Threads_Turn it over to engineering?

Hi: I often have had to do some design engineering going way past “control drawings” for some of the products I’ve worked on. I have had to study up on injection molding good design practices, etc. to spec. plastic parts properly.

Now when it comes to designing threads, like gears, I don’t feel qualified. Is this the wrong attitude or is it typical to say to a client, you’ve got to get a D.E. or M.E. involved for this aspects. On all these cool coffee and waterbottle designs, there must be an M.E. involved right? Do I at least need to learn about designing threads?

It could not hurt to learn about designing threads. When it comes to threads on bottles and similar products I think you will find that they are not terribly difficult to create.

If you want to consult with an engineer, there is obviously no shame in doing so. Wouldn’t you (and your client) rather know that your design is going to function properly before you hit production?

You can also consult with your molder to work out some details like this. They likely have done them in the past or can provide you with some resources to make sure they are suitable.

The big thing to remember with things like gears and threads, is that 99.9% of the time (at least) you will not be needing to design a new type of gear or thread. There are standards out there, and even though the diagrams and text explaining them can be intimidating they really aren’t that hard to follow. Just take your time to fully understand what they’re saying. If you have Solidworks, check out the Toolbox in the Design Library. Lots of easily configurable parts, including gears (complete with what seems to be a real involute profile).

The trickier part, and the part where consulting an engineer can help, is knowing which standard to use (ACME vs. Buttress vs. NPSM etc. threads, what pitch gear, etc.). I’d say you should consult an engineer in any new situation to make sure you’re using the right thing, but it sounds like you might be technically minded enough to take that info and run with it on any similar projects, but probably erring on the “if not sure, ask” side of things. A couple hours of an engineer’s time can’t be that expensive, especially compared to the costs associated with getting it wrong.

+1 to this. Talking to your manufacturer’s engineers can be extremely helpful.

When working with threads this is the book you need

It explains what standard threads exist, why the exist and how to dimension them.

I forgot to mention that book, good call Tim. It’s actually on the desk in front of me at the moment, open to “Buttress Threads.”

thanks a bunch. Wow really helpful people on this forum!