A few days ago, my kids were playing with my neighbor's son – he has a trampoline and is therefore the most popular little boy on the block – and I spotted my neighbor out, so I went over to say hi. My 3-year old daughter was talking to him and he was laughing his head off. I was curious what she was up.

My neighbor said, “your daughter just told me that you are building a CNC robot so you can make a Jonny 5 robot” and he chuckled. “Where do kids come up with this stuff?”

Hummm. I wonder.

I suspect she came up with the idea while she was holding a piece of aluminum angle I was working on and she asked if I was building Jonny 5. I told her that to build a robot, we first need a CNC robot that could help us make parts for a robot. I explained what CNC is (it isn't too complicated for a kid really) and showed her my plans. She is one of the most reliable and eager helpers I've ever had.

Here's the gantry (that's the part that slides over the top of the work piece and holds the tool doing the work) for our CNC table:

Essentially, you have a 2x4 with 3 1-1/2” holes drilled in it. On either side of the 2x4, you have a piece of aluminum channel (the type designed to be edging for a 1/2” piece of plywood) with some 3/4” EMT conduit on top of that. The conduit is tapped for 1/4” bolts.

If you try building this, there are two things that can be a bit challenging if you don't do this type of work much. First, you have to drill 3 holes in the aluminum channel to for the bolts to go through and you have to drill 3 holes for tapping in the 3/4” EMT. You also have to drill 3 holes from the sides of the 2x4 that intersect with those large holes you can see in the picture.

The holes for the aluminum channel are 3/8”; however, if you try to drill that large of a hole on aluminum with a hand drill, you will quickly discover your drill bit likes to dance. Use a punch - I like automatic punches – they are cheap and easy to use. This will put a small indentation in the aluminum; however, it isn't quite big enough, so use a smaller drill bit like a 11/32” and use it to make the indentation bigger, then switch to the 3/8” and it will do its job with fussing.

When drilling the EMT, this wasn't so much of an issue because the hole was much smaller so the indentation left by the punch was good enough. It is important to tap this hole straight. If you don't have a steady hand, I'd use some v-blocks on a mini-milling machine and use the machine to mount that tap.

The next challenge was getting the bolts in place. There are 2” bolts that have to go in those 1 1/2” holes, go up the 3/8” holes through the 2x4, aluminum channel and into the 3/4” EMT. Problem is they don't really fit. Here's a close up:

You can see where I used a 3/8” bit with my hand drill to notch out the bottom of the hole a bit. That helped, but didn't solve the problem. A hammer did.

Next up, we build the Z-axis assembly that will ride on the gantry.

If you like this post, don't keep it a secret!