cnc lathe overview 02

Here's a rundown of my CNC lathe conversion. The purpose of the vid was to demonstrated the CW/CCW spindle control, however I never got around to filming any actual machining using this technique. When using a boring bar, this will allow you to machine the inside of a hole first, then spin the spindle counter clockwise and machine the outside (back) of the piece too! All in one motion, no tool change required. It's pretty slick. It is a bit tricky to program, but for an OD fillet you just use the wizard, then convert all the X positive numbers into negative, switch all the G02's to G03's, then I replace "i0 k-..." with "R-...". This lets me face the part, bore the ID to the required size, skim the ugly off the outside and put a nice fillet on the inside and outside edge, all in one operation with one tool.

Category:

Science & Technology

Tags:

• lathe
• mach 3
• cnc
• grizzly 0602
• spindle control

[Trajiq187]

what kind of presision can you achieve?

[JohnGrimsmo]

@Trajiq187 I can easily make parts that are all the same within 0.002", tighter if I'm very careful about backlash and the way I choose my toolpaths. High quality ground ballscrews and tight properly adjusted ways would make a very accurate machine.

[Trajiq187]

@JohnGrimsmo Alright, i was just curious. How much does it cost you to build that machine (lathe include)? Im actually looking for a Mazak quick turn.

[JohnGrimsmo]

@Trajiq187 Totally different league than a Mazak or any high end industrial lathe. I mean this thing only has a 1hp spindle! But the lathe is only $1000 and you can expect to pay probably $1000 in hard materials for the conversion, less if you're thrifty. So for $2000-2500 in cash, plus a TON of time making the brackets and setting it up, you're golden.

[Trajiq187]

@JohnGrimsmo Yeah i know they are two different league loll i was just curious to know how much it cost to convert a manual lathe. I guess a bigger grizzly lathe will be more precise? What about the G4003? I was also looking a the Smithy Granite Max.

[JohnGrimsmo]

@Trajiq187 A bigger Grizzly lathe will not be more precise, but it will be stiffer and have a more powerful motor for HEAVY cutting. The precision comes in the way that you set it up for CNC and how well everything is adjusted. But even at 0.002" repeatability I can make pretty much anything that will fit fine. Most of my stuff is probably within 0.001" which is plenty for me. But for this price range of machine you have to live with certain compromises. 

[Liberty4Ever]

@JohnGrimsmo I wish I could buy the G0602 lathe without the lead screws, spindle motor & controls, and threading gear box. I won't need that for CNC operations. In fact, buying a stripped Chinese lathe and integrating a good CNC package would seem to be a great business opportunity. A lot of home machinists and small business owners would like to have a simple CNC system without making their own.

I think I'll have an easier time copying and editing G code than learning CAD/CAM software.

[Liberty4Ever]

@JohnGrimsmo It's easy to get excited, but I'm trying not to buy stuff I need to replace later. That includes steppers and drives, but it also includes lathe tooling. Aspiring to be a CNC lathe designer when I'm not even a manual lathe operator is the height of arrogance. I'm learning a lot about lathe operations and CNC on YouTube. How you use your lathe is very useful info. I might make a jog pendant for manual machining. EMC2 is good about that sort of thing.

[JohnGrimsmo]

@Liberty4Ever Yup, it takes time and practice to know what you will want in the future. I actually do a LOT of manual machining on my cnc lathe, just holding the keyboard and jogging the axis' as I want them. For full cnc work I've been using the stock toolpost with 3-4 tools in it, manually rotating it when the program calls for a new tool.

[Liberty4Ever]

@JohnGrimsmo I'm certainly thinking of some sort of CNC friendly tool holding. With no lathe experience, I figured I'd play with it first, as that stuff is difficult for me to imagine. I've been leaning toward the ability to put on the cross slide with a quick change tool holder for manual operations jogging in MDI mode, and swap to custom tool setups for short run production, probably with gang tooling, but I may manually swap tools on a QC tool holder at first while I'm learning CNC.