King 1440 and Craftex Threading

[John Conroy]

@PeterT & @John Conroy & @RobinHood

As I suggested, I spent some time assessing my own lathe and on that basis I made a few assumptions about yours and created the following complete metric threading chart for your lathe using all the levers and filling in all the empty boxes. It is apparent why some were dropped - they are simply duplicates of others.

I also created a spreadsheet that would fill in the chart for ANY Top and Bottom Gear. It is the far right group of cells in the photo. You simply enter the gear tooth count for the two gears at the top and the spread sheet will calculate the metric thread pitch.

Id appreciate it if you guys could check it over. If you like it, I will create an Imperial Version.

The next logical step is a feed-rate chart. And I suppose one could also create a spreadsheet that will suggest gear combinations to achieve a given thread pitch.

One quick question: Are there any more levers on your lathe besides 1, 2, 3, and 6? What happened to 4 & 5?

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Thanks very much for doing that, it is perfect for my lathe. Mine has a different arrangement for leadscrew/feedrod controls and it took me quite a while to get used to it as it is not intuitive. For some reason only numbers 1,2,3 and 6 are used for metric threading, 4,5,7 and 8 must feel left out.LOL They only appear on the imperial threading chart.

 

[Susquatch]

For some reason only numbers 1,2,3 and 6 are used for metric threading, 4,5,7 and 8 must feel left out.LOL They only appear on the imperial threading chart.

Ah ha! Well in that case, I can figure out their ratio and include them in BOTH!

THANKS JOHN!

Another version of the spreadsheet coming soon!

I'll also have to see if I can make it downloadable.

For all the neat tidy crowd on here, maybe prettier too...... LOL!

 

[PeterT]

You are trying to understand the nuances of the 127....
Yes, 127 is a prime number. That means nothing else can be divided into it. In other words, IT IS THE SMALLEST number of integer teeth that can be used to convert between metric and imperial. Please remember that for a few paragraphs as I try to explain the nuances of the magic 127 gear.

I'm still not sure about the prime number aspect. Here is my thought for the day. As you say we start with 25.4 conversion factor that needs to be resolved between IMP & MET standards. If I multiply 25.4 by N progressively, the lowest non fractional number is 127. It happens to be a prime number. Next one in line is 254...

What about if we had another random conversion standard
System A that was 27.5 per inch & repeated the routine. Lowest even gear tooth is 55. Which is not a prime number, divisible by 5 & 11 etc
System B that was 12.75 per inch = lowest even gear tooth is 51, divisible by 1,3,17

 

[Susquatch]

I'm still not sure about the prime number aspect. Here is my thought for the day. As you say we start with 25.4 conversion factor that needs to be resolved between IMP & MET standards. If I multiply 25.4 by N progressively, the lowest non fractional number is 127. It happens to be a prime number. Next one in line is 254...

What about if we had another random conversion standard
System A that was 27.5 per inch & repeated the routine. Lowest even gear tooth is 55. Which is not a prime number, divisible by 5 & 11 etc
System B that was 12.75 per inch = lowest even gear tooth is 51, divisible by 1,3,17

OK, now we are getting somewhere. I actually already explained this but probably not clearly enough because I didn't really understand your question. Maybe I still don't. But let's try to focus in on the 127 a bit more.

The fact that 127 is a prime number is just an accident. It is not a requirement for conversion of this nature.

If you could have multiplied the base number by some other whole number like your 55 life would have been wonderful. We could have divided by 5 or 11 to get a smaller number. But it just didn't work out that way.

It just so happens by accident that the smallest whole number you can have that is divisable by 25.4 and therefore gearable is 127. And it just so happens that 127 is a prime number. So it CAN'T be divided by other, whole numbers like 5 or 11. There is NOTHING that is a whole number that will evenly divide into 127.

Therefore a gear with a tooth count of 127 is required.

It didn't have to be a prime number. It only HAD TO BE AN EVEN MULTIPLE OF 25.4 THAT IS AN INTEGER. So only 127, 254, 381, 508, etc will work. Of those, 127 is the smallest and therefore the easiest to adopt into the gear train of a machine.

In summary, a prime number is not a requirement. It is just the smallest whole number that is an even whole multiple of 25.4 and it just so happens (by accident) and unfortunately, that it is also a prime number so it cannot be made smaller.

Life would be sooooo much easier if the conversion factor between inches and millimeters was 3 or 4 or 2 or 8 or 7 or any small whole number. Or even 1.2 or 1.3 or or or or. But it isn't. It is 25.4. Whether we like it or not doesn't matter. It is what it is. And that's why the 127 gear is required.

Does that help?

 

[Susquatch]

@PeterT - perhaps some simple math will also help.

How do you add 1/4 to 1/16th?

You convert the 1/4 to the nearest common denominator of 16 which is 4/16ths and then add 1/16th for a total of 5/16ths.

You add 1/5 to 1/6th by changing BOTH to the nearest common denominator of 30. So 6/30ths + 5/30s = 11/30ths.

In principal, this same effect is at play with gears. The lowest common denominator between metric and imperial is 127. And it just so happens that 127 is a prime number so it cannot be reduced to a lower common denominator.

 

[PeterT]

It didn't have to be a prime number. It only HAD TO BE AN EVEN MULTIPLE OF 25.4 THAT IS AN INTEGER. So only 127, 254, 381, 508, etc will work. Of those, 127 is the smallest and therefore the easiest to adopt into the gear train of a machine.

That's exactly what I was looking for. I've seen prior references to prime & never understood why.

 

[Susquatch]

That's exactly what I was looking for. I've seen prior references to prime & never understood why.

Hey! We communicated! That's AWESOME! In fairness, I did say it in the post before that, but I didn't emphasize it.

The prime number aspect really only comes into play by preventing us from using a smaller gear. That's why it gets mentioned all the time. I think it's easy to get trapped into believing it's a requirement. Then it never really gets challenged until someone like you digs their heals in and questions what others just accept.

Hopefully others reading this got something out of it too.

Now I'm gunna go see what I can do to complete that metric chart for everyone.

 

[Susquatch]

Ok, Here is the complete chart with all 8 levers on it.



It really is easy to see why the metric chart is so devoid of info. Its mostly all drivel.

Keep in mind that custom gears in the bottom right chart can be anything and make anything. Thats when the drivel might make sense!

Also easy to see why the metric guys like ELS..... LOL!!!!

I may or may not make it prettier sometime in the next few days......, but not today,

 

[John Conroy]

Perfect, thanks again.
Since I have never made a gear before I want to be ready when the cutter gets here. I have a Vertex super spacer and a set of dividing plates for it. I had to brush up on using the dividing plates. Since my super spacer turns 4 degrees per revolution of the handle that means it take 90 turns to go a full 360 degrees of the chuck. The first part of the math used to find the correct dividing plate is to divide the number of handle turns to get 1 rev of the chuck by the number of divisions you want so in this case it was 90/42. Since you have to work in fractions, not decimals, that works out to 2-6/42. The is no 42 hole circle on my dividing plates so i tried 2-12/84, nope no 84 hole circle either, i tried 2-3/21, nope, then I tried 2-9/63. Yes! there is a 63 hole circle. I set up the super spacer with the dividing plate for a 63 hole circle, the crank handle must be turned 2 full turns to get the 8 degrees and then an additions 9 holes in the 63 hole circle. I made a test run with a scrap steel round and made a mark at every division point with my height gage. Amazing-42 marks was the outcome! The 36 tooth gear will be easy, just cut a tooth every 10 degrees.

 

[PeterT]

Been a while since I looked at my spreadsheet but it finds the solutions based on the plates you have. Mine is 40:1. I could have sworn I made a 90:1 version but maybe not.
If you tell me your plate holes count I could probably amend it. There might be online tools too.

 

[John Conroy]

Well I feel pretty silly now. I had previously downloaded this chart from the Vertex website but forgot about it.

 

[PeterT]

great, I was able to update my tool. I spot checked a few & looks like its correct. It comes up with a few other solutions depending on the gear/angle, but I doubt you'll wear out your holes LOL

 

[John Conroy]

Thanks, my skills with spreadsheets involves printing a page and spreading it out on the table.lol

 

[RobinHood]

Well I feel pretty silly now. I had previously downloaded this chart from the Vertex website but forgot about it.

You should not feel silly at all: you did the math yourself and came up with the same solution!

You should be proud of yourself. You now have the skills to tackle any dividing head problem - that is what I call: “I learned something new today; therefore, it was a great day!”

 

[Susquatch]

Thanks very much for doing that, it is perfect for my lathe. Mine has a different arrangement for leadscrew/feedrod controls and it took me quite a while to get used to it as it is not intuitive. For some reason only numbers 1,2,3 and 6 are used for metric threading, 4,5,7 and 8 must feel left out.LOL They only appear on the imperial threading chart.

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View attachment 32318

I was just reviewing this thread John

That has to be the most comprehensive Imperial threading chart I have ever seen. 40 different choices with no overlap from 4 to 112 TPI. Best of all, it's very seldom we ever cut threads bigger than 8. Even me as a farmer! With no gear changes from 8tpi to 112, it's nothing less than totally amazing!

I checked against all my screw charts. None are missing. Not even one.

It makes me want to believe that there is probably an ideal gear combination that will cover the entire metric thread spectrum too.

Nice lathe!

 

[RobinHood]

Very impressive screw cutting capability indeed on that lathe.

There is one size missing: 27 TPI as in 1/8-27 NPT.

 

[Susquatch]

Very impressive screw cutting capability indeed on that lathe.

There is one size missing: 27 TPI as in 1/8-27 NPT.

Good catch! I have never cut pipe threads on my lathe so I didn't even think of it. I'll bet a few other pipe threads are missing too. My 44ft Hardi farm field sprayer made in Denmark is littered with threads and fittings no body has ever heard of. They are all flimsy fragile fittings so when they break I try to replace them with normal fittings.


My lathe actually covers the same range except for the smallest on the bottom row. I might make a gear/gears to cover that the day I need them. If I made it now I'd never need them.

 

[John Conroy]

Yeah I like that I rarely have to change gears. Only when doing metric.
The 16 X 40 dabbler and I were looking at one day at Modern can do pretty much all metric and imperial with no change gears.
I've never done pipe thread but you never know when the need may arise.

 

[John Conroy]

A little more prep work for machining the gears. I made an arbor that will hold the 19mm bored gear blank. It's 24mm on the end that will be in the super spacer chuck. It will be supported on the threaded end with a footstock. I still have to make a 22mm arbor for the cutter. It will also be 24mm on the other end and be held in a er40 collet chuck. I got a little single point threading practice with the 5 /8"-11 threads.

 

[John Conroy]

The gear blanks for the 36 and 42 tooth gears are done. It will probably be a month before the cutter arrives.