# Lathe options - 12x36 up



## FlyFishn (May 18, 2020)

Hi All, first post here. I stumbled in to this forum searching lathes and found several threads that either were here or pointed here from other forums (practical machinist for example). So I think I at least found the right place. 

I am studying metal lathes as I would like to add one to my collection at some point. That will open up a lot of doors with projects. I got a floor mount drill press last year and that has equally opened a lot of doors - even milling with a cross slide vice (not ideal, and not "precise", but better than nothing in a pinch). 

At the moment I don't have any size parts/work to base the sizing of a lathe off of, however most of the parts I can think of are nearly all close to the chuck - within 3" or so in length. I do have some shaft ideas - perhaps out to about 18" (bearing journals). Max shaft diameter might be 2" or under. Of course, threading is going to be a big help. As to what pitches - I don't see anything other than standard pitch threads in my future, but that gets in to the root of my question. Power feed in both major axis (x and y) would be a requirement, as far as I'm concerned. I am not sure how important the ability of tapered power feeding would be, but that, again, gets back to the root of my question.

I like the styes that have gear selections with levers as opposed to change gears (with the exception being switching between standard and metric pitch threading - that I can understand). 

Like a lot of the points made in a lot of the threads I've read - the machine doesn't make the machinist. Part of the art of machining is being able to get good results in sub-par conditions. Whether that is less than adequate tooling or excess looseness in machine tolerances, getting to know a machine and the tooling one has to use is the key - and not taking off too much material. Having said that, and understanding that the import market is about all there is in the price range of the usual garage/hobby machinist budget, I can reason looking that direction as opposed to a quality used machine. I'd also rather not chase lucrative "quality" (read that as still operable and not worn out) machines around the country. I would, however, want to check a machine over before bringing home (so ideally picking up in person as opposed to having shipped). 

Back to the import options - I realize that there are a lot of die-hard machinists out there that frown on them. However, I am also a realist and have done enough research on machines to know that there are good results to come out of some of the choices out there. My drill press, for example - its from Taiwan and is older than I am. It's not a pretty machine, but again - it isn't the machine that makes the machinist. 

Given the 12x36 ballpark size - and the features I've mentioned - are there any options that jump out to you that are worth mentioning in that class? 

Are there any features that you would like to have that you don't, or that you have that you are darn glad you have? Are any of those features able to be added after-the-fact (like a DRO, CNC, power feed, etc)? Or is there an option, or options, that a machine needs to be built with from the factory?

What I am trying to figure out is how to not get myself in to the hole of out-growing a machine. The idea of getting a smaller, more basic lathe is certainly there. Then use that as a "starter" lathe and upgrade later. I suppose I'll see what time brings in ideas and options.

I did pass up a big floor mount 3 phase lathe, around a 14x50 or so, back in 2009 as I didn't have a place to put it nor 3 phase power. That is one of those situations that I look back on and just wish things would have been better on my end to make that work.

I have run lathes before in school - even CNC and ProtoTRAK controlled machines. Its been years since I have done any of that, though. 

Power is a consideration. I think single phase 220 is probably the most ideal. I realize there are ways to get 3 phase with a home-brew rotary phase converter. That isn't out of the realm of possibilities, but I think that is one more thing that could make for an inconvenience. If going to 3 phase is key to getting in to a category of non-out-grow-able lathes then it might make more sense. 

One last point/question:
My understanding is that DC motor drives for variable speed ability (usually seen on smaller lathes - 10x22 or less - as an option) loose torque at lower speeds within each range. Variable frequency drives supposedly offer higher torque. What comments can anyone offer in regards to this? All the lathes I've run have been constant speed 3 phase motors - geared and belt drive, 2hp and up. 

On the same torque question/point - how important is gear range/RPM selection? Like some of the Grizzly's have 9 speeds and some have 8 speeds - 70-2000rpm range. Then some Precision Matthews in the same size range have 12 speeds 70-1200rpm or so. My theory is still the same "machine doesn't make the machinist" here - that the limitation in speeds isn't a big deal, but I would like some deeper thought/perspective from those that are using either - low speed count or high speed count, or variable speed drive? 

Lots of points, topics, and questions, I know. Thanks for any further insight.


----------



## Skierdude (May 18, 2020)

Welcome to the forum. 
Like you I went through the same decision process few years back. I didn't want to buy too small and outgrow the lathe too quickly and I decided on 12x36 as the sweet spot for what I wanted. My want list ended up with camlock chucks, quick change gears, DRO, QCTP.

Here in New Zealand our options for second hand lathes is very limited so I chose to look at imports. The Taiwanese offerings in this range were superior to the Chinese options although the Chinese options cram in more features, just not executed as well as the Taiwanese lathes.
What I bought was a 12x36 from MachineryHouse here in NZ. It is manufactured by Liang-Dei. It looks to be pretty much the same as the Grizzly G4003.
I've been very happy with the lathe. The only annoyance I have is that having low and high speed ranges via pulley change it's sometimes a pain to have to swap the belt if I want to go to the lowest or highest speeds. I intend to fit a VFD one day soon.
Oh and don't forget -once you have the lathe there's a whole wide world of tooling you'll need !


----------



## FlyFishn (May 18, 2020)

Skierdude said:


> Oh and don't forget -once you have the lathe there's a whole wide world of tooling you'll need !



Thanks for the input. I am very familiar with the tooling aspect. I've collected quite a bit of "stuff" for other processes on other machines so I expect that. 

A quick-change tool post is another requirement of mine. I did catch where one of the options (phase II perhaps) was aluminum, whereas some of the import options are hardened steel. The hardened steel is the route I would go - aluminum doesn't sit well with me for a tool post.

The G4003 is one I've looked at. However, the G4003G or G0750G are better buys. The stand for the G4003 is an extra $425, whereas the G4003G is (from what I can tell) an identical lathe, different paint, with a stand and light for a couple hundred $ more - less than half the increase in cost with the added stand. The G0750G looks like the next logical step up, same size and gears, and adds knob adjustments for the feed rate/threading as opposed to the lever/pin adjustments. I know there are more options than that, however.

I saw there are different adapters you can get for chucks. I think my drill press is an R8 whereas the tail stock on this size lathe (12x36 or so) looks like MT-3. If I upgrade my current drill press with a keyless chuck and all it takes is an MT-3 adapter to get it on the lathe that would make it universal. I already have a whole pile of twist bits (cobalt) for the drill press - everything up to 1" (cobalt lettered/numbered/fractional to 1/2" then black oxide to 1").


----------



## mksj (May 19, 2020)

I looked at the G4003G and G0750G many years ago for my first lathe, but ended up with the PM-1340GT which offers a bit more working scope and also a higher build quality. Getting a better built lathe was a big issue for me having some poor workmanship on a Chinese mill. The G0750G requires quite a bit of change gears for different common threads, you would be better off with the G4003G which has a Norton gearbox and no change gears for imperial threading. I worked with a number of people that had the G4003G and went to 3 phase with VFD which gives a better surface finish, there are also less motor issues with 3 phase. You can either use an RPC or do a VFD conversion (or a few lathes have a factory VFD). A heavier lathe will for the most part be more rigid and less susceptible to vibration. 

The lathes come with standard features which differ my manufacturer and model, the forum is full of comparisons of various models that I would review. They all should have power feeds in both axis in the 12"swing and above. Add ons like QCTP, DRO, etc. are just that, add on's. You can buy them installed at the by the distributor or add them yourself, you will get a diversity of opinions as to the benefit/cost equation, boils down to how big a machine you want and your budget. You need to figure out what kind of chucks you will need and a collet system, most of the chucks thrown into these "lathe" packages are pretty marginal in my experience. Better to purchase 1 or 2 better quality chucks, or upgrade. Most of the "PM" lathes have upgrade or preferred packages. Everything is to a price point so when all these extras are added to the package deal, they are usually of marginal quality at the lower price range of lathes. 

Lathe considerations, they are all going to have similar general features, most newer lathes use either a D1-4 or D1-5 which gives you a number of options. Once consideration is spindle bore, the Grizzly in this size range are 1.59" spindle bore, if you want a factory VFD then the PM-1440BV comes with a 2" spindle bore. The G0709 is also worth looking at in the same price range. If price is a limitation I would look at the PM-1236GT, go 3 phase and add a VFD. Add some quality chucks and other accessories, better you pick them out and select what you want.

CNC is a completely different equation on a lathe vs. mill, I would not factor it in as practical at this point. There are no CNC kits for these lathes.


----------



## NortonDommi (May 19, 2020)

Why not look at a 14 x 40? That little bit extra capability will be handy more times than you know.  What *Skierdude *said about limited choice here and cost led me to Mac House as well. I bought a variable speed and love it.  Like everything it has shortcomings but works well.  Unfortunately I could only buy metrickery and I had to make some needed change gears.  Only 2 HP but I have only come close to slowing it on one occasion when I was doing something it was never designed to do.
  Go for the biggest spindle bore you can and don't pass up a 3 phase machine if the price is right.  VFD's have dropped in price remarkably in the past few years and are incredibly reliable.  I haven't touched the VFD settings but mine goes from 35 rpm to 2010 rpm  The chuck is the limit on speed.
  I believe PM has similar models.


----------



## Mitch Alsup (May 19, 2020)

I have a G4003G and I think that it is a great little lathe and about as big as I could put in my shop. Its only drawback is that the spindle can only pass a 1.57" in inside diameter. {This is just fine, unless you want to machine 50 caliber barrels (which I will never do) and where a lathe with a 2.1" spindle bore would be the ideal choice--that is a 14-40-ish sized lathe.} I have found that this lathe is much better at machining than I am..... In any event, I would buy it again in a heartbeat.

The PM equivalent is just as good.


----------



## FlyFishn (May 19, 2020)

Thanks for the information thus far. 

I found a series on YouTube (https://www.youtube.com/playlist?list=PLDlWKv7KIIr_Znhfg8obxwcduFee5Ub5z) on upgrading a Grizzly G0602 to variable frequency speed control with a 3-phase motor. Interesting idea and gives me a lot to think about - even adding variable speed to my drill press. I will have to see what the parts cost - and of course factor that in to the potential investment in a lathe then compare to options already equipped with variable speed.

The G0602 I think is too small of a lathe to invest in, but the principal of the VFD set up is neat. I would be curious how the torque works out - going back to my first post here. When run in low gear the input RPM from the motor can be higher for any given spindle speed, so long as the target speed of the spindle lies in the range of what ever gear or belt selections there are. So the higher input RPM would equate to higher torque, I'm sure. I suppose that may even be able to be adjusted beyond spec on what ever machine by changing the gear ratios. That may be pretty far out there and not necessary, but having all the modification ideas floating around there on how to upgrade these machines I'd bet there are ways to do that. Though, the principal of the variable speed drive is to eliminate, or at least vastly reduce, the need to change gears/belts in the first place.


----------



## DavidR8 (May 19, 2020)

On the subject of the 3-phase conversion, I’m in the middle of converting my mill to 3-phase using the 2 hp version of that VFD and a 1.5 hp inverter rated motor. 

When all belts are connected, below about 10 hz the motor has insufficient torque to overcome the drag in the mill.

Up around 30 hz and there’s enough torque to drive a 1/4 tap into steel. 


Sent from my iPhone using Tapatalk


----------



## FlyFishn (May 19, 2020)

DavidR8 said:


> When all belts are connected, below about 10 hz the motor has insufficient torque to overcome the drag in the mill.
> 
> Up around 30 hz and there’s enough torque to drive a 1/4 tap into steel.



Thank you for the information. That lines up with what I would have thought. Can you overcome the torque issue gearing down and increasing the speed on the motor? Or are there operations/tools you need to turn that won't get down in RPM with any lower gear at the motor RPM you would ideally need to run? A couple examples I can think of would be surface mills or hole saws. I don't think a normal diameter 2 or 4 flute end mill could be big enough in diameter to give you the torque problem you describe, but maybe I'm wrong.


----------



## DavidR8 (May 19, 2020)

I have the VFD programmed to go to 120 hz so my intention is to keep the belts in the combination that provides the most torque and then increase the frequency to the motor to get the rpm to the required speed. 
Other than rpm the motor specs are exactly the same as the 3450 rpm version so I’m confident that it will be ok at 25 or 30% higher frequency. 


Sent from my iPhone using Tapatalk


----------



## Mitch Alsup (May 20, 2020)

FlyFishn said:


> I would be curious how the torque works out - going back to my first post here. When run in low gear the input RPM from the motor can be higher for any given spindle speed, so long as the target speed of the spindle lies in the range of what ever gear or belt selections there are. So the higher input RPM would equate to higher torque,



There is a speed below which TQ drops off, and there is a speed above which TQ also drops off. To a large measure these speeds are about 1/2 rated RPM (30 Hz) and 1+1/2 rated RPMs (90 Hz). I am not sure why TQ drops off towards the slower RPMs*, but TQ drops off at higher RPMs due to motor inductance.

(*) possibly due to not enough pulses per second at really low speeds.



> I'm sure. I suppose that may even be able to be adjusted beyond spec on what ever machine by changing the gear ratios. That may be pretty far out there and not necessary, but having all the modification ideas floating around there on how to upgrade these machines I'd bet there are ways to do that. Though, the principal of the variable speed drive is to eliminate, or at least vastly reduce, the need to change gears/belts in the first place.



I only change speeds on my mill about once a week.


----------

