Parting Off---To peck or not to peck?

bdhamp28 · Oct 3, 2018

Hello all,

Here is a little background info:

Machines

Okuma LB3000 lathe with subspindle
Tsugami B0385 swiss turn

Stock

HS220
8640
17-4 SS

(all stock is round and 1.5" or less in diameter)

Now, when parting off I am getting conflicting advice on whether or not a peck cycle should be used. I have a programmer that insists on pecking and tool vendors insisting that a peck is not necessary and to cut straight through. Any and all information is appreciated.

Mtndew · Oct 3, 2018

In 99% of situations, there is no need to peck. Feed it fast enough to where the chip breaks and falls away.

DMF_TomB · Oct 3, 2018

bdhamp28 said:
Hello all,

Here is a little background info:

Machines

Okuma LB3000 lathe with subspindle
Tsugami B0385 swiss turn

Stock

HS220
8640
17-4 SS

(all stock is round and 1.5" or less in diameter)

Now, when parting off I am getting conflicting advice on whether or not a peck cycle should be used. I have a programmer that insists on pecking and tool vendors insisting that a peck is not necessary and to cut straight through. Any and all information is appreciated.

.
so advice of programmer with experience with your particular machine you are ignoring over the advice of a vendor salesman who made how many 1000's of parts last year ? and vendor salesman might have been a corn flakes cereal salesman last month ??
.
i tend to record my own experiences making tens of thousands of parts and dont take long to have 100 to 1,000,000 times more experience trying things than a vendor salesman. but a programmer that actually makes parts on the machines i use would be my 1st choice for advice over a vendor salesman
.
not saying not to try different things but often a sudden tool failure is very very expensive. of course salesman would be happy to sell you more tooling

DMF_TomB · Oct 3, 2018

2% sudden tool failure rate for some thats no big deal.. also no big deal scrapping 2% of parts
.
for others thats way too high a scrap rate. even 0.2% scrap rate is too high

toolsteel · Oct 3, 2018

There is no 100% answer here.....I have rarely needed to peck while cutting off. I have needed it for large / deep grooves.
I personally "default" to no peck. I will only peck if experiencing issues.

dodgin · Oct 3, 2018

Mtndew said:
In 99% of situations, there is no need to peck. Feed it fast enough to where the chip breaks and falls away.

This.

If your cutting conditions suck and you're generating strings rather than chips, that's when you work in a peck on a cutoff/groove cycle. That's only after exhausting all other options though. In my limited experience, anyways.

Mtndew · Oct 3, 2018

bdhamp28 said:
Hello all,

Here is a little background info:

Machines

Okuma LB3000 lathe with subspindle
Tsugami B0385 swiss turn

Stock

HS220
8640
17-4 SS

(all stock is round and 1.5" or less in diameter)

Now, when parting off I am getting conflicting advice on whether or not a peck cycle should be used. I have a programmer that insists on pecking and tool vendors insisting that a peck is not necessary and to cut straight through. Any and all information is appreciated.

Just because that programmer insists on pecking, doesn't mean he's right. It could mean that's just what he knows or is comfortable with.
Show him this video:

ISCAR LOGIQ TANG-F-GRIP - YouTube

fmari --MariTool- · Oct 3, 2018

Salesman isn't going to help manage the big bail of hay like stringy chips you can sometimes get if you don't peck. Yes I know if your feed and speed is just right and the chip breaker on the insert is doing its job you shouldn't have long chips. But bar to bar alloy variances and while insert is wearing, or coolant flow is changing, or a coolant jet gets whacked out of alignment you will get some nasty stringy chips if you don't peck.

All you need is one long stringy chip to wrap around the turret while indexing to make a whole mess. Ive seen long stringy chips rip apart turret seals, move coolant lines, jam chip conveyors, and many other nasty things.

My 2cents, peck.

litlerob1 · Oct 3, 2018

The people who are telling you may not be the right people, definitely not a Tool salesman. First things first, I hope you aren't using Part-off blades, with their stupid wedge type insert. That POS design causes more problems than a free one with a box of ten inserts is worth. It's a most embarrassing Marketing strategy.

I use positive locking Groove Tools.

R

Oldwrench · Oct 3, 2018

Certainly no shortage of opinion about this, but pecking is never the first choice for parting off. It adds entry friction with each peck and can double the time of the operation.

guest · Oct 3, 2018

I do one shallow peck because I like to use the partoff tool to chamfer the back side OD. Other than that, no pecking unless it's to solve a problem like not enough coolant flow to the insert in hard to machine materials.

SWYooper · Oct 3, 2018

I'm going to pile on with the "normally not needed" crowd. Only time I've had to peck on cutoff is with a current job I'm running that has features that will grab the cutoff chip and wind it impossibly tight, despite my best efforts with high pressure coolant, speeds and feeds, etc. Pecking saved the day but as others have said, it was a last resort.

pcasanova · Oct 3, 2018

depends on material. I mostly do plastics so acrylic and acetal no, but get into polycarb or abs then yes.

Coadster32 · Oct 3, 2018

Kind of suprised nobody had mentioned cutting speed here. Parting off, like facing, can be very harsh on carbide. You can't spin the material fast enough when approaching X0. There are instances where I need to peck, but mostly at the diameter your speaking of, no so much. What is more importaint is to cutoff in G96, clamp your spindle at what your setup requires, and slow the feed down when you get to that clamped RPM. This is because at this point, you are starting to push the material, rather than cut it. It will destroy your insert, and inevitably lead to breakage. (You can even hear it "growling" if you listen well enough.)

I agree with the several view points, but if your shop guy says always one thing, always...perhaps he needs to open his mind a bit, and try something different. Just when you think you've done it all, either you get left in the dust, or you're too big for your britches. (No disrepect intended in that statement).

fmari --MariTool- · Oct 3, 2018

This is why I error on the side of parting. Parting normally means you are barfeeding, and normally means the machine is also running unattended and sometimes even lights out. Rarely do you get all material perfectly straight. You try spinning a 12' bar to 4500 rpms while parting with a slightly bent bar and the machine is going to rattle itself to death. So parting is never running under ideal conditions. Many times I do the parting manually instead of a canned cycle. Fzor example when parting 2-5/8 round. The first 1 Inch of travel I know the tool is getting enough surface footage so from 2.625-1.625 I may peck every .250 Inches. Then from 1.625-.625 I may peck every .150 Inches. Then from .625-0.0 every .100". Also many times I dont peck, just dwell. feed, g04 p500, feed, g04 p500.... You can also do g04P#720 and assign macro #720 and adjust it in the variable page. This way your not adjusting every P value in your program.

chip_maker · Oct 4, 2018

What I've done on bigger diameter SS cutoff is what I call a "short peck".

What I do is back off the parting tool .005-.01 on diameter as opposed to taking it all the way out off the cut.

This gets the chips out of there and gives the tool a rest.

I've found out (the hard way) it's not always good to push them hard enough to break a chip in 304/316.

DDoug · Oct 4, 2018

Lot's of good pro and con up above, I will just add:

I would like to listen to the tool when it goes back in, is there a chirp ?

Work hardening might be a problem, slightly chipping the insert with each
peck.

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Parting Off---To peck or not to peck?

bdhamp28

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Mtndew

Diamond

DMF_TomB

Diamond

DMF_TomB

Diamond

toolsteel

Titanium

dodgin

Hot Rolled

Mtndew

Diamond

fmari --MariTool-

Titanium

litlerob1

Diamond

Oldwrench

Titanium

guest

Guest

SWYooper

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pcasanova

Hot Rolled

Coadster32

Aluminum

fmari --MariTool-

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chip_maker

Stainless

DDoug

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