Conversion of Atlas/Craftsman lathe?

[jgourlay]

Gents, I've been reading about CNC long enough that I've just about got myself pumped up enough to go for converting my Atlas/Craftsman to CNC. If you would, I'd like some feedback about what I'm thinking.

The machine: 1944 12"x36" Atlas/Craftsman in exc. condition. No quickchange, belt driven (cones), w/backgear.

The work. 1. wood, so I'll need to southern engineer a router holder (bowls, chess pieces) 2. metal, including steel. I want to be able to do the truly basic shapes that are so ugly to do by hand: parabolic (convex and concave, both machined and ground finish), hyperbolic, spheres (machined and ground), as well as work using the milling attachment (I know this will be limited). So, brass balls, steel and aluminum parabolic reflectors, etc.

Vet my thinking please:

1. I want to preserve as much of the historicity of the parts as possible. In other words, I want to achieve functionally by unbolting THIS and replacing with THAT as opposed to MODIFYING this. This way, if I decide 5 years out to go with a better lathe, I can get a higher resale value off the machine than I could with a FrankenLathe.
2. Given that, can I integrate balls screws/accurate lead screws into the saddle? Or should I buy a used saddle off the bay? Southern engineer a saddle esp. for this project?
3. I am assuming I'll have to replace every drive screw including the main leadscrew (which is fine, I just need to know).
4. Am I right in believing that I need to drive the spindle with a motor that is also controlled by the control system in order to effect proper feed speed? Another way to ask this question: in a facing cut, will the control system progressively decelerate the rotational speed of the work as the cutter moves outward? If this is the case, does this count as "an axis"?
5. In my thinking, I'm counting 5 necessary axis' 1. spindle speed and direction, 2. axial (x) saddle motion, 3. transaxial crosslide (Y) 4. Cutting tool angle relative to axis (ie, if I'm cutting a ball the cutting tool needs to be continuously adjusted normal to the work) and 5. the milling attachment "Z" axis. Is this correct?
6. Do the current home-budget type CAM packages support lathe work and these axis? If not, and if I'm not a programmer, does this pooch the program?
7. Is it a major PITA finding itty bitty ball screws to replace all the screws in the milling attachment and crosslide?
8. Is it a major PITA setting the system up so you have both the CNC capability and good "jog" switches to allow "manual" use of the lathe? I ask this because there are going to be lots of days when the babies are screaming and all I want out of life is the run out to the garage, chuck up a piece of bar stock, and reduce its diameter by a half inch (in blissful peace and quiet).
9. Any of you guys done this with this lathe?
10. Crash detection: is crash detection a pretty well thought out issue, or is it going to be one of those hidden issues? I do a good deal of long/narrow spindle work so I've always good the steady rest installed....

[NC Cams]

Seems sort of like trying to turn a plow horse into a thoroughbred.

Some of the old Craftsman stuff is impossible to source anymore as Sears quit supporting that type of product decades ago - been there, done that. It is sort of hard to bolt/unbolt some things and you're better off with a more modern candidate.

To avoide the remorse of tearing up an heirloom, look into some of the Grizzly small lathes. They are affordable and the parts are readily available. You also won't mind modifying something that is not an heirloom.

Do a search of/for "lathe retrofit". SOme of the challenges you face are outlined. Do a search for Adobe Jim's postings on his lathe retrofit. You'll get further insight into what it takes to do what you''re planning/asking about.

[vulcom1]

I also have an Atlas TH54 and was looking at converting. I changed my mind and want to save for a smaller new type. I was going to make everything from scratch but it still requires modifying a lot of the components. Mine is going to stay stock and I will use it for making cnc parts for a newer one.
Just my opinion.
John

[in2steam]

My general thoughts on this subject are from about 2 years ago when I investigated the same thing, in order to have done this particular project I would have to purchase a 10F from a friend(about $800 at the time). I am a big fan of atlas machines and if I have my way I will own at least one of everything they made at some point in time for many reasons. But one thing they would at least in my opinion would have not been good for is CNC. They are easy to fix, they are fairly easy to get parts for, and some cases make. But things like belt drive and square ways(which are nice in some regards) would have made this entirely new machine vs a retro fit. I think if you are willing to stick out the process of doing so I would sell it and consider a import either done so or maybe if possible a southbend or logan. I agree with your historicaly aspect and I think you would be money ahead to keep in once piece instead of butchering it, because no matter how hard you try there will be something you have to change. Some parts although not many can be still had by atlas, or now Cluasing.

In regards to your questions,

1.Like I said above it would be hard, but not impossible. I held off and now have 2 lathes, one will be cnc at some point in time they both have prizmatic ways, one I think(not sure its a logan fairly old) might be flame hardenend which is also a plus.
2. You will not be able to intergrate ball screws with out drilling and tapping some holes, they would have to be well placed, if memory serves there is not alot of room in there, also you would have to remove the half nut lever and if you have it the cross feed assembly. Unless you went lower then the saddle but there might be some geometery issues then.
3.You only have one leadscrew?
4.This is software dependant, if you are using Mach then no. You can but you don't have to. I suggest you go to artsoft and look there instruciton manuals, they are good reading and might answer many of your questions and give an idea of what you can and cannot do.
5.You are getting way more advanced here, your lathe will have the normal 2 axises, the spindle control is seperate, in fact you don't even need to control that it can be left manual. The addtion of a milling attachment would actual be on the y axis, lathes are normally(i have seen y instead of x) x and z as they are 90 degrees out of normal perspective of machine cordinates. Since you don't have much cnc experience, you might want to slow down and just concentrate on the saddle and cross slide first. You would also be using a tool that can both face and turn, I also recommend a QCTP so you can change the tool out quickly, there would be no changing the angle on the tool only the tool.
6. There is no such thing, most of these start at several thousand dollars( at lest the ones worth anything), I don't know your budget but this was far more expensive when I came to pricing out then the rest of the whole project including my mill at the time. I have not looked in the last 8 months or so, so there could be more afffordable ones out there. MACH has some limited cam and what they call wizards I think with a little thought one could do alot work with those.
7.Yes and no, one thing you will find is that ground balls screws are not cheap, rolled ball screws are cheap, but they are not nearly as tight as ground. In some cases the ball screws that a rolled are no better then a good acme thread the only difference is they are typically quicker acting and less friction. A well desgined and constructed acme can be tightened wereas ball screws cannot.
8.The limits of how you put switchs on you machine is really up to your ablity you could set it up to look like a real cnc center if you want. Again this is software and hardware dependant.
9.Like I said above I decided against it, right now if I was to spend the money it would have taken I would by a Syil unit.
10. Crash detection would have to be done via a combo of soft stops and hard stops, you can run with out it al together, one, or both. Again if you are planning on mach then you should read there manual front to back it will tell you what you can and cannot get away with. There is not a practical way to have crash detection for a chucked item, that is just making sure you don't screw up.

Also I don't understand your thoughts in regards to a router holder could you elaborate?

One thing to note, I don't recommend people run wood and metal on the same machine, for mutliple reason, the primary being fire. Wood and some oils don't get along real well, wood dust also like to find its way into areas it should not be causing mainetenace issues, wood machines should be purpose built and not use metal ones as they tend not work well they typically spin to slow.

chris

[jgourlay]

Okay, well you guys have pretty much dissuaded me from doing this. I bought this particular lathe because I wanted to do wood and metal, but I have absolutely no more room in my shop. So I can't have a wood lathe and a metal lathe.

The 12" A/C has a pretty high top end as it was designed to do both materials. This means that I also have better luck with carbide tooling than a lot of home-machinists because my top end is almost 1000rpm higher than the top end of the standard-issue chicom bench lathe. And I've got back gear!

In2Steam, router on the lathe: the problem with cutting wood in a CNC fashion, or heck, even in a normal fashion, is twofold. First, once your tool dulls, forget it. You'll blow wood chunks at high velocity all over the shop. Also, the cutting edge angle has to be continously adjusted. This is very high skill. However, that goes away if you mount a router to the lathe.

So you chuck your work piece, or put it between centers, and month the router to the saddle and put something like a 1/4" carbide spiral upcut bit in it and go to town. As long as your not hogging material off you can both face and spindle turn all day. The finish isn't as pretty and forms not a delicate, but if you're just wanting to rough out something and then later go back and finish up with a tool or sandpaper, this is a great way to do it. Especially on dry hardwoods like oak.

I know what your talking about in terms of mess. After every pen, bowl, or top I have taking a sopping oily rag and meticulously clean everything down, especially when the next project involves the back gear.

On your CNC lathes, how to you get away with just an x/y axis when cutting parabolas and spheres? Round cutter?

[in2steam]

You need to either go to a cnc shop or go over to u-tube and watch some videos, curves are not a problem with cnc, esp if they are symmetrical, you are over thinking what you will need. Linear thought is hard get out of when you do cnc work at first, i am not a machinist(I am a millwright) but I was trained in cnc equipment I had the same problem. Its just like some one who can cut a cone or half sphere on a mill, albeit easier on a lathe they can be done on a cnc mill also. With a 5 axis mill you can cut a whole ball handle if you are good at programing.

Also you can use modified lathe tools to cut wood on the tool post, they don't last long but it does work, carbide would be the obvious choice here. Metal lathing you don't change your tool angle, you either grind it or change it on a QCTP there are some general form tools you use too. The older lantern style posts allow more freedom but also were a bugger to adjust to center, if you are not your cut will look like you have wood in the chuck....

I don't want to talk you out of CNC, you can still do it, its sounds like you need to do some more research though. When I did my research on the lathe, after about 3 times what I had money to spend on, i decided the mill would be a better alternative, of course my mill never made it home, I bought a model steam engine in trade plus the 9x20 lathe. So i am back to ground zero on cnc for the moment.

Like I said I don't recommend doing wood, I personally spent about 3 hours cleaning my 9x20 when I got it, the first owner only used it for wood, the second cleaned it some, but it still had a long way to go when I got ahold of it. It also sounds like you should investigate a ganrty router this might do what you want also.

chris

[NEATman]

One other option is to make a low-profile XY stack that can bolt onto the flat ways of your Atlas. Being a true "bolt on" it would not utilize the original carriage, and would be limited in travel, but it may just do the trick for smaller work. While in "CNC-mode" you could move the original carriage to the extreme right end of the ways, and even remove and reinstall the tailstock on the left side of the original carriage if you needed to manually drill holes. To turn the spindle on and off, you just would need to make a relay box that the spindle motor plugged into. Regarding the XY, perhaps you could "hack" one of these http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
I realize that it is 4.5" tall, so you would need to shorten the base, or perhaps remove the base entirely, and modify the dovetail to fit the square ways of the Atlas. That would reduce the height, and extend the travel along the bed.

There are also low profile pre-built XY tables available on ebay, such as this one (not mine!) http://cgi.ebay.com/Parker-Daedal-Po...QQcmdZViewItem

Anyway, this was just a wild thought I had a while ago for my 9" south bend, as I didn't want to modify it. Of course, that was before I bought an old Hardinge to retrofit.

NEATMAN

[jgourlay]

Your XY bolt on idea is pretty close to what I was thinking in a way. My idea was to take the current saddle, leadscrew, gearing, and pack them in cosmoline.

I would replace them with a saddle off the bay for this late, which I would then butcher as required. Replaced the leadscrew with a ball screw and either modify the screw to fit the existing A/C bearings, or pack those in cosmoline and manuf. some bearings for the ballscrew that would fit the current AC bearing hole pattern.

Frankly, I was thinking that for me the hard part would be everything that happened after Alibre and before the wires leading into the DC servo motors. I didn't think the electro/mechanical retrofitting would be that onerous. Guess I need to do more research, as you all suggest.

[jgourlay]

Originally Posted by in2steam You need to either go to a cnc shop or go over to u-tube and watch some videos, curves are not a problem with cnc, esp if they are symmetrical, you are over thinking what you will need. chris

I did what you suggested and saw a video of EXACTLY what I have in mind (a chess pawn). I was surprised to see how the machine cut the ball on the top of the pawn.

I was hoping you could answer some questions for me. First, it LOOKED like it was using a standard isoceles carbide insert, is this correct? Second, does that mean that when cutting the "facing cut" part of the ball, it was actually cutting with the side of the tip and not the tip of the tip?

Third, is this a "high stiffness only" cut? I ask that last because I once went to chamfer the edge of a shaft on my 12" Atlas/Craftsman. Now, I wanted a pretty good chamfer, .188" to .25" across the face. So I set the edge of the carbide insert at 45 degrees to the axis, and tried a very gentle cut. Oh boy, but the lathe didn't like that at all, not one bit. It made ugly noises, didn't want to cut, and scared me so I haven't tried it since.

Also, does the CNC process for cutting a CONCAVE hemisphere look just like the reverse of the pawn head procedure?

[in2steam]

Wow,

Well to start most of your questions are open ended I cannot comment on what someone else is using on there machine for tooling, only that you should use what works best for you and is the realm of your machine. You cannot change the basics of your machine, cnc does not really make it faster, or able to cut better, but it does do more consistantly and typically much nice then you are able to do by hand, and of course its repeatblity is very good also.
Carbide tooling is prefered in cnc machines for several reasons, but it does have some detractors that you should know about. Carbide is almost always recomended where the cutting speeds are at least double that of HSS, and the min. cut is always greater, thats to say that you need to work it harder then a piece of HSS. Carbide has for me atleast glanced across the surface of something before it cut, I had to apply more pressure and doing so screwed up the cut I needed, it like any thing else has it place and takes some getting used to if you used HSS, of course the converse is also true.

That said, I would assume that the person doing the cutting was using a tool which was designed to do both facing and turning, there many, many, many tools, I would be the last person to ask as to which is best there are more qualified people around for that one as I prefer HSS and use it about 5 to 1. At any rate yes, the cut you saw would require the most ridgid of setups. But you should always be set up as rigid as possible for the best results. There are boring operations and threading operations that require the tool to be far away from the post, but even then only as much as you need nothing more.
As for the process, I cannot comment as I don't know what they were running, typically a item which is more advanced would be done on cad/cam before being run on a machine as the line coding would be insane(I don't have a cnc lathe so I am at loss as to the exact coding) unless its a canned cycle of some type or a combo of the above. I recomend you download the manual for Mach and read it front to back it may enlighten you to the process some. Some of the other forums maybe able to answer the software specfic and coding specfic questions, I am by no means qualifed for that. Someone else maybe able to enlighten you, also provid the link you looked at and maybe that will help us understand what you are seeing. For the most part I am a hardware/mechincal guy so I don't mess with the programing part yet as I am not finished with my cnc machine.

chris