601 Inconel Job

rokstarr999 · May 9, 2018

I have a big Inconel Job coming up. Read through the forums for about an hour.

Lots of different techniques. Seems like the consensus is that it sucks and to go slow.

This is what I have on my plate.

10-24 x .700 deep
1/4-20 x .750 deep
3/8-16 x .750 deep.

Also need to turn down some 1.25 rod down to .750 Dia. These will be 12" long.

For the tapped holes I'm thinking of using the Vega Xen taps at 7-10 SFM. Will oversize the hole a bit and drill at 40 SFM.

For turning I was going with a CCMT insert with a .015 TNR at 90 SFM

Milling at 100-50 SFM Chip Load = Tool Diameter x .0036 per tooth

This is what I've compiled so far.

ANy tips appreciated. Thanks

Larry Dickman · May 9, 2018

Sounds like you really screwed the pooch. Your speeds and feeds sound reasonable for a starting point. I would recommend thread milling the tapped holes. If you're dead set on tapping them, Emuge has taps for Inconel that can't be beat.

rokstarr999 · May 9, 2018

Larry Dickman said:
Sounds like you really screwed the pooch. Your speeds and feeds sound reasonable for a starting point. I would recommend thread milling the tapped holes. If you're dead set on tapping them, Emuge has taps for Inconel that can't be beat.

Single profile thread mills? I had no idea you could thread mill a hole that small. Never encountered that before.

Milland · May 9, 2018

rokstarr999 said:
Single profile thread mills? I had no idea you could thread mill a hole that small. Never encountered that before.

https://sct-usa.com/wp-content/uploads/2015/08/Catalog2015_81015_UN_SPTM.pdf

You'll have to spin the shanks for the depth of the #10 and 1/4" threads, and I'd make multiple passes rather than one-shot the profile. SCT should be able to give you s/f suggestions.

Larry Dickman · May 9, 2018

rokstarr999 said:
Single profile thread mills? I had no idea you could thread mill a hole that small. Never encountered that before.

single profile work the best for me. Multiple profiles will greatly increase the load and you'll get a shitload of deflection and breakage. Threadmills go down to #0.

rokstarr999 · May 9, 2018

Sooo...just got off the phone with emuge and they said that you can't tap 601 Inconel. Said it doesn't shear and that it's too gummy. Unfortunately that's what the engineers ordered.

Limy Sami · May 9, 2018

Have you seen this ? http://www.specialmetals.com/assets/smc/documents/smw/mach.pdf

implmex · May 9, 2018

Hi rokstarr999:
Threading those holes is going to be very painful, especially since you have to go very deep.
Have you considered having them sinker EDM cut?
It's the obvious way to spare yourself a lot of pain, so I'd be inquiring about price and delivery sooner rather than later.

Find a good EDM shop local to you and ask them.
Even if you don't end up using them, you have it in your back pocket when you start breaking taps and threadmills.
The idea of threadmilling is a good one but the depth to diameter ratio is awfully unforgiving, especially for the 10:32 thread.

Try it in a bit of scrap first; if you booger it when only half completed on a job, it'll be the Devil's very own to pick up the half cut thread with the EDM electrode.

Cheers

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

rokstarr999 · May 16, 2018

I've learned an important lesson...the tool manufacturer's application guys don't always know what they're talking about. After getting a NO QUOTE from both Emuge and Vega I ordered the Vega XEN taps and went for it. I did end up getting a different guy at Emuge the next day who recommended some taps, but they were fast spiral and that scared me off. Have not had a single issue after a day of machining this stuff. I was able to get the engineers to reduce the thread depth to .625 This is what is working for me...

Precision Twist Cobalt .323 drill @ 40SFM / .003 IPR
Vega 3/8-16 XEN @ 8 SFM
Filled Hole w/ Moly-D
Approx 60-65% Thread

Milling @ 150 SFM / .002 FPT / .5 DOC / .06 Stepover
.5" 4FL Endmill Coated

SIM · May 16, 2018

rokstarr999 said:
I've learned an important lesson...the tool manufacturer's application guys don't always know what they're talking about.

Have not had a single issue after a day of machining this stuff.

I was able to get the engineers to reduce the thread depth to .625 This is what is working for me...

Another important lesson learned is when "someone" tells you something can't be done..it only means that "someone" couldn't do it.
I have done more then my fair share of un-doable jobs...mostly when I didn't know better to "know" it couldn't be done.

...and great job in requesting a little less depth! Don't know til you ask and however less deep you can go is an advantage.

charlie gary · May 16, 2018

It wasn't inco 601, but I've had great luck form tapping Invar. Balax made the taps, and they also made the lube.

rokstarr999 · May 16, 2018

That's all I use in 303/304. Love the Balax form taps. I was too chicken to try it in the 601. If I have some scrap after the job I'll give it a shot.

precisionmetal · May 16, 2018

Larry Dickman said:
single profile work the best for me. Multiple profiles will greatly increase the load and you'll get a shitload of deflection and breakage. Threadmills go down to #0.

I'm with Larry -- I thread mill whenever the going gets tough, especially on an expensive part where a broken tap would be VERY undesirable.

FWIW, thread mills are available down to M1.

mkd · May 16, 2018

I've threadmilled 2mm threads in 6al4v. prolly a cake walk compared to inconel.
Main milling tip is small stepovers.

rokstarr999 · May 16, 2018

I ordered a couple Scientific Tools thread mills just in case and started out programming it that way, but once I used their adjusted feed rate each hole was going to take around 30 minutes so I went with a tap.

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