Pm-1340gt Vs Pm-1440gt

[dogma]

am waiting for Matt to get the cast iron stands in for the 1340GT, I will upgrade to those (Matt is saying a few months) and then I will be done with the modifications to this thing. If you have larger projects that require a bigger lathe, go for the 14. I would have considered it had it been available at the time I bought the 13. Probably.

I've heard of various issues with the stand. Are you having trouble with specific resonance modes or general lack of rigidity?

 

[dogma]

For example, my machine can do 112 tpi and a .0011" feed according to published info but change gears can get it to 288 tpi and closer to .0003" feed. The point being that there is ability in both those machines that is not typically published.

So what your saying is, I also need a horizontal mill to cut gears?

 

[Rich V]

Dogma, welcome to the site!
To help answer your questions we would need to know what your plans are in metal working.
The only real benefits I see for the 1440 is the increased bore and larger swing. The extra power and possible rigidity increase may be useful but only if you plan on optimizing cutting for production of multiple parts. Most hobbyists will seldom use a lathe the size of the 1340 to it's maximum cutting potential since it takes time and effort to find the max cut. Most of us will be done with the cutting operation before we find the max cutting for a given setup. Such is the nature of one off part making.

Now the head bore size can be very useful and can never be 'too large' in my opinion. The only down side is larger bore usually translates to longer length of bore. If you plan on doing any gun barrel type work then a short bore length is very useful.
Same goes for how large a piece you can swing over the cross slide. You never know how big a piece you may want to work on so larger is better.

As for the 1440 being more rigid, if your comparison table is correct the 1340 & 1440 have the same size bed so there will be no increase in rigidity from that aspect. If the cross slide is larger/beefier on the 1440 then that will help in increasing rigidity. Again any increase in rigidity from the 1440 will be only useful on heavy cuts so the benefit if real will only be useful on occasion.

I have the 1340gt and I'm very happy with it.
You won't go wrong on either of these lathes, they are well built and both should last you a lifetime.

Oh just to make your decision harder there is another PM lathe you can look at, the ERL1340
http://www.hobby-machinist.com/threads/erl-1340.39331/ it is very similar to the 1340gt but much more heavily built.

 

[wrmiller]

I've heard of various issues with the stand. Are you having trouble with specific resonance modes or general lack of rigidity?

A few folks had issues with the stand. I've had none so far. Reason I want the extra weight/mass of the iron stand is because I spin a heavy 8" set-tru above 2000rpm at times and believe it will help when spinning unbalanced parts.

I'd forgotten about this since buying my lathe, but someone here mentioned fine feeds. This was one of my main desires, and a lathe that will only thread to fifty something tpi is way too coarse a feed for me. I specifically looked for a Norton gearbox so I could get the 112 tpi/feed rate I wanted. Larger lathes have fewer/coarser feed rates.

 

[dogma]

Oh just to make your decision harder there is another PM lathe you can look at, the ERL1340
http://www.hobby-machinist.com/threads/erl-1340.39331/ it is very similar to the 1340gt but much more heavily built.

Gee, thanks...

Matt told me this morning that the PM-1440GT is back ordered until September, so it may make this decision a bit easier.

 

[sanddan]

I've heard of various issues with the stand. Are you having trouble with specific resonance modes or general lack of rigidity?

I was one of the unfortunate ones to have issues with resonance nodes. The current stand can be modified to stiffen up the mounting pads which will eliminate the flex, not a hard job or excessively expensive. The cast iron stand came about as a factory solution (per Matt's suggestion). I built my own stand so I could add storage as well as increase stiffness and mass. Not a reason to not buy the 1340GT if this is the size that works best for you.

I've tried .100" DOC in aluminum, I could tell the lathe was working hard but it did it without a lot of drama. On that job I settled on .050" DOC (.100" total stock removal) at a higher feed rate. Still made short work of the necessary stock removal. I doubt I am pushing my machines very hard, still learning. LOL

 

[mksj]

The ERl-1340 would be on my short list (but has a smaller spindle bore of 1.57"), but probably looking at just as many months as the 1440GT. Did Matt mention the ETA for stocking the cast iron base for the 1340GT? Mass adds to rigidity and less vibration issues.

Similar to Dan, I usually do 0.050" DOC (0.100 total) in aluminum, 0.050-0.060" total stock removal in steel with no problems on the 1340GT. Type of tool holder/insert make a difference in how hard you can push it. Rigidity wise I would think the 1440GT would get the nod, if some of the added weight equates to heavier structural castings. Speed wise, they are basically the same with a VFD, a reasonable range for both would be 50-2000 RPM, you could go slower if needed. Since you mentioned you would go with the VFD, and probably a proximity sensor stop, having a very low RPM for threading is negated. There are a few times where I wish the feed rate had one step/slower gearing, but you get use to each machine. Not sure about needing very high TPI's, anything below 56 is all I have needed, but then I do nothing fancy with mine.

One thing to consider is that tooling will cost more than the machine by time you are through.

Agree, this was a real eye opener for me, but if you stay with the similar size machine 1340/1440 the tooling should be interchangeable if you decide to go beefer later. If you are planning on machining larger stock, then the 2" spindle hole may be the game changer.

 

[sanddan]

It's funny, I think I do more small parts than big. Just the opposite of what I thought before getting into machining. The 1340 seems big sometimes, or maybe just right.

Of course, bigger is always better! LOL

 

[dogma]

Did Matt mention the ETA for stocking the cast iron base for the 1340GT? Mass adds to rigidity and less vibration issues.

I just asked that question (waiting on response). However, I think it might be a fun project to weld up a heavy duty stand. IMS (a local metal supplier) has delivered heavy stock to the house for something like a $50 surcharge.

 

[dogma]

Of course, bigger is always better! LOL

I continue to be amazed by the wide range of project sizes a lathe (or a machining center) can accommodate. It's somewhat constitutive based on experience with [power] hand tools.