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Let’s assume you have a working CNC machine that you’ve just acquired, but that you know very little about CNC. Let’s further assume it is a mill and that you will primarily be focused on cutting metal. You’re probably ready to start milling custom chopper parts, build a tool changer, or maybe scratch build a Colt 1911 handgun. With CNC, you can build almost anything and you’re chomping at the bit to get started on your pet projects.
Not so fast! Remember, you just got the machine and you’re a beginner. You’re not ready for those projects yet.
Here are 10 things you should focus on to maximize your chances of becoming quickly successful:
1. Buy Some Decent Cutters
Don’t get the package of assorted sizes of imported Chinese cutters of indeterminate quality. You don’t need the solid green unobtanium aerospace cutters from Men-In-Black-Cutter-Supply, just get some decent cutters from a reliable source that has reasonable prices like Maritool.com. Try for a name brand, perhaps one that’s on sale at a supplier like Enco. Knowing you have a reasonable cutter eliminates a whole bunch of variables that govern your success or failure. I would also go with HSS when you’re just starting out. You’ll eventually want carbide for a lot of uses, but HSS is cheaper and more forgiving. Get yourself a few sizes:
Nothing smaller at this stage until you’ve learned on less delicate cutters. Buy 2 or 3 flutes for aluminum and some 4 flutes for steel. I’d get 3 of each in each size to start. You are going to break some cutters, so just get over it and be used to the idea. It’s a good thing at this stage to remind you to wear your safety glasses because you will break some cutters!
While you’re at it, buy a full twist drill assortment. HSS from a decent brand on sale will work fine. I like the idea of replacing the ones I break with cobalt over time.
2. Get a Decent Vise, a Clamping Kit, and a set of Parallels
Yeah, I know, vises are expensive, but workholding is very important. Get a decent Kurt-style vise for your mill, it’ll be money well spent on a valuable piece of tooling that will last for years. In my shop I have used Kurts purchased from eBay and a couple of brand spankin’ new Glacern vises. There is sneaky stuff that goes on when you clamp a workpiece into the vise. If you don’t have a good one, the workpiece will shift and you’ll be wondering what happened.
You’ll need a way to mount your vise to the T-slots of your table, so you may as well get a clamping kit too. Any old kit will do. Buy the one that is on sale at Enco or some place similar.
Lastly, you’ll need a set of parallels, at least until you get proficient at making step jaws.
3. Get yourself a misting setup for coolant and use it while being paranoid about chip buildup
If your machine didn’t come with flood coolant, and isn’t set up for it, get yourself a misting setup. I got mine off eBay for about $100. It’s a Noga. There are a lot of different brands. Get a jug of coolant to go with it. I use KoolMist, but again, there are a lot of brands. Now train yourself to be paranoid about chip buildup. Recutting chips is bad for cutters and in the worst case leads to breakage. Being paranoid means you’re watching the cut like a hawk and you fiddle with your mister’s nozzle until you figure out how to position it right the first time and every time thereafter to blow away the chips from the cut.
4. Learn how to use MDI
Your next step is to learn to run your CNC as though it was a manual mill with power feeds and DRO’s on every axis. In the process you’ll learn some basic g-codes so that you have some idea what your program is doing the first time you run a real g-code program (that’s a little ways away yet!). It’s very convenient to be able to do this trick, and you can learn all about it through the CNCCookbook G-Code Tutorial. Read the first 4 chapters and you’ll be ready to start playing with MDI. Start out with the cutter way high and don’t try make any moves in the Z-axis so you won’t crash the cutter into anything. Practice making moves in X and Y. Until the cutter goes where you want it to and you’re not making mistakes.
5. Get yourself a feeds and speeds calculator and use it
You’re getting close to making your first cuts, so why not do yourself a favor and get a feeds and speeds calculator so you can make sure your spindle speeds and feedrate are right on that first cut?
Rules of thumb and setting up by ear have little place in CNC, though they can work out okay but not optimal when manual machining. CNC is a much tougher work style for cutters, and they’re much more dependant on you to get your feeds and speeds right from the get go.
Try out CNCCookbook’s G-Wizard feeds and speeds calculator for 30-days free. You don’t have to use ours, though we think it is the best one on the market, but do try to find one you like and use it for every cut. You won’t be sorry!
6. Get yourself a Z-height measuring gizmo and learn to use it to touch off your tool lengths. While you’re at it, get an Edge Finder and use it to touch off your Part Zeros.
Your machine needs to know where the tip of the tool is or terrible things can happen. As a beginner, you tell it by using a Z-height measuring gizmo of some kind. The gizmo will involve a needle that you lower the tool until the needle is zeroed, a touch plate, or you can even get by with a gage block. Learn how to use these to tell the machine what your tool length is. This process tells your machine where the tip is in Z. To establish the position of X and Y you’ll need and Edge Finder. The first thing you’ll do after sticking a piece of material in your vise and inserting a tool in the spindle is to set these zeros.
You can learn more about touching off and setting part zero from our G-Code Tutorial. Also take a look at our 2-part series on Tool Data Management for information on Z-Height Gizmos (more properly called touch setters) and tool lengths. Use your newfound MDI skills from #4 to start using your Edge Finder and Z-Height Touch Setter.
7. Learn to Tram your Mill and Vise
Tramming is what machinists call getting things square by sweeping an indicator around. It’s a basic skill everyone needs to learn. When you first start machining, get into the habit of checking your mill’s tram every time you walk out into the shop. You’ll know later on whether you need to do it every time, but for now, you could use the practice. While you’re at it, be sure you know how to tram your vise so the jaws are aligned properly with one axis or the other. Let’s don’t try to square you mill just yet, but tramming the mill and vise are a good step at this stage. For details on how to do this, refer to our Mill Tips and Techniques page.
8. Start out with aluminum, brass, and mild steel. Avoid stainless.
Okay, the very next step involves making some cuts. Sorry if it seems like you had to do a lot before getting there, but I did say I wanted to tell you some things that will help you succeed and there’s quite a few things in that category!
One more is to avoid difficult materials for your first cuts. Stick with aluminum or brass. When you’re doing okay there, graduate to mild steel. Only after you feel like you’ve pretty well mastered cuts in these materials, you’re not breaking or wearing cutters out too quickly, and your surface finishes no longer look like the material was attacked by a pack of rabies-infected beavers should you even consider a difficult material like stainless steel. Take a look around some metal supplier catalogs. Google up “Speedy Metals” for example (Google so you can see some other suppliers too) and look through their site. Get an idea what “Mild Steel” might be and the different shapes and materials that are available to you.
9. For your first project, learn how to square a block of material and make yourself a few sets of step jaws in aluminum
Let’s quit procrastinating and make some chips. For this step, you’re going to start by learning how to square a block of material. Get your saw and cut out some pieces of material that are slightly oversized to serve as vise jaws. Google “Kurt Vise Jaw Dimensions” to find drawings of jaws if you need some. As mentioned, cut the stock slightly oversized from aluminum. Now you need to square those blocks. Squaring means you will make a series of milling cuts until all sides are properly parallel or perpendicular to one another, at which point the workpiece is “square”.
The proper steps for squaring a block of material are described on my Turner’s Cube page. The recipe described there is one I got from the great book, “Machine Shop Trade Secrets.” Pick up a copy to continue your learning process.
One thing about the Turner’s Cube material squaring: I use a Face Mill, but you should start out doing it with multiple passes and a 1/2″ endmill. Why? Because Face Mills generate a lot of force. You can stall the spindle, yank the work out of the vise and throw it across the room, and other shenanigans a beginner could do without. Leave the face mill in a drawer if you have one already and do it with a 1/2″ endmill the first time until you know a little more what you’re doing.
Having square the material, your next task is to cut it to size by continuing to mill it until it is a perfect fit for your vise jaws (you’ll need 2 square pieces, one for each jaw). The last step is to drill and countersink the mounting holes.
Actually, I wasn’t completely truthful. Once you have mounting holes, the last step is to mill a step along each jaw, maybe 1/8″ square. Now you can use that step instead of parallels when you drop material into the vise. Over time, you’ll learn a lot more tricks with aluminum jaws, but remember: it all started here with your first set.
10. Graduate to CAD/CAM
Friend, you’re now able to do the basics. Sure, there’s a lot more learning to do, but you’re in a position to have a leg up on the manual machinist down the street who has a Bridgeport and no CNC. Your next step is to start pumping out the g-code. To do that, you’ll need to be proficient with CAD/CAM. This is going to be your biggest step yet. Neither CAD nor CAM is very easy to learn. I give myself 2 weeks to feel comfortable with a new program, and I’ve had the luxury of learning quite a few so far. If this is your first time, get ready to drink from the firehose. I wish I could give you a bunch of pointers to make it easy, but unfortunately it isn’t easy and every program is different. If you can, choose which programs you’ll use based on an ability to get help from someone. Ideally, help from a friend who already uses the software and is proficient. If not, consider a course at a nearby community college–it’ll be well worth the time and money spent. If you have no help available in your area, you’ll have to fall back on the Internet. Start by watching a bunch of videos. Try to follow along with your software if you can. Find the online forums where people go to get help with these programs.
Our article on digital tooling might help. We also did a survey which can give you some idea of the relative popularity of the various CAM programs. Most of these programs have a demo or trial. Check them out.
Congratulations, you’ve got some Basic CNC Skills!
Congratulations, you’ve learned enough to start doing some useful things with a little confidence. If you can design and generate g-code for basic parts with CAD/CAM software, you’re particularly proficient. But stay tuned because we’re going to follow up on this article in a week or two (okay, it took a lot longer than a week, but it got done!) with another installment of things you can do to reach the next level of proficiency. There’s always something more to learn–it’s one of the things that makes CNC so interesting!