Hello guys

Exams and a streak of bad luck kept me away. A couple of weeks ago I was building a set of carb mounts. 4 tools needed per side, and I can only mount one at a time, so a lot of tool changes. ER nut started to feel a bit notchy, no visible debris in the threads. I gave it an air blast, still notchy. Grabbed a pointy sharp tool and had a go at the nut threads, something did come out, so I did that again meticulously on both nut and shaft. Squeaky clean and all was well, no hint of blemish or damage on either threads. Last part, last side, roughing operation finishes, I go to unscrew the nut to change tool, and it just seized solid. I've never seen anything like it before, no excessive mechanical stress, no thermal stress, no nothing, and it just seized. When I say seized I mean I held the nut on a vice, I grabbed a 21mm spanner and a 1m long lever and it STILL wouldn't budge. Eventually with a lot of patience and even more swearing I managed to get it out. Bottom threads were absolutely destroyed, nut too, but the worst thing is that trying to get it free I must have applied force in a way I shouldn't have and I damaged the bearings, shaft wasn't turning true anymore.

So, new bearings or new spindle? Two pairs of nachi bearings from bearingboys in the appropriate size were almost as much as a new spindle. So new spindle it is, it took almost 10 days to get here from Germany, ffs, but yesterday I got it. I mount it and straight away I noticed it was MUCH stiffer in rotation. Give it a spin by hand and it barely does one rotation. Hang on... Trusty Mitutoyo indicator doesn't lie, 0.025mm runout. Advertised as LESS than 0.005mm, that's at least 5 times more than advertised. Send the seller a message, hasn't come back to me yet, but I feel it's not going to end well.

In other news, I decided to make a small fly cutter, I wanted to see if it could be usable in that spindle. I had some 7075 bar (don't freak out, it's just a proof of concept), so I turned a 12mm shaft with a 30mm body and a 8mm slot on a 10 degree angle to mount a turning tool with a polished carbide insert in. Now, I would swear I had a 95 degree left hand tool somewhere, turns out it was right hand... The one pictured on the fly cutter is the only thing I had that would mount and make a cut, even though it's the wrong tool to use.

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Turned out quite nice though. I tried slow cutting air, to get a feel for the speed. Around 2200 rpm vibration starts being noticable, 3000 and it's too much. I tried it on the lathe at about the same rpm and it only had a really slight sort of harmonic to it. My guess is that whatever imbalance it has is greatly accentuated by the spindle runout. Anyway, 6082 plate, 0.1mm DOC, ~45mm WOC, 2300rpm, 300mm feed et voila. Not bad at all, spindle could handle it, I guess if it was runout-free it would give me much more confidence. Not that I would go deeper, I don't care about material removal, just surface finish.

Lastly, I decided to put the ATC project on hold for a while. I need to invest in other things first, an enclosure, a new cabinet for all the electronics, a half-decent hand-controller or panel etc. Most importantly I need a bigger, more reliable and robust method of workholding, so I could mount fixtures, jigs etc to be able to make multiple parts at once and minimize the frequency of tool changing. I got my eye on this, anyone tried it? http://www.arceurotrade.co.uk/Catalo...-Milling-Vices

Long post, that's all for now, cheers!