# Who can make sense of this?



## Tinker (Dec 13, 2020)

Hello everyone, I'm new here.
I really need help deciphering a 35 plus year old King 14x40 lathe's metric threading chart. I lost the manual a long time ago in a fire. It didn't help much anyways as it was a direct translation of the Taiwanese speak so it made little sense to me. So, I can make out the gears and their required position, but since I want to make a 1 mm thread pitch(per rev) on a shaft , where do I start?
Take a look at the picture. This is so odd.






Any help will be greatly appreciated.


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## Janger (Dec 13, 2020)

That is hard to decipher. maybe it's some sort of imperial representation of metric threads? How about reverse engineering it? cut threads with C4 and D4 and measure what it does?


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## Brent H (Dec 13, 2020)

That is a brutal chart - basically saying you can thread imperial threads by changing the gears to the pictured configuration and then moving the 40 tooth gear just gives you feeds that they list in metric?  very strange - what is the threading on your lead screw?  Is it metric or imperial


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## Johnwa (Dec 13, 2020)

Interesting chart!  It has metric transposing gears which suggests a metric lead screw.  But the gearbox seems to be imperial.  With that combination I’m not sure a thread dial indicator would work.  You would have to leave the half nuts engaged and run the lathe forward and reverse.

Anyway, the second set of numbers shows B2 will cut 0.98mm, which should be close enough. 
 The third set appears to be cross feeds.


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## PeterT (Dec 13, 2020)

Here is the equivalent chart on my King 14x40.


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## PeterT (Dec 13, 2020)

Its been a while since I looked at this. I know I have notes somewhere where I took inventory of the gears I have. But I think for 1mm pitch I can select
C-6 on 40-127-120-40 gears or C2 on 30-127-120-40 gears? This is with my IMP pitch lead screw of course, IMP lathe.


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## PeterT (Dec 13, 2020)

I was hoping to simply look at your corresponding gear/lever positions, multiply by 25.4 or something to come up with 1.0mm pitch, but the math is not cooperating. You may have a different gearbox layout than mine too, but I thought the gear ratios would work out to equivalent pitch. Do you happen to know the pitch of your threading leadscrew?


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## Brent H (Dec 13, 2020)

The gearing ratio's set up so that in Imperial threading the ratio is 1 : 1.058 and in Metric mode the Ratio is 1: 0.945  It basically would satisfy a lead screw that is imperial and divides into 24 - Like an 8 TPi lead screw  25.4/1.058 = 24 and 25.4 x 0.945 = 24 ..  I would gather that the chart you supplied @PeterT in Figure 11 is correct for the lathe.  I will check some math


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## Tinker (Dec 13, 2020)

Thanks for the help everyone. I told you guys it was odd. I will try C6 Peter's chart is showing. I'll also try and figure out if lead is metric or imperial.


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## Brent H (Dec 13, 2020)

@Tinker :  There are a few issues with the whole set up - check out what your lead screw is.  If it is 8 TPI and imperial there is a glitch, if it is a 3mm pitch lead screw - there is a glitch - but we have you covered:

If you have an 8 TPI lead screw you should have your gears set up like this for a 1 to 1 output for imperial threading:




If you have a 3 mm pitch lead screw you will need to set up like this:






Looks like you have a pretty mutilated threading chart.

The math behind it basically works out like this:  the gears in your selector box when put into C-6 gives you a 3:1 gear reduction.  If your lead screw is 8 TPI and you are rolling out 24 TPI then 8 x 3 gives you the 24 TPI you require.  If you are rolling metric out you have a gear reduction set up that provides a 1 to 0.945 ratio.  1 RPM x 8 TPI will yield a linear move of 0.118125" = 3.00 mm reduced by 3:1 gear reduction for a pitch cut of 1 mm.

If you have a 3 mm pitch lead screw the math is the same but opposite.  Gear ratio of 1:1 on the drive gears x 3mm lead screw through a 3:1 gear reduction = 1 mm pitch.  Reconfigure for Imperial or standard threading and you have a gear ratio of 1.058  So then (3 mm = 0.118125) x 1.058 ratio = 0.12498" (very close to the 0.125" of an 8 TPI lead screw) x the 3:1 ratio = 24 Threads per inch


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## Tinker (Dec 13, 2020)

Thanks to all who pitched in their 2 cents. Peter's chart works very well and is spot on. Yes after gauging the lead screw, it is 8 TPI. Brent your math is on the money and following your diagram confirms the butchery the Taiwanese made of the chart. I will print a new chart,etch it on a steel sheet and rivet the damn thing on it. Wow, you guys have no idea how frustrating this was for me. I'm so relieved and glad I found and joined this forum. Seems everyone is nice and no B.S. Thanks.............


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## Tinker (Dec 16, 2020)

Made a new chart.(copy of the one from above,post#6)


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## RobinHood (Dec 16, 2020)

Something doesn’t add up just yet: the picture in post #1 shows that in order to get Imperial threads, the 120/127 inch/metric transposing (compound) gears need to be in play (green box). That suggests to me that the lathe has a Metric Lead Screw. If it had an Imperial Lead Screw, the path would be either straight through the 120T gear or the 127T gear alone (not through the compound).






@turner : if you are sure that you have an 8tpi imperial lead screw, then the chart in post #1 for SAE threads may not be correct (could just be that they drew the power path wrong?). At any rate (either with metric or imperial), in one system, the compound gear is in play and in the other it is not. There is no such thing as both systems using the compound gear.

Perhaps some trial threading is required to determine what is actually happening. Then adjust the charts accordingly.


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## Tinker (Dec 16, 2020)

Ok, I will double check the lead screw. Be right back.


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## Tinker (Dec 16, 2020)

OK, I'm convinced it's a 8 TPI Lead. Here some pictures albeit not the best. I need third hand. The 8 is from an Imperial (inch) thread gauge and if you noticed it's not sitting very square to the screw so looks a little off. But I can assure you it does fit much better then the 3.0 mm . The 3.0 if you look at it closely, the further left you go the more off it is.
Let me know what you think.


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## RobinHood (Dec 16, 2020)

Sure does look like 8tpi.

So that would mean that there is a problem with the thread diagram on your lathe. The compound gear (120T/127T) combo will not be required while threading in SAE (Green boxed item above). So now you need to find out if you need to run the 40-120-40 combo or the 40-127-40 one to give you the correct SAE threads (either one is 1:1 output, but only the one might physically fit with the shaft / gear location / space). Once you know, might be worth to redo that diagram as well to avoid any future confusion.

The compound gear IS required for Metric with an 8tpi lead screw - your new chart that you made would be correct.

Very nice chart, by the way!


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## Tinker (Dec 16, 2020)

Thanks RobinHood, Yes for sure I'll test and find out which gear set does what. Below and to the right of that chart just above the switching levers, there is also this chart. Just to add more confusion.


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## Brent H (Dec 16, 2020)

@Tinker : That chart is correct for your lathe running imperial threading.  The mistake on the original chart is that the title should have been :Metric Threading and the chart filled in with the metric pitches


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## RobinHood (Dec 16, 2020)

That makes sense now. Thanks for explaining, Brent / Tinker.


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## PeterT (Dec 16, 2020)

The way I interpret my manual is:
If you have an 8 TPI leadscrew (or a 'screw leading stick' as some like to refer to it LOL) then only the upper chart red box applies
- the default 40>127>40 gears give you the TPI combinations on the left panel
- the 40>127*120>32 or 40>127*120>32 or 30>127*120>40 gear combos give you the metric threads on right panel
ps my symbol > means driving gear to gear and * means a face to face gear like their diagram

If you have a 3mm pitch leadscrew (a metric lathe typically) then only the lower chart applies
- the allowable mm pitches on the left & TPI on the right

Whatever leadscrew you have 8TPI or 3mm, disregard the other chart altogether. You cant achieve it because the leadscrew pitch is integrally in the driveline


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## PeterT (Dec 16, 2020)

I have this funky chart too & assumed it is feed rates? They show the headstock gear combination but no mention of which corresponding leadscrew (8 TPI or 3mm).
This has always puzzled me thinking there should be some math correlation to a longitudinal feed value on this table and screw pitch on prior table, assuming the same lever combination. But I cant see anything that computes. So either I'm not getting it, or maybe under powerfeed (vs threading select) a different or default drive gear is coming into play? Fortunately I never pay attention to feed rates haha

EDIT
There probably should be no correlation to feed rates & some multiple of thread pitch because the powerfeed bar is driving completely different set of gears in the apron in order to traverse the carriage & cross slide.


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## PeterT (Dec 16, 2020)

This is what I'm referring to. I don't see any mathematical connection to feed chart and like 1/TPI on the thread chart. Hence wondering if they are even comparable?

EDIT. There probably should be no correlation to feed rates & some multiple of thread pitch because the powerfeed bar is driving completely different set of gears in the apron in order to traverse the carriage & cross slide.


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## Tinker (Dec 16, 2020)

This is interesting. So PeterT, are you telling me that the chart you posted (#6) is wrong. But when I tested C6, I was spot on with 1mm and B6 was exactly 2mm. Are we over analyzing this? Should I have made the gear representation as Brent had hand drawn? You know, really, I'm happy I can do 1 and especially 2mm threads without changing any gears around. I never would of figured this out without your help. I mean everyone. I will do more testing and hopefully everything works out. I will modify my chart accordingly and post my final results.


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## Tinker (Dec 16, 2020)

Ha Ha Ha reading post #21 reminded me of what the original manual that came with the lathe was like. The direct translation from mandarin to english is Noooooooo............. good. It was very hard to make any sense of anything.


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## PeterT (Dec 17, 2020)

Tinker said:


> This is interesting. So PeterT, are you telling me that the chart you posted (#6) is wrong. But when I tested C6, I was spot on with 1mm and B6 was exactly 2mm.



No, I don't think they are wrong. At least for my 14x40 & we are hoping yours is the same. The Fig-11 chart in post 5 & 6 shows the metric pitch threads that can be cut with different headstock gear arrangements involving different combinations of 127,120,40,32,30 gears AND presuming the 8TPI leadscrew which you have established. So what my recent comments were about is

1) Disregard the equivalent chart that may be nailed on your lathe showing TPI & mm pitches that assume the 3mm pitch leadscrew. You cannot get those pitches (at least using those gear combinations) unless you have a 3mm leadscrew. I guess the manufacturers thought it best to publish both on plate & cover their bases regardless of how the lathe left the building, 8TPI or 3mm

2) The other chart we were trying to make sense I'm saying I have one of those too (post #21 & 22). But I think this is feed rate = how much distance traversed per revolution. Notice they provide both directions, longitudinal & cross feed. But this is automatic power feed mode. So in my case I switch a knob from thread mode to power feed mode & the threading half nut is of course not engaged to the threading leadscrew. And now that I think about it, there probably should be no correlation *direct match* to feed rates & some multiple of thread pitch because the powerfeed bar is driving completely different set of gears in the apron in order to traverse the carriage & cross slide. DUH, I took mine apart, I should know that. Sorry for the mental lapse I had gear ratios & threading on the brain. I amended the posts so it doesn't haunt me later.


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## Brent H (Dec 17, 2020)

@PeterT and @Tinker : seems both of you have some unexplained chart work - but, the good thing is, both your lathes can do metric and imperial threading with little changes to the back end gearing.

The feed rate chart has to take into account the gear reductions that happen in the apron and feed box  when you engage the feed verses the treading.  there will be some ratio that then further changes the feed rates.  On my lathe the cross feed is 1/2 the longitudinal feed so another gear reduction happens there.

Both of you have an 8 tpi lead screw it would seem so I would make up a Metric and Imperial threading chart that reflects that and if you are so inclined, a feed chart that reflects both the imperial and metric depending on you gearing configuration. 


Reading through your chart though, there are some pretty strange numbers - typically the longitudinal feed and the cross feed will be some ratio that does not change - like mine states the cross feed is 1/2 the longitudinal feed.  On the chart you guys have the cross feeds listed at C-2 and D-2 must be errors - they just do not fit the math.

Cross Feed should be :

C-2 = 0.06
D-2 = 0.03

C-3 = 0.056
D-3 = 0.028

They must have done some rounding off that went squirrely as the gear ratios are close together.  Only way to really get it figured would be to know what the gear ratio's are and calculate things out


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## RobinHood (Dec 17, 2020)

PeterT said:


> And now that I think about it, there probably should be no correlation to feed rates & some multiple of thread pitch because the powerfeed bar is driving completely different set of gears in the apron in order to traverse the carriage & cross slide



But there is: taking the 3MM lead screw (and the corresponding tables from post #22 above), the threading ratio to longitudinal feed is 2.7272:1. The ratio of long. feed to cross feed is about 8.1666:1. (There are lots of errors (decimal places in the wrong spot) and probably rounding errors as well). Yes, feed rod and threading lead screw are separate shafts, but they come out of the same gear box, so there is always some ratio between them as they have at least some of the gears in common.

Just as an aside: you can use the lead screw as a longitudinal feed. For the SAE system just take 1/tpi to give you the inch/rev. (eg: 128tpi = 0.0078 in/rev). In Metric the thread pitch is equal to longitudinal travel (eg: 0.7mm thread pitch = 0.7mm/rev).

as Brent sais: probably time to calculate whole new tables and take off the original ones - they are too confusing (and full of errors).


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## PeterT (Dec 17, 2020)

_Both of you have an 8 tpi lead screw it would seem so I would make up a Metric and Imperial threading chart that reflects that and if you are so inclined, a feed chart that reflects both the imperial and metric depending on you gearing configuration._

Regarding threading, I think you are saying the same thing as me. In my case, I don't think a new chart is required, just recognize the lower chart relating to 3mm leadscrew doesn't apply.
Regarding feed rates, yes I think table might be messed up.

Website is freezing right now, cant seem to upload pic. I'll try later


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