PM-1440GT Change Gear Thread Pitch Calculator

Bob, after digging into this, while it might be possible to make a "universal" chart with the numbers displayed in order from smallest to largest I don't see a way to do it easily.

For just threading with the lead screw, your lathe has 25 gearbox lever combinations of which 21 are usable.(Five have duplicate ratios, so four are not used.) For each lever combination there are 64 possible change gear combinations for each idler gear setting (127/127 $ 120/127) with the stock change gears. Times that by four for each control knob setting (A-D, B-D, A-C & B-C). You get, 21 lever combos * 65 change gear combos * 2 idler gear combos * 4 control knob settings = 10,920 possible combinations.

That does not take into account the 100 tooth gears used for the feed. If that gear could be used in combination with the 120 or 127 idlers then you would double the number of combinations.

Double all that for metric equivalents.

I'm not sure how or if all of that could be graphically presented with the numbers displayed in order from smallest to largest in a useful manner.

The feed rates are slightly easier as there are only 5 usable lever positions.

Making a chart for each change gear combination is quite doable but it would not be sequential smallest to largest. However in a spreadsheet or pdf file you could use the search function to find a near equivalent.
 
Jay
As Bob has pointed out the presentation of the feedrate and pitch on the printed tables on most lathes are based on what is easiest for the manufacturer to present in a compact form.
However they are not in a form that is very useful. My way of thinking is to first decide what pitch/ feed rate I require and then work out how to get there. I dont find my machine tables easy to do this!
Despite that most of the required data is actually present in the tables.
A spreadsheet in ascending feed rate or pitch which only includes what is already in the machine tables is what most of us would require. On some machines, some extra ( a few) combinations for missing commonly used pitch/feed rate could easily be added. I dont think most of us would require every possible combination.
Ron
 
Hi Ron,

If I understand what your saying is you would prefer if the published table was just reorganized in ascending order?

In Bob's example he was looking to cut a 27 TPI thread which is not published for his lathe. Based on his description of wanting the raw data represented in decimal form was to be able to find the decimal equivalent or near equivalent that could be used, 1.e. 27/1 = .03707. As far as I know the only way to find if that exists within the available gears/settings is to calculate all the available combinations.

Maybe I've misunderstood?
 
Sounds to me like a spreadsheet will do what you want still. Instead of a chart with over 10K possibilities, let the user set the parameters they want, and calculate what's available for that info. That way all 10K are available, but you only see what's relevant to your needs at the time. I can help out if you want.
 
Sounds to me like a spreadsheet will do what you want still. Instead of a chart with over 10K possibilities, let the user set the parameters they want, and calculate what's available for that info. That way all 10K are available, but you only see what's relevant to your needs at the time. I can help out if you want.
MikeWi has my intentions correctly. A physical chart of all possible combinations is not needed or wanted, it would be huge and not user friendly. 'All' that is really needed is a spreadsheet that shows all the possible rates of carriage travel per revolution, feed/speeds, in order from low to high, along with listing the required gear train components and settings for each. The columns would show the travel in decimal inch and decimal metric feed per revolution, as well as in revolutions per inch (TPI), that would make it quick and easy to use. Others have done this work for other lathes, it is by no means a new concept, and is highly useful when we need to make a "bastard" feed or thread (or for other uses.) I have the skills to use such a spreadsheet for my lathe, but sadly do not have the skills and knowledge to create one...

Programs like Jay posted above and others like http://www.lathes.co.uk/threading/nthreadp.zip have created let you learn the thread pitch any gearing combination will result in. I want the reverse of that. I know the 'answer' and want the spreadsheet to show me the possible combinations to get there, or close to it...

Edit: I know this is not at all easy to do, and I am not really asking for someone to do it for me. It is an awful lot of work to ask of someone. But if this information was out there, both I and many others as well with similar lathes would certainly use it, and it would be a truly useful tool.
 
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Kent KLS-1340A gear charts, although this would also apply to similar machines like the Grizzly G9036 and quite a few others that seem to have the same gearbox.

I believe that people are over thinking all the combinations, as opposed to looking at the available gear ratios and working backwards to what ratios you need to get a particular thread pitch. I have attached gear tables for both imperial and metric, basically just about every pitch is available using the gear selectors setup as either imperial (direct drive X:127 and 127:Y) or metric (X:127 and 120:Y). So if you wanted a 27 TPI, you would use any two X and Y gear combination that had the same gear number of teeth (i.e. the set used for metric 42 to 42 but both driving the 127 tooth gear) OR 48 tooth X input and a 32 tooth Y output on the 127 tooth gear, the gear selectors are set per the chart. The PDF is searchable, so just put in the pitch number you want to 3 decimal places "27.000" and search the table. This also applies to the metric, so say you want a 0.700mm pitch, there is only one combination which would be a 44 X input to the 127 tooth gear with a 55 Y output to the 120 tooth gear. This assumes one has a full set of gears per the gear charts shown.

You can fiddle with the tables to look at other gear combinations, but the easiest thing is to first figure out what you need and then make a simple table that works for you. I just use the spread sheets to look at the raw data and if additional combinations are needed. Like I said if you know the factory pitch, and you want a new pitch not listed, just figure the ratio relative to the factory setting and what gear combination ratio gives the same ratio.
 

Attachments

  • Kent KLS-1340A Gear Chart.pdf
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  • Kent KLS-1340A Gear Chart.xls
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Kent KLS-1340A gear charts, although this would also apply to similar machines like the Grizzly G9036 and quite a few others that seem to have the same gearbox.

I believe that people are over thinking all the combinations, as opposed to looking at the available gear ratios and working backwards to what ratios you need to get a particular thread pitch. I have attached gear tables for both imperial and metric, basically just about every pitch is available using the gear selectors setup as either imperial (direct drive X:127 and 127:Y) or metric (X:127 and 120:Y). So if you wanted a 27 TPI, you would use any two X and Y gear combination that had the same gear number of teeth (i.e. the set used for metric 42 to 42 but both driving the 127 tooth gear) OR 48 tooth X input and a 32 tooth Y output on the 127 tooth gear, the gear selectors are set per the chart. The PDF is searchable, so just put in the pitch number you want to 3 decimal places "27.000" and search the table. This also applies to the metric.

You can fiddle with the tables to look at other gear combinations, but the easiest thing is to first figure out what you need and then make a simple table that works for you. I just use the spread sheets to look at the raw data and if additional combinations are needed. Like I said if you know the factory pitch, and you want a new pitch no listed, just figure the ratio relative to the factory setting and what gear combination ratio gives the same ratio.
Wow, just wow! Thanks! Totally understandable, and if I can say that, you have a winner. There are lots of ways to my 27 TPI, and lots more as well. I am in your debt...
 
Kent KLS-1340A gear charts, although this would also apply to similar machines like the Grizzly G9036 and quite a few others that seem to have the same gearbox.

I believe that people are over thinking all the combinations, as opposed to looking at the available gear ratios and working backwards to what ratios you need to get a particular thread pitch. I have attached gear tables for both imperial and metric, basically just about every pitch is available using the gear selectors setup as either imperial (direct drive X:127 and 127:Y) or metric (X:127 and 120:Y). So if you wanted a 27 TPI, you would use any two X and Y gear combination that had the same gear number of teeth (i.e. the set used for metric 42 to 42 but both driving the 127 tooth gear) OR 48 tooth X input and a 32 tooth Y output on the 127 tooth gear, the gear selectors are set per the chart. The PDF is searchable, so just put in the pitch number you want to 3 decimal places "27.000" and search the table. This also applies to the metric, so say you want a 0.700mm pitch, there is only one combination which would be a 44 X input to the 127 tooth gear with a 55 Y output to the 120 tooth gear. This assumes one has a full set of gears per the gear charts shown.

You can fiddle with the tables to look at other gear combinations, but the easiest thing is to first figure out what you need and then make a simple table that works for you. I just use the spread sheets to look at the raw data and if additional combinations are needed. Like I said if you know the factory pitch, and you want a new pitch not listed, just figure the ratio relative to the factory setting and what gear combination ratio gives the same ratio.

I like the layout Mark.

What I was getting at is there are more combinations than just those that can be extrapolated from the machine chart. On Bob's machine there are 14 more lever combinations.
 
Bob, Attached is a comprehensive thread chart with TPI, decimal TPI and decimal MM. Doesn't fit on one sheet. LOL

It's a bit cumbersome and only really useful using the search function.

FYI the the data driving cells are hidden but the visible cells are not protected.
 

Attachments

  • KLS-1340A_Thread_Chart.xls
    1.2 MB · Views: 98
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