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Thread: Get me over the hump

  1. #21
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    Quote Originally Posted by BCRider View Post
    Watching some videos of the 7x machines running and trying to make larger diameter pieces it's clear that the motor simply has very little power. And it lacks the back gear needed to run at low spindle speeds with a proper motor speed to develop the power it should have.

    On the other hand if you could spend that money on a nice good condition old South Bend 9 lathe that has a lot more of the big lathe features over these neutered Asian machines you would be world's better off. And I don't usually recommend new folks to the hobby buying used. But both of these lathes have enough similar shortcomings that in this case I'd say that a used South Bend or Logan would be way better.... With either of those if you can fit it in teh chuck and it doesn't hit anything as it swings around then you can machine it decently well and in a reasonable time.
    I find this statement to be odd. A little research shows that a

    From the factory, you could order one of two motors with a 9"South Bend lathe.

    A 1/4 Or a 1/2 HP motor, 120/240 Volt AC, 1725 RPM for the US market.

    Both of those are smaller than the 500 watt BLDC motor on the 7x16 lathes. Sometimes the "venerable old iron" is not as superior as it appears.
    There is a profound difference between spare parts and extra parts.

  2. #22
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    Lowlyslows: Welcome to the forum. Most of the preceding info is good advice except for the part about buying an asian import lathe. I would advise you to get

    something such as what BCRider has recommended. Then I would tell you that owning a lathe does not make you a machinist. When you buy it, do yourself a

    favor and make a bunch of projects so as to learn to use it. You do not want to be learning to machine while working on valuable, non-replaceable automotive

    parts. Good luck.

    Sarge41

  3. #23
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    Quote Originally Posted by danlb View Post
    I find this statement to be odd. ...9"South Bend lathe.

    A 1/4 Or a 1/2 HP motor, 120/240 Volt AC, 1725 RPM for the US market.

    Both of those are smaller than the 500 watt BLDC motor on the 7x16 lathes. Sometimes the "venerable old iron" is not as superior as it appears.
    The SB has something neither of those Asian lathes has..... A back gear. And it's a slam dunk in my book that the SB will turn large diameter steel or iron parts more easily than on either of those Asian lathes when the speed is turned down. At that point the motors are not making their rated power by a long shot and the 1/2 HP on the SB is likely stronger at the motor shaft and has the benefit of the greater gearing ratio multiplying the motor torque.

    It would be different in direct drive mode and running fast on small parts. At that point the 1HP at full power would walk away from the SB. But when turning small parts or softer materials that also like high speed not much torque is needed.

    This Old Tony did a couple of videos recently on the trials and tribulations of the 7x lathe. It's pretty interesting and part of these videos is this issue with using the variable speed and how it neuters the motor power when turned well down. Yes, good work can and has been done on them. But they have some major limitations right out of the box. And further I take it as a pretty strong sign that the 7x lathes have more "how to modify and improve" videos on You Tube than ANY other brand. And perhaps more than any half a dozen brands put together.

    https://www.youtube.com/watch?v=05vUCdzhoe4

    https://www.youtube.com/watch?v=HYOgmhpBUJs

    But the other side of this is the 10x22 option.

    Now I've seen in passing the 10x22 at the local places and thought that they looked pretty good. But I never did more than glance at them. So I downloaded and looked at the manual for the PM 10x22 and 10x30 lathes. And I see that this model does not have a back gear either and that it only has two pulley positions and uses the variable speed to get down to low speeds. At that point I sort of sighed and realized that it was a sheep in wolf's clothing.... And that led me to suggest the South Bend 9 as a possible option.

    But PM isn't the only seller. I went over to Grizzly to check out there 10x22 for comparison. They've got a 6 speed non variable G0602 and a variable speed G0752.

    Let's go have a look at how the Grizzly G0602 6 speed lathe does it as shown on Page 42 and 43 of THIS PDF LINK TO THE MANUAL. This machine does not have a back gear either. But it does have a rather interesting belt drive arrangement where they flip things around to get 3 belt driven direct drive speeds in the low range of 150, 300 and 560 RPM and where the 1HP motor runs at full power at each setting. The 150 and 300 RPM settings are particularly usable and capable for larger diameter steel items where all the torque is needed to get the job done. In fact given what I see in the manual I'd strongly recommend the G0602 over the Precision Matthews model with the variable speed. I'll bet the Grizz lathe is quite the tough grunting machine in comparison at this size range. It also has 3 other speeds for the high range. It uses the imaginative pulley shifting options as a way to make up for not having a back gear.

    Grizzly also has the G0752 with variable speed model which at least has THREE ranges from with the lowest being 100 to 800 rpm. But it would have the same issue of low torque and overall turning power when running at under 400rpm. Better to have the motor running at full power and use gearing to slow it down and increase the torque.

    And before you or someone else says that it has constant motor torque... well, maybe it does, many it doesn't. But even if it does have constant torque HP is torque x rpm and some constant factor thrown in. So if the 1HP motor at full power is running at 1/8 the RPM even if it has the same torque it's still only putting out 1/8 HP when it most needs the FULL grunt if we're trying to carve away at a large diameter piece of steel. THE variable speed DC motors used on these lathes are simply not a good idea. At least not over THAT wide a range of RPM of 1:8.

    The 1/2hp motor on the SB9 might have been half the power. But when the owner wants to turn something large in diameter and tough he's got that back gear which lowers the RPM even lower than the G0602's 150RPM and delivers the grunt needed to do the work. I suspect the 1/4HP model was intended for school lathes and were intentionally underpowered so the students had less chance of breaking things when they crashed into the chuck and other antics. Because I do agree that 1/4hp is too low for proper work.

    So Lowlyslows, if you really want to buy new instead of used from what I'm seening out of the 10x22's I'm looking at here in this thread I'd hands down go for the Grizzly 6 fixed speed model G0602. Yeah, it needs you to futz about with the belts a bit more. But at least the motor will be giving you all the torque it can at each speed range all the time and you'll be able to turn well at any of the 6 speeds.

    But still, if you were to come across a nice condition South Bend 9 that came with a bunch of associated tooling that could be a pretty sweet deal too. Even if it was a student model and you had to buy a 1/2 or 3/4 HP motor to perk it up. AND you'd have a longer bed that way too.

  4. #24
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    Quote Originally Posted by sarge41 View Post
    Lowlyslows: Welcome to the forum. Most of the preceding info is good advice except for the part about buying an asian import lathe. I would advise you to get

    something such as what BCRider has recommended. Then I would tell you that owning a lathe does not make you a machinist. When you buy it, do yourself a

    favor and make a bunch of projects so as to learn to use it. You do not want to be learning to machine while working on valuable, non-replaceable automotive

    parts. Good luck.

    Sarge41
    I totally agree on learning by making a lot of your own lathe tooling. There's at least a dozen things you will find handy as blazes which you can make with the lathe itself and a drill press.. and some "milling" with a hacksaw and files.... And the lessons you learn will build your skills rapidly at the same time it saves you having to buy some of the things.

    Of the old classic smaller lathes the two I really respect are the South Bend 9 models and the Logan 10 models 1825 and 1815. There's also the Myford Super 7 but if you're in North America I think you'll find that they run pretty high in cost even though they are all used at this point. Meanwhile the South Bends and Logans show up at not too crazy a price here and there if you're a bit patient or are lucky enough to live in an area where old used machinery like this is fairly common.

  5. #25
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    When I buying new lathe longest one
    Used lathe try righ length it may be shorter than get but you at use and do have a great choice.
    Today I found a 9 x 42" (24" CC) South Bend Lathe from 1949

    Dave

    Quote Originally Posted by Lowlyslows View Post
    Hey all,

    I am new to machining and could use some opinions.

    I am trying to justify purchasing a lathe for my hobbies, mainly building classic cars. But, because of my ignorance with the use of a lathe, I canít picture what I would use it for other than making spacers, bungs, and parts for creating or fixing tools. Not sure how often I would actually use the lathe.

    Looking at the Little Machine Shop 5100 HiTorque 7x16 Lathe and the Precision Matthews 1022v lathe. I have toyed with spending the extra $100 to get the PM 1030v but I donít know if I will need the extra length.

    Anyway, could use some knowledge dropped on me to help me get over the hump on whether to make the purchase or not. Machining is fascinating to me and I know I would enjoy it but only if I actually do it / use it to support my main hobby in any shape or form.

    Thanks in advance!

  6. #26
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    Tell us a bit about yourself and where you are from..
    I mean if you are an amateur blacksmith, can tig weld and work on hydraulics for a living or complicated machinery.. then its a plus and you probably will get on to it fast..
    But if changing your oil is a big deal, and you don't change a fan belt or power steering pump yourself, and building a steering wheel puller seems like a major accomplishmentm then a 7 inch lathe will keep you busy for a long time.
    If not go bigger, pay attention to spindle bore and swing over cross slide sizes..

  7. #27
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    I became interested in machining for pretty much the same reason. I did a lot of custom work on cars, and realized that I was sending work out simply because I didn't have the equipment to do it, so bought a lathe. (which lead me to getting other machines....)

    Advice, get the larger lathe. You can always do 7x14 work on a 10x20 lathe, but you can't do 10x20 work on a 7x14 lathe.

  8. #28
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    Quote Originally Posted by 3 Phase Lightbulb View Post
    Take the swing capacity, divide that by 2. Pretend that's the size of your pecker. Is that enough?

    Or ask your wife if she would be satisfied
    Quote Originally Posted by gambler View Post
    succinct but classy, with a touch of whimsy.
    Don't forget to factor in shrinkage. Not sure about the classy part but it was definitely funny...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

  9. #29
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    Quote Originally Posted by danlb View Post
    I find this statement to be odd. A little research shows that a

    From the factory, you could order one of two motors with a 9"South Bend lathe.

    A 1/4 Or a 1/2 HP motor, 120/240 Volt AC, 1725 RPM for the US market.

    Both of those are smaller than the 500 watt BLDC motor on the 7x16 lathes. Sometimes the "venerable old iron" is not as superior as it appears.
    As was said, the back gear makes the difference.

    Motor power is proportional to torque x rom.

    Take a motor of 500W 1725 rpm direct drive. At full speed, it is 500W. Slow it to 500 rpm, and it is about 145W, weak, but probably usable.

    So you want an SFM of 200. With a 1" diameter workpiece, you want about 750 rpm. power applicable is just over 200W. meanwhile the 375 watt motor on the SB is putting out full power due to using a belt combination to get that speed.

    Now you want to get 200 SFM with a 4" diameter part. You want about 200 rpm. That 500W motor is now producing a whopping 57 watts.... And the SB is still producing the 375 watts due to the belt drive.

    In back gear, which is normally a 5x reduction in rpm, the poor little 7x machine will be down to just a few watts at the back gears speed, while the SB is still producing 375 watts.

    How's that big 500W motor workin out for yeh?
    Last edited by J Tiers; 01-10-2019 at 02:53 AM.
    1601

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  10. #30
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    Dec 2018
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    All,

    Thanks for the responses! To answer some questions: I live in Virginia, I have been welding for the past 18 years (TiG, MiG, Stick, Braze), I spent 10 years as an automotive tech and have done some machining on brake rotors and drums.

    I agree, I am no machinist and wont be for quiet some time or ever. Just because you can machine something doesn't make you a machinist, but it is fascinating to me and I do want to learn. I am probably the biggest fan of This Old Tony as I watch his videos to fall asleep at night, haha!

    Anyway, it was suggested to me that I strongly consider the PM-1127VF-LB lathe as it has a bunch more features and stronger motor than the 1022/30 for $900 more. Some projects on the lathe I'm sure will help.

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