Turning a CNC Mill into a CNC Lathe

[ThunderPhantom]

I was replying to a post about those 3in1 combo machines and said i wouldn't touch them with a 10-foot pole. Then i got carried away and wrote this thought it might be worth sharing. Nothing beats a solid Bridgeport. Before i got my CNC lathe i turned my CNC Bridgeport into a CNC lathe plenty of times.

Chuck your work in the spindle with a fixture or custom chuck (I used R8). Make a fixture to hold 4 or 5 gang tools even for drilling or boring. Programming gets tricky since you're working with radius not diameter so you got to trick the machine. You need to program the spindle too. To avoid tool change hassles, write down offsets move to each tool's position with some clearance (like .100), and program in incremental. Or if you can set all tools to the same zero using the spindle readout. its worth it if you are making lots of parts without a CNC lathe or if your lathe has not arrived yet and you got a job to finish. Great for contouring too! So if you're building a home CNC mill keep that spindle beefy you might want to turn some nice parts. More spindle power never hurts!

 

[Jeremywalker]

a beefy spindle always pays off, and repurposing a CNC mill as a lathe is a smart move when you're in a pinch, trickier to program, but if you get the offsets right, it's a game changer and definitely beats dealing with those flimsy 3 in 1 machines, hehe

 

[IVGrbn]

I was replying to a post about those 3in1 combo machines and said i wouldn't touch them with a 10-foot pole. Then i got carried away and wrote this thought it might be worth sharing. Nothing beats a solid Bridgeport. Before i got my CNC lathe i turned my CNC Bridgeport into a CNC lathe plenty of times.

Chuck your work in the spindle with a fixture or custom chuck (I used R8). Make a fixture to hold 4 or 5 gang tools even for drilling or boring. Programming gets tricky since you're working with radius not diameter so you got to trick the machine. You need to program the spindle too. To avoid tool change hassles, write down offsets move to each tool's position with some clearance (like .100), and program in incremental. Or if you can set all tools to the same zero using the spindle readout. its worth it if you are making lots of parts without a CNC lathe or if your lathe has not arrived yet and you got a job to finish. Great for contouring too! So if you're building a home CNC mill keep that spindle beefy you might want to turn some nice parts. More spindle power never hurts!

Nice, your creativity with the Bridgeport is seriously inspiring! Turning a CNC Bridgeport into a makeshift CNC lathe is genius, especially when you're in a pinch or handling a high-volume job without a dedicated lathe. Programming by radius and using incremental moves for tool changes are clever workarounds. It's clear you'd never regret having more power from a beefy spindle!

 

[lowerMCs]

Okay, so let me see if I understood right. You convert the mill into lathe, but can you go back to using it a s mill after that? Any limitations or something like that?

 

[mill4nddrill]

Yeah, radius programming and incremental offsets make it surprisingly workable. A stronger spindle definitely helps with consistency and finish, especially on tougher materials.

 

[Kwanda_Rosman]

Hell yeah, converting your mill to do lathe work is DIY gold. Your radius‑vs‑diameter trick, fixtures for gang tools, incremental offsets, that's creative hustle. Just watch the rigidity. Mills aren't built for the torque of turning... don't ignore potential chatter or deflection if you're pushing it.

 

[badfish22]

If you're thinking about doing this yourself, you can use a tool plate with adjustable holders. It'll make setting things up way easier and swapping tools a snap. And a spindle encoder will sync those RPMs when you're playing with contouring or threading.

 

[feed&steve]

It's always good to see a discussion with so many useful ideas being shared over time. I wonder if @ThunderPhantom ever uses the mill for turning now that they have a proper lathe.

The conversion is temporary and can be reversed by simply removing the tooling plate from the table, allowing you to return to milling operations. One major point nobody has brought up is safety, as a part coming loose from a spindle fixture at high speed is far more dangerous than a thrown part from a lathe chuck. You also have to consider the machine's geometric limits, like a very short part length due to Z axis travel and no way to support work with a tailstock. The mention of a spindle encoder is key because, without one, you cannot perform true single point threading. It remains a clever solution for small, complex parts when you are in a bind.

 

[fr13d turkey]

I was replying to a post about those 3in1 combo machines and said i wouldn't touch them with a 10-foot pole. Then i got carried away and wrote this thought it might be worth sharing. Nothing beats a solid Bridgeport. Before i got my CNC lathe i turned my CNC Bridgeport into a CNC lathe plenty of times.

Chuck your work in the spindle with a fixture or custom chuck (I used R8). Make a fixture to hold 4 or 5 gang tools even for drilling or boring. Programming gets tricky since you're working with radius not diameter so you got to trick the machine. You need to program the spindle too. To avoid tool change hassles, write down offsets move to each tool's position with some clearance (like .100), and program in incremental. Or if you can set all tools to the same zero using the spindle readout. its worth it if you are making lots of parts without a CNC lathe or if your lathe has not arrived yet and you got a job to finish. Great for contouring too! So if you're building a home CNC mill keep that spindle beefy you might want to turn some nice parts. More spindle power never hurts!

I've always thought about doing that, but the programming always seemed like a headache. You just made it sound a lot more manageable.
Have you ever run into issues with chip evacuation? I'd imagine the chips would pile up pretty quick without a proper bed