I need some advice from the turn & groove pros

[jeff]

40rc copper? I wasn't aware that you could harden copper.

 

2.75 overhang on a 1" bar is nothing.

I've had jobs where the ID groove would chatter no matter what I tried. It's amazing.

What type of bar are you using? Is it one of those that grip the insert or is the insert held with a screw?

If it doesn't chatter while plunging ,and just when taking a light cut finish, I would say that something is loose, or cracked somewhere.

Have you tried using a different bar holder on your turret?

[Brad Lisle]

maybe stating the obvious, but have you indicated the bar? Is the cutting edge on center? if not that could cause chatter on lighter finish passes. May need to adjust screws to level out bar.

[Dave.L]

quote:

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40rc copper? I wasn't aware that you could harden copper.

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Beryllium Copper, and yes it's 40 RC.

 

Bars are grip, not top notch.

 

quote:

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I've had jobs where the ID groove would chatter no matter what I tried.

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Yep, that's this job. Like I mentioned, I cannot even get it to work in Brass so I know it's not a material issue. The books all talk about deflecting the tool so it then becomes a single point. That said, I don't think I am loading up the tool enough.

 

The fact that the same paramters used on the OD work is whats really blow'in my mind on this.

[Odell]

This might sound a little silly but I have got rid of chatter by wrapping a heavy rubber band around my boring bar kinda tight. and sometime around the part. Doesn't always work, but sometimes I does. Give it a try, you might be surprised.

[heavychevy2155]

I've wrapped rubber bands along the shank of boring bars, its an old trick and it may help reduce the chatter.

[heavychevy2155]

Sorry odell, you beat me to it.

[chris m]

quote:

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The fact that the same paramters used on the OD work is whats really blow'in my mind on this.

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OD and ID are totally different animals, man.

 

Clearance angles and tool deflection are SO much more critical with inside work.

 

You might try setting the bar above center a few thou in the Y to see if that helps; you could also try rotating the bar back a couple of degrees to increase the clearance angle behind the cutting edge.

 

The super-slow surface speed is worth a try to get the ball rolling, but if you start building up an edge the vibration is going to get worse.

 

Have you tried changing bars? I had an experience one where the tool had been improperly manufactured [the thru-coolant hole was WAY too large and too close to the cutting edge] and I battled it for awhile before just swapping bars and voila the problem went away.

 

Another tool suggestion is a carbide or tuned bar, those like to soak up the vibes.

 

C

[jeff]

quote:

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This might sound a little silly but I have got rid of chatter by wrapping a heavy rubber band around my boring bar kinda tight. and sometime around the part. Doesn't always work, but sometimes I does. Give it a try, you might be surprised.

---

I've done this too, and sometimes it soaks up the chatter and vibration.

I duct taped a piece of rubber to my 2" bar that was hanging out 12" lol.

 

 

Dave,

What is the wall thickness like?

Can you groove the ID before you turn the OD?

Maybe that extra stock will help?

[gcode]

quote:

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Bars are grip

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screw clamp

or

srping tension??

The spring tension type are

useless for anything but part off

applications in my experience.

They are good for that, but

I've never had any luck with

turning or groove profiling.

[Dave.L]

Tom,

 

Screw clamp, but not top notch.

 

Chris, I like your suggestions. Some I have tried.

 

I really appreciate all the input from you guys. I will be back at it in a few minutes.

[Kevangel]

If it were me I would try 100 RPM...My machines chatter very easily on ID grooves...I would mix some EDM fluid and cutting oil (kerosene /cutting oil) and brush or squirt it also. If that does not work I would re-check tightness everywhere I can...I would assume nothing on tightness. Can you get away from the surface feed and just go inches per revolution to finish.

[Del.]

try putting a magnet on your boring bar.

[Kevangel]

Just one more thought since its heat treated copper and I don't know if it pertains, but machining ampco 21 (aluminum bronze) to make lifters for molds , you must use a brand new VIRGIN cobalt HS endmill that has never touched metal..even if it feels very sharp it won't cut right. I had a leading area moldshop give me a whole box of carbide cutters to machine some Ampco 19 and I just used cobalt HS and it was a breeze and they asked me how did I do that...maybe carbide is not sharp enough..

[chris m]

Following Kevin's train of thought; is this insert coated? Edge-rounding from coating might be an issue if it is; try an uncoated carbide and see if that helps.

[G10X0Y0Z0]

this is what works for me. i get better than a 32 fin

 

bar is from sandvik did not have any luck with kennametal. no modifications to insert

 

no SFM

RPM = 200

X Feed .002

Z Feed .004

[jeff]

quote:

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is this insert coated?

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I was just going to ask that

[Goldorak]

PHorn makes some very very good grooving tool with full carbide shank

 

i use a .046 (mini 108) id groove in stellite and hastelloy with a very good tool life

 

every other brands(iscar sandvik and kennametal) fail after less than one groove

[Ron Branch @ Verisurf]

PHORN would be my only choice in this application using the solid carbide bar. Use them on some 3" deep .787 id grooves in 52rc material and have no problems. Pricey, but quality cost money in my book.

[Chris Parish]

Dave:

 

since you don't have Mastercam lathe... it might be the "esprit" software that gave you the "G-code" toolpath .... J/K

[Dave.L]

Chris,

 

I have been waiting all day for that comment from you - no lie.

 

Still not there yet, but you guys that suggested slow SFM where spot on. I am now around 150-200 SFM w/ the Iscar tool and it's much better. The Iscar does not break up the chips well and the corner of the insert just broke.

 

I am going to try the Kennametal tool again at the slow SFM.

 

It's hard to say what happening when i tried it slow early on and got bad results - something else must have been the issue then.

 

It's hard to keep all the variables and test parameters straight. Had I known this would be such a nightmare I would have made a log sheet at the start.

[Kevangel]

"Dave Lelonek, please report to the Principals office".

[Dave.L]

Kevin,

 

I am now down to 200 RPM

 

Better but I have a wierd surface finish problem. The diameters have lines (only visual) that run the length of the part, in the tool Z axis feed direction. It's not the material, it's an effect of the cut. It's like a straight chatter form.

 

Very bizzare.

[Reko]

quote:

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no SFM

RPM = 200

X Feed .002

Z Feed .004

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+1

[Kevangel]

Its only an educated guess from fighting chatter on my machines when doing i.d. O-rings...but a cobalt HS tool that is "very sharp" with cutting oil would probably solve this. I made a .040 width one for some ring clip grooves in 420FSS 32-38RC several years ago and have still not sharpened it, but use it occasionally. This is on the o.d.

 

Even though material is fairley soft it is gummy...I have machine lots of copper-berlyium that was in the heat treated state for plastic Molds..

 

[ 05-18-2010, 08:55 AM: Message edited by: Kevangel ]

[Dave.L]

quote:

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but a cobalt HS tool that is "very sharp" with cutting oil would probably solve this.

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Maybe but this is a production job and not a one-off so that would not be practical.

 

quote:

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Even though material is fairley soft it is gummy

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This material is not gummy at all, it breaks a chip very well. It's abrasive though.