Introduction: How to Make a CNC Router From a Radial Arm Saw

A new CNC router was certainly not in the budget, but with lots of reuse, patience, and a few small purchases, my DIY CNC works! I can cut out and engrave things with computer control. You can certainly do better with more expensive components, but this project has given me the chance to learn a lot about CNC machines without spending a lot of money first.

A friend gave me his radial arm saw when he upgraded to a new miter saw and didn't have space for both. I had seen a CNC router made from a radial arm saw on YouTube and decided to give it a shot.

For now, I'll summarize what I did. I hope you find it helpful.

Before you try any of this, read up on woodworking and power tool safety, then proceed to Step 1...

Step 1: Begin With the End in Mind

This video gives a quick tour of the finished CNC router and all its major components.

Step 2: Materials and Tools

I did a lot of "use what you have" design of this machine. If you find clever ways to reuse old stuff for a similar project, please post it in the comments. You may have to buy some things that I already had lying around. If you do, try browsing your local thrift store, or look online.

For me, some of the items were reuse:

  • Radial Arm Saw (Mine has convenient tapped holes in the bottom of the motor assembly that were originally used for shipping.)
  • Cookie Tin
  • Old Laptop power supply
  • Old PC
  • Parallel printer cable
  • An old plastic toboggan
  • I already had a trim router like this one: Amazon
  • Obsolete non-standard phone chargers for use in the car make great voltage regulators for low-power control components and what else were you going to do with these anyhow?
  • Abandoned printers (I have collected several of these from various sources, including friends, my alley, the curb, freecycle.org)
  • An extra cabinet drawer my wife gave me when we moved. You can buy one like it: Amazon
  • Miscelaneous screws, nuts, cotter pins and other hardware from countless DIY home improvement jobs
  • Scrap 16mm plywood and 4mm hardboard
  • Scrap angle and channel from steel shelving

Others I had to buy:

  • Drawer glides for the Z axis Amazon
  • 7+ Sealed deep-groove ball bearings Amazon
  • NEMA 17 Stepper motors Amazon
  • 5mm To 5mm Flexible Coupling Amazon
  • 3+ drivers. I recommend a few spares: A4988 StepStick Stepper Motor Drivers Amazon
  • 6+ Limit Switches Amazon
  • I bought a separate graphics card to reduce latency Amazon
  • I bought a separate parallel port card thinking that, if I fry it, I might just have to replace the card Amazon
  • For my lead screws, I used 1/4-20 threaded rod, a very common thread size in the US. This is close to 6mm, which would work fine if that's more available for you. I recommend buying these from the local building supply store. I rolled them on the floor at the store to check straightness first.
  • Coupling nuts for the threaded rod
  • Lots and lots of Gorilla Glue Amazon
  • 3 Cat5 patch cables Amazon
  • 3 Cat5 sockets Amazon
  • Solder Amazon
  • Solder flux Amazon
  • Pre-tinned wire Amazon
  • Perforated prototype board with copper dots Amazon
  • Female headers Amazon
  • Conformal coating Amazon
  • Heat-shrink sleeving Amazon
  • Zip-ties Amazon
  • Grease for the lead screws Amazon

Tools

  • Soldering iron Amazon
  • Heat gun (for heat-shrink sleeving) Amazon
  • Various saws, table saw (Amazon), hack saw (Amazon), even the radial arm saw for some things, although I don't recommend it for ripping
  • File for breaking sharp edges of cut metal Amazon
  • Wrenches, screw drivers, etc. Amazon
  • Hand drill (Amazon) and drill press, if you have it
  • Tap set Amazon
  • Sand paper Amazon

Tooling I bought for using in the router:

  • Slot 1/4-1/8-Inch Collet Reducer Amazon

  • 1/8" 17mm CNC Router Bits Double Flute Spiral Set Amazon

  • 1/8" Flute Carbide CNC Router Bits Ball Nose End Mills 22mm Amazon

  • V-bit Amazon

Step 3: X Axis

For each of the three axes, you need to restrict motion to one direction and control the position with a motor and, in this project, a lead screw (first photo). As I mentioned earlier, I used a wire drawer made to mount inside kitchen cabinets. It makes a convenient stage for the workpiece to rest on while the router is cutting it. The weakness of this approach is that it's not very stiff in the Y direction. I improved on this by mounting bearings on the table where the sides of the drawer ride against them (second photo).

I extended the range of motion by removing the rubber stops and bending their supports out of the way. To drive the motion of the drawer, I mounted a coupling nut to the bottom of the drawer with a p-clamp (third photo). I drilled a hole through the clamp and nut big enough for a short screw to self-tap it's way in. I added a little glue to the screw threads to keep it from loosening. Make sure the screw and the hole don't interfere with the nut's threads. Make sure the lead screw turns freely in the nut.

I mounted the lead screw with a bearing on each end mounted in bearing blocks I made from hard board pieces joined with gorilla glue. I mounted the blocks in a channel of hard board. I mounted the motor on a bracket of hard board and joined it to the lead screw with a flexible coupling. I used 5mm x 5mm couplings so I could drill and tap one end to thread onto the lead screw. The coupling has set screws on both ends to keep it from slipping. The motors had round shafts so I ground small flats on the shafts for one of the set screws to hold.

The last critical piece of the axis is mounting the limit switches to the table where the nut reaches at the extreme ends of the drawer travel. I glued a piece of hard board to the bracket holding the nut to the drawer so it trips the switches.

Step 4: Y Axis

The motion of the Y-axis is controlled by the sliding rail of the saw. The trick to using it for this project is to mount the lead screw nut on the carriage. Fortunately, my saw has lots of useful threaded holes for this purpose. On both sides of the top of the carriage there were plastic covers held on with screws. Bingo! I removed the plastic covers and made a bracket of plywood to reach the holes at the bottom, reach over the top of the arm, and fit around all the protrusions. I added a couple of old pulleys on top of the bracket to add a counterweight for the router, but it wasn't needed after all.

Like the X-axis, I drive the carriage with a lead screw. The nut is attached under the plywood bracket in a similar way. The lead screw bearings and motor mount were reused from an old printer. The printer used a gear train so I attached the output gear to my lead screw by drilling a small hole through the gear and screw and installed a cotter pin. The bearing brackets required additional support for stiffness, so I built up some support with wood on the motor end and added a steel channel between the brackets. This lets me put a little tension on the lead screw. Limit switches are mounted at each end.

Step 5: Z Axis

My saw came with threaded holes for shipping, which are conveniently located on a flat surface that can be turned vertical as shown in the photos. I mounted a wood base to this surface, which holds the drawer glides, motor, bearing block and switches. I made a simple stage of plywood to ride on the gliders, driven by the lead screw. A separate router mount is bolted on, which may let me attach other kinds of tools to the CNC in the future.

Step 6: Driver Box

A big piece of this project is wiring. I made a lot of my connections in a box made from an old cookie tin as shown in the photos. Inside, I mounted the three drivers on a perforated prototyping board and soldered connections with wire to the copper dots on the back. I have attached a breadboard-style illustration showing the main inputs and outputs. My input power is an old laptop power supply. I use a couple of obsolete phone chargers to regulate my 3.3V for the drivers to match my parallel port card, and 5V to drive a small cooling fan I harvested from an old printer.

Since the drivers send no more than 2 Amperes, I got away with using Cat5 patch cables and sockets for motor power as well as for switch inputs. The parallel port on the bottom was removed from an old printer, too. I added a power switch on the side of the box to shut off all the power to the motors.

In the attached images, there is a wiring diagram and a table of parallel pin designations copied from the documentation for LinuxCNC, described in the next step. I used most of these pins in my project.

Step 7: Software

The computer runs LinuxCNC, which you can download free as a DVD image and includes the operating system and the CNC software. LinuxCNC supports many more sophisticated control systems. I am using the most basic parallel port control, which is well documented and can be set up with a wizard. The main limitation is the speed your computer can generate steps for the motors in real time (due to latency), a topic which is also fairly well-documented on their web site.

I found this program very helpful when troubleshooting connection issues from the computer to the limit switches: Parallel Port Tester.

To create the tool paths, I use more open source software (you will notice a trend here): I use PyCAM to generate the g-code. It's very useful, but you have to hunt for help on how to run it. Check out my next instructable on creating an engraving program using all Open Source Software.

I make 2D paths for engraving using Inkscape. PyCAM also makes tool paths from 3D .stl files, but I haven't tried it yet. I'll say more about that later, if I get the chance.

Again, I hope you find this project helpful. I have learned a lot and had great fun in the process. It is very rewarding to see the thing I made making things. I especially enjoy getting new life out of old hardware that would have been junked otherwise. Please post questions and comments, which I will do my best to answer.

You can find more of my projects at www.ChipsWoodShop.com.

Comments

author
MSawyer (author)2016-09-01

If you can find one Montgomery Wards sold a saw with a 30,000 rpm aux spindle for routing. I have one I am planning on doing the same thing with. I am using the depth control screw for the Z axis.

author
MSawyer (author)MSawyer2016-09-03

I have removed the gears and set the motor on top of the vertical tube. I am going to have to counterbalance the cross slide, probably with a gas spring in the tube.

author
ChipsWoodShop (author)MSawyer2016-12-17

Would you mind sharing some photos?

author
Molloy (author)MSawyer2016-10-02

were you successful using the depth control for the z axix?

author
ChipsWoodShop (author)MSawyer2016-09-02

I would love to see that! Please post when you do it. How are you planning to drive the jackscrew? Mine has a crank on the front that drives the screw through a pair of bevel gears, but it has quite a bit of backlash.

author
Molloy (author)2016-10-02

what do you think of using the arm raising/lowering mechanism for the z axis rather than building one?

author
ChipsWoodShop (author)Molloy2016-10-02

That's how I was going to try it initially, but it takes a bit more torque to drive the jackscrew than the smaller version does. The hand crank/bevel gear drive could be used to reduce the amount of torque needed, but it has a lot of backlash. Not that it couldn't work, this just seemed easier with what I had already. I have a couple of gas springs from my truck shell I started to use to balance the arm. If I get around to trying it, I will post what I learned. Thanks for the question!

author
MakerIan (author)2016-08-25

Very Very nice. I am having tool jealousy...

I've built a 3d printer or 3 and you could have saved some wiring using a ramps 1.4 shield, and can do some fancy stuff with an arduino. But thats always a money over time question I know. The common firmware for 3d printers doesn't take much mod to run a cnc mill. bonus they are RTOS

author
BalázsS5 (author)MakerIan2016-08-30

I love this "tool jealousy" expression! Beside tool jealousy I have side effects of skill jealousy and lack of time syndrome :) Thumbs so high for this project, awesome!

author
ChipsWoodShop (author)BalázsS52016-09-02

Thanks!

author
ChipsWoodShop (author)MakerIan2016-08-25

Thanks! You are right, of course. I was having fun learning with what I had, but I have looked at some of the other options. I actually did some of my first motor tests with an MSP430 (with Energia, it's sort of like Arduino).

author
MakerIan (author)MakerIan2016-08-25

I should have finished the video ofc you went cnc linux. Different toolchain, your way will scale up while the arduino and ramps hit their limit on the size of driver they can power right about the size of motor your at.

author
tipsyskipper (author)2016-08-30

Awesome build! Been wondering what to do with that radial arm saw in my shop. You've given me inspiration!

author

Thanks! Please post if you build one!

author

Thanks! If you come up with improvements, please post them.

author
TimothyJ999 (author)2016-08-30

Great Instructable and fantastic out-of-the-box thinking. I've had one of these saws gathering dust in my shop for years.

I thought this would be of interest to you, now that you have a 3D router. It's a poster showing digital wood joinery that wasn't really possible until the advent of CNC controls. The link below that is where you can download the gcode to produce the joints.

I just think it's pretty cool when a technology that hasn't changed much in a couple thousand years gets a reset because of technology.

https://www.flickr.com/photos/satiredun/1586830842...

http://www.flexiblestream.org/project/50-digital-w...

author

Thanks for the feedback and the links!

author
DylanD581 (author)2016-08-30

Awesome CNC machine! Much more affordable that a full-blown, feature-loaded CNC machine.

author
ChipsWoodShop (author)DylanD5812016-08-30

Thanks!

author
Lee Robinson (author)2016-08-28

I have a Grizzly bench mill with power long. travel, and 25" table Would love to do thid,so need info on the electronics. Am ex=physicist/engineer, computer programmer so the technicalities are not a problem. I just need to know what they are!!

author

If you have a mill already, you do NOT want to do it this way. The cuttin forces that you're going to see are going to be far, far more substantial and you'll stall out these drivers and motors the very instant the first flute of a cutter touches metal.

What model grizzly do you have? There are conversion kits and detailed DIY plans available for almost any Grizzly product you're likely to ever buy.

author

I forgot to ask; where do I find these kit and related topics? Lee

author

Okay, nice. Your mill was sold by Grizzly, but it's one of the more common benchtop mills out there. One of the earliest - possibly the original, I don't know - of that type was called the RF-30, made by a Taiwanese company called Rong-Fu. Look around on Google for Rong-Fu RF-30 CNC conversion kit. You'll find plenty of stuff available to buy off the shelf, or you can find the plans and make the mechanical parts yourself and buy all the electronics.

It's really a pretty easy conversion to do.

author

Hi Peter. Thank you for your reply. I have the G1007 which I purchased in 1995, along with a G1010 band saw, and a Phase 2 rotary table. I rebuilt the quill about 7 years ago with new bearings, and it is still going strong! I also have an old 6" Atlas/Craftsman lathe
with a 5" South Bend 3-jaw chuck!that I've had FOREVER it seems like! I spent many years building retractable landing gear for large RC model planes and even did some work for local auto parts stores/repair/parts. I'm pretty well retired now but like to keep my hand in on things. So the project caught my attention. I/m an ex-physicist/engineer, now 90, but still an inventive rascal of sorts!! I have to keep my 'ol noggin and hands working!! Lee

author

I used the A4988 StepStick Stepper Motor Drivers listed in step 2 to drive the stepper motors. You can use the "Amazon" links to buy any of the materials in the list that you don't have. I wired them up as shown in my cartoon schematic on step 6. I will add some more details about the parallel port pin designations.

author
BeachsideHank (author)2016-08-30

Your friend did you a
bigger favor than you know, I'm a bounty hunter freelancing the
recovery of Emerson Electric 10" radial arm saws manufactured
between 1958- 1992, yours may be one of them. Check out this link for
the details:

http://rasrecall.com/

In short, fill in their
online form with the data from the badge, located lower left on the
base front panel. They will provide you a free return prepaid FedEx
box for you to return the motor- simply dismount it, you can keep the
carriage too. Upon receipt they will cut you a check for $100 U.S.
this may take several weeks as it is a serial process, but the
money's good.

Radial arm saws are
more than robust enough for what you are doing, the design of them
revolves around a 1-1/2 H.P. motor used in a variety of positions and
with different attachments, there is little that is unknown about
their capabilities, I have restored Delta, Rockwell, and DeWalt
radial arm saws for decades now, and applaud your adaption using
contemporary control systems to give them new life and purpose.

Well done!

author

Thanks! I still use the saw sometimes, so I'll keep the motor on mine.

author

This is great! I had someone give me a nearly identical radial arm saw (and it doesn't have a blade guard, so likely a recall candidate). Have you done this with more that one saw? I think I might be able to track another one down. Thanks for the link.

author

I've done over a dozen, Emerson will pay for all you can get. I take it a bit further than just the motor, I have a home shop foundry so I melt all the aluminum from the saw, and save the steel rods, knobs, electricals for other projects. I also scrap out the copper windings of the motors before returning, Emerson seems to not mind this since the objective is to render the saw unusable forever. Play it right and this is a nice little revenue stream not many know about. ☺

author

Thank you!

author
3967 (author)2016-08-30

The machine looks like from a dystopian sci-fi movie :D .

author
ChipsWoodShop (author)39672016-08-30

Thanks! Maybe somebody needs a prop...

author
kev who (author)2016-08-26

how much did it cost?

author
ChipsWoodShop (author)kev who2016-08-29

The items I bought added up to US$172.

author
Yonatan24 (author)2016-08-25

This is INSANE, and especially because this is your first Instructable! You've earned a new follower :)

How much time did it take you to build it?

author
ChipsWoodShop (author)Yonatan242016-08-25

Thank you for such encouraging words! I have three kids, so I don't have tons of free time. I've been working on it among other projects for a year or so an hour here, a Saturday morning there, etc.

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Bio: Chip's Wood Shop is all about rewarding and enjoyable woodworking projects and ''use what you have''solutions to make all kinds of fun and ... More »
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