Boring in the mill with lots of chatter. Ideas?

[mikey]

I have no trouble with mine being straight. It cuts perfectly well.

I have never had to grind my import boring bars, you just have to be careful not to set too aggressive a rake angle, and make sure the bore radius is large enough for back relief. It’s possible to try to bore too small a hole for a particular bar and orientation.

I normally use cobalt HSS tools ground for use in a boring head so the flat on top of the tool is ground to center. However, I have brazed tools that are not and they cut fine. I will grant that the ideal is to have the flat on center but it is more important to align the tool so the tip is aligned properly or your leadscrew readings will be off.

 

[Tipton1965]

The bar isn't the issue . The stick out is .

My thought exactly on first glance. You have a springy diving board there.

 

[benmychree]

Lay the flat part of sliding part of the head on a flat surface; I use the anvil on my vise next to the mill. Now eyeball the flat on top of the tool so it is parallel to that flat surface. Your eye can get it straight to within a few tenths this way - good enough, I think.

A few tenths of what?

 

[mikey]

A few tenths of what?

Of dead parallel when compared to a reference surface.

 

[Larry$]

Interesting! I just bored some tough steel yesterday. Nice clean shavings, no chatter. Cheap Chinese brazed bars in a cheap Chinese boring head with R8 shank in a 18 year old mill. Bars have round shanks and I use the eyeball method of alignment. Slight positive rake. Bars have been sharpened but original profiles hit or miss maintained. .003" down per rev. combined with a .005 to .008 DOC. I'm turning it relatively slowly @ about 200rpm because it is a fairly unbalanced system. Total seat of the pants machining. IMHO the problem with chatter at the beginning of this thread is the diving board setup.

 

[benmychree]

Of dead parallel when compared to a reference surface.

Measurable by what method?

 

[mikey]

Measurable by what method?

Tell you what, John. Just put in whatever word or measurement that makes you happy, okay?

 

[Liljoebrshooter]

Here is my boring head setup Jeff.

Joe

 

[Janderso]

You should get a boring head with a 30 taper shank and mount directly into the spindle taper; way too much overhang, no wonder it chatters.

That’s probably the only way to do it. I didn’t know I could do that.
I tried to figure out how this head is mounted on the straight shank, couldn’t figure it out. It must thread on.

 

[Janderso]

Here is my boring head setup Jeff.

Joe

That’s a hell of a lot more robust than my ****ty set up.
Found this Criterion head with my taper. $800 on Ebay.