I need help identifying a gear on a Logan 920

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Rock

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While I have family members who are machinists, and have operated lathes for basic functions, I am a "newbee" to owning/working on a lathe,...I have recently acquired a Logan 920....when I purchased it, it had a gear (labeled the stud gear in the Logan parts manual) on the reverse assembly that someone had tried to 3-d print, and while the gear appears to be well made, it doesn't engage the other idler gears as it should, so the forward/reverse function of the lead screw doesn't work. I have tried to isolate what exact gear it is and how many teeth it should have off of the illustration in the Logan parts lists, but can't seem to do so.....so I am asking for help.
........I can measure the thickness needed, the bore size needed, etc,....but is there a way for me to figure out the total teeth this gear should have when I don't have the original one? (the nylon one that doesn't work/doesn't engage,...has 24 teeth)

Thank you for any and all advice
 

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Hi Rock. There doesn't need to be a gear there [(ops, incorrect! My bad). So not making contact is good. ] Looks like it is simply being used as a spacer like the outer gear below it. Maybe because it was convenient.


The forward/reverse is the lever in the right of the photo. It looks like it is in the neutral position. Lift it up or down to engage the lead screw. I can't quite tell from the photo if all the other gears are in full contact. Are they?
 
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It looks like you just need to adjust the banjo to achieve proper engagement of the gear train. Loosen the circled socket head cap screw and rotate the banjo assembly upward.
Lathe 5.jpg
 
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I see what you mean... 820 here, but similar setup... and in mine, the gear works with the rest of the setup...

IMG_7621.jpeg
 
Also there is on the left end of the banjo arm a support pin lever that needs to be adjusted too
 
You use a 24 and 48 gear with that gearbox.
Adjust the banjo to get the gears to mesh.
 
Rock said:
While I have family members who are machinists, and have operated lathes for basic functions, I am a "newbee" to owning/working on a lathe,...I have recently acquired a Logan 920....when I purchased it, it had a gear (labeled the stud gear in the Logan parts manual) on the reverse assembly that someone had tried to 3-d print, and while the gear appears to be well made, it doesn't engage the other idler gears as it should, so the forward/reverse function of the lead screw doesn't work. I have tried to isolate what exact gear it is and how many teeth it should have off of the illustration in the Logan parts lists, but can't seem to do so.....so I am asking for help.
........I can measure the thickness needed, the bore size needed, etc,....but is there a way for me to figure out the total teeth this gear should have when I don't have the original one? (the nylon one that doesn't work/doesn't engage,...has 24 teeth)

Thank you for any and all advice
Click to expand...
Hi again Rock. I just double checked the part numbers. The "Banjo" (change gear bracket) for a 19/9XX lathe is P/N LA-227. The P/N for the 18/8XX banjo is LA-478. The stop bracket, the part with the pin, for the for the 19/9XX lathe is P/N LA-517 for the 18/8XX is P/N LA-510. So both are different and accounts for what those of us with 18/8XX lathes are used to seeing.

The stock gears are a 36, 64, and a 72 tooth. The nylon is either the 36 or something made for a specific thread pitch. The issue I see now is the nylon gear isn't fully engaged.

There is a big bolt head to the left of the gears. That is to loosen the stop bracket. It is between the two long arrows pointing to the gears in the picture below. The stop bracket is probably all the way down, no slot showing above the bolt like in the picture below.

EDITS: Missed stating the the idler gear on the banjo must also be loosened and then slid into full contact with the stud gear. There are two fasteners, one is the idler gear on the banjo, the other is to hold the "spacer" gear. Then tighten the stop bracket first to hold up the banjo, next the idler gear, check contact in case it slid down, and then the banjo pinch bolt where the banjo mounts to the Quick Change Gear Box (QCGB).

1710278343423.png

You need to loosen the stop bracket, the idler gear on the banjo, and the banjo lock that is by the quick change gear box (QCGB) just to the right of the 72 t gear in the picture. The arrow almost points to it. Then pull the 36 tooth gear into engagement and lock down the stop bracket and banjo. I bet it simply slipped out of engagement while moving it. Then use the "Feed Reverse Lever" to put the gear-train in forward or reverse. Older lathes will have a 24 tooth stud gear & a 48 tooth gear tooth. The table on the QCGB will tell you what the lathe originally came with. A 36 tooth stud and 72 tooth screw gear will work just as well.
 
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Shiseiji said:
Hi Rock. There doesn't need to be a gear there [(ops, incorrect! My bad). So not making contact is good. ] Looks like it is simply being used as a spacer like the outer gear below it. Maybe because it was convenient.


The forward/reverse is the lever in the right of the photo. It looks like it is in the neutral position. Lift it up or down to engage the lead screw. I can't quite tell from the photo if all the other gears are in full contact. Are they?
Click to expand...

If you raise or lower the lever, the gears never engage,...that's the problem.
 
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