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Turning Molybdenum type 361 problems

TGA-Bucko

Plastic
Joined
Apr 6, 2018
Hello everyone! New guy here, I need some help trouble shooting a problem I am experiencing with Molybdenum type 361.

The part is simple design.
.250 OD with a .200 ID
The problem I am having is when I drill the material splits open. I am using a standard hss drill (#7) @ 40sfpm and .001 fpr

If anybody could give suggestions on how to resolve this it would be greatly appreciated!

Thanks
 
Your newer post referenced TZM moly & this one is moly 361 (likely powdered metal, all moly). Likely close but I don’t know about the 361. As a general rule none of these refractories are very ductile and are prone to chipping & just breaking. Much like cast iron when you try to push them around. At .001" IPR likely your drill is dulling & the increasing feed pressure is too much for the thin wall.

Rather than consult my metcut stuff I looked around & (shazzam!) found this US,ASTIA doc prepared by metcut & assoc. Searchable PDF here → http://www.dtic.mil/dtic/tr/fulltext/u2/296419.pdf

Talks about the abrasive nature of TZM moly & prolly good to note the recommendation (min DOC of .005” for finishing). Gives tool angles, coolants etc, etc.

Then there’s just the overview from a maker or distributor (google is good here) → General Guide to Machining Molybdenum and Molybdenum Alloys from Ed Fagan Inc.

I hope this all works out for you, really.

Good luck,
Matt
 
Matt,
Thanks for the good will bro. I reviewed that pdf, it's basically a study of tool life. Using old machining techniques, and the problem we are having is chipping and pitting, like porosity.
What's interesting is they say using high speed drills they would get something like 50 holes. We don't get more than say 5 or 6 before the drills crack the material and mushroom the entry of the hole.
I think most of our troubles are stemming from the design of the part, it's thin walled holes are close to the edges.
These parts are total p.i.t.a!
 
Flamesuit-On!

Shit like this ( .025 wall ) is when I bring out the ol' Hardinge, a 6 or 12 pack of Stella ( HB lately ), chase everyone out of the shop, put on 80's Eurotrash and go to town...


( Can anyone guess what I've been doing for the last 5 hours ???? )

Drill u/s, spring/finish OD with hand sharpened carbide, then spring/finish with hand sharpened Micro100 bar, cutoff.
Rinse-repeat.
 
Flamesuit-On!

Shit like this ( .025 wall ) is when I bring out the ol' Hardinge, a 6 or 12 pack of Stella ( HB lately ), chase everyone out of the shop, put on 80's Eurotrash and go to town...


( Can anyone guess what I've been doing for the last 5 hours ???? )
Sure glad all this gnarly s**t is in expert hands, these days! Other than mine, even BETTER!

I thot I was pretty good to cut Hadfield and Nickel Aluminium Bronze fifty-plus years ago, when the only other guy, three shifts, our shop, as could beat my time was 81 years old that year! Stayed over, Day Shift to see who TF on 2d shift was splitting his tolerances in half, too. Mind - he had run 26 parts, his shift, to but 6, my go, previous day. Became a great friend and mentor. I was the veritable Vulcan Mind Tap on oldsters those days, or tried to be. Most were glad to share if you just listened well 'coz that was so damned rare.

That part ain't much changed.

No music, those days, though. I still like it that way.

Every noise in the shop tells a story. Some can save holes in a bankbook, others, yerazz!

:)
 
Matt,
Thanks for the good will bro. I reviewed that pdf, it's basically a study of tool life. Using old machining techniques, :angry: and the problem we are having is chipping and pitting, like porosity.
What's interesting is they say using high speed drills they would get something like 50 holes. We don't get more than say 5 or 6 before the drills crack the material and mushroom the entry of the hole.
I think most of our troubles are stemming from the design of the part, it's thin walled holes are close to the edges.
These parts are total p.i.t.a!

More like a 100 hole recipe but likely a more solid section, they were about doing the machining... YMMV ;)

With all things metcut, it pays to look deep in the weeds for a difference compared to what you are normally doing. It’s there on the side rake for turning (boring gonna be the same). They don’t go into threading (tapping) in that doc but I’m pretty sure more than 50-60% threads would need the part heated up with single point or tapping.

{metcut_turning_drilling} said:
The chart in Figure 39, page 65, shows superiority of soluble oil (1:20) over a highly chlorinated or sulphurized oil (for drilling it’s the other way). The improvement in tool life with the higher side rake angle is presented in Figure 40.

on page 66 (still turning). The tool life was increased almost 4 times by increasing the (SR# on the chart) rake angle from 7° to 20°.

(drilling) Cutting speed tool life curves are presented in Figure 54, page 80, for two types of points and point angles. The 135° split point was appreciably better than the 118° plain point. For a drill life of 100 holes, the drilling speed was 125 feet/minute with drills having a 135° split point and approximately 105 feet/minute with drills having a 118° plain point. The tool life curve in Figure 55, page 81, shows that when the feed is increased from .005 to .009 inches/rev. the drill life decreases from 98 to 34 holes.

For turning short chipping abrasive material this is unusual… Add to that a side rake that high will tend to self feed if not controlled BUT will drop the shear pressure quite a bit if it’s all dialed in. That could help with cracking if breakout doesn’t become a problem.

As for old??? It’s better than a vacuum I think. BTW my personal metcut stuff doesn’t have any solutions for gun drilling (everything else but) & that’s the same then as now...

Good luck,
Matt
 
Sure glad all this gnarly s**t is in expert hands, these days! Other than mine, even BETTER!

I thot I was pretty good to cut Hadfield and Nickel Aluminium Bronze fifty-plus years ago, when the only other guy, three shifts, our shop, as could beat my time was 81 years old that year! Stayed over, Day Shift to see who TF on 2d shift was splitting his tolerances in half, too. Mind - he had run 26 parts, his shift, to but 6, my go, previous day. Became a great friend and mentor. I was the veritable Vulcan Mind Tap on oldsters those days, or tried to be. Most were glad to share if you just listened well 'coz that was so damned rare.

That part ain't much changed.

No music, those days, though. I still like it that way.

Every noise in the shop tells a story. Some can save holes in a bankbook, others, yerazz!

:)

Great way to say that. My ears are always working and my guys are always amazed when I tell them things about their tools and machines that they haven't discovered yet..like "hey, that insert chipped" or "change that tap it's gonna break"

I'm glad to know there are other people that let their ears do the machining.
 
Flamesuit-On!

Shit like this ( .025 wall ) is when I bring out the ol' Hardinge, a 6 or 12 pack of Stella ( HB lately ), chase everyone out of the shop, put on 80's Eurotrash and go to town...


( Can anyone guess what I've been doing for the last 5 hours ???? )

Drill u/s, spring/finish OD with hand sharpened carbide, then spring/finish with hand sharpened Micro100 bar, cutoff.
Rinse-repeat.
Sounds like fun! How many parts did you make? This particular job is for 3000 pieces. No way could I do that on a tool room lathe. Well i could but it would be very tedious and boring af. Although the feel of things probably helps when cutting this stuff.
 
Sounds like fun! How many parts did you make? This particular job is for 3000 pieces. No way could I do that on a tool room lathe. Well i could but it would be very tedious and boring af. Although the feel of things probably helps when cutting this stuff.

Thankfully not that many, just north of 100 pieces of a 45deg full rad .034 wide undercut on a threaded SS piece.

BUT!
I have in the past made 'bout 8000 pieces of a SS "washer" - .094-.093 ID x .124-.125 OD x .090-.087 thick, all on a Hardinge chucker.

Funny note:
I was parting them off into a small SST bowl, nice round one so I can take them out easily ..
Well, I had to sneeze once while bent over the cutoff tool looking through the magnifying glass.
That one sneeze cost me approx 40 pieces!!!
 
Thankfully not that many, just north of 100 pieces of a 45deg full rad .034 wide undercut on a threaded SS piece.

BUT!
I have in the past made 'bout 8000 pieces of a SS "washer" - .094-.093 ID x .124-.125 OD x .090-.087 thick, all on a Hardinge chucker.

Funny note:
I was parting them off into a small SST bowl, nice round one so I can take them out easily ..
Well, I had to sneeze once while bent over the cutoff tool looking through the magnifying glass.
That one sneeze cost me approx 40 pieces!!!

Whoa! 8000 pieces that is insane! I bet you were pumping em' out! Nothing you can do about the sneeze when your cranking handles! What a bummer though hah
 
Have you tried any changes to the drilling program? I probably would have tried something like a ~.100 drill followed by the final size, all in cobalt screw machine with a split point. And monitor both, come up with a change-out after so many holes if they show wear.

Have you tried looking at the machined parts under a microscope? Might help with tracking stress in the walls and spotting cracking trends. Do you have access to one?

Let us know (maybe in this thread) what happens with your job situation.
 
That's nothing to sneeze at!

LOL!

Yeah, well that is how I pretty much started out.
A Hardinge, clapped out BP, an even more clapped out bandsaw and a bench grinder, all in a 50K Sqf building, alone in the middle of the night ( after dayjob ).
Odd thing is: Sometimes I actually miss it!
 
Sorry for the tangent guys ....

Yeah, I'd miss the 50K' building too....


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

Think Snow Eh!
Ox

Ox, that building had the tendency to square the living bejeezus out of me at times.
For the most part, it was just one huge, 30' high, 160' x wickedlong single bay space for a beam fab shop. Cranes, welders and work-in-progress only, otherwise empty.
The damn thing echoed so much that if a mouse farted in one corner, I've had to listen to it for minutes.
It was also steam heat so as the pipes were cooling down, the steam-bangs were at a regular 5 to 7 minute intervals for hours.
And if that wasn't enough, in-between the bangs there was always something falling off, small pipes tipping over, pressure regulators blowing off, water collectors dumping ....

Seriously, Hollywood can't create scarier sound effects.
 








 
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