Internal screw threads?

[Funkart]

Hello Out There. 

 

This is my first question here and Greenhorn means what is says on the tin. My query seems both so easy and obvious that I am guessing it has been asked umpteen times before...only, search is drawing a blank or at least "thread" is bringing up the wrong answers, time and time and you guessed it, time again, whilst attempts to trawl through and locate and answer manually? I think I'd rather chew barbed wire.

 

I'm using 2017 fundamentals. I need to create an internal thread for an STL file (M8 some 40mm long as it happens but of course I'd like to go on and use it variously down the line) and well, I have not got very far.

Googling doesn't throw it up and creating it via a Sweep, both internal and external, keeps giving me the "impossible geometry" error and "go back to school and do it again" message.

So, I give in: What's the answer?..if there is one (in "fundamentals" that is)? 

 

thanks 

 

[bcd]

If you can draw it in negative >subtract solid

[Kevin McAllister]

There are tools to draw some 3d fasteners in the Detailing and Fasteners tool sets. Unfortunately I don't think either of these tool sets is included in Fundamentals.

 

Is your STL for 3d printing? In my experience you're better off to model slightly undersize holes and buy a tap and die set to thread them. 3d printed threads aren't likely to be accurate enough to match a machine screw and will likely strip the first time you insert one.

 

Kevin

 

[rDesign]

To follow on Kevin's reply, here is an article from FormLabs - Adding Screw Threads to 3D Printed Parts

[Kevin McAllister]

I originally learned about the tap and die technique in 3d printed parts from this web course - https://www.stanwinstonschool.com/blog/learn-how-to-build-an-animatronic-eye-mechanism

 

Kevin

[Funkart]

As ever many thanks for your prompt and expansive help. 

As you say, the thread tools aren't in fundamentals, hence the Q. 

Negative - subtract? I could not that make work, again, hence my Q.

The other answers will take a bit of time digesting but I am aware that in fine threads / repeated use and even modest loads, a built up thread is asking for trouble but in this application an M8 reasonably sturdy and will only be used very occasionally whilst the load not onerous. Still I agree and with caution the bye word it might well dictate that do cut the thread manually. 

 

Very much appreciated.

 

Arthur