What caused this

C

coyotechet

Chet
Had a friend bring to me a work piece that he had just threaded 7/8X14 using a Valenite lay down threading insert/ material was bought as 7/8Dia. O-1 annealed . I took it to another friend and had him that a picture with his microscope here is what the threads look like under high magnification. What caused the threads to look like this???:confused::confused:

Chet

14 tpi.jpg
 
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No idea, but those threads will sure hold oil!

Interested to hear what caused that. Maybe the insert wasn't tight in the holder, or there was a chip between insert and holder?

Justin
 
Too much chatter for a loose or chipped cutter. looks like the workpiece is of very low machinability.

What is the workpiece material supposed to be?

.
 
O-1 in the annealed state has a low machinability. It requires a high surface feet per minute with a high quality cutting fluid to acquire any type of finish.

Without seeing the setup, it’s difficult to ascertain the exact problem. I do this on a regular basis in my shop when one of my men are having difficulty. Can you give a description of his setup?
 
I personally think that Jackie is right on to slow of a speed (cut). I really have know idea both my friend and I thought 0-1 annealed would be the right material to use.
Here is what I know he has a really nice (like new) Clausing 12" lathe and was using a New carbide laydown insert he say's that it's a Valenite uncoated
was using [B]back gear at low speed 50/75[/B] and slow feed and light cuts because it was cutting (Sh###) from the first cut. I have never seen any thing like it before as he and I know that he has been cutting threads for a Long time like me he is not a machinist, but has been playing with lathes for well over 40 years.

P.S. Nice tight Lathe and Gears /the piece was being held with 8" 4jaw chuck and only sticking out little little over 2 inches.
I have not seen the 4 jaw chuck but he says it is old but good shape with very little ware if any.
He is out of town and won't be back for until mid week so until then I won't be able to ask more.


Chet
 
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I agree with what Jackie said but seeing the setup would help. Also, there are different inserts that are much more tolerant of low speeds, feeds and pressure.

What's the od of the part/thread?
It looks more like too slow with his given threading tool than it does chatter from poor setup, to me. I'd try it at about 350 rpm, if possible.
 
Interesting? Jackie would he have been better off to use a HSS tool bit at that slower speed with that material.
 
coyotechet said:
Had a friend bring to me a work piece that he had just threaded using a Valenite lay down threading insert/ material was bought as O-1 Annealed. I took it to another friend and had him that a picture with his microscope here is what the threads look like under high magnification. What caused the threads to look like this???:confused::confused:

Chet

View attachment 23662
Click to expand...

Looks like tool chatter.
As in holder not tight enough.
 
Yes 50 /85 is to slow using A good carbide insert (Valenite C6 grade laydown) 50/85 not sure of the slowest speed on the Clausing.


350/500 is to fast of a speed to kickout safely with out crashing for him (@74 plus and for me also @82today) that is why the slow speed.

He is going to try and recut/thread the same piece of O-1 annealed 7/8X14 using HSS (Crucible REX76) that I just gave him) in week or so.

Chet

PS I just read the above post. That is what I first said looks like chatter. Know way using a good heavy duty 8" 4 jaw with the part sticking out only 2 ½ max. every thing tight as H#!!.
 
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i saw this

mwezell said:
I agree with what Jackie said but seeing the setup would help. Also, there are different inserts that are much more tolerant of low speeds, feeds and pressure.

What's the od of the part/thread?
It looks more like too slow with his given threading tool than it does chatter from poor setup, to me. I'd try it at about 350 rpm, if possible.
Click to expand...
when tool chiped
 
Somewhere's on the innertube there's videos showing how a carbide tool removes metal VS how a HSS bit shears it like a knife.

When I see that look, which I call "pulling" it's a sure sign need to ramp the speed up.....'WAYYYYY up. Or dig in deeper and crank up the coolant. Or both.

Which I generally cannot do.

Two of my sons are engineers and when I talk about "feeds and speeds and what I'm fighting on my lathe" .......... they look at me as if I'm from another planet :)

I talk in "ten's" and "hundreds" of rpm's and surface speed, they talk in thousands.... And the stuff they machine, and the way they machine it is literally beyond the capabilities of my manual equipment. I'm personally just now getting back in touch with the equipment enough to know when to say "ooops! this ain't working!" and radically change something, like try a different material :)

Lathe I'm pretty good, Bridgeport is still day by day.

I will say this, In My Opinion that surface finish is a sure sign of "call it a day, this IS NOT a settings issue but instead a bad mix of materials"

For ME

In other words that's what I would do. ;)

Because I don't know no better
 
I had some threads awhile back that weren’t looking very good. It turned out that the adjustment knob that keeps the threading tool on center had moved and the threading tool was dropping down below center line. Moved it back to being in center and it fixed my problem. I’ve also seen problems if an insert gets loose. If the insert needs to be changed it doesn’t sound right when cutting the thread. I haven’t ever seen a thread as bad as the one in the photo. Hope he gets it figured out.
 
Out of center

That looks just like an out of center threading tool. Looks to be dragging. A HSS cutter would likely give a better finish with sulphurated oil. Some materials are nearly allergic to carbide cutters for a good surface finish.
 
Is this a small diameter workpiece? About 2 inches or less ?

Those chatter marks are too close together to be a tool geometry problem.


?
 
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