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Tiny internal threading challenge I need a fresh idea

Good to read that.

But what fancy thread is this anyway?

Internal 60 degree Vee thread 0.400" full threads long, 2 threads max lead out.
Pitch 0.03125"
Max diameter 0.146" +/- 0.001"
Root diameter 0.104" or 0.105" +/- 0.0003, 32 microinch or better
Pitch diameters 0.1235", 0.1245". 0.1256" and 0.1270" no tolerance specified.
Material 360 leaded brass

Seems to be the UN #7-32. http://www.practicalmachinist.com/vb/general/7-32-screw-size-does-even-exist-251655/

What is the customer screwing in for that root diameter? Does he want to fly to Jupiter with it? You can form tap and tell the guy that the male thread has to have crest flats and radius. Sorry for my excess energy. Foolish thing
 
Hi Mechanola:
It's actually not a thread, its a spiral fluid passage.
They need to get a certain flow rate and be able to manipulate it in top secret ways.
A 0.104" diameter core with other features is fitted into the bore and it has a low leakage tolerance but the fluid is apparently viscous enough that it works OK if the bore is accurate, smooth and cylindrical.
So the constraints are perfectly reasonable for the design; it's just not very obvious when you look at the drawing without knowing the purpose, and lots of the weirdass stuff I do is like that.

I'm just glad I was able to make some workable parts for them.
I hope they're still smiling after they get the bill, but it's not like I didn't warn them!!

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
Marcus,

What's the wall thickness on the part when finished? How many parts?

How about grinding a fully heat-treated steel (or carbide) male part that has the correct shape/size/form, and roll swaging the brass down onto that "mandrel" and then unscrewing it?

... just trying to think of some other "outside the box" ideas. :crazy:

Hi, great idea - I think you and implmex (although his thoughts were shot down) are much more likely to get the cost to where it needs to be (apparently).
Cold-working is so much more efficient than cutting material away - there would be no front-wheel drive cars without cold-forged CV joints!
For a 1st tentative step down this sort of process route, wouldn't a thread-rolling tap solve the problem? I know nothing about the details of design of such a tap, and I recognise that maybe there is insufficient material around the thread to allow for it as currently designed (the tube may well split), but it's got to be a better longer term approach than thread cutting and there's definitely no swarf to mess things up.
Good Luck, Phil
 
On the custom thread mill route, can you go as big as will fit and spiral down then spiral back out. Might keep a little more meat on the tool if you're not having to go to center for retract.

Fun problem!
 
Try Iscar they make some small boring grooving and threading tools that should do what you need. you may still have to modify the back side for extra clearance but they should work we do 2-56 threads all the time in things like titanium and stainless that deep and yes it's for medical research equipment. Circle tool used to make some even smaller but they are not available any more unfortunately. they were discontinued by Kennametal when they were bought by them.
 
Hi, great idea - I think you and implmex (although his thoughts were shot down) are much more likely to get the cost to where it needs to be (apparently).
Cold-working is so much more efficient than cutting material away - there would be no front-wheel drive cars without cold-forged CV joints!
For a 1st tentative step down this sort of process route, wouldn't a thread-rolling tap solve the problem? I know nothing about the details of design of such a tap, and I recognise that maybe there is insufficient material around the thread to allow for it as currently designed (the tube may well split), but it's got to be a better longer term approach than thread cutting and there's definitely no swarf to mess things up.
Good Luck, Phil

On the custom thread mill route, can you go as big as will fit and spiral down then spiral back out. Might keep a little more meat on the tool if you're not having to go to center for retract.

Fun problem!

Or maybe even something similar to a form tap to squish your wrinkles in there.

Try Iscar they make some small boring grooving and threading tools that should do what you need. you may still have to modify the back side for extra clearance but they should work we do 2-56 threads all the time in things like titanium and stainless that deep and yes it's for medical research equipment. Circle tool used to make some even smaller but they are not available any more unfortunately. they were discontinued by Kennametal when they were bought by them.

Just trying to be helpful for your involvement in the future. BUT all Three of you need to read the whole Thread before posting.

R
 
Yep, you too, see the above post.

Hey LR1, I HAVE read the whole post and still don't know what you are getting at - please explain rather than firing off snappy comments, thanks, Phil. ps I thought the whole point of a forum like this, like any brainstorming type situation was to throw in ideas, some wacky some not, and hopefully others will pick up and run with the good ones, while the not-so-good just get left in the dirt......
 
Hey LR1, I HAVE read the whole post and still don't know what you are getting at - please explain rather than firing off snappy comments, thanks, Phil. ps I thought the whole point of a forum like this, like any brainstorming type situation was to throw in ideas, some wacky some not, and hopefully others will pick up and run with the good ones, while the not-so-good just get left in the dirt......

In post #21 Zanrahd suggests a Form Tap, in post #28 Marcus responds to the idea of Form Tapping. Brainstorming is the entire point of this Thread, actually. But if something has been suggested, then turned away, then why would someone suggest it again? The redundancy is annoying, because when I see the Thread pop up again, I read the new post, by a new guy suggesting what has already been discussed.

R
 
I understand the annoyance, but:

You may have more time than I doo to read every post in every thread. There are plenty of threads that if I don't catch the beginning, that I leave it go, or maybe - if I doo decide to read it, but don't have time to read 3+ pages of bickering, I may post a response with quoting the initial post.

I agree that it is redundant, and annoying, but sometimes it's just not werth taking an hour to catch up, yet possibly we have some help.


-------------------------

Think Snow Eh!
Ox
 
I understand the annoyance, but:

You may have more time than I doo to read every post in every thread. There are plenty of threads that if I don't catch the beginning, that I leave it go, or maybe - if I doo decide to read it, but don't have time to read 3+ pages of bickering, I may post a response with quoting the initial post.

I agree that it is redundant, and annoying, but sometimes it's just not werth taking an hour to catch up, yet possibly we have some help.


-------------------------

Think Snow Eh!
Ox

That is very open-minded boss. I'll get there some day.

R
 








 
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