Hard milling threads with no hole

[Jeff]

Anyone have experience with using these types of thread mills?
Like this one from OSG?
https://osgtool.com/1664500511/

I've heard conflicting reports that they're great, to the end cutting area breaks down quickly.

I have a dozen or more holes to mill in 62Rc A2 material.
I have a choice to rough drill the holes before heat treat and then after heat treat helix the minor to size and thread mill them or go from solid after heat treat.

This is a remake of 4 pcs, the previous parts flexed and moved all over the damn place scrapping the parts. Never seen A2 move like that when hardened.

[riverhunter]

Have not used that exact tool.  but have thread milled 60+RC with carmex.  pre drilled them, helical milled the minor then thread milled them.  IIRC had to start adding comp after 6-8 holes but one tool did make it thru 40 ish holes.



  https://carmex.com/products/milling-tools/thread-milling/hardcut/

[gcode]

I have used these in inconel getting excellent cycle times and tool life
I don't know about 62 Rc though


Carmex FMT thread mills

[RobertELee]

I'd try it. Worse you can do is break it, then you'd be stuck drilling or helixing the rest out then thread milling.

[Jeff]

We decided to go with an Emuge thread mill. I'll just rough the holes before heat treat and finish them after so they are on location.
They want the location within .002" for these threads.
Lame.

[JakeL]

They want the location within .002" for these threads.

Is there ever a time where you'd actually need the location of threaded holes to be held that tight? I mean there's more than .002 of play in the threads isn't there? Am I missing something?

[Jeff]

Is there ever a time where you'd actually need the location of threaded holes to be held that tight? I mean there's more than .002 of play in the threads isn't there? Am I missing something?

I agree completely. But it has to be to print.
I don't have the print in front of me at the moment, it's either an aerospace part or for the military.
So that explains the stupid tolerancing.

[JakeL]

But it has to be to print.

I get it, we've had to hold some ridiculous tolerances before on features that don't matter. But like you said it has to be to print. It was an honest question tho, is there ever a time a location of a threaded hole should be that tight?

[RobertELee]

I get it, we've had to hold some ridiculous tolerances before on features that don't matter. But like you said it has to be to print. It was an honest question tho, is there ever a time a location of a threaded hole should be that tight?

That micrometer you're using likely has similar tolerances

[JParis]

Is there ever a time where you'd actually need the location of threaded holes to be held that tight?

Need to work where I do....it's a way of life.

I've argued it, "there's more tolerance in the the thread", only get some changed and then only grudgingly.

"If it doesn't go together we need to tighten up the tolerances"

[CNCAppsJames]

"If it doesn't go together we need to tighten up the tolerances"

That mantra makes up the entirety of Chapter 1 of the Idiot's Guide to being an Engineer.

#ChangeMyMind

I got an AI Survey recently and the ask was "What can AI do to make manufacturing better?" My reply "How about slap the stupid out of idiot Engineers and their moronic tolerances. That would REALLY help manufacturing."

Probably not going to get a response. 

 

[Newbeeee™]

Is there ever a time where you'd actually need the location of threaded holes to be held that tight? I mean there's more than .002 of play in the threads isn't there? Am I missing something?

Obviously very different beast if talking .002" as a positional, or .002" with a +/- attached....
But yes, the reality for a lot of applications where (eg) a cover is held down, is (More eg) use M3 screws and drill the cover hole 3.5mm. So there's plenty of room for errors and it will always fit together with no issues.
The unfortunate thing is lots of "designers" think the tighter their tolerances the better the product, and i've seen many occasions where screws have been used as locations for alignment of covers.
Which then goes really pear shape, when they don't specify masking of the holes from paint
CNC brochure specs hasn't helped as "machines are so accurate nowadays".
Lack of apprenticeship also hasn't helped.
Back in the day, +/-.005" was the norm (in a lot of cases).
Then positional tolerances became vogue, and +/- seemed to get dropped, and overnight everything started getting tighter....for no reason. And the CAD Jockey, didn't really understand what it all meant.
I remember one conversation I had where the company was +/- 0.1mm as the general tolerance, and the Jockey put positional 0.1mm all over and then argued "it was the same".
I doubt, much has changed....

[gcode]

I had a Ø2.25" x 6 UN bolt pattern rejected the other day.
They checked in on a CMM using a 4mm ruby.
They told me the holes were out of round, out of position and not perpendicular to the face.
I'm guessing at least half the hits fell inside the threads yielding a bad hit or even shanking out.
I've been trying explain this to our CMM guy for 17 years now and he continues to insist his CMM inspections
are golden and accurate to eleventy billionths of an inch...

[RobertELee]

I've been trying explain this to our CMM guy for 17 years now and he continues to insist his CMM inspections
are golden and accurate to eleventy billionths of an inch...

Dude is obviously more geniuser than everyone else.

[Brian]

"If it doesn't go together we need to tighten up the tolerances"

I've often thought that this really means "we don't really understand how this works, so we'll just tighten up everything just to be safe!"

Are folks using these when doing CMM inspection? https://vermontgage.com/gaging-products/thread-gages/thread-hole-location-gages

I can't believe that anybody would even try probing a thread directly-OMG! Even a gage pin in the minor diameter is better than that....