Lathe size

[Dick_Morris]

I'm not saying that you don't need a range of speeds from the gearing. However, when I was lathe shopping 15-20 years ago I found that most of the 12" Asian lathes had a low speed of about 80 rpm at 60 hz, twice what the Atlas 12" would do. (The lathe I finally bought third- or forth-hand has a slow speed of 75 rpm.) With the VFD I can slow the frequency to 20 hz or below, which should give about 15 rpm. It's nice to have when power tapping, single point threading to a shoulder, or to prevent chatter on large diameter work. Theoretically there are trade offs of lower torque and needing to watch the temperature on the motor, but after seven years of using a VFD and 3-phase, 1.5 HP motor these haven't been an issue.

[Gra2472]

You guys are awesome. Thanks so much for helping. You’ve given me some good points to think about.

[Sandiapaul]

What are planning on doing with the CNC lathe? Live steam parts? Because they aren't very many parts on a locomotive that make a night and day difference with using CNC. Wheels are an obvious exception. If you are planning on CNC I would save my $ for a CNC mill. However I would spend the extra money on a DRO for the lathe.

[Bill Shields]

I'm not saying that you don't need a range of speeds from the gearing. However, when I was lathe shopping 15-20 years ago I found that most of the 12" Asian lathes had a low speed of about 80 rpm at 60 hz, twice what the Atlas 12" would do. (The lathe I finally bought third- or forth-hand has a slow speed of 75 rpm.) With the VFD I can slow the frequency to 20 hz or below, which should give about 15 rpm. It's nice to have when power tapping, single point threading to a shoulder, or to prevent chatter on large diameter work. Theoretically there are trade offs of lower torque and needing to watch the temperature on the motor, but after seven years of using a VFD and 3-phase, 1.5 HP motor these haven't been an issue.

And what do you do when you need 10x torque multiplication to take large of heavy cuts and the motor stalls?

And get a so-so finish because the motor is clogging?

[makinsmoke]

Swing over cross slide as applied to the Grizzly page 1 means the top of the cross slide sits proud of the measured point of the bed rails by approx 2”? Radially from the theoretical center of the headstock?

Just making sure I understand.

Thanks,
Brian

[Ben.Smith]

I'd highly recommend shopping around the used industrial market instead of purchasing a new Grizzly (or similar) machine. When I first got into machine work a couple decades ago, I ended up buying a similar machine. It was really a much better boat anchor than a decent bit of machinery. There are a ton of great quality, used manual lathes (often with tooling) available all over the place. The quality of these pieces of machinery is vastly superior to the imported stuff. Plus, service and parts availability is quite a bit better. I've had great luck using bidspotter.com to source several pieces of machinery for my shop (everything from 2,000lb manual machines to 14,000lb CNC monsters). In your price point, you should easily be able to source and tool up both a decent manual lathe and mill. Definitely look for something in the neighborhood of 12" swing with back gears and a quick change tool post. A 5C collet chuck is also extremely handy. My manual lathe is a 1954 Monarch 10EE that I absolutely love. Even with its age, it holds a great tolerance, has plenty of power and I can still get parts for it.

[Gra2472]

What are planning on doing with the CNC lathe? Live steam parts? Because they aren't very many parts on a locomotive that make a night and day difference with using CNC. Wheels are an obvious exception. If you are planning on CNC I would save my $ for a CNC mill. However I would spend the extra money on a DRO for the lathe.

I already have a cnc mill that I use quite a bit. I’m slowly learning my way through the cnc machining processes.

Here’s a bit of honesty that might clear things up. I’m not an mechanical engineer, or a machinist. I’m an un-trained novice with mildly severe ADHD. I’m an historian with an emphasis on US history from the colonial period through reconstruction (1877). By trade I was professional locomotive engineer for 20 years, about half on steam. The last five years I was a dispatcher for a commuter railroad. Then my ADHD roared back to life due to the pain medication I was taking prior to and after back surgery. I decided to medically retire from the railroad at that point. I’m currently studying medical imaging so that I can work as an X-ray tech, though my wife is pressing me to be an ER nurse (she’s an operating room nurse).

I am using cnc because it’s much easier for me to make drawings and cam programs than to try to use a manual machine. I’ve done some manual machine work, but I lose my way in the steps and progresses. CNC is how I have chosen to address and adapt in a way that I can be both productive, and safe with my condition. I understand that’s it’s still dangerous. I know that the machine doesn’t do everything and make breakfast too. But with cnc, I don’t get ahead of myself and make stupid mistakes (been there done that, I lost 20% of my left thumb to that experience.)

I’m not really planning on building a production cnc shop, but I won’t complain if I get some small orders.

[Gra2472]

If anyone is interested. Here’s last night’s project. I made a jig to hold four journal box castings square in the vice. I have 16 of them to machine, so I wanted to have a repeatable means of work holding. There’s probably a better way, but I think this will work.

[pat1027]

And what do you do when you need 10x torque multiplication to take large of heavy cuts and the motor stalls?

Set it in the lowest speed available mechanically, run HSS tools and take lighter cuts. VFD's have come a long way in handling constant torque loads. I turned 8-3/8" drivers on a 9" South Bend 1/3HP 3P motor driven by a VFD. Easing through the cast finish was a bit tough on the tool but after that it was smooth sailing.

[Greg_Lewis]

Hi Gra:
Well, your question was about size. IMHO, there is no final answer. We use what we have. When I was shopping for a lathe many years ago, a dealer told me that 90 percent of what anyone does is less than three inches in diameter and within six inches of the chuck. I've built an Allen 10-wheeler and find that his prediction has been true. Most of the parts I've made could have been done on a 6-inch Atlas and a good number of them even on a Unimat.

So the question then becomes: Are you process oriented or results oriented? For me the fun is making parts. I don't mind at all the week it took me to machine the 8 1/2-dia. drivers on my 12-inch Atlas (with the toolbit hanging out in the air in front of the bed). Other folks would rather just get it done and move on. For them, my lathe would be a frustration.

So think about how many times you would need the maximum capacity and if there are other means of getting that work done. As GWRdriver in post #14 above says, if you have a friend with a 14-inch, the issue is less important.

What I have learned is that there is no substitute for mass. Get the heaviest machine you can. And a dealer once told me that many of the Asian machines have the same heritage but that the quality control between the final brand names varies. So buying from a source with a track record and good reputation is important.

And a comment for those who recommend used: It's a great idea and works well for many of us. But here in some parts of California, where the OP also lives, there isn't the industrial history that provides the supply that exists in some parts of the country. Used machines are not as common, and when one does come up for sale around here that's not clapped out or rusty it commands a premium price.

And Gra: If you ever pass through Fresno, contact me through here and I'll give you a tour of my meager shop.

[RET]

Hi,

What all the others have said is very true. As a hobby machinist, you will get a lot more bang for your buck in the second hand machinery world, but given your background, you would need someone with experience to front for you. I would recommend that you take a look at the Sherline website, not necessarily with the view of purchasing something from them (too small & light for your purpose), but just to see what they have. I believe they have both a CNC lathe and a CNC mill as a "turnkey" package.

About the year 2000 I bought a CNC mill turnkey package from Sherline (the only thing I had to supply was the monitor) and I used that for a few years to make parts like expansion links in mild steel and coupling rods in oil hardening tool steel for DART which is a small 7 1/4" gauge English tank engine. While the Sherline mill worked, it was too small and light for my purpose, so I decided to build a bigger, heavier machine. What I wound up with has an X travel of 16", a Y travel of 9" and Z travel of 8."

Since, because of your ADHD limitation you have a need for CNC, you might want to consider building your own CNC mill as I did. You can find the thread for the build on Chaski and you can also see another thread on the 3 1/2" gauge couplers which shows what the mill can do (cuts, tooling, etc.). If a mill the size that I built will meet your needs, you might consider going the "build it yourself" route. It isn't cheap, but quality machines never are. I used the same stepper motors and computer from the original Sherline setup, so while the machine is twice as big, the computer doesn't know the difference. By the way, the Sherline system can run all 4 axes at the same time if required so it is very versatile. I haven't needed to use all four at the same time, but there are a number of occasions (like the couplers and the power reverse) when I have needed to use 3 axes simultaneously (X, Z and A). A is the rotary axis.

I find that I like programming and using the CNC mill, its actually fascinating to see what you can do with it. The mill can work to tenths of a thousandth of an inch, but to program effectively, you need to know the speeds and feeds you would use for manual machining. Always use "climb" milling wherever possible, the finish is better and the cutters stay sharp longer.

You will find that the ideal shop is one with both manual and CNC machines and you use the one machine or combination of machines which best suits what needs to be done. In your case for manual machines, write down a detailed sequence of operations you need to perform on the machine and cross each one off as it is completed.

This is a whole new world you are entering. It is a lot of fun and there is a wonderful feeling of accomplishment you get when you finish making something and it actually works! Just realize that it can be dangerous too if you don't think about what you are doing before you do it. Plan ahead with all the steps you will need to make the part. When a design is needed, I usually come up with at least two, more likely three different designs before I do any metal cutting.

While there is a lot of freely offered expertise on this website, what you really need is someone not too far from you with both the expertise and equipment that you can draw on.

Welcome to our world.

Richard Trounce.

[RET]

Hi,

I missed the fact that you already have a CNC mill which you are slowly learning to use. Perhaps you can tell us more about it and its capabilities. With CNC especially, weight and stiffness are both important.

Richard Trounce.