Expanding Itchy: Mostly Victorious

Well, those lead screws didn’t need to be that long anyway.

Wait, they did? Oh. Well, let’s cut about 5mm out of this solid block of aluminium and add in some washers … there…

*lead screw falls out*

And use the pulley grub screws to hold everything together against the backlash. It’ll be fiiiiiiine.

If necessary, I can put the solid block of aluminium on the other side of the metal it’s attached to right now, and that’ll tighten things up, although I’d need to take some more length off the lead screws. That could never go wrong.

Iterating Wobblebot (and a side project)

I’ve laid the cable track, planned the new screws and bought another identical to the second…

So, as it turns out, not all lead screws are the same, even when they are supposed to be. The first one I bought has a thread that’s at the right pitch, and the right height, but the trapezium shape is too narrow. This was leading to a huge backlash problem, which I thought I would have to deal with by making anti-backlash nuts. However, the other lead screw, which I had bought thinking it was a pair, doesn’t have that. There’s more metal, and it fits snugly in the nut I have. That means there’s hardly any backlash at all.

I’m still interested in making the anti-backlash nuts, and I have other uses for a tap for that shape of screw, so I’ve ordered a length that I’m going to try to tool into a tap, with the lathe and the mill. Clamping it is going to be a right beggar – I might enclose it in a thermoplastic and clamp that instead.

Itchy: Improving stuff

The current base of Itchy is a slice of plywood on some 40mm blocks with some nuts used as spacers. I’m calling that ‘non-ideal’. It’s going to have MDF on a raised base of some kind, probably made of lengths of 20×20 extrusion. It might be removable, and probably should be, but ‘removable’ just means having countersunk screws, and maybe some kind of cover for them. ETA:I just remembered I know where there’s some sheet steel. I must remember not to overmake this.

The entire gantry swivels about the lead screw. This is slightly more than non-ideal. It’s a significant error. Mat’s been helpful about that, after he stopped cringing. (He called it an abomination. I’m so proud.) Two lead screws worked from the same stepper would move that squarely. I’ll have to add anti-backlash nuts, but that isn’t a problem – I have two bearing blocks on either side, and I tapped them both. Adding in the second cross-piece hasn’t been a priority yet. When I do it, I’ll have to do it properly and arrange everything nicely. Right now crosspiece #1 is held on with two pairs of corner braces that are bolted to each other. That was only ever temporary, but I’m impressed by how well it’s been working.

The head needs building, rebuilding, or re-re-building, depending on how I’m keeping track. The belts are currently attached to a piece of acrylic, which is not actually terrible given the amount of pressure on it. However, I’ll be wanting to put more pressure on it. This is another non-ideal part. It’s not a critical part of this round of improvements. The motor at the end of the gantry is held on by a single piece of 5mm acrylic and the power of hope. That /is/ a critical part of the current round of improvements. I need to make that out of metal, and have a bottom brace to it as well. I’d have made it out of metal but that all went badly wrong when I put it onto the rotary table on the mill. We don’t have a single bit wide enough to get the raised part of a NEMA motor sit inside a hole. On the head I got around that by not having enough of a hole in the first place, but I knew the head was temporary, and I want to do this properly. The best way is probably to make a threaded rod for the mill that has a cone ending, so I can centre-find. I’m likely to eyeball it all and hope, though.

The biggest features now are the splorted wiring everywhere like someone has disembowelled a pinata full of multi-fruit bootlaces, and the fact that some of those wires are inherently unsafe. The limit switches are currently push-to-make, and should be push-to-break. That was a speed thing, but I can invert them easily enough now I know what the firmware is, and that it’ll support the pin inversion. I have cable track now, so I can run them all safely. The head/motor holder designs both need to take into account limit switches and wiring anchor points. I tried 3D printing track, but the joints were not good enough.

In order of importance, there are the safety items first – limit switches and wiring – and then the thing that’s arguably a safety item, in that I don’t want motors to snap off and should therefore get rid of the acrylic – and then the wobble along the bottom axis, which different people call the X or the Y. I’m thinking of calling it ‘the axis with the motor nearest to me’ which is my kind of naming scheme. (It’s a bit weird, because it’s not like a graph where you plot things. It’s a graph where the axes are used to move the other axes. So a movement in the X, from left to right, can be made by a stepper that is sitting along the Y axis. This has been a source of massive confusion to me, so the milling course at makespace just has ‘long axis’ and ‘short axis’ and then nobody has to think. And, more importantly, there’s less chance of fucking up through people not thinking.)

In terms of what I’m realistically going to do first, it’s got to be the wiring, then it’ll likely be the wobbly bottom, then the motor mounting, and then a big redesign of the head. I can probably deal with the wobble a bit by only having three blocks, which would let me position the rods to minimise the travel available – but that’s the wrong way of doing it, and a double lead screw is the right way.

Moaaaaaare Caaaaaaane

A cane end, with brass of two different colours, one colour being an extentionI went back with the aluminium ending to my friend, who tried out the cane and decided it was too short. I smugged internally, very briefly, and then measured how much longer it needed to be. Then I ordered the brass.

I’ve cut this a little longer than he thought, because I can take it down pretty easily, and having a cane that is a touch too long isn’t a problem. However, there is a slight problem that the rubber end is starting to perish, so there may have to be some more repair work done.

The cane is now a lot heavier, but I didn’t want to thin down the extention too far. If it’s horribly heavy I can do that, but I rather like the swing of it, so I’m leaving it like this.


A wooden cue with a brass collar to which an aluminium extension has been addedA friend has a pool cue which converts to being a walking stick, by unscrewing the top and taking out the front part of the cue, then screwing that onto the front. The bottom of the walking stick part has a thread that needs protecting, and the cap is what hits the ground. The stick is too short for my friend, so I’m making a longer cap.

The thread on it is 3/8″ 12tpi. For those who don’t know threads, this is a weird size. It’s made for brass, which is brittle, so it’s a very coarse thread. I had to get expert help in sourcing s new tap to cut the thread.

Brass fix

I need to make a taper of brass with a female thread that’s 3/8 at 12tpi, which is a very coarse thread. It turns out a place called Tracy Tools in Devon carries these taps, so I’m not going to have to make one. However, it’s not a usual size, so I had to check with the person paying that I could get this one tool for this one job. I /could/ make one – but I really don’t want to.

Making an aluminium pen

I’ve now got the aluminium rod pen down pat. I make a centre hole, run the rod further out and use a centre dog, and run a chunky cutting bit down the whole length of the piece, leaving a small chunk of rod inside the chuck. Then I run the rod further in, and drill out the part I have centred with a 1/4″ bit to the depth of about 1″. Then I reverse the rod and cut down the part that was in the chuck, adding a couple of notches so the tiny difference in thickness is not noticeable. Then I run the same bit across the end to flatten it off, and I’m done. I also, for extra points, remember not to leave the chuck keys in the drill or the main chuck, so I don’t die. That’s always a bonus.

Making a better pen

A brass cylinder with a protrusion at one endAfter making the aluminium pen, I showed off pictures of it and ended up agreeing to make a couple more. I did one more in aluminium, and then turned to brass. If it were solid metal, a brass pen would be too heavy, but I can make it out of brass and wood easily enough.

I had a scrap bit of brass, and there was a failed thread already in there, so I took that off very very slowly, and as a consequence my chip size was tiny. It picked up a bit once I had a smooth cylinder. I had had to hold the aluminium at both ends, and the brass was a lot shorter, so although I was using the tail stock for some of the time, it wasn’t in the way, and I only needed to cut a section of it. There was very little chatter. I cut the shoulder slightly wrong, and it has a small step on it, but I’ll see how that goes. It may not need re-doing. I also added rings to the part that will sit inside the handle, to help with the attachment process, whatever that will be. Drilling out the inner part was not difficult, but a combination of lube and chip size meant I could not see what I was doing if I took the drill bit out, so instead of peck drilling, I checked my speed calculations and then pushed harder. Still alive.

We didn’t have a decent parting tool, and my brain was starting to complain about all the work I had done, so I cleared up on the lathe and took the part off the parent rod with a hack-saw. I’m glad I did, because it felt so different to aluminium. It’s really slippery, but it cut well anyhow.

I need to source some wood, make it into an approximate round, and then put it onto the brass part. Then I’ll sand the heck out of it until it’s properly round and fits the handle perfectly. A bit of hot glue, and I’m done. Then I declare tea and victory.

Making a pen

long aluminium cylinderI set out to make a simple dip pen. The ferrules are relatively cheap, and I don’t like the way wooden pens soak up ink and water, and split. Plastic feels wrong, and it’s too light.

I found a bit of aluminium rod that was about the right length, and squared off both ends in the mill. I used the lathe to bring it down to a comfy width, as well as put a shine on it. Because the rod was short, I had to reverse it, so there was going to be a shoulder. I made a feature out of that by notching where they met instead of trying to match exactly. I added a couple of other decorative notches as well.

The ferrule sits in a 1/4″ drilled hole, and I did that in the lathe as well, with a rather battered bit. It had been ground down to chip brass better, I think. However, it worked pretty well. Then I glued it in with araldite. It occurred to me afterwards that I should have used hot glue, because when the ferrule, which is steel, rusts, I’m going to want to get it out of there. Hot glue sounds ideal for something where metal would be involved, and the coefficient of expansion isn’t a problem in removal because the steel sheet is so thin. Whatever material it’s in, it should come out with a bit of force.