PM1440TL VS PM1440GT

All I can add to this conversation is do not buy a Chinese lathe. Taiwanese or old American iron. If you know what to look for some old iron can be had, but it takes time to find them.
I had a PM1022, sold that, and bought an Eisen 1440E. The difference between the two is shocking regarding quality and capabilities.
Good luck in your decision.
 
With a budget of around 13K, the 1440GT is the only lathe with a 2" spindle bore. The Sunmaster lathes (ERL, RML, TL) are a step up in overall build quality and mass, so a bit less chatter and smoother in operation, but you can hit similar accuracy with all these lathes. Availability and also price increases may be a factor in what you finally decide to get. I ended up with an ERL-1340 mostly because I had a large investment in BXA sized tooling/chucks and also the delivery issues of the 1440TL due to wt./size was more difficult. The 1440GT can be delivered via lift gate, which is around the typical weight maximum for many shipping companies. Over 2000 lbs you need a forklift to offload the lathe and often need a rigger for local residential delivery. So if you were to go with a heavier machine, something to checkout before you purchase. Examples below.
 

@Batmanacw


I have been looking at the threading gears built into my PM1440GT. Not talking about manually changing the gears under the cover. There are more than are listed on the cover, 6 times the 4 sets of factors of 2x=24. In concept there are 4x4 possibilities, 16: P,Q,R,T by W,X,Y,Z. The position labeled "I" does nothing for threads only for feeds. It is only used for the feed. The question is how many and are they of any real value. My first measurement of this indicates there will be 16, but at least two are the same or nearly the same. Also some of them are useless as far as standard threads are concerned

In doing so I have installed a counter to measure the spindle turns. It seems to work well and I will have results for you soon. However, in the mean time, if you have not pulled the trigger yet on the order you may want to look again at the PM1340GT. It is cheaper and appears to be a very nice lathe.... It is a smaller with a smaller bore, but it appears to have more TPI settings with easier access. More importantly, the way the TPI is selected is far better than the way it is done on the 1440GT. Look in the manual at the front picture. I find it very hard to get the 1440 levers to go to the selected letter position, but on the 1340 is is like my old Southbend .... much better.

If I can read the front of the 1340 it has 8 fundamental gear settings by 5 2x levels to yield 40 real TPI settings. My SB has 10 fundamental by 7 factors of 2x to yield 70 TPI settings. The 1440 has shown only 6 by 4 (2x) to yield 24. The extra possible ones are TBD if of any value. .

I have never tried to thread using the feed rates. In concept, if they could be used then there might be even more TPI values, but useful???

Dave

Sorry for this Edit. I originally had " My SB has 10 fundamental by 7 factors of 2x " backward. So I just fixed it.
 
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May be interesting to implement an Electronic Leadscrew on one of those larger lathes. I am now doing such on my 16-year old Grizzly G4000 9x20
:fireman::devil:
 
I agree, but some work. I am not fond of trying to position the levers and getting the gears to mesh on my PM1440GT. Where to put the electronics? Also, I have spent a lot of time doing my unconventional VFD conversion with extra features, https://www.hobby-machinist.com/thr...tronic-components-pm1440gt-vfd-3-phase.95058/ and so it would be nice to just make things for a while. With this VFD conversion and my RPM Hall sensor I was able to add a spindle rotation counter pretty easily.
 
Ok. Here is what I measured, so far, for the TPI and then the mm/turn for my PM1440GT. This also displays the lever positions not listed on the PM manual or front of the lathe for available TPI. Note I use my Hall effect spindle counter, which makes 10 counts per revolution (10 magnets), to count the number of turns over a 10 inch travel distance. So the numbers should be pretty good....assuming I did not make any mistakes in distance which might have changed the number a little bit (distance change of a few 0.001". So I did the measurement at 10 inches and 10x the revolutions so I essentially divided my final count result by 100. I am only giving this for the 8x gear position. If you want the 1x, 2x, or 4x then just divide by 8, 4, 2 to get the smaller TPI values. The RED numbers are the ones that are on the front panel of the lathe, but I did measure them again also. So, while the numbers are not really standard threads some maybe useful. For example T-X at 26.2TPI /2 =13.1 TPI. Maybe this of value and is a close approximation to the thread that the PM manual says requires an external gear change. The metric numbers were gotten from the inch table. I may go back and do the same for the feeds. Note that for threading the "I" lever position is not connected (NC), but works for the feeds. Some of the other lever positions also seem to work for feed rates. (not listed in the manual).

I will also attach the tables where the 2x factors have been computed. What would be interesting is to see if any of these odd ball numbers get cleaned up better by using a different set of external gears. The set used for these measurements are the same as the table on the front of the lathe.

Dave

1634999216394.png
 

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I read the whole thread, I have the GT and run it almost every day (it's not my first or only machine). You lost me when you said you aren't fond of trying to position the levers. They are about as simple as it gets. Maybe a cnc would suit you better than a manual machine
 
Hi @Scott-ak

Wow! Read the whole thread! Thanks for your comment, I am looking to learn more as I am still pretty much a newbie at machining. I am glad you are happy and satisfied with your 1440GT. Am I to assume that it is the PM version? I have a CNC mill. Don't think I want a CNC lathe yet. CNC commonly gets in the way of getting the job done.... However, I can see that an electronic lead screw would make my 1440GT much easier to use.

Yes they are simple, in concept, but on my machine... not easy to move nor easy to move to the correct position. Maybe after I have broken the machine in for a few years the edges of the gears will be worn off so that they slide together more easily. Maybe the edges of the gear teeth are still to sharp/precisely cut. Also, sometimes just getting either thread gear handle to move is difficult. Seems I spend a lot of time turning the spindle (by hand or via jog) to get the gears to align so that the levers will move. Then there are the couple of positions where the P-Q-R-I-Twill not drop in. I.e. nothing is engaged even though the lever is aligned with the letter. I have even started threading only to have the lever slip a bit and the gear drop out. The saddle just stops moving. Likewise for the A-D knob. Sometimes it just does not want to engage. Getting it to disengage does not seem to be as much of an issue. Yes, I am familiar with getting the gears to align, just difficult so far. As far as dropping out once engaged I think this is just a poor design. I suspect that there are small detent stops and springs with ball bearings that are suppose to fit into the detent (small depressions) to ensure that the lever is properly located. I found these in the speed levers, H-M-L, when I had the knobs off while making a new front panel. I posted a picture of these detent stops in my VFD conversion posting. If you want to see a picture of them then: See photo 14a at post #4 of https://www.hobby-machinist.com/thr...tronic-components-pm1440gt-vfd-3-phase.95058/ . Anyway this detent method is just not a good way to lock the lever positions. They should be spring loaded pins that drop in to place like what is done in the PM1340 threading levers or in my old SouthBend 10.

The middle position, M, is poor at best and sometime the gear does not engage, but more importantly, once running I find it sometimes jumps out of position and the spindle stops turning or grinds the gears. Once, again changing these positions is still difficult. Maybe with gear edge wear (break in) it will be easier. I am not the only one who has observed this jumping out of gear and it maybe partly due to the motor not running smoothly at a constant RPM. In all fairness to the lathe and motor, the motor is not designed to run at non-60Hz frequencies. But doing so is a good portion of why I went to all of the trouble to do a VFD conversion... to be able run at lower frequencies. I also purchased 3 phase because the motors are suppose to run more smoothly than single phase. (I may run some tests where I try to measure the motor frequency stability at both 60 Hz and at lower frequencies like 20 or 25. The motor does work at even lower frequencies as I use the 6Hz for jogging the spindle.) However, a 3HP motor designed for variable speed is not cheap. Some folks have changed this motor, but not to a true variable speed design. The worst example I have seen of this unstable motor running at variable speeds in in a you tube video. Here it is shown that the speed lever will jump out, and back into, the M position while accelerating up to speed. It is awful.
. I did not have nearly this much of a problem and thought I had it fixed by changing the VFD acceleration profile. So I posted that result on YouTube:
. The fellow replaced his motor with a Marathon E470 motor. But I do not think that this is a true variable speed motor. Still expensive.

So, my reference to changing gears is largely due to my having a Southbend Heavy 10 for the last 20 years. I purchased it use from a machine shop. I think it was built in the 1970s. This machine has the drop in pin style of gear box and works very well. Only a minimum amount of hand spindle turning is all that is ever needed to get engagement. These gears never drop out as the pins are secure. Wonderful old machine. The threading gear box has 10 main gear settings for each of the 7 factors of 2x gear settings to yield 70 possible TPI values. I suspect that you have seen it, I will post an attachment photo of the SB TPI pin levers gear box. Anyway one only has to move ONE lever to achieve 10 thread changes. (It was a disappointment that my modern machine offers so few, 6 an only if you move two levers.... see the red entries of the table I posted above, post #37)

Anyway, I thin the PM1440GT is over all a very nice machine and I am looking forward to using it for a long time. One thing I may do at some point is to rebuild the SouthBend cross slide parts so that I can make decent threads......and parts of the tail stock. But there are a lot of other projects in the que first. Most of the rest of it seems to be pretty good.

Dave.
 

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I think you should get some time on your 1440GT and become a bit more familiar with it, I do not agree that the motors cannot be used at other speeds other than their base speed/60Hz. The issue/limitation with a TEFC is they loose cooling efficiency below 15Hz, otherwise they run fine and typically will run to 2X their base speed with no issues. Newer motor will have constant Hp above their base speed until around 100 Hz at which point the Hp may start to decrease. Inverter vector motors (4P) will run to 5400-6000 RPM in constant Hp all day long. Standard motors have a 4:1 constant torque (15Hz), inverter motors are typically 10-20:1 (6 Hz) and vector motors 1000-2000:1 (0 Hz or 0 speed). Since the Hp drops in a linear fashion below the base speed, for all practical purposes you would not be running the motor on a lathe below 15-20 Hz unless jogging. In your case because you are doing slow speed (less than say 10 Hz) counting for winding, etc. the stock motor is not designed for that. But for its intended purpose and given the number of headstock speeds, the VFD just allows speed change on the fly and maybe to tune the speed to the work. Your motor will have tighter speed regulation then say a single phase motor, but absolute speed regulation is not needed in a manual lathe.

I installed the VFD control system on the first video 1440GT lathe, and I indicated that there were other issues that caused the motor to cog. In the vast number of cases, the motor cogging can be eliminated by shortening the acceleration to 2-3 seconds and going to linear acceleration. This is based on about a dozen 1440GT system installs that I have worked on and also reflective of the programming I provide to the system owners. I am doing more VFD installs with other VFD models so stock 1440GT might behave differently with other types of VFD's.

The Marathon E470 replacement on the 1440GT is usually used for individuals who had a single phase machine and wanted to convert to 3 phase/VFD. Only with one individual (in the video posted) did he switch to the E470 (CT 20:1), and I found him a new one at 1/2 list price. It is a better motor, but the stock motor does just fine down to ~20 Hz. I am currently doing another 1440GT control system and sourced a new Marathon Y541 (CT 1000:1) inverter/vector motor in a shorter than normal configuration. Should be a good fit for the 1440GT and was 1/3rd list price. The major issue with replacement motors for lathes with motor's in the back is space, on the 1440GT the overall motor body length in limited to around 10" and requires a new motor mounting system because of the motor electrical box. Either of these motors will run at a crawl all day long. I have also done quite a few inverter/vector motors replacements on many other lathes, it is all about the install and the tuning. In every case the motors could not be stalled, did not have a speed regulation issue, or even got warm with continuous use.

The gearboxes on the lathes mentioned in this thread, I have either owned or worked/run all of these lathes and for the most part have not had the issues you are noting with yours. When the lathes are new, the engagement can be a bit stiff, and require and understanding of when the gear is engaged. One key is to have the drive engaged and manually turn/rock the spindle and feel the gear engage and the lever detent. The same goes for the half-nut, on a new machine if it pops out then it was not fully engaged. With a proximity stop system I have always recommended to manually engage the half nut statically by slightly moving the carriage until you feel it completely engage and then leaving it engaged through the whole threading cycle. There is no issues with thread registration, and when turning at 500-600 RPM, hitting the threading dial mark can be very difficult. All of these lathes will cut most of the common thread pitches one needs, the 1340GT has additional gears for odd metric pitches and cannot do a 11.5 pitch, other than that they are all very capable. If you need have a lathe with a stack of change gears or need oddball pitches, then go with an ELS system like this one: https://www.rocketronics.de/en/els/

With regard to the original discussion of this thread, all of the lathes mention will do very accurate work, if the requirement is a 2" or larger spindle bore than it boils down the 1440GT, 1440/1640TL, RML-1440/1640. The latter two are made by SunMaster, they are a step up in weight/quality and have a universal gearbox (no change gears). If you are on a tight budget then go with the 1440GT if you can get one, if you have a bit more financial reserve and able to deal (delivery and moving) with a lathe that will be over twice the weight of the 1440GT then consider the SunMaster series. If you do a lot of metric threading then the universal gearboxes on the SunMaster's is a real plus. If you are going to be doing larger diameter or heavy turning then maybe consider the 1640. Cost wise the prices just keep climbing and availability may be the determining factor as to what you finally decide. I have worked with 100's of VFD installs on these different lathes, most everybody has been very happy with their lathes, you can't go wrong with any of them.
 
All I can add to this conversation is do not buy a Chinese lathe. Taiwanese or old American iron. If you know what to look for some old iron can be had, but it takes time to find them.
I had a PM1022, sold that, and bought an Eisen 1440E. The difference between the two is shocking regarding quality and capabilities.
Good luck in your decision.
I agree with the older iron Or Taiwan made machines. My mill is a Taiwan Sharp brand.
I was fortunate to find a Clausing Colchester 15x50 in very good condition. It was purchased from a machine dealer.
I paid less than $5,000 which left lots of money for tooling.
Quality machines are out there. This lathe is 2,700#= lots of rigidity and 7.5 hp with a spindle bore of over 2”.
New machines are tight and should be very accurate.
There are always so many choices.
The darn PM lathes are on forever backorder.
 
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