I am currently working on building myself a small CNC router, to be able to manufacture my own solid parts designed on my PC. Well, looking around online, there are lots of projects that are great inspiration, but many of these rely on expensive components.
One of the most commonly incorporated parts to be found in these designs are Dremel-brand handheld tools, using router bits, attached to the Z-Axis. Well, I took a look at Dremel tools, at my local hardware store, Wal-Mart store, Target store, and a few other places, but I've found that they're all very expensive, for use in my upcoming project.
Well, I tackled this problem today. I built my "router" on an arm that will be attached to the Z-Axis on my CNC machine. Hopefully, others could use a similar tool, and will find this interesting.
Step 1: Tools Required
Handheld Drill, 3/8" or larger chuck.
1/8" Steel-Cutting Drill Bit
3/32" Steel-Cutting Drill Bit
#4-40 SAE Tap
#1 Philips Screwdriver
#2 Philips Screwdriver
Step 2: Parts List
2 Timing Pulleys, and 1 Timing Belt of the same tooth pitch. (I found my set in a PC Printer from a dumpster)
1 Solid Metal Rod, 3/8" diameter (or 1/4", if 3/8" is not available).
1 #4-40 SAE Screw, to act as a Chuck
1 Dremel-Brand 1/8" or smaller Router bit
2 flanged bearings, with I/D the same as the diameter of the solid metal rod.
1 pipe, with I/D the same as the O/D of the bearing.
1 electric motor, AC or DC, high RPM, medium Torque. (I got mine from a broken cordless drill)
Brass hobby tubing, with I/D the same as the diameter of the solid metal rod.
Scrap sheet metal.
A handful of Wood Screws.
Step 3: Prepare the Rod
First, I drilled a 3/32" hole through the bolt, about 1/4" up from the end. Then, tap this hole.
Next, I drilled a 3/32" hole into the tip of the bolt, right in the center. I found it very difficult to drill right down the center of the bolt, not skewed to either side, but it was possible. This could be easier, if you have a heavy-duty drill press to use. After drilling this pilot hole, drill it back out to 1/8". Drill past the set-screw's hole, by about another 1/4". Clean up the threads for the set-screw after drilling.
Drill the center of the bigger timing pulley out to the diameter of the bolt. Slide the pulley all the way to the head of the bolt.
Cut a short (about 1/4") section of hobby tubing, using a pipe cutter, and Slide this on Next.
Slide one of the Bearings on next.
Next, cut some more of your Hobby Tubing. This has to be cut to a very exact length, so that there is a very tiny amount of slack between the bearings and the outer pipe, when fully assembled. I actually cut mine twice, to make sure I could get it exactly right. There is about 3 thousandths of vertical play, which is about exactly right. This fits between the two bearings, so that tightening down the assembly doesn't put stress on the ball bearings or the bearing races.Cut the outer pipe to length, and put the assembly into it, then slide on the other bearing, and tighten the whole thing down with the hex nut. Make sure that the rod spins freely, even when everything is tightened down securely, but, also ensure that the vertical play in the mounting of the bearings in the outser pipe is very minimal.
Now, insert the 1/8" dremel router bit into the end of the bolt, and install and tighten the set-screw.
Step 4: Prepare the Motor
The motor that I had that was closest to the right characteristics had a brass 9-toothed gear on its output shaft, originally. I used needlenosed pliers to gently pry this gear from the shaft, then pressed on the smaller of the two timing pulleys.
If your timing pulley is not a good fit, you might use epoxy to affix it to the output shaft of your motor. This has worked for me, on other projects, in the past, but centering the pulley is important.
Step 5: Screw the Assembly and the Motor to Something
Use your sheet metal to screw the outer pipe of the assembly down tightly to a chunk of wood. When you tighten it down, make certain that the assembly is exactly perpendicular to the wood. When preparing to put the screws in, pre-drill the sheet metal with the 1/8" bit and the wood with the 3/32" bit, so that the wood doesn't crack.
Attach the timing belt between the assembly and the motor, and pull the belt tight, then anchor the motor down, in the same way as you anchored the assembly.
Step 6: Wire Up the Motor and Test It Out.
Since I used a DC motor that was designed to run at 9.6V, I connected the alligator clips from my car battery charger to the leads of the motor, to test it.
Everything moved freely for me, and the router cut very readily, both plunging and cutting sideways.