I've been cooking on this project a little longer than i'd like, but I've just had so many irons in the fire. However, I've just about caught up on making customer parts and making parts for the G0704 (lol). I've been reviewing maxspongebob's 1228 conversion a lot, and I think I have a good handle on where I am going to get started with my conversion. I've also been using the lathe a lot manually, which is giving me a good ideas for the enclosure, stand, chip collection, coolant, and the generally how the frame and enclosure should work. I want to build out the stand, chip tray/collection, and coolant first. I will set the mill on the stand and use it manually for a bit while I work on the control. Finally, I'll build out the enclosure. I'm just not sure how much space I need around the lathe to work it when it is fully enclose. It's seems more simple than the mill, but I don't want to build an enclosure then hate it.
Additionally, I've got my electronics picked out. I am going to go with a UC300eth-5lpt with Mach 3 at first. Risky move, but UCCNC mentioned they will officially do a lathe release and I'd like both my machines on the same control. So eventually the plan is to move off of M3 to UCCNC on the lathe. Also, I own Mach3, so for now this is a nice cheap route. I have an MX3660 with a blown driver, which will get me started with the two needed axis and will provide a BOB. Again, a nice cheap place to start. Obviously I will steppers, which I think I have both of. The lathe control is going to be so much more simple than the mill.
I still haven't ordered ballscrews. I am on the fence about double nuts or single nuts. Everybody seems to struggle getting the backlash out of cheap double nuts, so what's the point?
I am going to add this turret from the get go. I saw a review from CNC4XR7 and he had good things to say. I am one dude and running two machines simultaneously is not of any interest to me. Especially when I rely on my mill to run by itself while I do things machines can't do.
The final part I am kind of on the fence about is going with a servo or just a BLDC for the drive. I am tempted for a servo, but it's going to be expensive. Not that the BLDC won't, but I can get a lot of BLDC for like 30% less than the servo it seems. The only benefit of the servo is if I set up the spindle as a C axis I could do all sorts of other fun stuff, but I'm not even sure I need it. DIY live tooling would be sweet though.
I'll grab some pictures as I start work, as is the lathe doesn't look too different from the pictures on the website.
I am flattered that you are looking at my design. I too, was on the fence about the motor. After spending a lot of time trying to find a new BLDC driver for the motor that came with the lathe, I finally found an adapter from Little Machine Shop that gives me CNC control of the motor. Here That being said, I wish I had gone with a servo to get a wider speed range. Note that with a servo and a timing belt drive you should be able to simplify your spindle indexing without needing to build a separate spindle encoder like I did.
Let me know if you need any help, I am glad to assist.
If you are trying to get the X axis nut inside the cross slide, then a double nut is right out. There's not enough space in the slide to fit a double nut. As for a double nut on the Z, plenty of space. I setup mine for 2 single nuts that are opposed. I never had to implement the second nut however as backlash was only a couple thousandths. I think that backlash on a lathe is less of an issue than on a mill. On a lathe the cut is only in one direction most of the time anyway so as long as you do your zeroing in the same direction as the cut then there will be less of an issue.
So with my G0704 I quickly ran out of patience for the stock motor. So I bought a better one, and then ran out of patience for that in the next two years or so. Now I have the 2.2kw BLDC and it will dish out more than the machine can handle. On top of that the 1128 VFD stinks the RPM pulses even when not loaded. So it's no good long term.
The lathe works great manually, but I assume I will be taking harder and doing faster cuts via CNC. Perhaps I am wrong? I was thinking maybe 3k RPM at the spindle would be good? With steppers the axis are going to be a bit slow anyways.
The 1500w motor below, the H model looks good to me. The H model is 6k, which sounds good to me, and I'd run it 2:1, which would mean quite a lot of power for this size lathe. It would also allow me to run at like 200RPM at the spindle or something, so not super slow, but slow enough I think.
But I will have to run an encoder (starting with M3 a single pulse) later in UCCNC I can run an actual rotary encoder. And there's no brake, so a servo of comparable specs might be better, although more expensive.
Thoughts on that all? My mill motor is the 2200w Adlee, and the quality of the stuff is fantastic. Also, they are real snappy. My mill motor arrived in just 5 days.
As for ballscrews, I agree with you on backlash, and I could always repack the nuts to get them a bit tighter. Did you cut your screws or get them custom made by the gent on eBay that a lot of people buy screws from? I was thinking about just buying the screws then cutting them on my lathe, maybe grinding them with some home made grinder on the lathe, or hoping the discount carbide will do the job.
The bearing blocks and what not should be simple, and I intend to make a similar tool post as you did, even with plans for the turret.
I found that the most important thing that I did in the conversion process was to make an accurate 3D model of the lathe bed and saddle. Then as I designed parts I assembled them virtually to see how they fit and what the clearances were. I think this made the rest of the build easier. I did it all in AutoDesk Inventor but Fusion 360 would probably work as well.
That 2.2Kw BLDC looks nice. When I was doing my build I could never find a good BLDC controller, but that one looks sweet. 3K RPM would be good for constant surface speed turning. Mine is limited to 2k RPM and it isn't enough for small parts. I use the original belt pulleys that came with the lathe. The high speed setting is about 2:1 while low is about 4:1. I don't think I have ever used the lower speed belt setting.
My encoder was the first part that I made in the conversion process. It works really well. I suspect that your lathe has the same gearing system that mine did. There is a 65 tooth spur gear mounted on the spindle shaft. I used that gear to drive an identical 65 tooth gear on my encoder. The encoder puts out Index and A & B signals with 500 pulses/revolution. I am using Mach 4 and an Ethernet Smooth Stepper which takes advantage of all of those signals to do threading.
There were several parts that I used the manual lathe to create before taking it apart. The encoder shaft was one of those. Also I turned the ballscrew ends using the manual lathe. I went threw several carbide cutters before deciding to just heat the screw ends to remove the temper first.
I made my own bearing blocks so that their mounting holes would match the holes already in the lathe. In the bearing blocks I used thrust bearings instead of deep groove ball bearings. I did this to let the screws float as much as possible around the same axis as the ballnut.
I bought the ball screws off ebay. They were already threaded and machined but longer than I needed. The screws both have a fixed end, with thrust bearings as I said before, next to the motor and the far end is floating with a single ball bearing. This made cutting the length and machining the end, farthest from the motor, easier.
Modeling the lathe seems like a good idea. I suppose I will start working on that.
Great info on turning the ballscrews. Removing the temper sounds easier and safer than putting my 4.5" grinder on the lathe somehow. Also, interesting idea on the thrust bearings. That's something I'll have to think about some more.
I don't think I've looked under the cover at the drive train since I cleaned the lathe up almost a year ago. I can't remember what is under there. I do recall thinking a motor upgrade would be easy on this compared to the mill. Doing a mill as my first conversion was a bad idea, so much harder in just about every respect.
The bearing blocks have an inner and an outer bearing. Below is a cutaway of both the Z and X axis motor side block. The bearings I used are 51201 on Z and F10-18M on X. Very simple.
Here is a cutaway of the spindle encoder. Bearings are 688Z and the encoder is HEDS-5540. You can pick any gear that matches the gear on your spindle. The gear I used is QTC-KSSY1-65, steel with 65 teeth but you could use a plastic or even 3D printed gear. The cylinder on the right mounts to an unused bolt hole that is already on the head and the encoder assembly slides onto it with a couple setscrews once the teeth are properly engaged.
I actually thought about 3D printing the whole thing but went with a more permanent solution.
Last edited by maxspongebob; 12-13-2021 at 04:17 PM.
I started on the CAD model and am still waiting on ballscrews. I've been looking at various options for how I want to do the enclosure. My shop is small and I am quickly running out of space. I intend to build the enclosure so that it has a chip tray and built in coolant system. It will be an iteration of my mill coolant system though with a lot less flow and way more refined. Anyways, I have been looking for a set of drawers (likely a toolbox) that I can put under the tailstock end of the lathe, ala Clausing lathes (and many others). I need the storage space as my two big tooling boxes are full of mill items at this point. Once I find something suitable, I will order the material and build the enclosure, chip tray, etc. with that included. I just haven't found the right stuff yet. That's pretty much all the progress I have made. My wife lost her job after her company lost their largest contract. So we are a little tighter on money than I anticipated. We aren't broke or anything, but I have been trying to be more careful with my funds. Meanwhile I just operate the business and continue to make money, which ultimately will allow me to build the lathe, but like I say i'm not exactly going spending money on it. Especially when I don't mind running the lathe manually for a lot projects.
Precision Matthews 1127 CNC Conversion
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