Kent vs Victor lathe

great advice. I dont want to have to change anything but the controls. The kingston has no gears to swap. I dont know about the victor. I am trying to find a owners manual for it.
 
All the Sunmaster lathes sold by Kent, Acra, PM/QMT have universal gearboxes with no change gears, you can download the manual for the models at the Acra website. Grizzly Southbend are the same, as well as a number of other distributors. They all basically operate the same, when you get to the next level $$, there are more features like power drives, I have not seen any of these style of lathes with an ELS. All these lathes will outlast us, and are all very capable. If you want to look at them, then make take a trip out to southern CA (LA county where Acra, Kent, Victor and Kensington are all located). Worth a trip if you are spending this kind of money and you need to check out the machinery. As I mentioned, I own the Sunmaster lathe, and also installed the VFD control system an used my friend's Acra 1640, and they are very capable lathe, the Kent would be no different. The fit and finish is top notch, and there is no issues with rigidity.

My lathe is the ERL-1340 model (made by Sunmaster) that I purchased from PM/QMT many years ago, it has the a D1-4 chuck mount which I went with that because I was already heavily invested in chucks and tooling, otherwise I would have gone with the 1640 with a d1-6 chuck mount and a 2.5" spindle bore. Beyond that size, chucks get way too big and heavy, and most of my work envelope is small stock as well as a lot of metric. There are no change gears unless you need to do dp/mod threading, all feeds, metric/inch threading is done with the gearbox levers below, this design has been around for many decades. Victor is also the same, change gear is only for dp/mod, say it on the website. I also wanted to go with a lathe model that had been in production for many years and parts would be available for decades, as opposed to some Asian model that was imported for a short period of time.

Looking at picture in brochures and such, as well as comparing specifications, one often gets lost in the numbers as opposed to the what you need and the function of the machine. The limitation at this level is the operator and not the machine. Also when you start pricing out everything, you need to factor in that some machines come with two chucks, steady rest, follow rest, light, etc. where the Kensington and Victor do not. Cost of tooling will also be significant, and then the addition of a 3 phase converter if needed.


1740TVS (2-1/2″ Bore) Precision Variable Speed Gap Bed Engine Lathe – ACRA Machinery

acramachinery.com acramachinery.com

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Mark, the Acra 1740 looks very nice and stretches the speed range as far as I've seen on a lathe of that size. Lots of low end grunt but the top range looks to be 435-2300. That seems very wide for a 7.5 hp motor to maintain. I would have expected a little wider range in the middle speed to keep the hp higher over the 600-1200 sweet spot for that size machine when running in high. Dave
 
Any 17" lathe running at 2300 RPM is scary fast! My 15" has 2200 but has never seen it. I'm about to get a collet chuck for it, then I can let it rip!

Most large chucks cannot get to 2300 RPM anyway, but a small or smaller steel chuck can.

Add value for D1-6 and subtract for D1-8. D1-8 stuff is very uncommon, expensive and HEAVY. My D1-6 has a 3 3/8 through hole which is large enough for almost anything.
 
Beckerkumm said:
If you go the conventional route, you might also want to consider a clutched lathe. It isn't as important when running off a vfd but very handy and i'd argue more safe, when running of PP or RPC on a powerful machine.

Dave
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The Acra/Kent use a 3 speed head on the VFD models, so no issues with the grunt factor. The factory VFD versions of the Sunmaster lathes also come with an electric pressurized headstock lubrication system, they typically top out at 2300-2500 RPM. Interesting that the non-VFD versions by Kent is 1800 RPM. One also needs to consider the chuck speed rating when you get to the larger chucks. I primarily use the 1800-2000 RPM range mostly for finishing and polishing, big chucks at speed are scary, one reason why I like using my 5C chuck for the smaller stuff.

A 5Hp motor is very manageable if running off of single phase, 7.5 and 10 Hp you need a pretty big single phase service, and I believe the 10 Hp and above are all 3 phase in the VFD models that are available. Aukai who purchased the Acra 1440TVS (VFD version), they downsized the VFD from previous versions, so it also required him to run it off of his RPC. So I would be sure to check with whatever vendor/lathe you purchase if you are purchasing the VFD version, that you verify in writing that it can be run off of single phase.
 
The amps may be the limiting factor but I still am surprised at the motor/gear choices. The 16" machine runs a 5 hp motor while 17" runs 7.5 and the same machine in the big bore runs 10 hp. The bore really has little relevance to power needed although both 17" machines are heavier builds than the 16". The speeds imply a hz range of 25-120 unless I'm missing something. Given those three speed choices, 600-1200 rpm which is kind of a sweet spot are not using full hp. If I were spending 25K on a 17" lathe I'd want the 10 hp motor ( which is probably available ) and a 7.5 hp on the 16". I'm sure I'd never need 10 hp but also feel that for that money I'd want more than 3.5 hp at certain speeds, and certainly more than 2.5 on the 16" machine. I have no problem with the 5-7.5hp motors on a conventional geared lathe.

Dave
 
There is a huge issue about worrying about HP on a lathe. You concern should be torque. A VFD rated 5 hp motor on a vfd will run at almost full torque to 1/12 of its rated speed, or about 150 RPM. if it has any gearing at all, that is more than enough. Even for commercial work.

At 1/12 of its rated speed, at full torque, is only putting out 1/10 of its horsepower, with full load amps, but enough torque to rip the gears apart.
I encourage people with small lathes with 1.2 or 2HP single phase motors to upgrade their motors 1 size up when converting to a VFD. This is only for longevity of the windings and the electronics in the VFD. There are a bunch of technical reasons for this, but all of them disappear at the 5HP size and up.
 
All very fair points. For our use, the differences may not be important. My comments which probably weren't clear, was that I wouldn't spend the extra for the heavier 17" build unless removing more metal was part of the equation. It can be argued there are vibration issues with lighter machines although the 16" are still 3500 lb machines. A 1740 TVS with three speeds and a vfd will only remove the same metal as a conventional geared head lathe when the motor is running at 60-90 hz and the gears are proportionally the same on both machines. At lower or higher hz, the conventional will remove more. Feel free to correct me if I have that screwed up. Whether there is a need for extra turning power is a different issue. If I were buying a new geared lathe designed to turn X DOC at a certain speed, I'm not sure I'd pay extra for less DOC if I could compensate with a different motor. An 1800 rpm 7.5 or 10 hp will be the same frame size and not priced enough differently but the real answer is I'd pick the 16xx series unless there are other reasons.

Dave
 
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