# PM 1340GT max spindle RPM with VFD



## Carcajou (Feb 7, 2020)

Hello, I am considering buying one of these lathes, but do a lot of small diameter collet work in plastics and soft metals.  What would be a reasonable maximum spindle speed to expect with the stock 3ph motor and the Hitachi VFD many here have used?  Thank you for all the detailed information provided here on this topic, I have read most of it, but could not find an explicit top speed, most seem more interested in low end for threading.  I would also be open to swapping pulleys and giving up low end if that is a practical option.


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## mksj (Feb 7, 2020)

Probably 2,000 RPM, beyond that you are risking problems with lubrication since it is not a pressurized system. Typically the maximum speed for splash lubrication in a lathe headstock would be in the 2200-2500 RPM range. Also be sure to use an ISO32  oil in the headstock and allow it to come too temperature if the ambient temperature is cold. A synthetic oil might be an option after breaking it in if working over a wide temperature range.


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## davidpbest (Feb 7, 2020)

I was curious myself what was possible.   My 1340 has a VFD with max output at 100Hz.   I run a 1.9" small pulley on the motor, and the stock larger 5.5"  pulley on the spindle drive, and in top gear at 100 Hz VFD output I get 2060 RPM.   Assuming I turned the pulley around and made the spindle pulley the 3.5" side, that speed would increase to 3800 RPM or close to it.  But like Mark said, the limit here is lubrication and bearings, not what's possible with the pulley drive train.


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## Carcajou (Feb 7, 2020)

Got it, thank you for the quick replies.


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## Carcajou (Feb 7, 2020)

Mksj, are you aware of anything about this lathe that would limit it below the 2200-2500 range you mention?  The pm1440gt spins to 2200 rpm stock and I believe the maximat v13 and Harrison m300 at 2500rpm were also splash lubricated though likely with better bearings.  David’s theoretical 3800 sounds fairly terrifying but I am frequently north of 2500 on the HLVH at work in similar situations so even 2200 would be nice in intermittent use If that wasn’t foolish.


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## parshal (Feb 7, 2020)

I, too, have the 1340 with VFD that MKSJ built for me and I flipped the pulleys.  I run it with the slowest speed lever and only use the VFD to adjust speed.  In the other lever positions it's just way too fast for my work, even in Delrin.  I can't keep the feed rate slow enough to keep smooth finish if it's running that fast.


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## mksj (Feb 7, 2020)

There are many factors that limit the upper speed range, I would be concerned about using the norton gearbox at high speed, you also have limitations of the internal rotating gears and bearings in the headstock. My ERL-1340 in the gear head (splash lube) version goes to 2500 RPM, and the factory VFD version is rated to 3000 RPM. But the factory VFD version only has a 2 speed head, vs. 8 speeds so a lot less rotating mass. With the 1340GT I do not foresee an issue of short periods with speeds on the  in the 2000-2500 RPM range but not for extended time. You would need to use a high grade oil with good anti foaming properties, there are also issues of oil drag and shear at the higher speeds.  I would monitor the bearing temperatures and make sure the machine is broken in before extending the upper end speed range. In the VFD builds with the stock motor, I often suggest flipping the motor pulley so you are running from the large motor pulley to the large headstock pulley, ~1.5:1 pulley ratio. This requires a slightly longer belt, I have seen both BX26 and BX27 used but varies by belt manufacturer. With the stock motor set pushing it to 100 Hz would be in the neighbor hood of 2000 RPM, 110 Hz would be 2200 RPM. Alternative is if you are primarily doing high speed work is to just run the belt position in the stock high speed belt setting which is close to a 1:1 drive ratio with a maximum motor speed of 80 Hz would give you 2,400 RPM.


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## Carcajou (Feb 7, 2020)

Parshal, David, mksj, thank you for the detail and confidence check.  It sounds like that setup would be great for my uses.   2000 rpm would be fine for the vast majority and for the small but critical portion in the Itty bitty diameters   I would be just fine with swapping belts/pulleys and low duty cycle.  Noted about break in, temps and oil selection.  Thanks!


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## davidpbest (Feb 7, 2020)

Carcajou, you didn’t talk about feed rate requirements, which might also be a consideration. FYI, the slowest carriage feed rate on the 1340 at 2,000 RPM is ~4” per minute using the Norton gearbox.


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## Carcajou (Feb 7, 2020)

Thanks for the heads up, I would be ok hand feeding for the smaller parts at top speeds.  Can’t have it all in a $5k new lathe.  It doesn’t seem like there is a great new option for smaller capacity lathes in between toolroom lathes and China hobby  lathes.  Grizzly heavy 10, anything else I should consider?  The extra capacity of the 1340 is appealing on the bigger end.


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## mksj (Feb 8, 2020)

The 1340GT is a nice balance between size, weight and quality for what you are looking for. There are smaller high speed lathes, some people will use use these as a backup for very small projects. I used a 5C collet system on my 1340GT and did some very small work and for finishing work would run the lathe at high speed for polishing. Even with carbide tooling I  didn't need high turning speed above 1600 RPM. The D1-4 machines will handle smalls and also larger turning projects very well, the fit and finish on these Taiwanese machines are very good at the price point. On the belting, if running a VFD I would use a single fixed belt position, there is no real need to switch the belt positions otherwise. The stock motor works well with a VFD even though it is not inverter rated. A few 1340GT owners have switched the stock motors out for 2Hp TENV inverter/vector motors, I usually run these to 125 Hz using a 2.3-2.5" motor pulley. These motors have an upper maximum frequency limit of around 200 Hz, the vector type motors are designed to only run off of a VFD.

I would go with the 1340GT which has hardened gears vs. the 1236GT. At this price point I do not have any other suggestions for lathes, I would not consider the SB lathe line which I feel is overpriced for what you get. The 1440GT is going to cost another 3K, would give you a bigger working range with the larger spindle bore. All of these lathe should be fine to run to 2000 RPM on a regular basis and intermittent under 2500 RPM.


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## davidpbest (Feb 8, 2020)

I’ll second what mksj says.  I replaced the factory motor with a vector drive unit and VFD electronic controls that mksj produced, and have been very happy with the machine.   I did do a lot of customization work on *my PM1340* and it’s a terrific small lathe provided you are ok with the Norton style gearbox.  Support from Precision Matthews has been excellent.


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## wrmiller (Feb 8, 2020)

I too do a lot of smaller diameter stuff, including threading. I have a 5c collet chuck for when I'm doing small things in a batch, and I have a ER32 that I can just grab with the big chuck for doing quick jobs.

But I also do enough larger stuff that would be difficult to do on a smaller lathe, so the 1340GT is a decent compromise. I'd love to have a dedicated lathe for the smaller work, but Santa Claus still hasn't delivered my Hardinge HLV-H.


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## Carcajou (Feb 8, 2020)

Davidpbest I’ve seen your setup here and it is impressive.  

Wrmiller, that would be my ideal setup as well.  This will mostly be used next to my PCNC 1100 for prototyping in my freelance mechanical engineering work and usually efficiency is the deciding factor in whether I can make something cost effectively for clients vs shopping to China shops or protolabs.   But time is limited for my fun projects too as most can relate. The shop I most enjoyed working in had a 618 toolroom lathe with collets next to a chucked 13x40 engine lathe, backed up to 2 vertical mills with different workholding setups and being able to spread out on a project without changing chucks and indicating vises all the time is such a huge time saver.  Out of the question for my home setup in the forseeable future .  There it’s more about getting the lost out of the space and this machine definitely seems to be the Goldilocks of the category.


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## Carcajou (Feb 8, 2020)

I can’t dispute the comparative value of the 1340gt and barring any good fortune on the used market I will buy one this year and love it.  But this research project mostly left me feeling the resellers and manufacturers of home shop lathes are a little overdue for some new product development.  The norton box is a very elegant solution in my eyes but she’s no spring chicken.   The 50 year old Emco designs seem to be the last purpose designed high end home/small RD shop lathe lineup.  For example one could take the 1340gt castings with different machining ops and for very minor RD cost present a variant of this lathe with servo driven lead screw with a super simple control for any feed or thread fancied.  Same goes for a factory integrated version of mksj’s vfd with prox sense.  I don’t see why this couldn’t be under $10k, and there seems to be plenty of enthusiastic home  shop folks with comfortable budgets to buy one, I would.  When all your customers are doing the exact same modification to your product I would take that as a sign you are missing the mark, and in 2020 you should not need to take to the internet to figure out how to cut a m5x.8 or m12x 1.75 on your brand new lathe.   Pro machinists might scoff at the Tormach products but they seem to sell plenty by filling a needs driven niche rather than grinding out scaled down versions of ancient industrial tools.  In a culture where people spend god knows what to “build” their flavor of ARs to dump 30 little pieces of lead into a gravel pit wall super quick or kit out their jeeps to go round the ‘burbs why do we need to settle on machine tools?


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## davidpbest (Feb 8, 2020)

Totally agree with your comments on the lack of value added in these Asian machines.   FWIW, there is at least one guy here who's putting the Clough42 electronic lead screw (*https://tinyurl.com/w6jlnqf) *on a PM1440.   I have long commented that on the knee mill side of things, we are well over due for a replacement of the conventional Bridgeport J-head.   That head is positively 1890's technology.


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## Dpaul7 (Feb 14, 2020)

parshal said:


> I, too, have the 1340 with VFD that MKSJ built for me and I flipped the pulleys.  I run it with the slowest speed lever and only use the VFD to adjust speed.  In the other lever positions it's just way too fast for my work, even in Delrin.  I can't keep the feed rate slow enough to keep smooth finish if it's running that fast.


Do you know if MKSJ is still making VFD setups?


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## davidpbest (Feb 15, 2020)

MKSJ would love all the business you can throw his way.   He is a tremendous resource.  Help support the knowledgeable.


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## Dpaul7 (Feb 15, 2020)

Thanks for the reply. I am new to this forum. Actually I am new to forums in general. How may I contact MKSJ? By the way, extraordinary work on your 1340GT set up. Very inspiring. Hope I can come even close to something like that.


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## NortonDommi (Feb 15, 2020)

These lathes are limited to around 2000 rpm because the chucks used at that size have a speed limit - usually 2000 rpm.


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## Dpaul7 (Feb 15, 2020)

Thanks, that's good to know. 2000 rpm is plenty for my application.


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## davidpbest (Feb 15, 2020)

Dpaul7 said:


> Thanks for the reply. I am new to this forum. Actually I am new to forums in general. How may I contact MKSJ? By the way, extraordinary work on your 1340GT set up. Very inspiring. Hope I can come even close to something like that.


Click on his name “mkjs” in his post above and you can “start conversation” which will be a private exchange.


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## Dpaul7 (Feb 15, 2020)

David, would you be willing to share the dimension you settled on of your 1340GT stand, length, depth height etc.? I haven't taken deliver on my machine yet and wanted to get started.
David Paulson


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## davidpbest (Feb 15, 2020)

I post most of my shop project details on Flickr, including dimensioned drawings on most items.  The link to the the complete archive *is here*.

The link to the lathe stand specifically *is here.* If I were to do the lathe stand again, I would increase the height of the slot for the removable chip pan by ½-inch, otherwise very happy with the design.

Sing out if you have questions.


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## Dpaul7 (Feb 15, 2020)

Awesome work!!! By the way did you purchase your 1340GT as 1ph or 3ph before you upgraded it?


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## davidpbest (Feb 15, 2020)

Thanks.  I bought the 3-phase 1340GT.  I sold the original motor on CL when I bought and installed the vector rated replacement.  I think I got $75 for the original motor.


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## Ozbusa67 (Mar 24, 2020)

Dave where did you buy the motor and vdf from I'm looking at doing a upgrade to a 1236t

I wish I had that shop it is a  Beautiful job And well planned


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## davidpbest (Mar 24, 2020)

Thanks.  It’s David BTW.  Dave is my dad. I bought the VFD from Precision Matthews.  The motor was NOS on eBay.   They are hard to find at reasonable price.


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## Bamban (Mar 25, 2020)

David,

With your stand and adjustable feet, what is the spindle center height of your 1340GT?'

Nez


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## davidpbest (Mar 25, 2020)

The bottom of the stand legs are 2⅜” off the floor by virtue of the leveling feet.   The CL of the spindle is 49½” above the finished floor, which for me (5’-11”) is a comfortable working height.  Keep in mind that this stand was designed around the particular tool storage cabinets I had on hand.  The two cabinets on both ends are 23½” high and 21” deep. Finding low-boy tool chests like that which are also over 16” deep and don’t have a flip-up top lid with tons of wasted top storage is challenging today, and it’s the height of the chosen cabinet that drives the spindle CL height.  The center cabinet consists of two of _*these nightstands*_ with the legs cut off, stacked and tack welded together - they are surprisingly functional.  I detest cabinets down low with door access, so coming up with all drawer storage and a removable chip pan were the aspects that drove this design.  I have been extremely pleased with this design.


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## davidpbest (Mar 25, 2020)

One other point.  Another user here asked how I fabricated the swing-away/ lift-off convenience trays, so I put up additional photos of that aspect _*at this link*_ that illustrates that design.    Details on the tool racks and everything else can be found_* at this link.*_   Let me know if you have any questions.


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## Bamban (Mar 25, 2020)

David,

Thank you for the detailed writeup. I do like your design? How would you modify the design to get the center height down to 43 inches from the finished floor? I am just barely 5' 6" the center height on the PM1440TV is perfect for me. Rough scaling it is about 43 off the floor. 

Another question, with the tool boxes and their contents, what would be your best guess of the weight of the stand?

I am on the plan to replace my ACER 1236 with a 1236T, I am thinking about finding a local guy to clone your design, scaled to the 1236.


nez


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## davidpbest (Mar 25, 2020)

To get the spindle CL down to 43" off the floor, you'd have to employ less tall drawer cabinets and just shorten the legs.   I spent a lot of time trying to figure a way to get all drawer storage without having the spindle height too high.   So I recommend you start your activity by finding the tool chests you'll use and design around that.   For a 43" spindle height, you'd want a tool chest that is no taller than 17".      You could start with _*something like this*_ and cut that flip-up top section off the chest.   I do not recommend you lighten up on the C-channel height or thickness to lower the spindle height - that HR C-channel is 10" wide, 2 1/2" tall with 1/4" webs and is very effective in dampening harmonics and keeping the lathe bed aligned. 

As for the weight of the unit, I'm guessing here, but the stand itself is about 200 pounds, the tool chests are another 200 or so, and as the lathe with all the tooling sits in my shop, I'm guessing the total weight is just over 2,200 pounds.   I have a lot of gear in those drawers and that collection of BXA tool holders is also quite heavy.   The center leveling feet are important supports for all that load, so don't eliminate them.

Attached is the complete set of dimentioned plans for the lathe stand FYI.   What's posted on my Flickr site is a subset of the attached.   Hope this helps.


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## Bamban (Mar 25, 2020)

David,

Thank you for the help.


Nez


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## advmaker (Aug 27, 2020)

I am close to selling my 1127 and getting a 1340GT. I can't figure out what frequency to normally keep the VFD at. I understand that people sometimes use a knob to vary the freq to reduce rpm lower than 90rpm for threading, but what is the default recommended frequency?


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## davidpbest (Aug 27, 2020)

60Hz, plus/minus 30Hz for the factory supplied motor.   I can run my 1340 at 24RPM in lowest geared setting with the VFD turned down to 30Hz, and well over 3K RPM at highest gear setting (well beyond the specs of the bearings).    *Click on THIS LINK* to see my 1340 in lowest gear combination with the VFD running from 30 to 100HZ. I replaced the factory supplied motor with a vector-rated Baldor which provides better torque at the lower speed ranges and widens the possible frequency choices to ~20-120Hz.


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## advmaker (Aug 27, 2020)

Thanks a lot.

I will be ordering a WJ200-015SF outside PM as they are out of stock. I see that it is rated as 2HP for constant torque and 3HP for variable torque. Is it something we can choose when wiring?

Sent from my ONEPLUS A5010 using Tapatalk


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## davidpbest (Aug 27, 2020)

I believe the difference between "constant" and "variable" torque has to do with vector-drive motors only.   The PM1340 from PM does not come with a vector-drive motor.   Tread carefully here - this is not something to gloss over.   You might tune in with Mark Jacobs on this topic - he's the resident WJ200 guru here.   He goes by *mksj* here on H-M.


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## mksj (Aug 27, 2020)

Variable torque is for driving pumps, constant torque is used for machinery. There are also ratings based on normal duty and heavy duty load, as well as various deratings. There are various programming parameters that need to be adjusted based on the application and function, what is important is to look at the rated output amps of the VFD for your motor and application. The WJ200-015SF will work well with the PM-1340GT stock motor, or a replacement motor of the same size. Vector motors allow a wider range of constant torque, typically form almost 0 Hz to 60 Hz, and constant Hp above their base speed to the maximum rated RPM which is typically 5-6K RPM. A vector motor can either use a shaft encoder if absolute position is required, or typically w/o an encoder but run in sensorless vector mode which gives around 0.1% speed regulation. Vector motors can only be used with a VFD, the standard 1340GT 3 phase motor runs well in the 15-90 Hz range. There are many vendors for the Hitachi WJ200, as well as other VFDs. The WJ200-015SF has been very reliable and works well with the 1340GT, the recommend programming parameters have been posted and/or are available from QMT.

Recommended vendors are below that also provide warranty and technical assistance, there are other on-line vendors. Please beware that there are many VFD models that may be very close but are not the same, some models lack a fan and require mounting to a heat sink. A 3 phase input VFD cannot be run on single phase without a significant derating and often require other components to function properly. A braking resistor is required for quicker stopping times.








						WJ200-015SF
					






					www.driveswarehouse.com
				











						VFD, 2hp, 200V, Single Phase, Sensorless Vector, I
					

VFD, 2hp, 200V, Single Phase, Sensorless Vector, IP20, High Starting Torque




					www.wolfautomation.com
				



Mark


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## advmaker (Aug 28, 2020)

Thanks a lot Mark, this is very helpful.

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