Multi thread cutting

[mekanik]

Hi Rob Can't get my head round what you are trying to do ?
You can put a 2mm pitch thread on practically any O.D. (within reason)just make the depth correct as per your Zues book, lots of manufacturers make odd size threads on some of there equipment but they would manufacture special taps to match,are you trying to make a nut ? or a male thread on 30mm bar ? I do have some info on specials but i think they are Imperial, not sure if there is info in Machinerys Handbook, i have seventeenth edition.
Mike

[birchy]

Yeah, it's not totally clear what you are trying to achieve? If you decide to search for the (essential!) book mentioned above, it is ZEUS and not Zues. Zeus Precision Engineers Metric Data Charts Reference Tables Book Drill/Threads | eBay

Threads may not be the correct solution for your problem, so maybe you could tell us what you are ACTUALLY trying to do so we can bounce ideas of each other?

[cropwell]

OK - here's the problem : Velleman make a 3D printer kit for £700, it is cheap, but nasty. The Z axis is a piece of threaded rod with a standard nut. That strikes me as sloppy by design and I am looking at ways of improving the design by creating a nut with three bits of threaded rod with ends turned to fit into bearings (3x10x4), putting the whole thing together with some end caps so the thing becomes a sort of ballnut that fits on the existing Z axis. I am playing about with the whole idea at the moment. That's what I do (play with ideas, since I lost interest in playing with myself ages ago). I didn't want to go public as the idea may be plain stoopid and I don't want the position of Forum Clown, even if it is vacant.

Having said that the Velleman K8200 kit is crap, it still looks like a cheap way in to 3D printing. You get a lot for the money.

Maybe someone has already done what I am trying out and got far enough to reject the results, or maybe you can buy one from China

Cheers

Rob

[mekanik]

Hi Rob
Gotcha now, i was looking into this the other weekend on one of the US CNC forums for a cheap ballscrew alternative. so all you need is 3 pieces of the bar threaded with 2mm pitch, diameter will have to be bigger than the smallest bearings you can get unless you were just going to put oilite bushes in the end plates, still relying on accuracy of the studrod but as it's rolled it should be near enough for making bits of plastic.
Mike

[John S]

I don't want the position of Forum Clown, even if it is vacant.



Rob

Nope, someone has just filled it

[cropwell]

Sorry John, I meant even if it WERE vacant.

[mekanik]

Had a picture of a roller screw that i had saved when i was looking @ them the other week but dumped it the other day when having a clear out of my desktop.think it was CNC zone but it was a huge thread.

[mekanik]

Olsen Engineering - Roller Screw Linear Actuators

[FatFreddie]

You can get a 3d printer much cheaper than that if you don't mind assembling it yourself - Home - RepRapPro from £400ish. Or look for Mendel90 (a better design).

The z axis doesn't need a ballnut because gravity (and a spring) takes out the backlash. I have a RepRapPro Mendel and it seems pretty crude but produces quite reasonable results - the Mendel90 is much more rigid and I would expect very good results from that.

[cropwell]

Hi, Thanks Fat Freddie.

The Velleman Kit requires assembly anyway. On first glance I like the Mendel90 especially with the Dibond frame.


Cheers,
Rob