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PM1340 - the Best & Jacobs Full Custom Edition

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davidpbest

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#61
In my case, the VFD connects to the branch circuit via a plug, so I did not include a conventional fused disconnect.
 

Alan H

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#62
Yes, it
Yes, I've heard the party line that fast acting fuses protect the components. With only one load on the branch circuit, I still ask "protect the components from what? What electrical anomaly is going to occur that requires a fuse to protect the VFD if the VFD is the only device on the circuit?" No one has been able to answer that to my satisfaction. Some people wave their hands and start talking extemporaneously about "surges" and "lightening strikes" etc. and fine, if that occurs, my $300 VFD gets fried. BFD I say. LOL
Yes it would be a BFD. You'd have to spend the money to buy a new VFD and worse yet, deal with the funky Hitachi software to get the new one configured! I have fuses, 'cause I like fuses and an expert friend of mine explained that fuses and breakers are like people. They all behave differently. :)
 

davidpbest

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#63
After all I’ve done on this lathe, replacing a cheap VFD would be a piece of cake. Still looking for a cogent argument about what electrical anomaly a fuse would guard against. ‘splain that to me please. :)
 

mksj

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#64
One thing that people forget is that a fuse can protect the equipment from line surges, the other component is that the fuse maps closely to the overload characteristics of the VFD, a breaker does not. I have had 240VAC wiring shorts and despite being on the breaker the wire did not do that well, a fuse would have been quicker and resulted in less damage. So a fuse offers a higher level of protection, which is more important the more costly the VFD/electrical systems. But agree, in the 2-3 Hp range the VFDs are most likely considered disposable if they fail. Have not seen one fail yet, excluding the HY VFD's.

So on my PM1340GT I have a power disconnect at the machine and it is connected to a dedicated 20A breaker. My 3Hp mill is connected to a dedicated 30A breaker, it does have local fast acting fuses in the VFD cabinet. Both are connected to a sub panel with a commercial surge suppressor, and also at the service entrance. Out in Tucson we do get a lot of lightening strikes and the power can get a bit wonky when the power comes back on. I have had a few neighbors that had electrical equipment get fried due to the line surges, but this was connected equipment not disconnected. Given that fusing and holder can be had for around $50, it is a reasonable option, but a breaker can also be used. Most lathes and mills come equipped with fuses as the standard equipment.
 

davidpbest

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#65
All good points Mark - thanks for posting. I'm still happy with my decision not to fuse the VFD. To each his own I guess.
 

GL

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#67
David,

First - As others have said, very nice and inspirational work - truly hit out of the park. I find it interesting how many people who start in wood, find metal as a hobby and vice versa. Woodworkers seem to have an artistic sense that comes out in their metalwork. This project certainly reinforces that observation. Thank you for sharing your artistry and your time.

So questions (mostly because you have had a chance to live with it awhile and there's always something else to think about - the shoulda/woulda/couldas):

The base - I too like the build vs buy equation. As I look at your base design, that of bss1, and the purchased ones I see differences and similarities. The 1340gt is a bench lathe. In theory, if the "bench" it is mounted on is not flat, and is very rigid, it might be possible to overpower the bed and induce a twist that would be difficult to level out with the feet or would have to have shims installed between the mounting surfaces and the bench. Bss1's base has 4 feet near the headstock and 2 at the tail, similar to a "conventional" base. Purchased ones seem to follow a two rigid columns (headstock end with 4 feet) with a flexible section between - which might allow the base to flex instead of the bed. Your design, with the center channel, appears to be more forgiving. Do you think you lost anything with only having the 4 feet in the corners? Maybe in a perfect world, the mounting surfaces get machined to be in plane with each other. Did you notice this situation as you bolted it down, or am I just overthinking the problem (which is entirely possible)?

The VFD - There has been much praise and discussion about Mark's work. Based on the pictures, he too is an artist. There have been comments about just buying his system. I probably missed a link along the way, but is there a good way to connect with him?

Been looking for a new lathe for several years now. Your build and my last chuck adapter project on too small of a machine has probably pushed me over the edge. Time to get on with it. Thanks again.
 

davidpbest

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#68
Thanks for the glowing remarks - much appreciated. This was definitely a labor of love. This machine was under glass cabinet on tour for a solid three months with Taylor Swift as the warm-up act prior to local unveiling and touchy-feely encounters. Just kidding. But I'm close to pulling the trigger on my next customization project involving a PM935 mill. Hold your breath, this is going to be a Mardis Gras experiment in celebratory style. LOL

I'm certainly no expert on stands and lathe mounting arrangements, but I understand your question. Yes, you might well be guilty of overthinking this a bit, just like me. Two things were paramount in the lathe stand for my PM1340GT: 1 - it had to have all drawer storage below (no deep cabinets with hinged doors or shelves), and 2 - a removable chip pan. Bss1 and I were actually working on parallel paths at about the same time. Obviously, we took different directions in some regards, and my guess is that we're equally happy with our decisions (not speaking for Bss1, but how could you NOT love what he came up with?).

One of the design differences between our two stand builds is that Bss1 took a more traditional 4-pillar approach to the section under the headstock. The commercially available stands are out of the same school of thought, and I'm in no position to question or criticize that approach. It's probably the more conservative route, but those who know me at all would quickly remark about my rebel nature. The design philosophy with this approach is to support the headstock platform by mirroring the headstock base bolting arrangement. I thought a lot about this when I did my design, but all the concepts I came up with that mirrored the headstock base attachments were in conflict with the two objectives mentioned above. There is NO drawer cabinet that I could find that was narrow enough to fit under the headstock platform, and deep enough to make use of the space. I even explored a $4,500 solution from Lista and even that was unsatisfactory to me.

So as you can see, I elected to take a different approach entirely, supporting the entire lathe on a robust C-channel steel beam at both ends. That gave me lots of freedom to include a removable chip pan, and to have tons of flexibility below the main beam to use drawer cabinets for storage. I'm guilty of lathe leveling paranoia in a couple of areas (which I think is also your paranoia if I read your original post correctly) in that I elected to use fine thread leg levelers (coarse would have been fine) and I duplicated the lathe bed leveling arrangement by having one set of levelers at the floor interface level, and a second set of levelers at the support beam level.

Based on my experience with this lathe and the custom stand over the past year, I can offer the following observations:
  1. I'm glad I stuck to my goal of having all drawer storage below.
  2. I'm also glad I used drawer storage units that were full depth, and did not employ the flip-up-top variety found everywhere. I've been a sailboat owner most of my life and really value every inch of available storage space. Making my own cabinets below was worth the effort, but not something I'd advise for those devoid of OCD.
  3. After every job I do, I pull out the chip pan and rinse it down over a garbage pail, so that was a good decision too.
  4. As for leveling, I first made sure that the four corners of the stand were on solid concrete footing. This required drilling out my plywood subfloor and putting in 3" diameter aluminum supports sized to the difference between the concrete floor and the plywood subfloor above it. That gave the required "footing" for the lathe stand. Thus far, I have only used the floor leveling feet to adjust the alignment of the lathe bedways. The duplicate set of adjustments at each end of the C-channel were frills. As I move into my 70's they may come to serve their intended purpose, eliminating the need to get down at floor level to dial in the bedways.
  5. I bought and used an MT5 precision ground alignment shaft to dial in the headstock. This is a wise investment IMO no matter your lathe stand configuration. Saves a lot of time and makes it super easy to verify the headstock is precisely aligned to the ways. I found the one I bought on eBay. Here's an example: https://www.ebay.com/itm/5MT-LATHE-...697186?hash=item3d36298aa2:g:yFsAAOSwCGVX2Zw6
  6. Were I to do this over again, I would make a few changes. The leveling feet I used were fine thread 1/2-20 when coarse 1/2-13 would have been fine. The removable chip pan could use an additional 1/2" clearance under the C-channel - when it's full of chips, it's difficult to remove without the chips being displaced onto the top of the storage cabinets below. I think next time I'd use a conventional Alkyd enamel paint on the stand instead of the 2-part (expensive) epoxy paint that is very difficult to apply and clean up.
But from a leveling and alignment perspective, based on my experience with this setup, a six-pillar stand is not necessary to provide the required rigidity, or to dial in alignment so long as you anchor the four corners to a very solid footprint, and the stand itself is rigid enough to not go into helicopter gyrations on it's own when the lathe is under stress. The lathe bed of the PM1340GT responds just fine with four leveling points provided you also dial in the headstock after the ways are level.

I know several people with this lathe that have had issues with vibration from various sources impacting surface finish. Some of those problems have been the stand employed (which became the motivation for Matt to pursue a cast iron stand alternative), some have been badly balanced drive pulleys or crappy V-belts, and some have been harmonics from the motor with plenty of evidence that single-phase motors are worse in this regard. Although my stand design is probably a poster child for setting up tons of harmonic vibrations, I have experienced ZERO problems in this regard. I attribute my success in this pursuit to the fact that I swapped out the OEM motor for a Baldor 3-phase vector-rated motor, replaced the pulleys/sheves with new balanced cast iron versions, and also replaced the v-belt with Gates BX27 Tri-Power belt. See details here: https://flic.kr/p/N3Gobh If the machine is well balanced in it's drive system, I'm not convinced that a cast iron stand is required, but it certainly removes a lot of fear, uncertainty and doubt.

After all that, I will add this final comment: I got lucky as well.

As for the control system, Mark Jacobs is an absolute gem - a delightful person, sharp as a tack, with a knowledge of the control system subculture beyond imagination. I am forever thankful to him for his assistance in my education and his contribution to this project. Mark is present on this forum under the user name mksj - you can message him directly on this forum.

Hope this was useful - it was fun to pen.
 

Alan H

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#69
David, You mentioned drive pulley imbalance that some folks have suffered with. Did you replace both motor and machine pulleys?
 

davidpbest

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#70
Alan, I replaced the pulley on the motor and had the factory pulley on the lathe drive shaft balanced at a shop in town. The motor pulley is a TB Woods BK2878 - 7/8-inch shaft to match the Baldor motor, 2.95-inch OD. The belt is a Gates BX27 Tri-Power, 21/32-inch width, 13/32-inch height, 30-inch outside circumference. Fits perfectly for this pulley setup.
 

Alan H

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#71
Thanks David,
As usual, this is excellent information you have shared.

Can you tell me how you searched for and found someone to balance your lathe's drive shaft pulley? Having an idea where you started and better understanding what you asked for would be very helpful.
 

davidpbest

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#72
I asked around at various places to find an outfit that did precision surface grinding. Those guys have to balance their grinder tooling, and know the techniques and have the equipment. Took a while to find a path to someone willing to do it. I never got a straight answer on how far out it was and if it would have had any impact on surface finish, but they drilled a small hole that's about 1/8" diameter down about 2mm on one area of the center hub of the pulley to balance it - so it couldn't have been very far out.

There was lots of discussion about all this a year ago here, and I visited another PM1340GT owner near me (sanddan) who was the first to bring up the vibration issues. He ended up building a custom stand, and another member here (Rio) even went so far as to secure his stand to threaded rod he'd epoxied into the floor.

Here's the first thread that caught my attention: https://www.hobby-machinist.com/threads/how-are-you-mounting-your-pm1340gt-lathe.42112/
Here's another on the same topic: https://www.hobby-machinist.com/threads/1340gt-surface-finish-problem.55358/
 

petertha

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#73
I'm really looking forward to your mill project David. The lathe job was just top notch.

Regarding motors & belts & hinge plates, my Taiwan 14x40 showed some new vibration when I changed to a new belt. It was smaller circumference compared to my (obviously stretched & worn) original so I had to adjust the motor position to compensate. It didn't feel right running, I kept thinking the new one was too stiff or maybe wrong cross section for sheaves. But turns out the motor mount hinge plate needed tweaking. It wants a certain amount of belt tension, but more importantly it cannot free float like self-tensioning under its the weight. It starts to get bouncy-bouncy harmonics, you can hear it & feel it. There is a locking bolt to fix the motor plate I misinterpreted its use. I can also see this needing adjustment every so often as the belt wears.

Regarding a degrading or otherwise poor finish turning on these type lathes, I can vouch with my own experience that the power feed driveline is certainly something to look into when motors, vibrations & other issues don't seem to cure things. We live & die by the ability of the carriage to traverse smoothly & accurately for a good finish. Anything amiss in the power feed rod runout, alignment to its bearing assembly or apron gear mechanism it drives, will rear its ugly head & transfer that onto your work. My rebuild/improvements episode link below. I'm happy to report it runs much better than it ever did, even when new.
https://www.hobby-machinist.com/threads/14x40-lathe-power-feed-improvement.64907/#post-540127
 
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