With the 6040 becoming operational and the Grizzly being rebuilt, we don’t have much use for a 3rd mill, the Sherline won’t make a good mill without significant investment, and its current limitations shouldn’t necessarily make it a bad lathe. It was originally a lathe so I plan to turn it back into a lathe.
Initial State
The Sherline was set up as a mill with a vertical axis.
There’s a lot of backlash in the X axis (to avoid confusion, the axis that goes left/right when looking at the machine, or to/from the lathe spindle)
There is only one spindle belt, there was a prior harvesting of the lathe belt to replace the broken mill spindle belt
The Y axis (forward/backward when looking at the machine) has a little bit of backlash, but far less than the X axis.
The Potentiometer for the lathe spindle is missing. Ideally this should instead be controlled by the controller
The Y axis motor has a broken pin
We actually have lots of tooling and accessories (such as boring bars, etc)
Problems to overcome
Spindle speed control should be controlled by the controller so dynamic speeds can be utilized.
Tool holding, there’s only one tool holder, a future improvement would be to make an automated tool turret, the Y axis bed is quite large so right now a lot of tools could be mounted in individual tool holders.
Work holding, there’s no chuck I could find, determine if we have collets that could work
Swing over Y axis bed is quite short. Tools probably will need to hang over the edge, probably not that bad, but make sure there’s nothing else to be done.
Coolant (seems the machine is fairly well set up for coolant, might be nice to set it up at least as an option.
Shield – Before getting it working as a lathe, it seems prudent to build an enclosure to prevent accidental flying objects.
Questions to anyone who knows
What’s the state of the computer and controller? Would it be better to use a GRBL board or use the current setup?
Anyone know of any concerns that I’m missing?
Work I’ve done at the time of this post
Opened headstock cover to assess spindle
Swapped mill spindle belt back to lathe spindle belt
Obtained new drawbar for boring bar (though it requires some fudging so I’ll seek a better one still)
Removed milling UHMW plastic milling attachment to assess bed.
Next work I’ll do
Determine how the missing spindle potentiometer could be controlled via a controller
Clean the machine (lots of swarf and dust bunnies)
Remove mill Z axis
Relabel axis to be the more common lathe coordinates
Take measurements and photos
Notes
Lots of to those who have traveled before me on this machine. If this runs contrary to anyone’s desire for this machine, please let me know and I’ll stop and/or undo any work I’ve done.
I like this a lot, and I agree that we don’t have much utility for it as a CNC mill right now. A CNC lathe would be neat.
Keeping in mind that it’s been almost 5 years (!) since I’ve touched the thing:
Do you have pictures or more info on how it’s wired up?
Unless something has changed since I last looked at it, I think the current computer/controller combo is fine for now. When the computer inevitably dies due to conductive dust / filthy coolant ingress, we can see about replacing the controller with something that doesn’t need a parallel port. Right now I believe it’s Good Enough™ and effort should be focused elsewhere.
I’ll try to get it minimally viable first then see if we can task out improvements.
Since I like build logs, here’s my update for this morning:
I did some more investigation to get used to the machine, I started removing the z axis but it looks like I have more to go than anticipated and may require disconnecting the x axis ways to take it off.
I made some connector cables for the speed controller but now I’m considering using the mill speed controller instead since it is known to be working and is nice and enclosed.
Just a quick update, I got several hours to work on the lathe last night. It is no longer a mill !
Unfortunately I was too tired to think about taking photos, but here’s what I’ve done:
Axis Conversion
I dismantled the vertical axis (Z in the context of a mill). I took the opportunity to diagnose the (mill X axis, Z lathe) and the backlash does not appear to be a result of poor threads, but actually that the pillowblock had a lot of slop. I was able to fix it up so there’s about 20% of the slop that was present, but I think we can get it better.
The Y axis (lathe X axis) is pretty good and I’ll leave it as-is for now.
I’ve re-hooked up the motors and selected the best ones, so as far as the X and Z axis, I think we might be good to test the steppers.
Lathe Spindle
As far as the spindle. I swapped the mill spindle with the lathe spindle because I initially thought the lathe spindle had swap, but now I think it might have been a loose set screw. Both seemed good without running a dial on them, so we can evaluate which is better once I can start dialing everything in. The vertical mill axis (z) had a riser block to pull the mill spindle away from the rail. They are standard across the machine with tapered captive pins and indexing keyways, so I was able to move the spacer block over to the lathe spindle to give us some more swing.
The downside of the spacer block is that we’ll need to cut the enclosure to handle it. I might just get everything working without the spacer block and then raise it later now that we know we have the option.
We are using the mill motor which has the mill speed controller. That doesn’t give us programatic control over the spindle speed, but I’ll count that as a future upgrade.
Next Steps
Remove the spindle riser block for now and reinstall the motor again.
Clear out all the extra parts (nicely, organized, and ideally stored in the cabinet)
Clean and lubricate all threads, ways, etc. Ensure there’s no gunk (there was a lot I cleaned as I went, but it needs some serious cleaning. There’s caked dust from years of storage.
Validate wiring and install the end stops in a fixed fashion.
Boot control machine, configure new machine setup and validate motion.
I’ve decided, after some real pondering, not to go with the control computer that is already in the cabinet. I’ve had some success on another project building a driving board for larger steppers from a GRBL board (replacing the slot-in stepper drivers with just obtaining the step/direction/enable).
I’m going to replicate that using GRBL-mega and a RAMPS 1.4 board. An old Raspberry Pi will be the host computer and you can use a laptop or machine around the space to upload gcode via cnc.js
If (and really, when) the CNC computer dies, getting a decent replacement machine with a good parallel port is increasingly more difficult
cnc.js is really slick
Going with a RAMPS/GRBL Mega is pretty cheap and easily replaced if needed.
Spindle Motor
I fired up the old spindle motors and I’m not super impressed. They aren’t horrible, but given the time investment, and some silly things I’d rather not go in to detail about, I’ve decided to go a different direction with the spindle motor. I’m actually going to try to drive the spindle via a large stepper/servo hybrid motor.
I’ve purchased a 2Nm stepper/servo hybrid motor and power supply. I built a little test rig to see how it operates and I’m pleased so far. The plan is to allow this motor to be driven both by the controller’s spindle PWM as well as. a C axis. I’m hoping that this can potentially become an XYC horizontal mill in addition to a lathe, giving us the ability to do some very interesting milling operations in-place.
Wednesday
I’m headed down to the space on Wednesday Night to work on the little beast. Here’s my todo list, hopefully I get through a lot of it. If anyone wants to join, please give me a heads up so I can plan distributing work.
Move all spare parts into a box
Remove the PC
Evaluate the electrical box, document current connections.
Clean the machine and lubricate
Remove old controller and store
Install Arduino/GRBL/Pi/Power Supply
Install endstops (may require part fabrication)
Test motion
Install new spindle motor (may require part fabrication first
So when we dropped this due to COVID, we had come quite a bit further with this project. Right now we are working on getting the couplers made. I think @Hekseskudd has one done; if anyone wants to help, let’s get this exciting CNC up and running. (I’m looking for help)
Yep I bored one coupler out to fit properly and will do the other one. I also have drafted spacers required to mount the steppers to the machine. I just need a measurement for thickness and I can machine those up.
to those who have traveled before me on this machine. If this runs contrary to anyone’s desire for this machine, please let me know and I’ll stop and/or undo any work I’ve done.
!