sherline's tools. They carry the whole cutting load on the lathes and that plus the weight of the head stock on the mills. You need to check them regularly.

Eric