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PM 1340GT with Simgle Phase Power

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MWCurl

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Guys

I am considering purchasing a 1340GT for my farm shop. I do not have 3 phase power at the shop. Therefore, I would prefer a lathe that uses single phase power. Does anyone cut threads with single phase machine? If so, what has been your experience? Any issues for me to consider?

Mike
 

kb58

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Get a VFD and have no issue running a 3-phase unit on single phase. Also, AFAIK, a lathe's ability to thread has nothing to do with the power supply.
 

MWCurl

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kb58

I appreciate your prompt response to my post. I am familiar with the VFD option ...... but it adds about $500 to the cost of the lathe. Also, I understand a VFD would allow a continuous control of RPMs ..... in addition to acting as a converter for the single phase voltage. However, I do not envision the need for the continuous speed control.

The reason I posed the question is because I saw one review that indicated that a 3-phase motor would cut a smoother thread than a 1-phase motor. This is based on the fact that 3-phase power produces a smoother current that 1-phase power. The comment stated that this difference in "smoothness" of current would be translated to cutting the threads. Although I understand this reasoning in theory, I question if it is an issue as a practical matter.

Therefore, I posed the question to persons who are cutting threads with 1-phase lathes.

Mike
 

kb58

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Fair enough, and I've never threaded with a 3-phase lathe so I shouldn't handing out advice!
 

mikey

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Practically speaking, no, not a major issue.
 

zjtr10

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I own a PM 1440 GT single phase and I have no problems with threading
 

pacifica

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On the 1340 gt the slowest speed is very fast for a novice at single point threading. When you are learning the 25 to 60 rpm speed is where you will feel most comfortable. But... higher speeds usually produce better surface on the thread flanks. Like speeds of 150 rpm on up.Factors:
rigidity, type of tools, sharpness, type of metal, etc.
 

MWCurl

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Thanks for your comments guys. Pacifica ..... I was a little concerned about the 1340GT’s slowest speed being 90 RPM for threading. However, I am currently taking a class at the local community college and we are threading at 80 RPM on a 1340 Standard Modern lathe. Hopefully I will make any “newbie” miatakes on it!
 

john.k

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When i closed the shop,I took home some small machines ,and simply changed them over to single phase........They dont run as nice,but the do run ,and are usable for anything they were usable before.The only possible issue Im aware of is that single phase motors can be limited to so many starts per hour,due to heating.............but if you dont start big chucks at top speed ,this isnt an issue,and certainly not an issue with threading ,where motor starting loads are light.
 

Chipper5783

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Threading a coarse thread (say 3/4 - 10 tpi) up to a shoulder at 80 to 90 rpm would certainly give me some serous pucker factor! One of the guys at work does 4tpi at 120 rpm, to a shoulder - "no problem", on a full manual machine! I can't do that.

There are good work arounds (i.e. thread from the groove, going outward in reverse), thread into a groove of width that make you comfortable.

Higher end lathes will often have a better speed range. I have an 11" English toolroom lathe that has a speed range 30 - 2500 rpm in 12 steps. It is very nice for threading to a shoulder (especially since it allows speed change on the fly, without effecting the threading take off - since the gear changes are earlier in the drive train than the take off for threading).

My larger lathe has a speed range of 45 - 2000 rpm. I find it very rare that I ever use the top speed, but I use the 45 rpm quite often - and sometimes wished it was slower. I have long thought about changing the belt drive ratio (never quite gotten aroundtoit). Perhaps that would be an option for your machine? Do you really need such a high top speed (sacrifice a little and get a more useful bottom end)? Make your self a pair of two groove step pulleys?
 
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parshal

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I've always threaded barrel tenons to a shoulder around 60 rpm. I've got a 1340 nearly ready to run and I don't know how comfortable I'm going to be at that speed. I've got Mark's VFD upgrades with a proximity stop on it's way but I'd like to somehow be comfortable without using the proximity stop.
 

MWCurl

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Parshal please tell me more about a “proximity stop” ..... how one works and where one can be purchased.
 

parshal

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There's quite a bit of info on this forum. Mark Jacobs makes one but it'll cost you about $1100 in addition to the cost of the VFD, braking resistor, enclosure and a couple other odds and ends.

Here's his YouTube video showing it in action.
 

Boxster9

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I installed a Mark Jacobs Control Board with proximity stop on a three phase PM 1440 GT and eliminated the anxiety of the thread dial engaging and disengaging. Well worth the effort and joy of threading all materials against a shoulder without the fear of stopping in time. Check out Mark's video on the Proximity Stop at MKSJ on this site.
 

pacifica

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Parshal please tell me more about a “proximity stop” ..... how one works and where one can be purchased.
I made a swing up toolholder http://www.hemingwaykits.com/acatalog/Swing_Tool_Post.html.
You can come very close to the shoulder -even when traversing quickly when cutting threads. Doesn't cost that much and works well for me.
theoretically stopping a 3 phase motor in milliseconds can cause damage .:guilty:
 

pdentrem

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I like my VFD system as it allows me to change the rpm on the fly. At times chatter makes it appearance and a twist of the knob can help reduce or eliminate it. Threading is also nicer as I can rapid back to my start position and restart the cut at a slower speed. This when I am cutting metric, as I am not sold on the idea of disengagement of the halfnuts like others claim to do.
 

bitpool

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I'll gladly trade my single phase motor for your 3phase.

Sent from my Pixel 3 using Tapatalk
 

jbolt

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I have seen some example of finish issues with single phase motors on some of the Chinese lathes. Can't imagine it would affect threading at all. I have never heard of a single phase PM-1340GT having finish or threading issues.

I have a VFD / 3PH setup on my PM-1440GT. It is hard to beat the soft start, variable speed control and having both forward and reverse jog that can be tuned to your liking. I find the fwd/rev jog feature invaluable for power taping. I also have the proximity sensor setup but didn't find it very useful. After a few times of steel swarf tripping the sensor in the middle of a cut I took it off.

I do all my threading away from the shoulder at 200 rpms or more.
 
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