This article describes how you can use Mach 3, the popular CNC controller software, to automatically
Find the edges of your work piece (and therefore the corners)
Find the centers of holes and their diameter
Set your cutting tool at a known height above your work piece or table
What’s involved
This feature is very easy to implement and use and it will cost you almost nothing. You don’t even need a licensed copy of Mach 3. Here’s what you’ll need to do:
Download and install a free screenset for Mach 3 that has the buttons you’ll need to operate these features. There are a number you can choose from. Keep reading to find some of them.
Connect a wire to an unused input on your CNC controller board. This is the circuit board your steppers motors are hooked up to. You probably have a spare input unless you’ve used them all up for home or limit switches. If so there is probably an inexpensive way to add more. You may also have to add an inexpensive and easy-to-find capacitor if have a problem with electrical “noise.” I didn’t have to.
Go into Mach 3 configuration menu for ports and pins and enable the “probe” and assign the pin you hooked your wire up to. You might have to also change the “active low” setting from its default but that’s easy to determine and do.
Connect the other end of your wire to a touch plate. If you’re working with wood or other non-conductive materials you’ll just need a flat straight piece of metal for finding edges. There’s at least a few different kinds of probes and touch plates you can use to find the center of holes and their diameters. One is simply a short straight piece of metal rod mounted in your spindle. If you’re working with metal then your touch plate or probe will need to be electrically insulated from your work piece. So it will require a little more effort to make one.
It took me only about 40 minutes to get it working on my mill, although that doesn’t include all the research I did first. I also made a quick-and-dirty touch plate and I still need to make a couple of better ones. I’ll be writing more about that later.
More details
“Erniebro” on CNCZone didn’t come up with the idea for an auto edge finder, but he deserves an enormous amount of thanks for publicizing this method and making it easy for others to start using it. He designed the first screenset for adding this feature to Mach 3, made the video above, posted excellent instructions on CNCZone describing how to install it and patiently provided help and support for those who needed it. Others have built upon his work and made improvements, but if you want to try this I suggest you start with ErnieBro’s instructions.
One of the first things you’re going to want to do is download Erniebro’s Mach 3 screenset. I just want to let you know that if you’re NOT a registered member of CNCZone and logged in, you’ll get an error message that might make you think the file is no longer available.
There’s a very good chance you won’t have any problems getting your machine to work properly. If you do there’s also a very good chance that someone else has had the same problem and you’ll find the solution in Erniebro’s forum thread. Unfortunately, the thread has grown to almost 400 posts and it takes a lot of time to read them all (trust me, I’ve done it). So I suggest you take advantage of the “Search this thread” link you’ll find near the top of each page, just above the messages on it. You’ll need to be logged in to use it.
Hoss’ version
Hoss, of Hossmachine.info, has an incredible X2 mini-mill CNC conversion. He built on Erniebro’s work and developed another Mach 3 screenset with some additional features that you’ll probably want to use, especially if you have a mill instead of a CNC router or some other kind of CNC machine. He also uses an electrically isolated probe for his spindle instead of a touch plate that is held on the work piece. He includes plans for making one.
I still haven’t played enough with Hoss’ version to write about it yet. You’ll have to stay tuned for that and the story I have about the spindle probe I made and then promptly ruined the first time I tried to use it.
This picture shows just a small part of the steam engine exhibit area at the annual Cabin Fever Model Engineering Expo in York, PA. The show is huge and unfortunately I don't have any photos that can show you just how big it is.
“Cabin Fever” is one of the oldest and largest shows of its kind, and certainly the largest in the Northeast. I think you would be welcome to exhibit any kind of model at the show but most are made from metal. So it’s a bit of heaven if you’re interested in machining and metalworking.
What you’ll find
Model engines of every kind, which you will often be able to see in operation. There will be steam engines, Stirling engines, hit & miss engines, and more of all kinds and sizes. Compressed air is provided for steam engines that will run on it and internal combustion engines are allowed to run on small amounts of clean-burning lantern fuel.
Model trains, including “live steam” railroads.
Model steam boats and submarines operating in a huge indoor tank.
Other models such as cars, airplanes, guns and who knows what else.
Over 100 vendors selling all kinds of new and used tools, machines, materials, parts, plans, kits, books, and much more.
Seminars, demonstrations and more
Some suggestions if you go
Exhibit something, even if you only have one thing to show. Anyone can exhibit and it’s free with admission. You’ll get table space, a chair to sit in and some other perks. Admission is $10 for the entire weekend.
If you’re coming that way, make a small detour and and visit the Grizzly Tools showroom in Muncy, which is near Williamsport. It’s HUGE. By the way, you can’t stop there on your way home. They’re not open on Sundays.
There’s lots of things to do in the area if you have family members who don’t want to attend the show. You can tour the Harley Davidson assembly plant in York on Friday. You’ll also be in the middle of Pennsylvania’s Amish country and nearby Lancaster has a huge amount of shopping and other attractions.
There’s a concession stand at the arena that was better than many others I’ve experienced, but from noon on it was very hard to find a place to sit and eat. You may want to plan ahead and bring a lunch to eat in your car or go to a nearby restaurant.
Try to avoid the traffic and stop lights of Harrisburg at rush hour on Friday night, which is what my GPS led me into.
How about dinner after the show on Saturday?
The only thing I didn’t enjoy last year was eating dinner by myself after the show on Saturday. So I’d love it if you’d either join me or let me join your group. I’ll be easy to recognize. I’ll be one of the tallest people there and I look something like this, only a little grayer.
A couple of Harbor Freight digital calipers and a long-lasting SR44 battery. The top one costs a little more but it can also display fractions. More importantly, it has a bigger and brighter LCD display and it works a little smoother.
Unfortunately, my budget hasn’t allowed me to invest in a nice $145 Mitutoyo digital caliper like the one shown in the tutorial. I’m still using Harbor Freight digital calipers that you can buy on sale for about $20 or less. My first was HF’s least expensive 6-inch stainless steel digital caliper, which I think you can still find on sale occasionally for about $10. It still works well, although I did manage to break the tab that holds the battery cover on. Black electrical tape now does that job.
About a year later I bought a slightly more expensive 6-inch HF digital caliper that could also display in fractions of an inch. I found that feature to be pretty useless but its slide works much smoother and I really like its bigger LCD display. I haven’t seen this caliper (#98851) in my local Harbor Freight store in a while and it also recently disappeared from their web site where it used to sell for about $25. I’ve been using mine for about 3 years now without any problems, although it doesn’t get the amount of use a professional machinist would give it. I have verified its accuracy with a very good set of gage blocks, although I haven’t done it in awhile.
I didn’t know this until just now, when I was looking at HF’s web site, but their digital calipers have a lifetime warranty.
Battery Life
The battery in the Mitutoyo caliper is supposed to last at least 3.5 years. The batteries in Harbor Freight calipers seem to last somewhere between 2 months and a year. Many don’t seem to know this, but you can use either LR44 or SR44 batteries in them. They come with LR44s, probably because they’re cheap. You can sometimes buy 10 for a $1, but they don’t last very long because they have a lower voltage output. The SR44s are silver oxide batteries and they produce a higher voltage and store more energy. So they’ll last a lot longer before their voltage drops below what your caliper needs to operate.
I haven’t tried any name brand SR44 batteries yet so I don’t know what they cost or if they’re much better than the ones HF sells for 99 cents. You can either buy the cheap LR44s and constantly change your batteries, or you can buy the more expensive SR44s and change them maybe once or twice a year.
Your Opinion?
I’ve never had a chance to use an expensive digital caliper so I can’t compare my HF calipers to one. I’d love to know your opinion if you’ve used both, or if you have other knowledge about digital calipers that you would be willing to share with us.
My story is that I am a professional engineer and run my own consulting firm in the Southeast USA. My Dad (Bob Jorgensen) did most of the maintenance at his family lumber mill until he retired. Since the lumber mill was originally powered by two large steam engines and associated boilers, Bob was intimately familiar with steam engines and such. Being of a creative mind, Bob started making simple small toy oscillating steam engine models when he retired, and progressed to the point 12 years later where he had created from scratch (34) model steam engines, (3) hot air engines, (2) steam-powered bicycles, and a Stanley Locombile type steam automobile.
What Bob did not leave was a description of how he designed and machined all those engines and things, so my task since Bob’s death in 2006 has been to reverse engineer some of the engines that Bob built, and publish that information along with Bob Jorgensen’s original photographs and hand-drawn vellum sketches.
This process got me curious about steam engine design in general, so I began researching steam engines, and have a collection of about 1,000 old steam engine engravings on Bob’s website.
I also have gotten into steam engine animations, and can bring the engines of old back to life, like watching the actual engine run. I am currently designing a twin-cylinder steam launch engine, and hope to built that some day.
So what started out as building a simple web site to share some of Bob’s photos has turned into quite a learning experience, and I continue to be surprised every day at the variety and complexity of the steam engines designed mostly in the 1800′s, and the sophistication of the engineers who did this work. Luckily, there are a large number of public domain steam engine design books that can now be downloaded online in the US for free, and I have posted a list of about 100 of these titles on Bob’s website. It is a fabulous story of technology from the past that changed and modernized our world in a huge way.
“The price of success is hard work, dedication to the job at hand, and the determination that whether we win or lose, we have applied the best of ourselves to the task at hand.” -- Vince Lombardi
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