Parting Question: Seems Feed Is Really Fast.....

[mikey]

You're using a P3S blade, which is 1/8" wide. It will take more pressure to cut than a thinner blade will.

If you look at the front relief angle with the tool holder on a level surface you have maybe 5 degrees of relief? With high feed pressure you may have some contact with the work. I would try increasing that to 10 degrees and see if that makes a difference.

 

[higgite]

David and Mikey beat me to my other suggestions while I was typing with my usual hunt and peck aplomb, but I'll throw this out there to chew on.

I can’t speak to your angled tool holder because all I have used is a horizontal one. I part on my 8.5x20 with a 3/32” blade with no chatter or squeal with steady drip of fluid and faster-than-you-think-it-oughta-be manual feed, especially with aluminum.

The squeal could be the blade rubbing, either on the front of the blade from not enough relief due to the angled holder or on the side from not being perfectly perpendicular to the spindle axis. Or both.

I don’t know that it would make any difference, but just for grins, you could turn the blade end for end in the tool holder and grind a small flat on top so the cutting edge is horizontal. And of course, grind some front relief. If that doesn’t help your problem, you wouldn’t have altered the “good” end of the blade and can just flip it back around.

Tom

 

[great white]

You're using a P3S blade, which is 1/8" wide. It will take more pressure to cut than a thinner blade will.

If you look at the front relief angle with the tool holder on a level surface you have maybe 5 degrees of relief? With high feed pressure you may have some contact with the work. I would try increasing that to 10 degrees and see if that makes a difference.

that's just a pic I grabbed off the 'net as an example. It's not actually mine.

Comments noted though once I have a look at my actual tooling....

 

[Paul in OKC]

Agree with the more front relief. I wouldn't touch the top of the tool. Might angle the cutting edge about 5 degrees, instead of square with the od of the part, if that makes since.

 

[Dranreb]

Have you checked for tiny chips or maybe a small ding with a raised edge in between your tool post and compound? Check the mating surfaces of your toolholder dovetails as well.

There was a number stamped under my milling attachment and the tiny raised area around it caused me no end of headaches trying to mill without chatter, until I found it. Once I'd cured that it was a different machine, smooth and all chatter gone.

Bernard

 

[Grumpy Gator]

GW,
You say you are parting 6061 but neglected to give us the OD.
Your parting tool might be getting hot and expanding there by touching the sides of the cut.
I was taught to feed into the piece and when chattering occurred to back out and move the tool to increase the diameter of the cutting slot on the waste side.
******Just Saying********G***********

 

[great white]

Have you checked for tiny chips or maybe a small ding with a raised edge in between your tool post and compound? Check the mating surfaces of your toolholder dovetails as well.

There was a number stamped under my milling attachment and the tiny raised area around it caused me no end of headaches trying to mill without chatter, until I found it. Once I'd cured that it was a different machine, smooth and all chatter gone.

Bernard

Worth a look. I'll check next chance I get.

 

[great white]

GW,
You say you are parting 6061 but neglected to give us the OD.
Your parting tool might be getting hot and expanding there by touching the sides of the cut.
I was taught to feed into the piece and when chattering occurred to back out and move the tool to increase the diameter of the cutting slot on the waste side.
******Just Saying********G***********

Recently, 38 mm.

Steel doesn't seem to matter. Any diameter, intolerable screech and chatter.

 

[Bill C.]

It sounds like you're doing everything right. The only thing I can think of is that you may not be quite on center. If your tool is a tad high it can require higher feed pressure to cut. Try taking a very light facing cut with the corner of your tool at the current height and see if there is a tit on the work.

If you're using that horrid tool holder that holds the tool at an upward angle you may want to increase the front relief angle a bit more; this can make a difference.

-----------------
If you ever see your parting tool and holder take a dive when you start your cut you will know your are just below dead center or the parting tool is not sturdy enough for what you cutting.

I used to double check my parting setup by moving the carriage to the face of the part. Then move the blade until the parting tool cutting edge is in contact with part. Doing so makes the tool parallel with the face of the part. Carefully tighten the QCTP so your settings didn't move. If I wanted to double check my setup while the blade is against the face of the part I would lock everything down and take a very light cut if the was a hair thin shaving I was ready. You should be ready to move the carriage back to where you want to cut off the part.

 

[TomS]

I've fooled around with my on center a fair bit. Doesn't seem to make a difference where I have it.Horrible screeching chatter.

Spindle bearings are adjusted IAW the Atlas manual instructions.

I don't' run out of power, I'm running a Baldor CDP 3440. 3/4 horse. Runs super smooth.

I use the simple formula 4XSFPM/diameter = spindle rpm to set my rpm for cutting. Doesn't seem to matter if I do half it or double it, I still get chatter.

I do think I am using the references "horrible angled holder". Looks like this:



Can't remember off hand what the tool width is.

So, how should I try and adjust the rake if using this tool? more angle or less on the cutting surface? I'm not really understanding how less angle could be helpful. Doesn't that mean the chip edge would be broader/blunter?

I have the same holder and parting blade. The problem is the holder is not made for that type of parting blade. The holder has no relief for the top portion of the blade that is wider than the body portion. What happens when you install the blade flush with the holder the blade is not held vertical and it is somewhat tilted to the side. What you need to do is mill a relief slot in the holder so the body portion of the blade can be mounted flush to the holder. Hope I'm making myself clear. I can take a picture of my holder in the morning and post it if that will help.

Tom S.