large diameter parting blade

meowkat · Sep 24, 2020

I'm trying to figure out the right parting blade and holder for parting off this 5" diameter brass with a 0.390" through-hole.

The surface finish I get with a kennametal A2 size 3 inserted blade (max diameter ~4.7") is pretty terrible. It works, but not well. I would opt for one of the Y-axis parting blades if my old machine would let me do turning with the Y axis unlocked :nopity:

So, I need a parting blade around 0.150" thickness with max part diameter 5"+ through interruptions in brass & associated insert. I called an industrial supply hoping they might be able to recommend something and the guy literally pretended he couldn't hear me and put me on hold.

Side question, which tooling companies will examine an application and suggest a tool? I have spoken to OSG about endmills in the past and the process was fantastic even as a small company. I don't know who to contact at companies like kennametal/iscar/etc. about this sort of thing. So, any thoughts are appreciated.

Guest · Sep 24, 2020

I know they are pricey, but I think most of us prefer Iscar for your parting application. I would just call their technical support.

Cole2534 · Sep 24, 2020

Sounds like a job for a well ground HSS blank. I'd probably get one as tall as I could to help with deflection then relieve it the bear minimum to prevent rubbing.

Garwood · Sep 24, 2020

I bought a J&L 8A-5 with a bar feeder that made 2.5" nuts from 4.5" 4140PH every day from about 1975 through the early 2000's

Old dude that owned it said the only parting tool worth a shit for that kind of use was manchester.

Sold that turret lathe years ago, but I still use that same Manchester parting holder.

meowkat · Sep 24, 2020

Cole2534 said:
Sounds like a job for a well ground HSS blank. I'd probably get one as tall as I could to help with deflection then relieve it the bear minimum to prevent rubbing.

I think grinding a HSS blank is a bit too old-school, surely a blade and carbide insert is available that can do the job.

Cole2534 · Sep 24, 2020

meowkat said:
I think grinding a HSS blank is a bit too old-school, surely a blade and carbide insert is available that can do the job.

Probably so, and if it wasn't brass I'd not even suggest it.

Sent via CNC 88HS

atex57 · Sep 24, 2020

Use an insert blade as tall as you can fit and hone or grind a flat on top of the insert and possibly on the front clearance face. That makes it very sharp and less likely to wander or leave a bad finish. HSS blades have to be perfectly aligned to prevent binding or cutting on the side. A negative rake may be best also.

Ed.

Delw · Sep 24, 2020

if your having bad finish issues, start the cut with a shorter blade.
alum sharp inserts work very well on brass. best tool I ever used for big dia part offs is manchester carbide tipped and sharp

Mtndew · Sep 25, 2020

meowkat said:
Side question, which tooling companies will examine an application and suggest a tool?

All of them.

DDoug · Sep 25, 2020

meowkat said:
I think grinding a HSS blank is a bit too old-school, surely a blade and carbide insert is available that can do the job.

What ?

You doo whatever it takes to run the job.....

Mtndew · Sep 25, 2020

meowkat said:
I think grinding a HSS blank is a bit too old-school, surely a blade and carbide insert is available that can do the job.

That's a pretty narrow minded way to think about machining.
If you can make something in 3 minutes and cut the part vs searching, ordering, waiting for a new tool then cut the part you're doing it wrong...usually.

BT Fabrication · Sep 25, 2020

Bandsaw to length.... then machine.

litlerob1 · Sep 25, 2020

The idea of parting 5" Diameter anything is dumb. That's 2.5" stick out. Waaaay too much. Parting regular stuff off AND achieving a good finish is already a bitch. It's never going to be Parallel to the Face. The finish will never be good. The OAL will only occasionally come out right.

Scrap the idea, not the part.

R

LKeithR · Sep 25, 2020

BT Fabrication said:
Bandsaw to length.... then machine.

That was my first thought. Machine as much as you can in first op then flip the part to finish. I have a
decent, albeit import, manual machine that is rigid enough to let me do most parting jobs with no worries
but I'd be a little scared of going that deep in brass.

Depends to a degree on how many you have to do. If you have a large number to machine then parting
will be faster IF you don't have to fight it. If the parting operation becomes an issue you only have to
mess up one or two parts to lose any time you might have saved...

MattiJ · Sep 25, 2020

litlerob1 said:
The idea of parting 5" Diameter anything is dumb. That's 2.5" stick out. Waaaay too much. Parting regular stuff off AND achieving a good finish is already a bitch. It's never going to be Parallel to the Face. The finish will never be good. The OAL will only occasionally come out right.

Scrap the idea, not the part.

R

And Iscar has parting blades up to 10" diameter :ack2:

Need some balls on the lathe to use 1/2" wide parting tool with 5" stick-out

that is some parting blade: Self-Grip Indexable Grooving Cutoff Blade Toolholder ISCAR SGFHR 53-12 2300559

gregormarwick · Sep 25, 2020

MattiJ said:
And Iscar has parting blades up to 10" diameter

Need some balls on the lathe to use 1/2" wide parting tool with 5" stick-out

that is some parting blade: Self-Grip Indexable Grooving Cutoff Blade Toolholder ISCAR SGFHR 53-12 2300559

I actually have one of those. Haven't used it in many years, but I bought it to part 3" wall thickness duplex pipe in a big hollow spindle lathe, needed a really robust tool to handle the irregularity of the pipe without any "surprises". Worked remarkably well.

As to the op, it's absolutely possible. 6mm blade would be appropriate, through the blade coolant with something approaching high pressure makes a big difference when deep parting. I prefer Sandvik 123 with single ended inserts when doing difficult parting and deep grooving. Not the most cost effective way of doing it, but gets the job done with minimal hassle.

Ox · Sep 30, 2020

The only Manchester tool that I know of that will get in there is #341101.

It is 1/4" wide and has .010R corners.
I am not sure if you can git angled "cut-off" type inserts for it tho?
Any that I have had for it are just "grooving" inserts. (0*)

You will likely need to make your own holder for the blade tho?
I'm not sure if they offer a straight shank type adaptor?
Make sure to check Tool Flo as well. (owned by Warren (not Jimmy) Buffet)

A traditional Manchester tool won't get above 3" solid.

On a different note:

You say that you are gitt'n a poor finish, but of course you are - trying to fetch all those chips out of that small / deep groove.
If you are able to keep your tool running straight (not convex/concave) then you are really all but home already.

Just start further away in Z-, maybe .050?
Make your cut, but don't quite cut it off.
Come back up and go back down at Z0 to take a clean-up pass.

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

I am Ox and I approve this h'yah post!

TFC · Sep 30, 2020

This will handle parting up to 5.670" diameter with a 0.250" wide insert.

TGSU 35-6-IQ (blade)
TAG N6.3J IC808 (insert)

Your choice of blocks:
TGTBU 19-35 (0.750" block)
TGTBU 25.4-35 (1.000" block)
TGTBU 31.8-35 (1.250" block)
TGTBU 38.1-35 (1.500" block)

https://www.iscar.com/eCatalog/item.aspx?cat=2302193&fnum=2848&mapp=TG&app=51&GFSTYP=I&isoD=1

large diameter parting blade

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