I need some advice from the turn & groove pros

[Dave.L]

Hi Guys,

 

Doing a part with a series of ID grooves.

 

Plunge roughing, no issues.

 

Profile finishing and I can't get rid of the chatter. I tried Iscar and Kennametal tools and have the same results. Both tools plunge rough perfect but both tools squeal when finishing.

 

.008 corner rad insert and .016 corner rad tried.

 

- tried .008 finish stock up to .06 (in diameter).

 

- Rotated tool above center

 

1" bar, overhung 2.75" (needed) but I tried choking up on the bar as a test and no improvement.

 

Any idea's from the pro's with experience in this area?

 

Thanks Guys!!

[Mr. M]

What is the groove and insert width? And what material?

[Dave.L]

I have tried .08 & .157. Material is copper, but I played with brass as well so I know it has nothing to do with the material.

[Kevangel]

Dave have you tried slowing down RPM to the extreme and see if that helps and then start speeding back up.

[Dave.L]

Kevin,

 

Yep. I went as slow as 400 RPM.

 

I have mostly been running 800-1000 SFM. I am now thinking of trying 1200 SFM.

 

BTW, the material is HT 40 RC. But as I said, I cannot get this to work even in soft brass.

 

I must be really missing something.

[Mr. M]

I use .062 width top notch inserts with good results leaving .005" or so for finish

[gcode]

If the grooves are wide enough...

Get 2 bars

Use the skinniest inserts that you can

Grind left hand releif on one grooving tool

right hand relief on the other

and turn the groove, blending in the middle

[Dave.L]

Tom,

 

I like your idea. The problem is that when I used the .080 Wide insert, they were deflecting so much that I cannot get straight walls. The only way they stayed straight is in a plunge with material on both sides. (EDIT and I need to profile the inside corner rads)

 

Also, I need to hold a 32 finish and I think blending will be a problem. I am also out of turret stations.

 

The same part has an OD groove and I am using the same tool (insert, etc) and I have no issues with the OD - None, it is perfect.

 

By the end of this week I will be bald.

[K2csq7]

Workholding? Think of where the cutting forces are going & try to support the area behind. You may not like thinking about it right off the bat but, changing your setup to better support the section of the material giving you the issues almost always works!!!

[Dave.L]

Keith, it's a slug on a lathe with plently of hold on stock. Workholdling is not the issue on this one.

[Mr. M]

Try less finish stock (.002-.003)

[J Coulston]

Simple, but have you checked the perpendicularity of the insert and center height??

 

Can the ID work be machined first?

[Dave.L]

Mr M it not usually a good idea to leave less stk then the nose rad. But, in the begining I did leave only .005.

 

I have the tool set just above center and The OD work is minor but I think it important to do first to take out runout vibration

 

thanks for the ideas guys.

[gcode]

It almost sounds like the pocket of your boring bar is damaged.

 

 

kiss the face of the inserts on the diamond wheel. Break the face at a slight angle all the way to the corner radius.

If you do it right you've got an .008R turning tool,Do one left, one right and meet in the middle.

If you keep the stock at no more than 30% to

the insert radius it should run pretty good

 

other options

solid carbide boring bar

 

one more

Iscar has some really good insert geometries for this kind of issue.. so does Sandvik

[Dave.L]

Tom, the bar is not damaged. While I like your ideas, I need to get this done with off the shelf tool because this will run every month for years.

 

Tommorrow I will try over feeding the tool to load it up. I think that may not give the finish I need but at least I can see if it will work

[Mr. M]

quote:

---

Mr M it not usually a good idea to leave less stk then the nose rad.

---

Ya don't have to try it then (but it does work sometimes)

gcodes idea of the 2 groove tools also works quite well.

How deep and wide are the grooves Dave?

[gcode]

quote:

---

I need to get this done with off the shelf tool because this will run every month from years.

---

you can buy left right and neutral groove/turn inserts off the shelf for Iscar

[Dave.L]

The part has 6 grooves in the ID. 3 wide .452 and 3 narrow .210 with a land between each. It a pattern of 1 wide and 1 narrow. They are not deep about .16.

 

The tools I tried just will not turn worth a damm. Plunge works great

[gcode]

Iscar groove/tun ought to tear this job up

[Dave.L]

Tom I tried an Iscar tool today, sent UPS red. Same issues as the Kennametal tool.

 

Its really bizzare

[Mr. M]

Which kennametal tool are you useing?

[Dave.L]

A4 with gup chip breaker

[kunfuzed]

Just thinking out of my butt hear, but can you try in in a different machine?

[Reko]

Dave,

 

I think Kevangel had the right answer, slow the spindle to the extreme. You said you went down to 400 RPM... go down to S100 if you have to. I realize cycle time will be compromised a bit, but at 40 Rc this may be necessary.

 

Remember, you have to decrease the SFM because the insert has more surface area in contact with the part than a conventional insert does. Single point finishing with a grooving tool is problematic.

 

Also, a solid carbide bar is a must, IMO.

 

Good luck.

[Mr. Wizzard]

just a thought, but i've had pretty good luck on grooving/profiling with ph Horn tools.