Boring bar chatter

[Wino1442]

Hi all....I am in the process of slightly increasing the bore on a couple of wheel spacers for a friend and I am getting a lot of chatter. I have tried several combinations of speeds, depth of cuts (which is the hardest thing to change because there isn't a whole lot to take off to begin with so I don't have a lot to play with), and feed rates and I still get a lot of chatter. I have tried hanging a weight off the end of the boring bar with no success. Another problem that really can't get around is the amount of stick out of the boring bar. It's sticking out about 3.5". These reason for this is because the spacers have the wheel studs pressed in and I would really rather not bang them out. I've tried turning the spacer around, but studs prevent me from seating the spacer deep enough into the chuck to secure it.
I was wondering if you all thought I would get less (or no) chatter if I were to set this up on the mill and use a boring head.
Any advice or opinions would be greatly appreciated....Thanks

 

[jwmelvin]

Solid carbide boring bar or a larger-diameter boring bar. Or wrap your boring bar with clay, etc. Did you sharpen the cutting edge (or make sure you’re using an aluminum-specific insert)?

Or turn the spacer around and clamp on blocks on a face plate? (tedious)

 

[GrifterGuru]

A couple of things here...

With any amount of stickout, dependant on DOC/Spindle RPM and material, you will always get chatter. To that end, have you taken progressively lighter cuts to see if/when the chatter disappears?

Do you have a way to apply a sprung pin to the bar so the spring absorbs/reduces the chatter? (someone posted a phot on here of one recently)

You do not mention whether the spacers are alloy or steel

You say you have a mill, so do you have a boring head suitable to to the task? It may well be the better option providing you can properly centre the spacer.

 

[Batmanacw]

Are you absolutely sure you are on center with the boring bar? Try going a little above center to be sure the bar is cutting and not rubbing the side of the insert. Take very light passes with faster feed. Maybe 0.005" per side @ 0.010" per rev feed.

 

[Huub Buis]

In general, to reduce chatter, you have to increase the rigidity of the setup and/or reduce the load on the tool.

• Use a thicker boring bar
• Let the boring bar stick out as less as possible.
• Keep the boring bar holder above to tool post
• Reduce the depth of cut
• Reduce the RPM
• Reduce the Feed/Rev
• Use a sharper tool
• Use a tool having a smaller tool nose radius

If nothing fixes the chatter, I use a CCGT or DCGT insert for aluminum (super sharp) that has 0.2 mm tool nose radius to reduce the load on the tool. That works on POM, brass, aluminum, steel , stainless, etc.

Sometimes, taking a deeper cut and/or feed faster can reduce chatter because there is more tension on the tool.

 

[Weldingrod1]

Of course, it's a great excuse to buy a carbide boring bar!

If your boring head can go inside the ring of studs and allow you to use a much shorter boring bar then it's probably the winner...

Sent from my SM-S911U using Tapatalk

 

[Huub Buis]

Of course, it's a great excuse to buy a carbide boring bar!

In my boring head, I use 12 mm lathe boring bars that are shortened. I have made some 12 mm boring bars on the CNC router. In the past, I have made insert holders on the manual mill. It is time consuming but not that difficult to do.

I assume a lathe is used to enlarge the spacer diameter because it is hold by a chuck!!

 

[Batmanacw]

Of course, it's a great excuse to buy a carbide boring bar!

If your boring head can go inside the ring of studs and allow you to use a much shorter boring bar then it's probably the winner...

Sent from my SM-S911U using Tapatalk

I like using solid carbide boring bars in my boring facing head.

 

[Jeff.64]

In addition to the previous great suggestions, two things I've done that worked.

I placed a 20 lb hunk of cast iron on the bed to the right of the carriage. Adjusting the distance from the headstock until the sweet spot was found. Kinda like a tuned absorber?

Another is to rotate the tool holder around to allow the boring bar oriented upside down to cut on the back side of the bore.
Of course, these things might have been a fluke or dumb luck on my part.

Interesting, but not practical for most of us, unless a winning lottery ticket can be had is the Silent Tools boring bar from Sandvik.
I just saw this a few days ago. Great stuff if you can afford it!

 

[mksj]

Enjoyed the video, thanks for posting. I has able to pick up a lightly used 1" carbide boring bar at a very reasonable price, the difference in deep boring without vibration was impressive. Below was boring over 8" in 4140, at best my 3/4" steel boring bar would chatter boring a few inches deep. Using a sharper cutter and insert nose profile can also make a significant difference. Typically the insert pocket in neutral or positive. Carbide boring bars are expensive, the mass dampened ones must be outrageous priced, but very cool.