Question about this rotary table set-up

[Janderso]

Hi all,
I hope you are well.
This is a set-up and chatter question.
Over the weekend I made some progress on my rotary table pallet-work table.
I don't have very much experience with boring on my mill.
It's a full size Sharp 3hp knee mill. I locked down X and Y, I used the auto down-feed feature at slow and medium with different cut depths ranging from .025 to .075".
I held it down as sturdy as I could think of. I placed the 2-4-6 blocks inward to reduce chatter. I started out with a 1/2" hole, I am boring to a depth of .500" and I'm going out to 1.625"
This is a 2" Shars boring head. I started out using a Criterion boring bar which I touched up and honed but found it had too much flex as the chatter was bad. I switched to a shorter and thicker bar = same issue.
The boring bar I am using in the picture allowed me to get the job done. The finish was very good.
I had to play around with feeds and speeds as the hole got bigger. I went into back gear around 350 rpm at the end.
My question,
Is there a better way to stiffen up the part?
Is there something wrong with my set-up?
Ideas?
Thank you.

 

[4ssss]

My advice is to shorten the boring bar. You're only going down 1/2". Also 1/2 of your table is just sitting with no support.

 

[Janderso]

My advice is to shorten the boring bar. You're only going down 1/2". Also 1/2 of your table is just sitting with no support.

I'd have to cut the bar as it is in all the way.
After thinking about this. I could have fastened it directly to the table and not used the 2-4-6 blocks. I had it this way as I originally drilled out and did not want to hit the table.
I used a coaxial indicator to find center and locked everything down. I assumed this thick piece of aluminum would be rigid, no it is not.

 

[benmychree]

You should be using those clamps the other way around where the most leverage is to be had; I doubt that this has anything to do with chatter, just a bit of direction. So far as the chatter is concerned, look at the way excessive distance from the spindle to the tool, you should have a shank that has
R-8 and screws directly into the boring head instead of using the collet adapter to hold it, shortening things up considerably.

 

[benmychree]

I'd have to cut the bar as it is in all the way.
After thinking about this. I could have fastened it directly to the table and not used the 2-4-6 blocks. I had it this way as I originally drilled out and did not want to hit the table.
I used a coaxial indicator to find center and locked everything down. I assumed this thick piece of aluminum would be rigid, no it is not.

There is nothing wrong with using the blocks under the part, it would be quite rigid as you set it up, other than the clamps being backwards.

 

[Janderso]

The clamps are backwards? Well, don't I feel silly.

 

[benmychree]

You always want to have the stud as close to the job as you can to take advantage of the leverage, true with any type of strap clamp.
Do you suppose that Bob K. is in hibernation? I have not seen him post in some time.

 

[Janderso]

Calling Bob Korves......
He does have his hands full at present.

 

[benmychree]

I'm sure he still stares at the screen, as we all do ---

 

[Liljoebrshooter]

Yep that's a lot of stick out. I bet an insert bar with a nice sharp aluminum type insert would be better also.

Joe