Metric Thread Pitch on PM1340 Lathe

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.
 
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.

Thread-Feed-Chart.jpg
pm1440gt thread chart.jpg
 
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. :drink:
 
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
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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.
 
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.
 

Attachments

  • PM1340 - PM1236T Thread Gear Chart.pdf
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@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.

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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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.
 
@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
 
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.
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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.
 
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.
Click to expand...

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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