# Threading chart confusion g0602



## bosephus (Aug 21, 2014)

Ok so i am a bit confused .
I am trying to cut 14 tpi .. my chart shows a 36 and 52 tooth gears .
I put those gears on and i cut a perfect metric 1.5 .. not even close to 14tpi .

Am i reading my chart wrong ? 

The other threads i have cut have all been corect 

Ooh and its a grizzly go602


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## bosephus (Aug 21, 2014)

I miss typed .. i did mean 36 and 56 tooth


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## bosephus (Aug 22, 2014)

Never mind ... woke up at 4 am with the answer right at the front of my mind .

I forgot to reverse the spacer and gear on the bottem gear ... duh


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## RVJimD (Jan 1, 2015)

I know I'm late to the party here but I just have to say/ask.  Does anyone else wonder why the chart is so specific on the outside gear on the next to last set?  It does not drive a gear and makes no difference what gear is there.

I think they did it just to cause people like me to scratch their head a few more times as they stand in from of the machine staring at the chart. anic:

jim


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## higgite (Jan 2, 2015)

The chart shown in bosephus' photo is for inch threading with the "b" gear engaging the 127T gear. Not shown is the metric threading chart where the "b" gear engages the 120T gear. (You can only see "20" in the photo, but it is "120".) That's what bosephus is referring to in post #3 when he mentions reversing the spacer and the gear.

Tom


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## RVJimD (Jan 2, 2015)

Tom,

At first I just wanted to say "but it still doesn't matter".  

BUT, I went and found both the imperial and metric charts and looked at the again.  Here is what I ignored in the passed and why I posted my comment.  I hope someone else can benefit a bit from my slow comprehension.

For EITHER imperial OR METRIC threading the 'a' gear ALWAYS drives the 127 gear (the 120/127 set is always the same position with 120 outside and 127 inside)

But now for the difference, for imperial the b gear goes onto the shaft before the spacer and this means the b gear is driven by the 127 gear, while the 120 gear on the outside of the 127 is just there as a spaces and does nothing.  But for metric threads the b gear is placed on the shaft AFTER the spacer.  This means the b gear is driven by the 120 gear and the 120 gear turns because it is on the keyed bushing WITH the 127 gear which is driven by the a gear.

I ignored all of this until now because I was not cutting metric threads, but I did NOT completely understand it.

thanks for letting me sound this out and hijack the thread!  Now you guys no how my wife feels when I come in from the shop scratching my head and I say to her, "Honey, I know you might not completely understand this but see if this makes sense..."  This is when she puts her nose back down to her iPad.

ji


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## bosephus (Jan 2, 2015)

not having any machining experience at all when i first got the lathe .. all the charts was dang confusing to me .
it wasn't until i just sat down and started changing gears and knobs that the light bulb clicked on for me .


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## Ulma Doctor (Jan 2, 2015)

i've been messing with some form of machinery for about 35 years now.
i found out that sometimes you learn more when nobody tells you the answers and you figure it out yourself!
by doing that you have knowledge that is yours.
 another way of saying the same thing is that you have an understanding of Why it works or what it does.

you can share the knowledge with others, or keep it to yourself.-it's your knowledge and understanding now.


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## DexterTripod (Dec 21, 2022)

Sorry to dig up an old thread, but having just screwed up 3 test tries at what should've been an 'easy' 1/2-13 thread, I found RVJimD's response above to be VERY helpful.  I didn't even know there WAS a spacer on that bottom gear!  

It also explains why I kept wiping out my threads when I tried using the thread dial.  Unbeknownst to me, I was setup to do some mystery metric thread that can't use the dial.  It was even more frustrating that when I left the halfnut engaged, the thread that was coming out was ALMOST 13 TPI so  I was really scratching my head as to why it wasn't working.


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