Metric Thread Pitch on PM1340 Lathe

B2 said:
@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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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.
 
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.
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Where do you see the 1340GT is supposed to come with a 35? Only extras I have are a 30 and a 32.
 
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.
 
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.
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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.
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Would you mind posting the spreadsheet please? I can't make out your chart with it broken across pages. Thanks.
 
It’s a numbers spreadsheet from my iPad, doesn’t look like it will let me attach it.
 
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-FeedLowExGearMid1GearMid2GearTopExGearmmPTh
14.628570.003210.00161311.24620OneCLeadScrew32127127351.73633
14.628570.003210.00161311.24620OneCLeadScrew32120120351.73633
14.666670.003200.00160312.05674FiveBLeadScrew40127127301.73182
14.675560.003200.00160312.24586SevenBLeadScrew32120127301.73077
14.666670.003200.00160312.05674FiveBLeadScrew40120120301.73182
14.400000.003260.00163306.38298TwoCLeadScrew32127127401.76389
14.400000.003260.00163306.38298TwoCLeadScrew32120120401.76389
14.468500.003250.00162307.84051EightBLeadScrew35127120321.75554
14.514290.003240.00162308.81459SixBLeadScrew40120127351.75000
14.514290.003240.00162308.81459OneCLeadScrew30120127351.75000
14.578180.003220.00161310.17399TwoCLeadScrew30127120351.74233
14.552080.003230.00161309.61879FiveBLeadScrew40120127321.74545

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.
 
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?
 
Ischgl99 said:
It’s a numbers spreadsheet from my iPad, doesn’t look like it will let me attach it.
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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.
 

Attachments

  • PM1340 - PM1236T Thread Gear Chart.pdf
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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?
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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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