# Threading on 11" Logan



## shovel80 (Feb 7, 2015)

I'm trying to cut an 5 TPI Acme Thread....I have changed the gears as in the manual. When I set the levers of the quick change to the columns
I believe needed, I only get about 13 TPI.
Looking at the chart on the machine and in the manual, The Longitudinal Feed  Rate at the lever setting shown for 5 TPI....are only .0800.

I believe in order to achieve 5 TPI I must have a feed of .200 per revolution.

The Highest Feed shown in the manual and on the machine shows .1000...

What am I missing here?????

Thanks, 

Terry


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## JimDawson (Feb 7, 2015)

I would go back through the gear train setup, you may have made a mistake in the positions.  That's the only thing I can think of.


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## shovel80 (Feb 7, 2015)

I'll check it again tomorrow...I've checked it twice already and counted the teeth too...

Thanks, Terry


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## shovel80 (Feb 8, 2015)

I don't see any mistake in my setup in the gear train according to the Logan Manual!..
I don't see how it is possible to cut a 5 TPI thread yet....
The thread and feed chart in the manual and also on my lathe list .100 as the maximum feed rate.......
I believe a 5 TPI Thread would take a feed of .200......Correct?......
Has anyone here Ever cut a 4-7 TPI Thread on one of these lathes??....
My lathe is a model 1920H...

Thanks, Terry


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## JimDawson (Feb 8, 2015)

Yes, a 5 TPI would require 0.200 feed / spindle revolution.


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## shovel80 (Feb 8, 2015)

Thanks for the Reply Jim!

Terry


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## wa5cab (Feb 8, 2015)

I'm not familiar with that lathe and haven't any idea in detail as to how you would achieve it.  But if 0.100 lead is the fastest that the stock gearbox can be set at, you need to introduce a 1:2 speedup compound gear somewhere between the spindle gear and the input to the gearbox.

Robert D.


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## shovel80 (Feb 8, 2015)

For All threads from 8-224 TPI, it uses a 36 tooth stud gear too a 72 Tooth Idler gear too another 72 Tooth gear turning the shaft into the gear box with a 64 tooth gear on the side of the 72 tooth stud gear not used. From 4-7 TPI, It says to use the 72 Tooth gear for the stud gear, with the  64 tooth gear as the idler driving the other 72 tooth gear into the gear box shaft.

I thought I'd try the 72 Tooth gear as the stud gear, with the 36 Tooth gear as the idler, driving the other 72 Tooth gear, but with the 36 as the idler and the 64 as the unused gear, the 64 tooth gear wont clearance the hub on the 72 Tooth gear driving the gearbox input shaft.

I may turn a spacer to replace the 64 tooth gear that I could try as the unused gear and see what kind of travel I get in the Apron.

Terry


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## Jon In Tucson (Feb 9, 2015)

This was the rookie mistake I made with my Logan the first time I ever tried to cut threads...  I didn't engage the half nut lever but instead, I engaged the clutch lever.    So now I know better...  God Bless.
Jon In Tucson


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## shovel80 (Feb 9, 2015)

Jon in tucson,

I've cut many finer threads with the half nut lever....I wonder if this time I tried to use the clutch???

I'll check tonight after work!

Thanks, Terry


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## shovel80 (Feb 9, 2015)

Jon in Tucson, was right! For some reason I was engaging the clutch instead of the half nut lever....

I came home found out the mistake and went ahead and cut my 5 TPI Thread!

Thanks for all the answers.......Sometimes it isn't what would be thought.......Especially after cutting threads on this lathe for about 3 years!

Terry


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## Jon In Tucson (Feb 9, 2015)

Yea!  Problem solved...  As for me being right:  even a blind hog will find an acorn once in a while.  God bless. 
Jon In Tucson


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## Alphonse (Mar 22, 2015)

JimDawson said:


> Yes, a 5 TPI would require 0.200 feed / spindle revolution.





shovel80 said:


> For All threads from 8-224 TPI, it uses a 36 tooth stud gear too a 72 Tooth Idler gear too another 72 Tooth gear turning the shaft into the gear box with a 64 tooth gear on the side of the 72 tooth stud gear not used. From 4-7 TPI, It says to use the 72 Tooth gear for the stud gear, with the  64 tooth gear as the idler driving the other 72 tooth gear into the gear box shaft.
> 
> I thought I'd try the 72 Tooth gear as the stud gear, with the 36 Tooth gear as the idler, driving the other 72 Tooth gear, but with the 36 as the idler and the 64 as the unused gear, the 64 tooth gear wont clearance the hub on the 72 Tooth gear driving the gearbox input shaft.
> 
> ...


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## Alphonse (Mar 22, 2015)

SO...Terry...what gear conbo did you end up using!   I have to do a 1"-5 acme thread soon on my Logan 1875.    I've never messed with the change gears.  I understand the need for the 72 T gear to be switched onto the top stud, but do you have to seperate the the 64T gear for it and put the 36T gear[presently is alone as the stud gear] ?  Any reply appreciated.


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## Jon In Tucson (Mar 22, 2015)

Alphonse,
I am going to assume that you have a 72 tooth gear driving the QCGB, and a 36 tooth gear in the stud gear position.  Here is how I understand the stud gear positioning.  On Logan's threading chart, threads of 4 to 7 TPI have to have a 72 tooth  stud gear to have a 1:1 ratio of revolutions from the spindle to the QCGB.  The remainder of the thread pitches will require a 2:1 ratio of revolutions from the spindle to the QCGB.  That is the more common 36 tooth stud gear and 72 tooth gear box drive.  Any gear that will fit on the banjo between the stud gear and QCGB drive will work.  This is the lasting lesson I learned as a newbie as I had a compounded idler gear on my Logan 1957.  When none of my threads looked anything like threads, I was scratching my head.   For you to cut a 5 TPI Acme is to have a a 72 tooth stud gear, 72 tooth QCGB drive gear, grind a tool, and don't forget to engage the half nuts rather than the clutch.  Another lesson learned...  God bless.
Jon In Tucson


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## wa5cab (Mar 22, 2015)

Right.  Some brands of threading charts will call gears that don't matter "Idlers".  For these, you can actually use anything that will fit.


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## Alphonse (Mar 23, 2015)

Jon In Tucson said:


> Alphonse,
> I am going to assume that you have a 72 tooth gear driving the QCGB, and a 36 tooth gear in the stud gear position.  Here is how I understand the stud gear positioning.  On Logan's threading chart, threads of 4 to 7 TPI have to have a 72 tooth  stud gear to have a 1:1 ratio of revolutions from the spindle to the QCGB.  The remainder of the thread pitches will require a 2:1 ratio of revolutions from the spindle to the QCGB.  That is the more common 36 tooth stud gear and 72 tooth gear box drive.  Any gear that will fit on the banjo between the stud gear and QCGB drive will work.  This is the lasting lesson I learned as a newbie as I had a compounded idler gear on my Logan 1957.  When none of my threads looked anything like threads, I was scratching my head.   For you to cut a 5 TPI Acme is to have a a 72 tooth stud gear, 72 tooth QCGB drive gear, grind a tool, and don't forget to engage the half nuts rather than the clutch.  Another lesson learned...  God bless.
> Jon In Tucson


Thank you Jon,  I kinda thought so, as you explained so well  I have a fresh pic of my change gears in my photo area. I was wondering what to do with the 64T gear that is on the outside of the 72T gear, but now it is more clear to me.


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## Jon In Tucson (Mar 24, 2015)

By Jove,  I believe you've got it!  Move the 72 tooth gear to the stud gear position, 64 tooth gear to idler position,  with the 36 tooth gear in the position of outside on the idler shaft.  And you'll be making chips!   God bless. 
Jon In Tucson


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