# Supermax 1338 threading issues



## sasanifab (Jan 10, 2021)

I have to state for the record that I have completely gone through the machine and have replaced basically everything. The lathe has little to no backlash now when threading. The lathe came with a 8 tpi lead screw. When cutting standard threads its100% dead nuts. My issue is with metric threading. I notice that when checking with a thread gauge the first couple threads line up but the remainder are off a couple thousands.... very very minimal. Still enough to make installing a nut impossible. What could be causing this ? The change gears are correct and like I said , standard threading is dead nuts ??


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## sasanifab (Jan 10, 2021)

sasanifab said:


> I have to state for the record that I have completely gone through the machine and have replaced basically everything. The lathe has little to no backlash now when threading. The lathe came with a 8 tpi lead screw. When cutting standard threads its100% dead nuts. My issue is with metric threading. I notice that when checking with a thread gauge the first couple threads line up but the remainder are off a couple thousands.... very very minimal. Still enough to make installing a nut impossible. What could be causing this ? The change gears are correct and like I said , standard threading is dead nuts ??


Can someone explain this to me , the top says 30 gearx127x60 .... metric is different


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## sasanifab (Jan 10, 2021)

For the record , the bottom gear is 60, the middle  larger gears are 127 facing in and 120 facing out . Above that is the change gear or “A”


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## benmychree (Jan 10, 2021)

Not clear in your picture, but on my lathe, the spindle drives the 127 tooth gear, and the companion gear (100T) drives the screw gear. I know your gearing is different, but at any rate the spindle gear should drive the 127 T and it's companion, whatever its number of teeth should drive the screw gear, I am seeing in the picture that the 127 is driving the screw gear, I think this is incorrect.


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## sasanifab (Jan 10, 2021)

So like in this picture , I have a 30 tooth gear at the top which turns the 127 which then turns the 60 tooth - 30x127x60 for standard threads. For metric is says a/127 x 120/60 . I don’t understand this ....



benmychree said:


> Not clear in your picture, but on my lathe, the spindle drives the 127 tooth gear, and the companion gear (100T) drives the screw gear. I know your gearing is different, but at any rate the spindle gear should drive the 127 T and it's companion, whatever its number of teeth should drive the screw gear, I am seeing in the picture that the 127 is driving the screw gear, I think this is incorrect.
> [/QUOTE


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## benmychree (Jan 10, 2021)

The screw gear MUST mesh with the gear attached to the 127 tooth gear in order to effect the metric translation, otherwise, the 127 as shown in the picture is just acting as an idler, having no effect on the ratio; the screw gear needs to be moved outwards and meshed with the smaller gear, which I suspect to be a 100T gear.  The mode shown in your picture just above is the mode for imperial threads.


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## benmychree (Jan 10, 2021)

Reading your post, I now see that the outer gear attached to the 127T is 120T, that gear MUST mesh with the screw gear; yes what you wrote is correct, but you did not understand what it meant, that is, again, the  gear on the spindle needs to mesh with 127T and the 60T needs to mesh with the 120T gear that is attached to the 127T gear, you need to remove the screw gear and the spacer, and replace the spacer on the shaft then install the gear so that can mesh with the 120 T gear.


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## sasanifab (Jan 10, 2021)

You sir are the mAn, I would kiss you if I could. Why this didn’t occur to me ...[

QUOTE="benmychree, post: 813207, member: 25152"]
Reading your post, I now see that the outer gear attached to the 127T is 120T, that gear MUST mesh with the screw gear; yes what you wrote is correct, but you did not understand what it meant, that is, again, the  gear on the spindle needs to mesh with 127T and the 60T needs to mesh with the 120T gear that is attached to the 127T gear, you need to remove the screw gear and the spacer, and replace the spacer on the shaft then install the gear so that can mesh with the 120 T gear.
[/QUOTE]


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## benmychree (Jan 10, 2021)

Glad to be of help!


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## sasanifab (Jan 11, 2021)

benmychree said:


> Glad to be of help!


Got out of work and put it to the test . M12x1.25 dead nuts


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## markba633csi (Jan 11, 2021)

Was about to jump in but John beat me to it   
-Mark


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## benmychree (Jan 11, 2021)

All's well that ends well!


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## sasanifab (Jan 11, 2021)

benmychree said:


> All's well that ends well!


M12 x1.25


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## sasanifab (Jan 11, 2021)

It’s really awful using a lathe with worn parts, threading can be extremely frustrating when you have a large amount of backlash due to a worn half nut.  Maybe it’s a good thing, I put a lot of time in and practice because of it


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