Rebuilding A Bridgeport Mill

It looks like the Internet’s resident steampunker is moving up a century or two. [Jake Von Slatt] rebuilt the CNC portion of a Bridgeport Series II mill so it can interface with a computer. It’s a feat even more impressive than moving the mill into [Jake]’s garage.

The first step of the build was tearing out the BOSS 5 industrial microcomputer and replacing it with a Win XP laptop running ArtSoft’s Mach 3. This allows G-code to be displayed directly on the screen. The old power supply for the mill did give [Jake] a few problems. The Gecko stepper drivers that replace the old electronics couldn’t handle the voltage of the old power supply. That can be dealt with by opening the transformer and removing a few turns of wire.

[Jake] has been sending in a few of his hacks as of late, so it’s good to see Hack a Day has another fan, especially one of [Mr. Von Slatt]’s caliber. There is a problem with the mill modifications though – [Jake] hasn’t figured out how to program it. If any HaD readers would like to chime in on the best way to program G-code for the mill, feel free to leave a message in the comments.

40 thoughts on “Rebuilding A Bridgeport Mill

  1. G-code can be programmed by hand for simple parts, though you’d be better off to start with some sort of CAD software that supports G-code generation directly from the model. There are free versions out there, though I can’t think of any at the moment. SolidWorks (with an addon) and Surfcam are commercial versions used in many machine shops, however a single seat license is $$$.

    1. I’m thoroughly annoyed with Solidworks. I supported it since 2005 and it is was a great product with signs of being ported to Mac among other things.

      Then they became a Microsoft partner.

      The next three versions not only seriously in price but became buggy and unstable as all hell. And it didn’t show any signs of stopping.

      That said they release Draftsight for 2D drafting for free so I can’t complain too much. Especially since it works on Linux natively.

      I’m open to suggestions for 3D parametric modeling apps that run on Linux/Unix/OSX and don’t cost a fortune. Preferably with an NC package available.

      1. There are a couple out there, FreeCAD is probably the most feature-complete but it still can’t compete with SolidWorks or AutoDesk Inventor. There is also Heeks CAD which I’d put in the same category.

        Even if you have SolidWorks or Inventor, there are still no built in CAM extensions to generate NC Code so you still need a separate plugin or program for that.

  2. I have considered doing something like this with my Tree mill, but it’s been a few years since I’ve looked at the options. Better CNC control, with drip feed, would be nice. It would also be nice to remove some of the large cabinets to make the machine smaller.

    One gotcha is losing the original controls on the machine. They’re *very* good. I hate the thought of using a keyboard. Being able to jog the mill around with industrial toggle knobs, being able to control the feed rate with a knob that goes from 10 to 140% of programmed speed… those are things I’d hate to lose.

    I’m also not looking forward to losing the original DRO position display.

    My machine has large servos that work very well. Replacing them is not much of an option – the replacements would likely not be nearly as good.

    I’m not sure I want to spend a bunch of time messing with it. It’s the age old question of whether you want to mess with interfacing and cobbling as you attempt to reinvent the wheel (rather badly), or use a refined tool. A lot of people just recommend buying a machine with a better controller. Sometimes I want to do the project, other times I think it’s a waste of hundreds of hours of work on a one-off.. I only have 2 axis control at the moment – getting a third would be nice.

    If you decide to do a project like this, I strongly suggest learning how to use a mill first. That includes mandatory safety training with someone who really understands the dangers. Learning what is different about real cnc mills and non-cnc mills is important for selecting the right machine. Ballscrews, etc.

  3. On moving large machines… I’ve done it a lot. It can be fun. And it is quite dangerous.

    I like to hire wreckers to hoist the machines off of flatbeds or trailers. No way would I build a gantry when I can pay a wrecker $50. Don’t trust “eyebolts” for lifting. They can tear out. Don’t have single points of failure. Wrap chains around structure. To promote stability, lift from high points, not low points.

    I have a solid steel pole that is 10′ x 1.25″. It allows me to lift the machine. I use about 12 pieces of 3/4″ pipe to roll it across the floor. It moves fairly easily.

  4. Visual mill starts at $1k….goes up to $4k with all the bells…

    Rhinocam, a visual mill based plugin for rhino 3d, starts at $1k..$1.6k bundled with a copy of rhino…also available with “bells” at a significantly higher price.

    MecSoft, the makers of visual mill, has a free basic gcode genware called freemill thats a bit limited but isnt a bad place to start.

    BobCad/cam ($2.4k) is one of your better featured “budget” options.

  5. Bobcad can be had for well under 1k if you look around. I use v23 daily in my full time job in a job shop. its not nearly as powerful as mastercam / gibbs etc, however it costs about 12K less then them, so what do you expect


  6. Having worked with GCode fro 3D a homebrew 3D printer, I would recommend taking a look at ReplicatorG. It’s a nice, lightweight, open source interface for loading .stls (most big CAD packages can export to .stl) and generating GCode. The software that actually generates the GCode lives under the hood of ReplicatorG and is called SkeinForge. It has hundreds of configuration options and can be set up to generate tool paths for reductive milling instead of additive manufacturing processes. Finally, Pleasant 3D is a nice way to check the resulting tool paths visually.

    (SkeinForge is available separately, but is trickier to use:

    1. I looked at the result from Skeinforge for cutting a simple cube. It wasn’t pretty!
      Like do 2 sides, jump up and over back to the start point for the next 2 sides, then jump back over the cube to start the next 2.
      Lots of apparent repetition and jumping that you don’t need.
      BUT it does get you started!
      I didn’t spend long looking at it, but I couldn’t find options for things like tool diameter, backlash avoidance, and some others that I thought would be very useful.

    1. Oh! Thanks! I’ve been playing with HeeksCAD CNC but it was immediately clear that I need a little G code knowledge before I could generate tool paths. So I got the Smid book and have spent the weekend immersed in tool offsets, compensated cutting, and circular interpolation. Getting there.

  7. Last time I wrote GCode, I wrote my own program to automatically generate it.

    I was 14 at the time, I think.

    (Actually, I may have hand-written some GCode in Notepad later than that. Uphill. Through the snow.)

  8. I third the recommendation for HeeksCAD/HeeksCNC. I just tried it out on my latest project and was very pleased with the results.

    pyCAM is free and works well, but very slow at generating toolpaths.

    For 2D routing I use my machine control software ( to directly import and translate paths exported as DXF from Inkscape (or Altium Designer).

  9. CAMBAM is the best option for simple part making and PCB milling around. It supports many different milling formats and allows for 2.5D milling as well. Also its free unless you want to spring for the premium beta which I highly recommend as its a minecraft like update system 10bulls has.

  10. I don’t understand- Jake, can’t you just program the code at the machine? I never learned Mastercam, and worked as a carbide CNC machinist- we did all our programing at the machine.

    Unless you need to make crazy things like facial 3d profiles, why not just program at the machine? It’s not hard to learn the codes, if you don’t already.

    Try this book: “CNC Programmming- Principals & Applications” by Michael Mattson. I learned recently while I worked, using that current book. It made it quite easy, I highly recommend it.

    If you need advice for input programs for the crazier stuff, I can’t help. There was some cool new visual editor in the latest issue of Digital Machinist that looked very easy to use- maybe check that out.

  11. Ha! what a load of crap people are posting here. Although 3D cad programs should have gcode generation ability directly onboard (they do have an edge because they hold the unadulterated model), you can get good results from a 3 step process (design->gcode->machine)
    Since most 3D programs can export to stl, that is the lowest common denominator used most as intermediate file. For the gcode ‘programming’ we use either deskproto or pycam. Deskproto has a very nice interface, but cannot do some basic 2D stuff.
    And programming directly at the machine is something a machinist that is afraid to lose his job would say. There is little honour or sense in repetitive boring jobs.

  12. Drop me a line if you’d like some help on learning G-code. I’ve been programming by hand alot longer than I’ve been doing it with Mastercam. The automated route can save you time, but if you don’t have that option …

    I’d say for simple stuff, just do it the old fashioned way without G-code. You can still turn the handles on that thing, right? I think that learning tooling selection, feeds and speeds, and all the other stuff that goes in to machining was alot harder than G-code. Even on complex stuff, G-code just boils down to knowing geometry pretty well.

    Oh, my contact info: I’m a professional machinist. I do this stuff every day. I’d love to help. One thing to consider is that if you make the right contacts, you can just pay someone to generate the g-code for you, then tweak it by hand. There are services for that… or you can just ask someone nicely that has access to the software.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.