CB CNC Part 4 – Assembling X and Y Axis & making ACME Locking Collars

In the previous video I made the PTFE anti backlash nut blocks, and in this video I will now assemble the x and y axis as well as make the locking collars for the acme threaded rods.

So when I bought the parts for this machine I used aliexpress for smaller items, which I could buy in bulk saving quite a bit of money. But I decided to get the acme rod and aluminium extrusion from a local company called Ooznest.

I am now at a stage where I can start assembling the x and y axis of the machine, but I want to try think ahead and avoid dismantling the machine at future stages, if I can help it. The first thing I am going to do is fit the z axis c beam to the gantry plates. I haven’t finalised the plates for this part, which is what I will have to work on in the next video.

This machine will use three 500mm 20 by 40mm aluminium extrusions, three 500mm c beams, and one 250mm c beams. I decided to make a smaller machine first as I didn’t want to start cannibalise the x carve and realise I still needed it to cut parts out.

Here I am struggling to fit the gantry plate assembly on the c beam, and this was because I hadn’t tightened the machine screws so they would clear the aluminium.

Once that was done it went on nicely, and I could start taping some holes on the aluminium extrusion. The c beam mounting holes was already tapped but I am using longer machine screws so I need to extend them. I then placed some t nuts on the underside of the x axis, which will hold additional brackets to the y plates. TheFlamingChalupa suggested this to me and I thought it was a good idea.

I then screwed the y plates onto the c beam, using the drill to do most of the work and an allen key to finally tighten them. I am using stainless steel machine screws, which don’t feel are as hard as the high tensile variety.

I then mark the bracing aluminium which will fit between the bottom ends of the y plate, and cut that out on my mitre saw, which was coincidentally made on a CNC machine.

I tapped the holes and fitted this on.

The bottom brace, along with the aluminium corner brackets which will eventually go under the thick c beam will all help prevent play along the x axis.

I then slid the y axis in place, and assembled the base of the machine. This was pretty straight forward, as the end plates should pull everything together, and square the machine providing they were cut square.

I placed the t nuts on their machine screws and sliding the part onto the aluminium extrusion, lining up the holes of the c beam, and screwing them in place. I did place some more t nuts on the underside of the y axis c beam which I will eventually fix some flat aluminium bracket too. These are are still on the x carve and I’ll have to finish this later.

So I am loosing a bit of movement because the 40 by 20 aluminium extrusion is actually a bit longer than the c beam, so I’m going to mark these, pull them out and cut them.


I re-assembled the machine and tested the movement by holding the z axis and waving my hand around uncontrollably. The axes are very smooth although a little more so on the y than x. I will have to re-adjust the eccentric spacers on the gantry plate assembly at some point.

Once I stop enjoying the success of the moment, I noticed the x axis was not square to the front of the machine, or that back for that matter.

I’m getting contact here, but on the opposite side I was getting a 1.5mm gap. While the lead screw would eventually force this into place, I’d like to try assembling this machine as square as possible. I decided to remove the bottom brace, and re-checked the gap in case anything changed. I could have cut that at a slight angle by accident, but it didn’t seem to do anything. I also checked if the frame was square, which it was.

It is more likely that the plates could have warped or the c beam was cut a little off. There’s not much I can do about the plates, as they are birch ply, but while checking the c beam, which was fine along the long edge I noticed it was a tiny bit off along the short.

I decided to cut the x axis c beam and y plate brace at the same time on the table saw, so they were identical and see if that made a difference. The smaller piece went neatly between the c beam and while feeling the ends, I could tell they weren’t the same length either.

So I made this corner bracket, which goes at the back of the sledge. I’m pushing everything against this end here, and I’m going to clamp it down.

I ran the pieces pass the blade, taking off a shaving, and levelling the two faces on one side. I then flipped it around clean the opposite edge.

By cutting these pieces, I noticed that the tapped holes on the other c beam were slightly raised, and this has been removed by levelling on the sledge.

You can hear my nail getting caught onto something.

Cutting the two pieces together seems to have reduced the gap to less than half a mm but I then noticed the plates were a little skewed along the x axis – I didn’t check this before, so I can’t compare. I used the bevel box to level the blade on the tablesaw, but my fence might have warped over time. I could just live with this, and level the spindle to the wasteboard when the time comes, or I could flip the c beam upside down and see if that changes anything?

There’s still an angle, so I’m going to take the bottom one off. It’s the plates, it might be the wheels. I was hoping it would pull itself. Ok I’ve just adjusted the wheels a little bit so they still the same, so I think what I’m going to do, is when I go to fit the spindle I need to make sure the z axis c beam is square to the waste board. And to do that I need to be able to access the machine screws which hold it in place. So there are two which happen to be right behind the c beam. I am just going to drill a small hole somewhere along the middle where I can adjust my machine screws.

So there’s still a gap, and I’ve swapped this around the other way and it’s definitely the plate or the wheels. I don;t think there is much I can do about it. As long as I can make sure the z axis is square, it shouldn’t make too much of a difference. It’s a little bit off but this and that, will keep it in position.

Ok so I can loosen this, and adjust it to the left and right which means I can compensate for the tilt in the plates.

I am now going to make the acme locking collars, and I am using 14mm aluminium round bar to do this. After deciding the measurement I cut a small section on the table saw. Because the pieces it round, you really have to clamp it down otherwise it will spin. I made a 15mm segment which I drilled out to 8mm on the lathe.

I know I am using a wood-lathe for this, but you could also drill this out on a pillar drill with the pieces carefully secured in a vice.

I then drilled and tapped a hole which will hold a 6mm m6 grub screws, which is how I’ll be securing these to the acme threaded rod.

When one worked, I made the rest and assembled the lead screw on the x and y axis.

If I had a metal lathe, I could have taken a bit off here to create a step which would do a similar job as a washer. I just tried to reduce the diameter of these washers on the lathe… and failed miserably.

So this is starting to look more like a CNC machine. It’s a shame that the plates were a bit off but I think they will be rigid enough, and I’ll be able to adjust the z axis to still make the next set of plates. So in the next video I am going to make the plates for the z axis and installing the spindle. Thanks again for watching, and if you enjoyed this videos please leave a comment down below and sacrifice a thumb.

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