Parting off... Help,new project comming up tommarow...

Hey all...

Just finished my LONG part run...
We stoped at 50 units...

Now, tommarow...

Something new...

Damn, with all the ultra knowledge in this forum, i wish i could post blueprints without numbers...
Is there a way for my to post an autocad drawing without numbers, and without a way for you to figure the numbers out ? If i post an autocad drawing for you, and remove the numbers, and maybe take the image out of scale a bit, would you guy be abble to get the numbers from a .jpg image?

Anyway...

back to what i was thinking...

Tommarow there is this part, that i haveto make...
5 radii 3 angles surfaces, 2 chamfers , 1 center , and its ( aproximately ) 4.5 inches long... Dont know the exact steel it is...
But its Steel, and its Rockwell C scale 28-30 hardness...
So its pretty damn hard... Anyway... the stock is 4 pounds, and the finished part will be just about 2.5 pounds...
Basicly what i want to do it, face and center the part, bring up the tail stock, and machine the part at HIGH SPEED!!! ( as high as i can, that is ) Then i want to cut it off...

The cuttoff diameter is 1.770 and i was wondering... If i leave the tail stock engaged... How far can i cut before i should remove it ?
cut with tail stock engages untill there is .125 material left ? .250 ? .375 ? .500 ?

Or no tail at all ?

Also, lets say, i cut untill there is .125 left, in the center... i retract the tail stock...
then i plunge in for the final cut off...
What speed and feed should i use , so that i dont have these 4.5 inches of steel swinging all over the place... ?

PS : i did a nice long run of parts with cutoff and bar puller not long ago... But the part was only .250 long... and was drilled before cutoff too... so that was much easier...

this part being 4.5 inches long and 2.5 pounds has me a bit worried...

should i not worry, and just go for it... ?
is there something i should be carefull about... ?

PSS : this will be given to me in 6 foot long sections... I will be using the bar puller as well... There will be no spindle liner becuase the material is 2.010 and my spindle shafts ID is 2.060... so .050 extra... im not going to make a .025 thick donut... its not worth it...

Also 6 feet of stock means 1 foot sticking out the machine...

if no one is in the area, is that going to be ok ?
or should i just ask for 5 feet instead ?

PSSS : i love jobs where i got to use all the cool M codes!!!

thanks

I'd run them 3 feet at a time, thats a lot of metal to be spinning, especially without any support from behind. Skip the tailstock for the partoff its really only there for support when working on something long, and hopefully your parting off near the chuck. If you want to run fast on the partoff, thats cool, but slow it down to damn near nothing when it gets close say 3/8" to go, that way it won't come flying through the sheetmetal, though it you want a new lathe (and possible a new job), that might not be a bad idea.

3 feet at a time ?
darn

No tail while cutting off ?
no problem

cutoff untill .375, then come back at 200 rpm for the final cutt ?
ok

Don't take it as the absolute be all and end all. I would go for about 3 feet myself, if your machine will hold 5 in the spindle, you could probably get away with that. I was just thinking 12 foot bars. A big bar spinning while only supported at the chuck can throw you off, especially if its not supported by at least a bar feeder. If your using the tailstock that will help out a bit.

You should be able to rip on this one. 2" material with a tailstock 4.5" out!! I hope you blow up an insert or two just to find out where you can go. Just for Solars info, I do 90% of all the tool ordering and though I'm not usually on the lathe, destroying a tool, not just the insert but the whole holder is not that uncommon, especially in a job shop where we work with tons of different materials and are pushing all the time. Just keep yourself a notebook, or do what I do and hope you remember.

Hey thanks...

I will be pushing alright!!!

Finally found these really cool Triangular inserts that work GREAT!!! and last forever...
They are especially made for roughing...

i think i may start out at about...

1,000 rpm
F.010
D.050

But quickly move to...

1,250 rpm
F.012
D.080

And if im feeling a little spicey...

1,500 rpm
F.015
D.100

I wonder if i will hit 90-100% load at that rate ?

This material is about 28-30 C scale...
So i may not be abble to get anywhere near what im shooting for...

But i can dream cant i ?

hahaha

First, I thing everything depend on what kind of machine.I like to work with sandvik WNMG 4025 PR to rough out steel. with 0.25" to 0.3" DOC on diameter and a feed of 0.012" to 0.014". I run it at 750sfm in 4140 (18 to 20 Rockwell) or 500sfm in 4140 HTSR (Heat Threat Stress Release)wich is about 28 to 32 Rockwell I think.

For this piece you have to make, you could start 0.25" DOC with 0.012" feed and 500 sfm.

parting tool can be push hard sometimes. 0.125 width tool at 0.006" feed 350sfm no tailstock, down to 0.3" Dia. then reduce the feed at 0.002" and the rpm you feel compfortable with.

thats my general reference in steel (4140)
I hope that could help you out.

acctually...
walligator...
that did help me out...

thanks...

so 500 sfm for 28-32 C scale huh ?
thats acctually not too shabby...

the .025 DOC makes me feel sad...
I wanted to really push the machine...
But my 4140 steel at about 5 C scale is a lot different then what i will be cutting tommarow

I really appreciate it

So thanks for the help ...

PS : yes, my part off tool is .125

Solar, RE-read Waligator's post.
He said .25" DOC. Not .025"!!! (.025??? that is not even worth talking about)
THat is 1/4 of an inch per cut on the diameter.
*I* would program for a DOC in that range too.
My lathe has more HP than yours, but .125 radially is not too much.
4140 HT is butter. Rip that stuff off.
YOu will not want to go back to 1018 [crap] sttel after machining 4140 HT.
I run around 450-600 for ruffing. The deeper the DOC, the lower I go in the SFM range I just mentioned.
Do not use the tail stock when parting below .5"
If you are parting next to the chuck, then don't use the tailstock at all. (except when turning)
Watch out for tool overhang in regards to your tailstock
Have fun, and good luck.
Doug.

On those kind of jobs, I usually part off to .25 dia, then stop the machine and break the part off manually, rather than risking the part getting clipped by the chuck.

I agree with Hu about breaking the part off manually . If 1/4 is too much to break off easily you can take it smaller gradually until you get to the point that it will break off the bar fairly easily by hand. If it does a little wobble wobble as it gets real small, it can pop the insert and twist the parting blade, and thats close to a hundred bucks down the drain. I sometimes rig up a parts catcher on the 2nd turret when I'm doing bar parts. Thats simple on a 2 turret lathe. On a single turret machine it can be done, but its a lot more difficult to get everything placed just right so that it works as it should. A parts catcher can also be rigged up and moved into place with the tailstock M codes, but you can only do that with parts where you're not using a center in the tailstock for the turning operation.

6' long - leaver hang out!

No tailstock needed.

I have found that the cutoff tools in that material want to run a LOT slower than manufactures recommendations doo to chatter. I don't like carbide tooling "singing" the song of death! Almost the same as SS. Slow and hard IMO.


Think Snow Eh!
Ox

To doug...

The material im cutting now is 4140...
its only about Rockwell C scale 5...
the stuff im talking about will be about 6 time harder... C scale 30... Do you really think i can cut .250 per pass, on something of that hardness ?

If so , thats pretty impressive...
Dont know if my 11 killawatt can handle that...

To everyone else... thanks
I am still not sure about the cuttoff cycle...
I still think i may try it for 1 or 2 cycles...
If there is a failure, i will stop and have the stock pre-cut for me... on an automatic saw...

thanks again

correction...
i am confused...
the material im cutting now is not 4140, its 8620... i WILL be cutting 4140, and its really hard...

Solar, I don't know if the lathe *will* handle .125 DOC, but I would think that it would.
Watch your load meter. The biggest hint if the lathe cannot handle the cut, is when the spindle stalls.
I don't think that will happen though.
I have never had to run 8620 bearing steel, but I do run LOTS of 4140HT. All the time!
.125 doc (per side) is not a problem.
Seriously, RC28-33 is not a big deal.
You will find that you like to cut it, b/c it will chip well.
Make sure to start with the mfg.'s recommended SFM. Work your way up, or down depending on what the tool life looks like. Remember, you will only get a "GOOD 15 minutes" in cut for an insert edge.
Then rotate the insert.
THe only tricky part about machining hard stuff is keeping control on the SFM, and for turning you have a bigger margin of error, than say drilling with a HSS twist drill.

Once you have mastered Rc30, then you will get to machine some RC40, then RC50, then Rc60
Those get a little trickier to cut.
You will get to use (say it with me) ceramics OUUUHH AHHHHH!
Then the fun starts.
Doug

doug!!!

hey thanks man...
i appreciate the tips...

i ussually get about 3 hours of acctual CUT TIME per insert nose... So if i only get 15 minutes per nose i will be very dissapointed...
i want to try and get 1 hour of cut time per nose if possible...

if that requires me making deep cuts, at low sfm and low feed, then i will...

it takes too long to change a tool insert... i dont want to be changing 4 times per hour...
1 time per hour of cutting is fine as a minimum...

From what i gather, a deep DOC does not really effect tool life very much... But too high a feed does, and too high an sfm does as well...

So maybe to make up time, i will go for...

F.010
D.100
S 300

we will see...

Solar, while I understand wanting to get lots of life out of an insert, think of it another way.
yes, you can baby an insert. IE..taking small cuts, and not using much in the way of SFM.
So yeah, you can get lots of life from an insert.
But at what cost????
You will save $10 worth of cutting edges, but the parts take 3x as long.

SO look at it this way.
Push the ever loving dog snot out of the insert.
SPend $10 an hour on the insert.
Now you are making 3-4 times as many parts per hour.
YOu have just tripled, or quadrupled your profits in a job!

Inserts are made to wear. That IS their job.
Your is to make you boss as MUCH money as possible.
Hence, you get a raise (hopefully), your boss buys newer/better equiptment, and everybody is happy.

Just my .02$
Doug.


PS. Use a WNMG 432 inserts for the ruff off. They give the strongest insert geometry, and you will get 6 cutting edges per insert.
after you have used all the edges until they are dull, put that insert in a boring bar.

Watch your load meter. The biggest hint if the lathe cannot handle the cut, is when the spindle stalls.

No truer words have been ... er ... spoken(?). LOL!


-----

Inserts are made to wear. That IS their job.

You must be buyin' your inserts at the wrong store! Mine are made to cut. Hmmmmmm........ ????

LOL!


Think Snow Eh!
Ox

doug925 is right. when i can hit 15 to 20 minutes per cutting edge, I'm happy.
We macine High Temp alloy (nemonic) sometimes. I use the cheapest insert I can find (Kennametal K68)wich i can get only 2 to 4 minutes machining time. But, cycle time is short and my boss happy.
I tried all different sort of inserts, cheap, expansive, ceramic, name it. cheaper is better for this alloy.
SO, every job is diferent. you can't expect same cutting time on every job. it depend on material, insert used, set-up and what finish you need.

LAME!!!

new job got postponed becuase of some stupid blue prints i had to create...

3 rotor heads
2 thrust plates
1 ball gear

LAME LAME LAME!!!
WIll finish tommarow, but not in time to start my next cnc job... Then the stupid weekend...
I have to wait till monday to get machine time...

Lame lame lame!!!

LAME LAME LAME!!!
WIll finish tommarow, but not in time to start my next cnc job... Then the stupid weekend...
I have to wait till monday to get machine time...

Lame lame lame!!!

Click to expand...

I'll bet the boss makes you wait until Tuesday at least.. That's my prediction.
Pete