Iscar boring bar

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FrankieB

Aluminum

Joined

Jun 28, 2019

• Apr 1, 2020

• #1

Hello all, i am running an 1” iscar bar with a cnmg332 insert. I am having a hell of a time dealing with chatter. I have tried 400 sfm down to 300rpm. I am feeding around .007 to .008 per rev with a doc from .035 to .050 per side. It is being held with a vdi holder. An decent suggestions to stop the chatter?

Thank you

 

W

WRL

Plastic

Joined

Mar 4, 2015

• Apr 1, 2020

• #2

Is the extension more than 3x Dia.?

 

David Ferguson

Cast Iron

Joined

Aug 13, 2008

Location

Paso Robles, CA

• Apr 1, 2020

• #3

you don't mention what material you are cutting, but increasing the DOC usually helps.

 

F

FrankieB

Aluminum

Joined

Jun 28, 2019

• Apr 1, 2020

• #4

The material no, bar stick out is 5” and i am boring back 4.5”.

 

F

FrankieB

Aluminum

Joined

Jun 28, 2019

• Apr 1, 2020

• #5

The material is 4340 pre-hard.

 

J

J_Copeland

Aluminum

Joined

May 13, 2011

Location

Warren,Ohio

• Apr 1, 2020

• #6

FrankieB said:

The material no, bar stick out is 5” and i am boring back 4.5”.

Click to expand...

Try running a lower SF,like 150-200. D.O.C. .020-.025
If your machine has SSV use that also


Sent from my iPhone using Tapatalk

 

ChipSplitter

Titanium

Joined

May 23, 2019

Location

Maybe

• Apr 1, 2020

• #7

FrankieB said:

The material no, bar stick out is 5” and i am boring back 4.5”.

Click to expand...

Oooo........ you say you have a 1" bar and it's hanging out 5" and you're running 4340 PH? Not an ideal situation by any means.
Things to try:
1) Do like someone else above mentioned and vary the RPM constantly. Like uuUUPPP ANd down aND UPpp and .. you get the idea.
2) Try changing the bar stickout by .25" either in or out. Don't laugh, it can be a lifesaver sometimes. It keep harmonics from building up.
3) Make the workholding as rigid as possible.
4) Use a different insert geometry that is more free-cutting, i.e. a finishing insert instead of a rougher.
5) Try tweaking the DOC.
6) Make sure your bar is dead on center or a few thou. above.
7) If all else fails, use a solid carbide or dampened bar. Lots of $$$, but it could save the bacon. If you get a new bar, make sure you get the right insert for the job. I like CCMTs for deep boring, but I know some people don't............

 

S

SIM

Titanium

Joined

Feb 19, 2004

Location

Staten Island NewYork USA

• Apr 3, 2020

• #8

CNMG 332...try something with less radius, sharper, positive and uncoated.

VDI-s suck at times. Hanging bars out in the breeze, held by a couple set screws.

I used to make snug sleeves for the bars with flats to locate. Bars had to be tapped into the sleeve, then that needed to be tapped into the holder.

 

Shop Supply Guru

Hot Rolled

Joined

May 3, 2016

Location

Ohio USA

• Apr 3, 2020

• #9

A lot of great advice already. Steel bars are generally meant for 3xD applications. With different manufacturers tweaking stuff to get 4xD. I would suggest going to a bigger bar with a positive insert like a CCMT if possible. Carbide bars are generally rated for 5xD like you are running. If not possible lower depth and feed like crazy.

 

ChipSplitter

Titanium

Joined

May 23, 2019

Location

Maybe

• Apr 3, 2020

• #10

Shop Supply Guru said:

A lot of great advice already. Steel bars are generally meant for 3xD applications. With different manufacturers tweaking stuff to get 4xD. I would suggest going to a bigger bar with a positive insert like a CCMT if possible. Carbide bars are generally rated for 5xD like you are running. If not possible lower depth and feed like crazy.

Click to expand...

True.
I have run 4xD but you have to have everything right. I was using a CCMT on that application. IMO, "X"NMG inserts are for medium to roughing. You can get a finishing chipbreaker on them, but they're really overkill for that.

 

W

WRL

Plastic

Joined

Mar 4, 2015

• Apr 3, 2020

• #11

If I read this right you might be better off internal grooving and boring.

If you have a bigger bore in the front of the part maybe you could put the boring bar in a sleeve, giving you the extra dia. you need.

Good luck.

 

F

FrankieB

Aluminum

Joined

Jun 28, 2019

• Apr 3, 2020

• #12

Thanks for all the suggestions i finally got something to work fair. What i really need is to get my hands on a sandvik de-vibe bar.

 

ChipSplitter

Titanium

Joined

May 23, 2019

Location

Maybe

• Apr 3, 2020

• #13

FrankieB said:

Thanks for all the suggestions i finally got something to work fair. What i really need is to get my hands on a sandvik de-vibe bar.

Click to expand...

What did you end up doing?
Just curious.

 

F

FrankieB

Aluminum

Joined

Jun 28, 2019

• Apr 3, 2020

• #14

Slowing everything way down. Rpm was around 135-140 and feed was 0.0054. The
finish was junk but i hit it with paper and got it good enough.