Bushing Questions

[speedre9]

I have been playing around with this issue for a long time. It concerns my mini lathe cross slide and compound saddle assemblies. I think I have found a solution that fits me, but. As we all know the lead screw is in a larger hole with no real support, it can wobble terribly. This causes the nut to be nearly impossible to adjust, many of us have had this issue drive them crazy. So I want to put a bronze bushing into the saddle casting but I'm not familiar with working with bushings. The lead screw is 0.3865" diameter where it enters the casting, anybody know of a bushing with a inner diameter like that?
By the way after disassembling my Grizzly mini lath and making detailed cad drawings it seems that a shim of 0.040" will help stabilize the nut and help center the screw in the casting. Comments welcomed.

 

[British Steel]

Hi Speeder, 3/8" bushings are a little too small, but you have a lathe....
More of.a.concern, you'll need to centre the bushing on the leadscrew, where it passes through a (presumably) roughcast hole in the apron/carriage.
First step would be to check that the leadscrew is parallel to the.ways[1], and adjust / shim the tailstock end bracket so you have it running through the same space.
Step two would be.to make.the bush(es) and some way of centring it(them). If you can't find a.way to bore the carriage /apron, you could fit the.bushings in stout metal plates, spot through holes in those and drill and tap to bolt them to the.apron?
Just my ha'pennorth

[1] I'd probably run a DTI along it, magnetic base on the saddle - take readings of the gauge deflection both on top of the leadscrew to see whether the tailstock end bracket needs to be raised or lowered, and.against the.side for shimming/relieving it where it bolts to.the lathe bed. YMMV If you did.this using the.leadscrew to move it, the.DTI finger would follow its pitch and ride nicely on the.leadscrew thread's peak, no need for a shim, v-block etc in between!

 

[kd4gij]

Is this the part you wan't to pot a bushing in?
https://littlemachineshop.com/products/product_view.php?ProductID=1386&category=5

 

[royesses]

I would ream the casting to the next standard size and turn some bearing bronze sae 660 for a press fit and then ream for the lead screw with an adjustable reamer. I think the sloppy fit is actually intentional to make up for variations in the castings. I've seen some ball bearing conversions on the internet that seemed doable too.

 

[speedre9]

No, that is not the part, it is the saddle casting itself I was describing. It has a machined hole of 0.4385" dia. and the lead screw is 0.3865" dia. in that area. My initial thinking was to center the lead screw in the casting creating a wobble free zone enabling true adjustment of the nut with a shim to take up the space between casting surfaces. I spent at least ten hours so far this week trying to get the lead screw nut adjusted to use my lathe to no avail. I'm sick of trying using this lousy arraignment for adjusting this nut!!! I've come up with an alternative to this idea. I could, theoretically, accomplish the same ends by adding a piece of plate stock 0.250" thick, to the end of the casting with a jam screw into the center drilled hole at the end of the lead screw itself thereby centering the screw and making nut adjustments a straight forward job. Comment welcomed.