# Interchangeable gears on 7 x 12 King Canada lathe



## Robert Gallagher (Mar 26, 2021)

Hi, 

I just purchased a Mini lathe.

I have never understood how to install the différent gear for thread shaping. Exemple: I need to make 3/8-24 thread; the label indicate that you need a 40T on the A spindle and a 60T on the D spindle. My understandind is no gears are needed on spindle B and C. When I go that route, gears A and D cannot engage.

what am I doing wrong here?
Thank you in advance.


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## DPittman (Mar 26, 2021)

So you know some gears move on the "banjo" assembly themselves and the banjo assembly also moves?


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## RobinHood (Mar 26, 2021)

The “stud gear“ is gear A in your chart (red circle). For 24 TPI, according to the chart, it needs to be 40 T. Gear D (blue circle) is 60 T. You already have that. Put any size, single gear in the middle ( ”B”, green circle - like the top gear train diagram shows [A-B-D]) to close the gap using the slot in the banjo and the banjo angular adjustment. All gear B does in this case is change direction of rotation of the output D. So you will need to use your feed direction lever to get the lead screw to turn the correct way.

Edit: when both the lead screw and the lathe spindle turn in the SAME direction, you will produce RH threads; when the lead screw and the lathe spindle turn in OPPOSITE direction to each other, you will get LH threads.






Let us know how that worked out.


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## Robert Gallagher (Mar 27, 2021)

RobinHood said:


> The “stud gear“ is gear A in your chart (red circle). For 24 TPI, according to the chart, it needs to be 40 T. Gear D (blue circle) is 60 T. You already have that. Put any size, single gear in the middle ( ”B”, green circle - like the top gear train diagram shows [A-B-D]) to close the gap using the slot in the banjo and the banjo angular adjustment. All gear B does in this case is change direction of rotation of the output D. So you will need to use your feed direction lever to get the lead screw to turn the correct way.
> 
> Edit: when both the lead screw and the lathe spindle turn in the SAME direction, you will produce RH threads; when the lead screw and the lathe spindle turn in OPPOSITE direction to each other, you will get LH threads.
> 
> ...


Hi Robinhood,

your answer has been a tremendous help understanding the gear change. Knowing that the B and C gears has effect on the ratio for thread cutting is the secret here. Yesterday night, after I purchased some tools from an old man close to home, I have been able to fabricate a piece. I will try to make the thread today.
Thank you very much.


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## Robert Gallagher (Mar 31, 2021)

Hi folks,

after some noodling on the minilathe, I have yet to find the way to slow down the carriage speed. I though of installing the gear for  52 TPI, but it has no effect the carriage speed. So once again, I hit the wall.

Can someone chim in?

Thank you very much.


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## David_R8 (Mar 31, 2021)

This may be useful to you. Pretty much all of the mini lathes have the same gearing arrangement.


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## YYCHM (Mar 31, 2021)

Slow the carriage speed?  What is it you are attempting to do?


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## Robert Gallagher (Mar 31, 2021)

YYCHM said:


> Slow the carriage speed?  What is it you are attempting to do?


Hi, I am merely trying to make a pass using the carriage engaging thing? ( don't know the exact word........)


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## David_R8 (Mar 31, 2021)

Robert Gallagher said:


> Hi folks,
> 
> after some noodling on the minilathe, I have yet to find the way to slow down the carriage speed. I though of installing the gear for  52 TPI, but it has no effect the carriage speed. So once again, I hit the wall.
> 
> ...


When threading, the carriage speed is related to the spindle speed.  
For example if you are cutting a fine thread, say 32 tpi, the carriage will feed slower than cutting an 8 tpi thread.


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## Robert Gallagher (Mar 31, 2021)

David_R8 said:


> This may be useful to you. Pretty much all of the mini lathes have the same gearing arrangement.


Thank you very much David.


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## David_R8 (Mar 31, 2021)

Robert Gallagher said:


> Thank you very much David.


For what it's worth, when I owned a mini lathe I ordered a set of 3D printed change gears because even with the largest gear the carriage feed was too fast. I'll see if I can find the link.


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## YYCHM (Mar 31, 2021)

Robert Gallagher said:


> Hi, I am merely trying to make a pass using the carriage engaging thing? ( don't know the exact word........)



I think you're talking the half nut.  That's actually more for threading than anything else.  When I had my mini I just used the default gearing (feed rate) and jockeyed the spindle speed to achieve the finish I was looking for.


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## David_R8 (Mar 31, 2021)

YYCHM said:


> I think you're talking the half nut.  That's actually more for threading than anything else.  When I had my mini I just used the default gearing (feed rate) and jockeyed the spindle speed to achieve the finish I was looking for.


On the mini lathe the half nut is the only way to power feed the carriage.


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## YYCHM (Mar 31, 2021)

David_R8 said:


> On the mini lathe the half nut is the only way to power feed the carriage.



Yup, I realize that and the default feed rate is a pretty good compromised for most things.  I was just asking what he was attempting to accomplish.  If he uses threading gearing to control the carriage feed rate he will be cutting a thread.


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