# Metric Thread Pitch on PM1340 Lathe



## davidpbest (Jun 19, 2017)

The common (coarse) thread pitch on M5 screws is 0.8mm.   On M12, it's 1.75mm.    For the life of me, I can't figure out how to configure the PM1340 for 0.8 and 1.75 mm thread pitch.   Those commonly used pitches are not listed in the online manual, nor on the thread/feed faceplate on the machine.   At least, if it is listed there, I can't find it.   Maybe I'm going blind.   I've cut other metric pitches, but these two elude me.  

Has anyone here have a clue how to configure the PM1340 for those thread pitches?

If all else fails, I can probably figure a way to use adjustable split dies in a tailstock die holder, but on my current job I need to really dial in the thread depth for a very close fit, and turning the threads would be a lot easier.

Thanks


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## RJSakowski (Jun 19, 2017)

I looked at the manual for the PM13450 and it looks like you can cut .8mm threads by replacing the 30 tooth gear in Fig. 3-18 with the 32 5tooth ger and the gearbox position C6.


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## davidpbest (Jun 19, 2017)

RJSakowski said:


> I looked at the manual for the PM13450 and it looks like you can cut .8mm threads by replacing the 30 tooth gear in Fig. 3-18 with the 32 5tooth ger and the gearbox position C6.



What am I not seeing here?   This is the Fig 3-18 from the PM1340 manual posted at QMT web site.   No such configuration noted here.  Scratching head - again and again.


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## RJSakowski (Jun 19, 2017)

In the last figure the ratio between the drive gear and the driven gear is .75 (30/40) . If you substitute the 32 tooth gear, the ratio becomes .80 (32/40). In the third chart, the C6 gearbox setting gives .75mm pitch with the 30t gear.  With the 32t gear, it should give you .8mm pitch.  It's just an undocumented combination.  

Unfortunately, I am looking for something that will give you the 1.75mm pitch but haven't found anything yet.  Still looking.

My Grizzly G0602 has hundreds of undocumented combinations.  Many of them are useless or redundant but there are some useful combos.


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## davidpbest (Jun 19, 2017)

Thank you RJ.   This ratio figuring puzzle would be a nice spreadsheet, or iPhone app - put in the pitch and it spits out the configuration data.   I did ponder the ratios behind the published combinations and speculated that the answer is in there somewhere.   But I thought about puzzling it out for about 3 seconds based on the published ratios, and then reached for the gin bottle to dampen my head spinning.     If you can give me the formulas, I can do the spreadsheet and post it for others to use.


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## RJSakowski (Jun 19, 2017)

Dave, It looks like a 35t drive gear, 40t driven gear, gearbox B6 would get your 1.75mm pitch.

As to the spreadsheet, I've done one for the Grizzly G0602 and G4000.  I haven't ventured into other lathes.

In order to understand all the ratios, you have to know what;s going on in the gearbox.  The A, B, C, D, & E positions are in the ratio 1:2:4:8:16 (as you go from A to E, the pitch decreases and the tpi increases).  It appears that the ratios of the numbered gears are 16:18:19:20:22:24:26:28 for positions 1- 8.  More than likely, this is the actual number of teeth on the gears.

When the drive and driven gears are equal, position C6 gives 1 mm of travel for each revolution of the spindle.  Increasing the ratio of drive to driven increases the travel by the ratio of the gears so changing the driven gear from 40t to 30t will increase the travel by the same ratio (40/30)  or 1.333 mm per revolution.

My head spins as well but I find hitting the brandy bottle just makes it spin worse.


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## mksj (Jun 19, 2017)

I have attached a gear chart with the different imperial and metric pitch for various gear ratios, these are generated for both TPI and metric pitch mm thread to thread. Several combinations will give a 0.800 mm pitch, one will give a 1.745mm pitch which should be very close. It is in a PDF file so you need to zoom in to see the fine print. If someone is wants the excel worksheet PM me. There may be other combinations by flipping the 120/127 gear, but I did not generate those numbers. Not to difficult to add if there is some other combinations you want me to generate.


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## davidpbest (Jun 19, 2017)

Thank you both, very helpful.   I knew that place would have all the answers.   Terrific resource.


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## jer (Jun 20, 2017)

Somewhere I remember an article that included a spreadsheet that would give you all the possible thread combos using the available gears on a lathe. As stated many were duplicates and several weren't mentioned in the manual. Maybe an internet search would find it.


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## [X]Outlaw (Jun 20, 2017)

When I was waiting for my lathe to arrive I notice some gaps in the metric threading chart. This is a link to a spreadsheet I developed to calculate all possible thread pitches from any combination of change gears not just the stock set. I have included a link to the spreadsheet below.

From my notes I don't think its possible to get 1.75mm pitch with the stock change gear set, you would need to place a 42 tooth gear in the top change gear position and the stock 32 tooth gear in the lower position, then set the QCBG to C2

Using the spreadsheet:

Gear A is the top change gear
Gear B is the lower change gear
B1 to E8 are lever positions on the QCGB
Ratio is the effective ratio of the QCBG at a particular setting
Pitch in MM is the metric pitch for a particular QCGB setting given the combination of change gears 

Excel spreadsheet:

http://s000.tinyupload.com/index.php?file_id=41165643326520255331

Let me know if there are any problems with the file.

Chevy


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## davidpbest (Jun 20, 2017)

Chevy,   The PM1340 comes with 40, 30 and 32 tooth small gears, and 127 and 120 large gears.   So the possible combinations are 24 gear arrangements.   Your spreadsheet doesn't cover all the possible combinations - looks to me like you're assuming there is only one large gear tooth configuration.   Like I said originally, this makes my head spin so I could be all wet.    Working with mksj's spreadsheet, I found a path to the 0.8mm pitch for M5 coarse threading that I need just now, but I haven't tried all possible gear combinations yet, so have been unable to solve for 1.75, 0.2 and 0.35 (all of which are found in standard metric coarse or fine threads).   Here's where I am so far:


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## [X]Outlaw (Jun 20, 2017)

Hey David,

If you change the fields Gear A and Gear B in my spreadsheet, the column Pitch MM will be automatically recalculated based on the change gear combination you input.

Chevy


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## davidpbest (Jun 20, 2017)

Sorry, I still don't see all possible combinations because the lower small gears can mesh with either 120 or 127 tooth large gears.      Maybe I don't understand your spreadsheet, but I don't see how to specify which of the two large gears are meshing with the lower set of small gears.   Seems to me there are three variables, not just two.   These are the possible combinations.


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## [X]Outlaw (Jun 20, 2017)

Ah, I understand what you are saying David.

When I made they sheet I did it with the assumption that the lower change gear will always me meshed with the 120T gear and the upper gear will always be meshed with the 127T gear as this is what was shown in the manual for cutting metric threads.

I've modified the spreadsheet. There is a new field called transposing gear. This only applies to what gear the lower change gear is meshed with. The formula still assumes that the top change gear will always be meshed with the 127T gear.

http://s000.tinyupload.com/index.php?file_id=36905162139584955074

Chevy


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## jbolt (Jun 20, 2017)

Question, how do you go about figuring out the gears / gear ratios in the gearbox? I would like to do this for my PM-1440GT


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## mksj (Jun 20, 2017)

David, I recalculated the spread sheet flipping the 120/127 gear and looking at the metric combinations. Based on the calculation you can cut every metric thread pitch up to 6.0, with the exception of the 5.5. The 0.200 pitch works out to 0.201, the 1.75 to 1.745. I have attached the worksheets, you can plug in your gear ratios and see other combinations.

Jbolt, let me look at the manual and gear chart and see what I can put together for you. Have a few other things so it will take a day or two.


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## [X]Outlaw (Jun 20, 2017)

How I did it with the PM1340GT is like this.

The lead screw is 8TPI
When setup for imperial thread cutting the 127T gear is just an idler between the upper and lower 40T change gears.
This setup gives a 1:1 output to the lead screw (Before the QCGB comes into play).

So without the QCGB coming into play we are essentially setup to cut a 8 TPI thread.

We can calculate the ratios for the QCGB by taking 8 and dividing it by each QCGB setting on the imperial threading chart.

So for example in the 1340 imperial threading chart A1 will give 4TPI.
8/4=.5

So A1 has a ratio of 1 : .5

I'm sure there is someone that could explain this a lot clearer than me but this is the way I came up with the ratios.

Chevy


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## jbolt (Jun 20, 2017)

mksj said:


> David, I recalculated the spread sheet flipping the 120/127 gear and looking at the metric combinations. Based on the calculation you can cut every metric thread pitch up to 6.0, with the exception of the 5.5. The 0.200 pitch works out to 0.201, the 1.75 to 1.745. I have attached the worksheets, you can plug in your gear ratios and see other combinations.
> 
> Jbolt, let me look at the manual and gear chart and see what I can put together for you. Have a few other things so it will take a day or two.



Thanks Mark, no hurry.

Looking at you spreed sheet helps. I will take a crack at it myself.


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## jbolt (Jun 20, 2017)

[X]Outlaw said:


> How I did it with the PM1340GT is like this.
> 
> The lead screw is 8TPI
> When setup for imperial thread cutting the 127T gear is just an idler between the upper and lower 40T change gears.
> ...



Thanks Chevy,

You explanation is clear enough.


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## brino (Jun 20, 2017)

jbolt said:


> how do you go about figuring out the gears / gear ratios in the gearbox?



For my Southbend 9" since I did not find a manual that matched exactly, I saw two ways of doing it:
(from the manual the PM1340 looks similar)

1) using a known setting from the chart, the tooth counts of all the visible gears, and the lead-screw pitch attempt to reverse calculate all the QCGB ratios. The problem here was that the number of levers made it a pain to work out for all the different combinations.

2) using a mirror, a flashlight and standing on my head I peaked under the open bottom of the QCGB and carefully counted the teeth on each gear. I would wipe the lube off the side of a tooth, mark it with a dot of paint, then slowly spin the input shaft and count teeth until the dot came around again. I made several little sketches of how the various gear were slid in and out of mesh.

Using the tooth counts and sketches I put together a spreadsheet showing all combinations.
Some time and effort invested, but well worth the understanding.

-brino


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## jbolt (Jun 20, 2017)

On the PM-1440GT gear box there are 2 knobs A-B & C-D. These are straight forward as they are doublers, (A/D =1x, B/D = 2x, A/C = 4x, B/C = 8x) but there are two levers, one with 5 positions and the other with 4 positions.  And then there are the 4 change gears for TPI and 5 for metric. 

I should be able to modify mksj's spread sheet and then reverse calculate from there.


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## jbolt (Jun 21, 2017)

I was calculating the various ratios for the lever positions on the PM-1440GT and discovered an error on the thread chart.

On the TPI chart for the 5.75, 11.5, 23 & 46 threads using the 69T lower gear the shift lever setting should be R-X. It is currently listed as P-X.

When I first ordered the lathe they were still being made at the factory. Matt had sent me a thread chart for a different machine with the same gearbox. That thread chart is correct.


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## Jason812 (Dec 6, 2021)

I know this is an old thread but I just want to say thanks and info like this why I love this site.  You would know the first metric thread I needed to cut was M12x1.75 to make an anti rotation tab for the MT3/ER40 holder to fit the tailstock.  The info was on the money.  Top gear set 32/127.  Bottom 40/120 and B-5 on the gear box.


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## B2 (Dec 7, 2021)

jbolt said:


> Question, how do you go about figuring out the gears / gear ratios in the gearbox? I would like to do this for my PM-1440GT


Hi, Jbolt,

When I was looking at my PM1440GT at PM there was a hard bound manual in the grate.  I think PM normally tosses this and tells the user to download the manual from the PM web site as Matt says there are errors in the factory manual and he got tired of folks bringing this up.  However, if you did get this then on the parts lists for the gear box you will see the gear teeth numbers and gears listed.  On the downloaded manual only some of these are listed but not all of them ... at least not for the 3 gear assemblies.    However with these listings in the factory manual, if they are correct, I think you can figure out the ratios for the various gear handle positions you are after.  There are several instants of this.  For example, in the downloaded manual , the PM-1440GT v9 2021-03 manual page 39 ("SADDLE FEED GEARBOX COMPONENTS  Fig 8"--which seems like a strange title to me), lists for part reference #21 as "Gear assy 14DP2" whereas in the factory manual page 36 , Gear box (Gear & Shaft) Inch Type, the part reference #21 is listed as, "GEAR (14Px24Tx30T)(M2.25x20T). I think these three ##T notations are telling you the ratios of the combined gear assembly for this shaft. It is a similar story for part number 5. where the factory manual has "GEAR (14Px27Tx30T)(M2.25x21T). Most if not all of the 2-gear assemblies in the online manual are complete. In the factory manual the next page of parts are for the same drawing, but for the Metric version of the lathe and the number of gear teeth are different. (I don't think the metric version of parts is included in the online manual.) Total number of pages for the online manual is 47 while it is ~70 for the factory manual. However, there are ~5-6 pages of calibration and trouble shooting info in the factory manual.

On the other hand I am sure that one could figure all of these out with enough physical measurements.  But....

I made a promise to Matt that I would never ask him any questions about the material in the factory manual .... and I have not.  Hence, I am also hesitant to just post it and create problems for Matt and PM.  If you do not have the factory manual and you want any other the gear box gear parts listings I can share them with you privately.   Maybe you can figure out if they are accurate or not!  I have not spent the time trying to yet, but I originally looked at this because I was thinking about building a spread sheet to get all of the gear ratios.  I just never got around to it. 

Dave L.


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## davidpbest (Dec 7, 2021)

If you look back in this same thread about 10 postings, you will find complete spreadsheet calculating all the gearing/threading possibilities for the PM-1340GT from Mark ( @mksj ).  Attached with this posting is the updated but simplified version of the data that strips it down to the common thread sizes.  This 4-page threading chart is what I have laminated in plastic at my 1340 for quick reference.  If someone wants the source spreadsheet that leads to these results, DM me.


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## B2 (Dec 7, 2021)

@jbolt 

By the way, if you look at the photo of my PM1440GT front you will see that my gear box table has the sequence QZ-60, "RX-69", PW-60 combinations rather than the incorrect machine you mentioned QZ-60, "PX-69", RW-60.  So I guess PM got this straightened out before I got my machine.  



			https://www.hobby-machinist.com/attachments/07b-imag3287-front-panel-finished_prox-stop-imag3287-jpg.378080/
		



jbolt said:


> On the TPI chart for the 5.75, 11.5, 23 & 46 threads using the 69T lower gear the shift lever setting should be R-X. It is currently listed as P-X.


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## xr650rRider (Dec 7, 2021)

With the Clough42 ELS, you select leadscrew on gearbox, press button to switch to threading, press button to switch to metric, press up arrow until you get to 1.75, then cut your thread.  Love this thing.


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## jbolt (Dec 7, 2021)

@B2, I appreciate the lengthy responses however my posts were over 4 years ago. I have become intamently familiar with my lathe in that time. 

My lathe was one of the 1st 10 built. I made Matt aware of the thread chart error back then and he had it corrected. He sent me a replacement chart for my lathe but it had a different mounting pattern so I never swapped it. I corrected the original with a sharpie. 

Like David Best, I have done a spreadsheet that calculates all the pitch combinations.

I am curious about the factory manual you got. I think the one that came with mine was about 10 pages. 

PM didn't release their manual for another year or so after the lathe was first produced. 


Sent from my SM-G981U using Tapatalk


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## davidpbest (Dec 7, 2021)

xr650rRider said:


> With the Clough42 ELS, you select leadscrew on gearbox, press button to switch to threading, press button to switch to metric, press up arrow until you get to 1.75, then cut your thread.  Love this thing.


James has come up with something really helpful with his ELS for the home hobby type.  I do wish he'd done a more "industrialized" display/button panel arrangement instead of putting *so* much emphasis on size.  I find his ELS pretty toy-like in terms of the button sizes, etc.  Kind of reminds me of my kids GameBoy.  I've been considering _*these units*_ for my 1340 instead.


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## xr650rRider (Dec 7, 2021)

davidpbest said:


> James has come up with something really helpful with his ELS for the home hobby type.  I do wish he'd done a more "industrialized" display/button panel arrangement instead of putting *so* much emphasis on size.  I find his ELS pretty toy-like in terms of the button sizes, etc.  Kind of reminds me of my kids GameBoy.  I've been considering _*these units*_ for my 1340 instead.



In use, I find it little different than most of the DRO interfaces.  I like the KISS approach and it works well.  There is code on his Github depository for a touch screen interface.  We're not using it to control the space shuttle, you read the RPM or press a couple buttons to change mode, feed rate/thread pitch.  You can change feed rates on the fly but that's really only time your pressing buttons with the machine running.  The meat and potatoes is the code running on the TI processor with motion control capability's built-in for $40.  Could add a gold plated control panel to house the electronics?


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## davidpbest (Dec 8, 2021)

xr650rRider said:


> In use, I find it little different than most of the DRO interfaces.  I like the KISS approach and it works well.  There is code on his Github depository for a touch screen interface.  We're not using it to control the space shuttle, you read the RPM or press a couple buttons to change mode, feed rate/thread pitch.  You can change feed rates on the fly but that's really only time your pressing buttons with the machine running.  The meat and potatoes is the code running on the TI processor with motion control capability's built-in for $40.  Could add a gold plated control panel to house the electronics?


I'm glad you like it.  Functionally it adds a lot of value and convenience, but I prefer more industrial designs for my equipment.  To each their own.


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## Cletus (Dec 8, 2021)

xr650rRider said:


> With the Clough42 ELS, you select leadscrew on gearbox, press button to switch to threading, press button to switch to metric, press up arrow until you get to 1.75, then cut your thread.  Love this thing.


Oh yeah! ....Last month I implemented the @clough42 ELS System on my trusty old Grizzly G4000 and while at it, I also implemented an electronic (regenerative) spindle foot-brake.  Words cannot convey how much more user friendly my good old lathe is now.


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## B2 (Dec 10, 2021)

jbolt said:


> Like David Best, I have done a spreadsheet that calculates all the pitch combinations.


Can you post/share your spreadsheet.  I some times miss the post dates.  Someone adds to the post and then I see an earlier on in the string and make a response to an old post.  Sorry.    However, I learned from your reply!!!!  Can you post/share your spreadsheet or if you already have maybe you can sent a link.  
Thanks.


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## jbolt (Dec 10, 2021)

B2 said:


> Can you post/share your spreadsheet.  I some times miss the post dates.  Someone adds to the post and then I see an earlier on in the string and make a response to an old post.  Sorry.    However, I learned from your reply!!!!  Can you post/share your spreadsheet or if you already have maybe you can sent a link.
> Thanks.


My CAD/Hobby computer is still packed from our move so I cannot get to the chart file right now. That is task 66,637 of the 100,000 things I still have to do so it will be awhile.

I did find a thread calculator I made. It is in an excel file which I have attached. If you do not have excel I may be able to export it to a different format...maybe.

In the top chart each of the colored cells is a drop down to select the desired change gear. Select a gear combination and it shows all the available pitches for that combo.


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## B2 (Dec 10, 2021)

jbolt said:


> My CAD/Hobby computer is still packed from our move so I cannot get to the chart file right now. That is task 66,637 of the 100,000 things I still have to do so it will be awhile.
> 
> I did find a thread calculator I made. It is in an excel file which I have attached. If you do not have excel I may be able to export it to a different format...maybe.
> 
> In the top chart each of the colored cells is a drop down to select the desired change gear. Select a gear combination and it shows all the available pitches for that combo.


Thanks.  I will have a look.  Yes, I have Excel.  I run 2010 rather than becoming a cloud user.  Is the chart any different from the Excel or just images of the various pull down situations.  

If there is any thing particular about the manufacturer's manual you need just sent me a PM and I will see what I can do.    I am still pretty new with my 1440 so am still learning.  I am sure you could teach me more quickly.  I assume you saw my post about the VFD conversion.?


B2 said:


> VFD conversion using solid state electronic components.


That took me  a while.  I am currently writing up an Excel program which auto generates  Gcode for making a new instrument panel holes at arbitrary locations, angles, number of devices etc..  It is working, but not well written up yet.  When I get it done I will share.


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## jbolt (Dec 10, 2021)

B2 said:


> Thanks.  I will have a look.  Yes, I have Excel.  I run 2010 rather than becoming a cloud user.  Is the chart any different from the Excel or just images of the various pull down situations.
> 
> If there is any thing particular about the manufacturer's manual you need just sent me a PM and I will see what I can do.    I am still pretty new with my 1440 so am still learning.  I am sure you could teach me more quickly.  I assume you saw my post about the VFD conversion.?
> 
> That took me  a while.  I am currently writing up an Excel program which auto generates  Gcode for making a new instrument panel holes at arbitrary locations, angles, number of devices etc..  It is working, but not well written up yet.  When I get it done I will share.


The cart is something that can sit in a drawer for quick lookup vs having to go to the puter.

I had not seen your thread. I will definitely read it when I can. 

My participation here has been hit and miss for the last two years while working on our Cali home to get ready to rent. That should finally be done before xmas. My lathe has not been run since I think March of 2019. Hoping to get power run to it between xmas and the new year.


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## Christianstark (Feb 11, 2022)

Called PM today to see if they had any 35T gears. They do not. Looks like I need to consider making my own…eventually.


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## B2 (Feb 11, 2022)

@Christianstark 

Which metric thread do you want to make first.?  Maybe I can figure out another gear configuration that is close.


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## B2 (Feb 11, 2022)

Do you have all of the PM standard external gears.  The list that I show were suppose to come with the 1340 is  40, 35, 32, 30 but you say you do not have a 35T?   I was suppose to have had a 57T with my 1440GT and it was missing.  Matt sent me one. 

So if not what gears do you have?  I will plug that into the spread sheet I am working on.

Also, do you know what your z-feed rate is?  I am not for sure I believe the lathe label, but you maybe able to feed and thread and get close.  I can check those as well if you have the feed rate.


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## Ischgl99 (Feb 11, 2022)

I didn’t get a 35T gear with my 1236T either.  I made this chart using the gears I have and you can get the missing threads using the 32T gear in a different combination than documented.


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## Christianstark (Feb 11, 2022)

B2 said:


> @Christianstark
> 
> Which metric thread do you want to make first.?  Maybe I can figure out another gear configuration that is close.


I was making M12 1.75 jack screws, but I used Tap and Die for that. Took a bit of work to get it perfect, but once I got a round die I was able to cut the thread enough to fit the tapped hole. I don't need anything right now, but 1.75 is a common thread pitch in metric, so I would eventually want to be able to cut it. 

Nothing pressing now.


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## Christianstark (Feb 11, 2022)

B2 said:


> Do you have all of the PM standard external gears.  The list that I show were suppose to come with the 1340 is  40, 35, 32, 30 but you say you do not have a 35T?   I was suppose to have had a 57T with my 1440GT and it was missing.  Matt sent me one.
> 
> So if not what gears do you have?  I will plug that into the spread sheet I am working on.
> 
> Also, do you know what your z-feed rate is?  I am not for sure I believe the lathe label, but you maybe able to feed and thread and get close.  I can check those as well if you have the feed rate.


Where do you see the 1340GT is supposed to come with a 35? Only extras I have are a 30 and a 32.


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## mksj (Feb 11, 2022)

The 1236T/1340GT do not ship with a 35T gear. It is also not shown on the gear chart. Very few people do metric and the 35T only adds  pitches  0.350 and 0.700 which are uncommon and typically would use a tap. Seems like a wild goose chase, unless you do a lot of metric threading.


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## davidpbest (Feb 11, 2022)

Christianstark said:


> Called PM today to see if they had any 35T gears. They do not. Looks like I need to consider making my own…eventually.


They don't stock them, but they can get them from the manufacturer in Taiwan.  I know three people who have done this including me.


Ischgl99 said:


> I didn’t get a 35T gear with my 1236T either.  I made this chart using the gears I have and you can get the missing threads using the 32T gear in a different combination than documented.


Would you mind posting the spreadsheet please?  I can't make out your chart with it broken across pages.  Thanks.


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## Ischgl99 (Feb 11, 2022)

It’s a numbers spreadsheet from my iPad, doesn’t look like it will let me attach it.


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## B2 (Feb 11, 2022)

I am not for sure where I got your info now.  But, I have been looking around the web for a while...

PM re-writes the manuals and for some reason when the do this they leave out the gear info (tooth count and tooth size for some critical gears) in the parts list.  In the case of the PM4040GT, 57T was listed on the lathe face plate so while did not catch this missing gear when I got the lathe I did later.  However, if you may find an equivalent old manual on line and  sometimes the extra gears are shown on the parts list, or better still on the illustrate gear shafts page.  In my case, I happen to have the manual that was shipped with the lathe from the factory, which PM normally discards. There are a whole pile of possible gears that are shipped with the machine sometimes, both for the upper location (5 in TPI) and the lower location (2 for TPI and and 5 more if you have the metric lathe version).   The factory manual has the drawings and parts list for both English and Metric versions.    More importantly, I found an on-line version of the  Eisen LD-1440E Manual and it is very similar to my factory shipped manual, but does not have the external gears listed in the illustration or the parts list, but does supply info on the gears inside the machine in more detail, especially the gear assemblies .  If you search the web you will find the Eisen manual, but the link is also provided *HERE* .  The front page of this manual also says 1340 on it, but it does not have a Norton gear box so is probably not exactly the same as yours and so would not have the same change gears.   If you search you may find yours.  If you do let me know as I am trying to understand the feed rates to higher accuracy in these machines.  The lathe label says the x-feed rate is 1/2 of the Power feed rate (z-axis).  However I am pretty sure that this is not right at all.  It is more like 1/3.14 or something like this.  Others on the thread  *HERE*  that I set up has found 1/3.25, but I am a bit skeptical as this is in the third decimal place and you need lots of spindle turns (work) to get this accuracy.   I do not have access to a 1340 to measure the feed rates accurately and it is a bit much to ask someone to hand count a 1000 turns!  I have both an electronic counter built into my spindle as well as an old mechanical counter so I can do this on the 1440.  

Anyway, I only have the 1340 manual to get a Power feed rate from the front panel label.  It says in the gear position A-One it is 0.047"/turn.  I can put that in to my spread sheet to generate all of the possible TPI you could get using the Power Feed rather than just the using the 1/2 nut.  Not as accurate a cut and has no thread dial but it gives you a lot more possibilities of threads a might cover the metric mm/T you are looking for.    

Currently my spread sheet just walks through all of the possible gears both internal and external and generates a long table of the results.  Depending upon how many external gears are at your disposal this number gets very large.  Right now my spread sheet has some duplication and it is not clear whether one wants to put the external gear at the top or bottom location so may have some entries where one gear is being used at both positions.  For these reasons it is important to feed the spread sheet with the right info.   

When I provide my spread sheet it will have macros in it which allow you to search the listings. My sheet currently searches on TPI but provides the mm/T info as well.   I just ran the 1340 with the gears I thought came with the machine (5120 possible TPI values with some redundancies)  searching for ~14.5??? +-0.1 TPI which yields 11 hits using the 1/2 nut, i.e the lead screw.  None using the Feed rod.  Of these these there are 5 that you could make with the 32T gear. You will see that some of these are just about as good as with using the 35T gear.   For example the last entry, 14.55TPI is only off by 0.05/14.5 or ~ 0.34%. However there are several others that are nearly as good.  I will paste a table below.  I think I can do that on HM.  


ENGLISH:PM1340GTGEARPOSITIONSorTEETH:METRIC:TPIFEEDXFEEDFEED_TPI1 to 8A to ELS-FeedLowExGearMid1GearMid2GearTopExGearmmPTh14.628570.003210.00161311.24620OneCLeadScrew32127127351.7363314.628570.003210.00161311.24620OneCLeadScrew32120120351.7363314.666670.003200.00160312.05674FiveBLeadScrew40127127301.7318214.675560.003200.00160312.24586SevenBLeadScrew32120127301.7307714.666670.003200.00160312.05674FiveBLeadScrew40120120301.7318214.400000.003260.00163306.38298TwoCLeadScrew32127127401.7638914.400000.003260.00163306.38298TwoCLeadScrew32120120401.7638914.468500.003250.00162307.84051EightBLeadScrew35127120321.7555414.514290.003240.00162308.81459SixBLeadScrew40120127351.7500014.514290.003240.00162308.81459OneCLeadScrew30120127351.7500014.578180.003220.00161310.17399TwoCLeadScrew30127120351.7423314.552080.003230.00161309.61879FiveBLeadScrew40120127321.74545

Of course none of my spread sheet calculations have been verified by anyone else yet.  Hope I got it right, but let me know if you find an error. So no test before you cut important material.   Feed rates are suspect to my lack of calibration data.  

Hope this helps.

Dave L.


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## B2 (Feb 11, 2022)

PS.  Mid1Gear is in contact with the bottom gear and Mid2Gear is in contact with the top gear.  Not obvious, but they are next to each other in the columns.

@Ischgl99   PLease check out the two entries (Third and fourth from the bottom) for the exact 1.75 mm/T and tell me if these are the gears that you find in your tables?


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## davidpbest (Feb 11, 2022)

Ischgl99 said:


> It’s a numbers spreadsheet from my iPad, doesn’t look like it will let me attach it.


That's ok, I was able to extract what I needed.   Attached is the revised threading chart in a format I find useful for setting up the lathe.


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## Ischgl99 (Feb 11, 2022)

B2 said:


> PS.  Mid1Gear is in contact with the bottom gear and Mid2Gear is in contact with the top gear.  Not obvious, but they are next to each other in the columns.
> 
> @Ischgl99   PLease check out the two entries (Third and fourth from the bottom) for the exact 1.75 mm/T and tell me if these are the gears that you find in your tables?


No, I used the 32 gear at top to the 127 gear and the 40 gear on the 120.  It’s not exact 1.75, it is 1.7454 which is close enough for just about everything.  I have done several M12 threads using that combination and the error was never noticed.  I threaded my machinist jack body using a quality tap 34mm long and single pointed the jack thread using that combination and there is no indication the threads are not exact.  If you are doing really tight tolerance threads, then my chart using the 32/40 combination might not be suitable, but for everything else, it has been working.


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## Ischgl99 (Feb 11, 2022)

davidpbest said:


> That's ok, I was able to extract what I needed.   Attached is the revised threading chart in a format I find useful for setting up the lathe.


Nice chart, thanks!


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## B2 (Feb 12, 2022)

Hi @Ischgl99 

I think my spread sheet must be working ok as we are in agreement.  



Ischgl99 said:


> No, I used the 32 gear at top to the 127 gear and the 40 gear on the 120. It’s not exact 1.75, it is 1.7454


That IS the last entry of the table of gears that I generated via my spreadsheet.  See:



B2 said:


> I will paste a table below.



I will re-paste the last line below, which agrees with your statement.  See the last column:

ENGLISH:PM1340GTGEARPOSITIONSorTEETH:METRIC:TPIFEEDXFEEDFEED_TPI1 to 8A to ELS-FeedLowExGearMid1GearMid2GearTopExGearmmPTh14.552080.003230.00161309.61879FiveBLeadScrew40120127321.74545


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## Ischgl99 (Feb 12, 2022)

B2 said:


> Hi @Ischgl99
> 
> I think my spread sheet must be working ok as we are in agreement.
> 
> ...


Sorry, I missed that one, I was looking at your chart with the gears the other way in mind with the first gear column as the top.


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## xr650rRider (Feb 12, 2022)

B2 said:


> Anyway, I only have the 1340 manual to get a Power feed rate from the front panel label.  It says in the gear position A-One it is 0.047"/turn.  I can put that in to my spread sheet to generate all of the possible TPI you could get using the Power Feed rather than just the using the 1/2 nut.  Not as accurate a cut and has no thread dial but it gives you a lot more possibilities of threads a might cover the metric mm/T you are looking for.
> 
> Dave L.



The manual on PM website is wrong for feed rates on the PM-1340GT and even though wrong it has position A-8 as being .047".turn.  The corrected feed rate chart is here. Position A-1 = .05896"/rev, A-8 = 0.03369"/rev. I confirmed those rates when setting up ELS. My crossslide is not 50% of feed rate but is closer to 60%. I can set ELS to .005" on feed rate and get .0501" in 10 turns of carriage movement or change to cross slide and get .0313" in 10 turns. Doesn't really matter unless your paying attention to a feeds and speeds book.


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## B2 (Feb 12, 2022)

@xr650rRider 

Thanks for your help.  @Ischgl99 and I have figured it out completely/exactly.  The PM1340GT and the PM1440GT have the same gear box, so as long as you reference the feed rate to the power bar turns and not to the spindle it all becomes clear. Then you can relate it to the spindle turns by knowing the gear box.   I just posted what I think is our summary to the nth decimal place! The Ratio of the x-feed to the power feed is: 3.13540842.
The actual feed rates per power bar turn are also given.  So perhaps you can calibrate your ELS even better if so inclined.

Check it out on the other thread we have been using:  
https://www.hobby-machinist.com/threads/x-feed-rates-on-pm-lathes.98071/page-2#post-924729

Wishing for an ELS!!!

Dave L.


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## xr650rRider (Feb 12, 2022)

No calibration necessary as it's all based off of an encoder on the spindle.  Previously I had DRO setup for diameter instead of radius mode.  So quick test.  Set the ELS feed rate to .040"/rev.  Took out backlash and then turned spindle 20 times.  Z reading was .8018"/20=.04009" of travel.  (error is just where I was visually observing a turn).  Flip lever to facing, took out backlash and turned 20 times.  X reading was .25520"/20=.01276"/rev.  Ratio X/Z=.3183 or Z/X=3.1418.  That's all gear ratio between feed and face and will not change no matter where gearbox is set, mine is just driven by a servo.  Only way to change is modify the gears in the apron.

The feedrate is actually a calculation using the ratio between the threading and feeding.  Using the updated chart the ratio on the PM-1340GT is exactly 4.2405 for every gear change.  So looks like the feed is calculated very accurately.


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## B2 (Feb 12, 2022)

@xr650rRider 
Interesting.  I came to the conclusion that one could not see the error in the 3rd digit with so few (20) turns even if one was very precise in coming back to the same position on the spindle turn.   So you got Z/X=3.1418 but we found it to theoretically be  be 3.13540842.   I ran several experiments where I let the number of turns be much higher and found that as I went up the 3rd digit could easily change between a 3 and a 4.  I understand that it is extremely anal and that no one really cares beyond the third digit, but if so then why do people insist on an integer TPI when threading. So an error of .005/3.1354 = 0.15%.   One has to wonder if the teeth on the Rack are cut to that much precision anyway.  I suspect that the gear teeth in the Apron at lease average to the correct value and the lead screw on the X-stage is probably dead nuts on if you go far enough in motion.  Anyway, I just did a run where the spindle turns was 1000.0 for both feeds as counted with both my my electronic counter and my my mechanical counter.  The distances were measured by my magnetic DROs after the backlash had been rotated a way.  For that I found that the ratio was 3.13112.  So my guess is that even with 1000.0 turns one does not necessarily get the 4th digit correct.  (My electronic counter and my 10 magnet(sensor) yields 10 counts per revolution.   That is it resolves a count every 36 degrees.  I marked the spindle at a point just after one of the counts took place so that I knew how to get back to the exact spot.  But even a couple of degrees shows up on the DRO.  So, one needs more turns than 1000 to distinguish that 4th digit. )  Think I will just stay with the theoretical value for the spread sheet I almost have built. 

By the way, thank you for the chart!

Dave


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## xr650rRider (Feb 12, 2022)

So you think it's a coincidence that changing from radial to linear movement that there is a constant so close to π ?? I believe the 3.1418 I got is backing out that constant.


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## B2 (Feb 12, 2022)

@xr650rRider         Sorry, I guess I do not really understand what you are saying.  It is probably not critical that I understand as long as you are happy.  

There is no coincidence, just the physics.....  What I was trying to say, or thought I had said,  is that the power feed rate has a factor of Pi() in it, which is due to the linear Rack threads.  As @Ischgl99 pointed out, the Rack threads matches the M1.5 18T gear to yield a tooth spacing of 1.5mm*Pi() = 4.71239.....mm. (This was essentially the same value that I had physically measured on the Rack: 330mm/70T= 4.71429..., but is theoretically exact.)  This Rack tooth spacing is used in the Power feed calculation.  Since the X-feed drives a gear tied to its lead screw the x-feed rate does not have a factor of Pi() in it. .  So when one takes the ratio there is a factor of Pi() involved.  

Dave L.


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## Dpaul7 (Feb 18, 2022)

I would love to have this spread sheet but for some reason I can't seem to download the file. I just get a "failed to ope the page" message.
Could you email it to me in excel format? daconpaul7@gmail.com Thanks.


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## B2 (Feb 19, 2022)

Hi @Dpaul7 ,

I am not for sure if you are asking for my spread sheet tool or some other.  Anyway, I am still polishing my tool up, but when I am finished I will be happy to sent it you.  Yes, I am writing it in Excel.     I am traveling a bit currently so am not really working on the spread sheet ... for a while.  I will let you know.    By the way, in the future I would suggest that you sent a private message to folks rather than posting your email address for all the world to see. ...unless you do not care.  

Which model lathe do you have?   Is it a PM1340GT  ?  Do you have the standard set of change gears for the PM1340GT or did you purchase a 35T gear in addition?   

Perhaps what I can send you, at this time, is a pdf print out of a table  of all of the threading options/possibilities for the standard set of gears plus the 35T for the PM1340GT.  There will be some duplication in it as I have the spread sheet set up to put a gear at either top, bottom, or both of the external gear positions.  I will see if I can get that generated now and if so I will attach it for you.  If you cannot download it I will sent it to you via your email.  The table has two types of threading: 1) via the conventional leadscrew and 1/2 nut.  2) by using the power feed which may not be as good.   The later opens up some non-conventional TPI values.   For each of these, it is sorted by increasing TPI.  Anyway, maybe this is of some use to you for now.  The titles describe the column content. Note TPI is at the far left with other distance per turns info following in a few columns.  The gear settings are in the middle and immediately following that is the Metric info.

I make no guarantees about this being correct.  Take a look and let me know what you think or how it could be improved.  When the spread sheet is complete the table will be something that you can customize or improve upon..   

In the spread sheet that I will be trying to provide,  will have macros that allow one to sort one a column or search for any TPI value with wild cards.  etc. There are other macros coming that will be provide additional features.  Within a limited format one can change lathe properties to generate this sort of table for any lathe the user wants to describe into the spread sheet.  So far I have input three different lathe models.   Determining the feed rates accurately has turned out to be a challenge.   

You maybe interested to follow this thread where we have been discussing X-Feed rates and Power feed rates.   https://www.hobby-machinist.com/threads/x-feed-rates-on-pm-lathes.98071/

Dave L.


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## Dpaul7 (Feb 19, 2022)

Thanks for getting back. The spread sheet I was referring to came from the following thread - (See link below) - regarding a metric threading question posted by David Best.
https://www.hobby-machinist.com/threads/metric-thread-pitch-on-pm1340-lathe.59976/

The link to the spread sheet in question is part of the last post at the bottom of the above thread. (see link for spread sheet below)

http://s000.tinyupload.com/index.php?file_id=41165643326520255331

Re: my lathe: I purchased the 1340GT 2 years ago with the standard gears 40T and 32T w/ the 120T / 127T
I am interested in being able to cut 0.8 and 1.75 mm thread pitch same as in the post. Also need a 46 tpi which is not readily available as far as I know. Thanks again David P.


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## B2 (Feb 19, 2022)

@Dpaul7

Yes, that is a very old link and it does not work for me either.  However, others  have posted simple spread sheets for your lathe.  The issue with the Lathe manuals is that they only provide a few of the gear combinations for the exact threads that are available and usually none of the approximate threads.  

Meanwhile I provided you what you need if you just look at the table I posted for you last night.  Remember that TPI=1/(mm/T)/25.4).   Just look for the equivalent TPI value and then scan across the table and you will find the MM/T calculated, just after the last gear tooth list column.    The PM1340GT is suppose to come with 30, 32, 40, 40, 120/127 gears.  So how close can you get to what you want without the 35T gear.  I content close enough and sometimes exactly.    The pdf table I supplied you has the TPI listed in the first column.   Or you can search this table for 3 digits of what you are seeking.  For example use the pdf find command on 31.7 and see if it does not work.  So:

31.75TPI   is the same as 0.8mm/T   You will find multiple options for cutting this thread with the gears that you have.   See Pge 18 of the pdf table. 

1.75mm/T is the same as 14.51286TPI  So when you look up this TPI in the table you will find options that are very close, but unless you have the 35T not exact.  However, within less than 0.03% error.   Is this not close enough???   Try 14.55208 (5-B-30/120/127/32)  or 14.40000, where the last gear listed is at the top near the spindle.  Even the error on the last one is only 0.1/14.5123~ 0.6%.  Unless you are really very good at threading want the threads really tight this should be fine.   Besides who says the mate for this thread will be this good.  See page 12 of the table. 

As for 46TPI.  Your 30,32,40 gears will yield 45.9619TPI (3-D-40-120/127-32), which is very close. 0.04/46 <0.088% If you have the 35Tyou can be exact but is there really much difference!.  You can also reach 46.5667TPI (~1.2%) with your gears.  See page 22 of the table.

There is a lot of info in that table.  

Dave L.


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## Dpaul7 (Feb 19, 2022)

That is an awesome table! That should get me where I need to be.  Thanks!


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## mksj (Feb 19, 2022)

Paul,
I had posted a complete gear table years ago for the 1340GT and a few other lathes. A 30-127 and 120-32 will give you a 46.03 TPI under D7. In metric a 0.8 pitch is a standard gearing 40-127 and 120-30 with D4. A metric 1.75 requires a 35T gear, I had one and sold it with my 1340GT but you might check with QMT if they might become available down the line. My current lathe has a universal gearbox, so if there is something you need threaded I might be able to help you.


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## B2 (Feb 19, 2022)

@mksj  & @Dpaul7 

Interesting Mark.  I had just over looked the 7-D 30-127 and 120-32 listing, in the pdf table I posted for Paul , but it is there.  The difference is that my calculations indicate that this yields a 46.06299~46.063 not  46.03.     Are you sure about your number?  I did not check your work.  
It all is rather moot as it is unlikely that there are very many lathes/operators that will work with that precision anyway!

Paul, it also appears that my statement that a 35T would get you an exact 46 was not correct either.  At more like ~ 46.3 it it would not be as good! It appears that with the 30, 32, 35 40, 40 gears you cannot get an exact 46TPI.  You can look at my table and see all values that are possible, then select one and you have a gear set that got that number.    

Dave L.


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