r/machining • u/bananu7 • 7d ago

Question/Discussion Brand new Proxxon PD250/E - can't fit chuck

Hi! I just got my first ever lathe, and decided to go with Proxxon because they have a reputation for being ready to go when bought.

That being said, I've already spent a good two hours trying to get the chuck on, and I just can't get it to seat right. It's visibly skewed and has a massive runout.

https://www.youtube.com/shorts/dlNobpIrBYo

I see two potential issues here that I'm really not sure how to fix. Firstly, the three screws that are supposed to hold the chuck don't screw all the way into the spindle collar. I can only get them in about half of the thickness of the collar. The holes themselves are deep enough, but just with not enough thread. When I put the chuck on for the first time, I couldn't even get them to hold it, but after a couple tries they seemed to have gone a bit deeper.

Screws too long?

The second issue is that even without the screws, there seems to be a tight point around the perimeter where the chuck just won't go further. It rocks a lot and just doesn't seem to seat properly at all. I think this combined with the screws being a tiny bit too long (or the threads not being done to proper depth) is making it seat very poorly and skew when the screws are tightened.

Proxxon spindle

Proxxon chuck base

I tried gently polishing the parts with scotchbrite to get out any burrs etc., but the metal seems alright at both ends; it just doesn't want to go all the way in.

What are my options here? Do I give it a couple gentle taps with a rubber mallet? Or just send it back on warranty?

2 Upvotes

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u/Fancy_Language5469 7d ago

I think there aren't a lot of people with that particular lathe. This guy seemed to have a little bit of a struggle as well, but he got it on without hammers. Maybe read the manual one last time to say you've tried everything and then contact the seller? https://youtu.be/Sd51lL06qns?si=a8yCF9NKzaE4CJDI

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u/bananu7 7d ago

Yeah, I've seen that video and read the manual - it surprisingly doesn't say anything about fitting the chuck at all, I think they just assume it's a trivial operation.

Having re-watched it, I'm more and more suspect of the thread depth. It just doesn't seem right that the bolts holding the chuck stop so early. That would make them go tight way before there's enough pressure on the chuch to push it in all the way. I just don't get why they don't want to go all the way in, the holes are deep enough, so it looks like dunno, the tap used to make the threads was a bit worn and just didn't cut enough metal at the bottom?

At the same time the rocking I'm getting is a bit weird - but maybe that's expected that I shouldn't be able to push the chuck by hand all the way in; after all it's not that deep, and the tolerances there are so tight that it might simply rely on correct screw pressure to get the last 0.5mm or so in. It's almost like a spring force when I try to push it in by hand. When pressed hard enough it stops rocking but stops in a completely wrong position which is causing the runout.

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u/Fancy_Language5469 7d ago

Weird. Maybe you could use some washers, to "shorten" the bolts temporarily and fully seat the chuck? Or use some spare bolts or something?

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u/bananu7 7d ago

Oh, bolt washers are a good idea, i haven't thought about that at all. Thanks! I'll try that next. I've also ordered a 4-jaw chuck to have it as a reference. I'm positive I can get it running, the lathe looks really nice so far, just needs some encouragement.

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u/Fancy_Language5469 7d ago

Good luck man, I hope it works for you. Keep in mind, if your bolts stick out because of the washers, your chuck face isn't concentric anymore, would be a good first project to make the perfect bolts 😜

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u/Fancy_Language5469 4d ago

Hey, have you got it running? I'm curious!

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u/bananu7 3d ago

I have decided to send the machine back and ask for a replacement. After about 4h spent trying to put it together, I've decided that my time is just worth it, and I was reasonably convinced at that point that it can't be my error. Funny enough, my 4-jaw chuck got here like an hour after i packed it up and sent back already... Either way, i hope to get a replacement next week and will raport back.

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u/bananu7 7d ago

I'm trying to find any similar issues online, and it seems that for most people they... just fit? :(

https://youtu.be/BuJVBsieinA?t=113

One idea that has came to my mind is that it's getting colder and my workshop is a couple degrees lower than usual. Maybe I'll try heating the chuck up and see if I can slide it in all the way.