Boring in the mill with lots of chatter. Ideas?

[Janderso]

I have yet to be able to bore with this mill. It’s not the mill. I have a 30 taper, I can use the ER40 chuck or the 30 taper holder.
I must be missing something.
I have way too much flex with my options available.
The best I can do is 8” with a short Criterion bar To the spindle lugs.
The boring head is a 2” Shars. The table is locked, the quill is locked, the gibs on the boring bar are tight.
Ideas? I can make this thing sing big time with terrible results.

Heck, my wore out BP with an R8 did a better job.

 

[rabler]

I guess my first thought is have you put an indicator on the business end of the boring bar and tried to move it with finger pressure? Then working back up the stack to see where and flex comes from? It does look like a long setup so I'm just shooting from the hip here.

 

[DavidR8]

Aside from yours being a 30 taper I have the same setup.
I'd opt for the ER chuck if you can push the straight shank on the boring head further into the collet.

 

[derf]

Try changing the angle of your boring bar. Sometimes the attack angle is under the centerline.

 

[woodchucker]

from the picture, it looks like you have the cutter facing 90 degrees to where it should be.
The cutter should be aligned with the heads sliding direction, not 90 to it.

It would be better to be able to enlarge the pics more, just too low on detail. from your pics this is 90 off

 

[mikey]

I have a couple of guesses:

• You have the boring head on a long shank that is sticking about an inch from the end mill holder at the end of your 30 taper. That is a lot of interfaces with a lot of extension. Ideally, you want the boring head adapter, the part that screws into or onto the head, as short and as close to the spindle taper as possible. Is there a 30 taper adapter that will screw right into that head?
• You are using a long boring bar. It should be as short as the bore depth allows.
• As stated above, the tip of the bar is misaligned. The flat on top of the bar should be dead on the axis of movement of the sliding part of the head. If you don't do this, the depth of cut adjustment will be totally inaccurate.

 

[MrWhoopee]

Shorten the shank on the boring head
Shorter boring bar.
Give us a close-up of the grind on the bar. Those brazed bars require a LOT of grinding to get the geometry suitable for a boring head. As purchased, when the cutting edge is in the right orientation to the boring head you end up with negative rake.

 

[jwmelvin]

The flat on top of the bar should be dead on the axis of movement of the sliding part of the head.

What’s the best way to do this? I’ve sometimes held a 6” scale on the tool’s top surface, but sometimes by eye.

 

[jwmelvin]

As purchased, when the cutting edge is in the right orientation to the boring head you end up with negative rake.

As in, they need additional radial clearance below the edge?

 

[Janderso]

I have a couple of guesses:

• You have the boring head on a long shank that is sticking about an inch from the end mill holder at the end of your 30 taper. That is a lot of interfaces with a lot of extension. Ideally, you want the boring head adapter, the part that screws into or onto the head, as short and as close to the spindle taper as possible. Is there a 30 taper adapter that will screw right into that head?
• You are using a long boring bar. It should be as short as the bore depth allows.
• As stated above, the tip of the bar is misaligned. The flat on top of the bar should be dead on the axis of movement of the sliding part of the head. If you don't do this, the depth of cut adjustment will be totally inaccurate.

I’ll have to do some homework to see if there are shorter hardware options. I could always cut the bar.
Regarding the cutting edge, I just stuck it in to show the length.