9a with gear box feeds too SLOOOWWWW

Hey everyone, so I just picked up my first south bend, a 9a precision, everything looks good so far...I do have machining experience, just not much with this machine, and machines in general that aren't set up correctly.....and I don't think this one is set up correctly....

I dont think my gear train is set up properly to get the feed rates i'm supposed to be getting when I switch the tumblers....I've got it set on 8tpi/.043 and if I do a scratch threading pass on those settings, I get about 28-30 tpi....I dont have a thread gauge here with me currently, so don't kill me....also, if I put an indicator on the carriage and turn the chuck by hand, I get about .034" per rotation of the chuck....at 8tpi that should be more like .125" per rotation...currently I've got it set on direct drive, speed 2 out of 12....so i'm WAY off on what it should be feeding at....

Here Is a pic of my gear train.....sorry if this is an easy one, I could probably look all day and not find the answer, being that there are so many threads in this forum....

You recognize of course that the "feed" and "thread" mechanisms are different on that lathe. Threading is done by engaging the half-nuts with the lever on the right side of the carriage apron. Feeding is done using the lever or star wheel located near the center of the carriage apron. The two systems are mutually exclusive. That is, if you engage the half-nuts you cannot engage longitudinal or cross feeds and if the feeds are selected you cannot engage the half-nuts.

You may want to get yourself a copy of South Bend's "How to Run a Lathe" which explains all this stuff in greater detail.

I've got two SB lathes but not a 9A so take this into consideration. But, some SB lathes have a gear set that your reverse on their shaft for cutting very coarse threads. If it does, it should show that on the feed/thread plate on your quick change gear box.

Check out the gear set of two that are on the adjustable shaft with the slot cut into it in your picture.

Just a thought...
Ted

Gear train is jacked up...likely set up to cut a metric thread.

Here is how the standard set up should be...

http://www.wswells.com/data/howto/paula_stephens/9_10K_geartrain.jpg

Sounds to me like you are using the apron clutch instead of the half nut lever. Using the half nut lever WILL result in .125 per revolution

Thumbnail illustrates

Nathanhamler said:

.I've got it set on 8tpi/.043 and if I do a scratch threading pass on those settings, I get about 28-30 tpi...at 8tpi that should be more like .125" per rotation.....

Click to expand...

Check out this video at around the 10 minute mark for what I was describing. This may or may not be the issue but it's good info for you to know.

South Bend restore #9 installing gear box and drive train - YouTube

Good luck,
Ted

Damn...those banjo gears are setup low enough to pull a tree stump lol...

Yeap, gears are wrong. Should be 20, idler, 56. Not using the compound gear's outer layer.

allan

iwananew10K said:

Gear train is jacked up...likely set up to cut a metric thread.

Here is how the standard set up should be...

http://www.wswells.com/data/howto/paula_stephens/9_10K_geartrain.jpg

Click to expand...

I thought something looked off on his compared to mine- you are correct- it is not right...

Scott