Hi Martin, now that I go back and read your message again, it seems that was part of your question was how to figure out where to place the line. Sorry I did not quite pick up on that part, I was thinking you were just looking for a way to build it since Chamfer will not do that kind of result itself (it will on a cylinder but not here).

Well, as far as I can tell it's simply not specified in the drawing, so that would seem to me that it's precise placement is not considered all that important.

If placing at some spot that just looks good enough is not a good solution for you, I guess you would need to go back to the source that gave you that drawing and tell them that the drawing is underspecified and that you need more data in order to reproduce the shape properly.

- Michael

Thanks Michael, i have figured out your way, and yes it had to be done by eye, but at least it works. It's not a clients drawing, it's just one plucked off the net for what i thought would be simple a simple task for MoI, which it as long as you have all the data to translate, is there any way you could add something like a lathe option/tool. It would certainly come in handy here at times.

Martin

Hi Martin, could you describe a bit about how you would want the lathe tool to operate? How would it be different than doing a revolve like I showed above?

- Michael

It's a bit difficult to put into words, but I'll have a go .... two starting curves to converge as a cutting point, which can then be rotated around a given path or radius, to cut into the target solid object to a given depth and to give the resulting cut the equivalent to a boolean merge.

I hope that makes sense. I just might have to do an example ;)

Martin

Hi Martin, yup an example would definitely help!

But in your own description there you say: "give the resulting cut the equivalent to a boolean merge." ..... So if you want a result that's the equivalent of boolean merge, can't you use boolean merge to do that right now?

What I mean is - doesn't doing a revolve plus a boolean give you the same result that you're looking for with Lathe?

If that's not the case and you're asking for something that you cannot do currently with Revolve + boolean, then that would definitely help to get more explanation.

If you can get the same result using revolve + boolean, then that's the method to use for doing your "lathe" right there - I usually don't like to put in a totally new tool that replicates functionality that is already easily obtained by using a couple of existing tools in combination with each other. Having tons of specialty tools tends to lead to a complex and "bloated" UI which then causes problems for people just trying to find any particular tool to use during regular operation... The main way to have specialized tools like that would be to do it as a plug-in at some point so that it would not clog up the regular UI.

- Michael

Ok here is what i mean. It takes a whole heap of messing about to produce the shapes, and then the boolean results wont unite back again, and the solid don't behave as a solid, it behaves as a skin with no real density/mass. If it's this difficult using the tools provided step by step, then I am seriously flawed in my methodology, yes it can be achieved with profiling and revolve etc, but if all i want to do is to add some patterning to an object some way along the line, without thinking about it at the time of construction, then i would have to restart that part over to add the pattern.

Now i can see how much of a pain it could be programmatically and understand the complexity it could add, it's perhaps because of the way the "Solids" don't behave like solids that i find it frustrating and just too much darned work when all i am doing at the moment is learning and playing with MoI. So in reality i guess my wish is for solids to behave as solids, if that's possible ?

Martin

Hello,

The great thing about creating models in this way is that there are multiple ways to get it done. I find that sometimes it is easier to scribble out an idea and think of commands I'd like to use before I sit down and work in MoI to make an object. If you'd like to see one way I make screw threads Michael posted a link in the Resources page on this site. Here is an M6 nut. It also helpful to have those core cutting profiles so you can make an infinite number of types of nuts and bolts while being able to make it look believable.

Looks good OSTexo - I will get there .... slowly. Moving from 2d pen and paper to 3d is a hard journey for me.

Martin

Hi Martin, the result that you have at the end there is not a solid - it's a bunch of separate surface pieces. So that's why it's not behaving like a solid, because it is indeed not one...

It looks like your original sweep in this case is done with an open curve:




It can be ok in some situations to use a surface as a cutting object, but only if it fully divides the solid - your cutting surface in this case does not fully divide the solid at the very top and bottom spots I don't think. So it would be better to form a solid as the cutting object in this case instead.

You can make a solid for the cutting object by drawing in a line segment on the ends of that open "V" curve and then select the V and the line and use Join to make a closed triangle profile curve. Then the sweep result of that will be a solid.


Also you'll probably be better off making the cylinder be slightly shorter than the cutting object rather than having the cutting object stop right where you have it currently since that makes a sort of teeny little notch at the end.

See the attached 3DM file for an example - here I've shortened the cylinder so that the cutting object runs cleanly off the end, if you wanted the same sized cylinder as before you would probably instead want to make the helix path slightly longer instead.


At some point in the future I could see making a "helix cut" type plug-in that would automate this particular type of thread type stuff, but that probably won't happen anytime too soon though.

You can probably find a lot of various premade standard parts like this in IGES or STEP format so that you wouldn't need to model it at all though - I'd recommend checking out http://grabcad.com, and also see the links here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1826.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=3505.3

- Michael

Hi Martin, also the screw threads tutorial on the Resources page that OSTexo mentions above will take you to his video tutorial here: http://vimeo.com/30765016

And also some previous discussions here on the forum:

http://moi3d.com/forum/index.php?webtag=MOI&msg=4623.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=767.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=490.36

- Michael

.

Just watched the videos you did with threads and knurled finishing - Impressive stuff. You must come from an engineering background as you made that look so easy too, even working with fractions that i have to faff about with for hours. Landscaper v's Draughtsman = Embarrassed landscaper. LOL

Nicely done OSTexo

Martin

Thanks for the links Michael - Excellent stuff

Martin

Hi Michael, will have to try this cutting solid with solid some more, I normally end up having to loft or blend holes left by cutting objects. It was 3am after all - That's my excuse and i am sticking to it lol

Martin

Edit ... Eureka! - That's what i am looking for, now i feel reel dumb and need to coin Homers catch phrase DOH!

Hello,

Just a great deal of trial and error. The Wikipedia article on screw threads helped me a great deal to realize that instead of having to use a calculator for anything all that was needed was the base pitch number and everything else is ratios. I also thought it would be good to have MoI do the precise calculations for me rather than rely on pen and paper. FelixPQ was kind enough to send me some engineering handbook scans as well for reference.

Well here is my result, I got bored and decided to play with my nuts :¬)

Also this link may be of use to someone else with what was our conundrum ... http://www.roymech.co.uk/Useful_Tables/Screws/Hex_Screws.htm

Martin