Smithy lead screws/nuts

[mac1911]

I sent off a email to smithy but that generally takes some time.

The Longitudinal Scew “nut” is worn as is the cross slide screw nut
I was going to attempt to make them as its $200 plus shipping for replacements from smithy.

The Cross slide seems pretty straight forward
Appears to be 5/8 x 10 tpi RH threads

The lead screw or as smithy parts diagram calls it Longitudinal screw/nut is a bit different
Its a half of a half nut and just a brass/bronze ring , its worn enough that when I use it to feed the carriage under a heavy cut will skip/strip past the threads

As I went to measure It appears the manufacture used metric stock and cut 10 tpi
Looks like 20mm x 10 tpi LH ?

14 is the cross feed nut
22-23 is the Longitudinal “nut”

 

[GeneT45]

5/8"-10 isn't a standard acme thread size. Neither is 20mm-10. I think you're looking at custom sizes,The good news is that both holes are fairly large. It shouldn't be too hard to make some new nuts, the hardest part is getting the angle / side relief right on the threading tool.

GsT

 

[markba633csi]

If your machine will cut 10 tpi then you can make them- providing your worn half nut will cooperate long enough to get the job done

 

[RJSakowski]

Your cross feed nut appears to have an adjustment for backlash from the drawing. There should be a set screw that is tightened to increase the separation between the main section of the nut and the thin section. This forces the two sections apart, taking up backlash.

On my Atlas/Craftsman 6x18, I had replaced the half nuts because they looked worn. Years later, i looked more carefully and what looked like worn threads was actually gunk filling the threads. A good clean with a fine wire brush and a pick restored them to almost new condition.

 

[mac1911]

Your cross feed nut appears to have an adjustment for backlash from the drawing. There should be a set screw that is tightened to increase the separation between the main section of the nut and the thin section. This forces the two sections apart, taking up backlash.

On my Atlas/Craftsman 6x18, I had replaced the half nuts because they looked worn. Years later, i looked more carefully and what looked like worn threads was actually gunk filling the threads. A good clean with a fine wire brush and a pick restored them to almost new condition.

When I got the lathe the back lash “plate” was just free floating and the screws where just sitting in the valley of the cross slide.
The nut is worn not exactly knife edge but getting there.
The carriage/longitudinal nut and wedge are definitely worn. Im going to see if I can flip the wedge around for now

 

[mac1911]

Looks like Im going to have to wing it. Pretty much what I though.
Now to find a few chunks of material to start the process.
And pray its some sort of standard acme thread
Lathe has gearing to do 10 tpi

 

[markba633csi]

Whatever the thread profile is you could grind a tool to match it from HSS
One reason why learning to grind HSS tooling is so useful

 

[mac1911]

After the response from smithy I figured the factory used what ever they had on hand to make these parts?
So not only will I be grinding some more tooling I’m probably gonna take a stab at making a boring bar

 

[markba633csi]

Also take a look at "fishtail" internal threading tools- those can be homemade as well
Doesn't have to be expensive to get the job done

 

[mac1911]

Quick look around for brass stock
Roughly 2” square. I must be looking in the wrong places?
$50 for a 2.5” square.?

I might have to do some casting now?