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palanisamy
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Join Date: Aug 2012
Location: coimbatore
Posts: 6

Chatter Mark on Bore Inside

09/13/2013 6:56 AM

Dear sir ,

I am using on spm machine .process for fine boring on single spindle .

bore size 93.6 mm

bore length - 180 mm ,

I st cut - 1 mm,

2 nd cut - 0.5 mm

tool carbide insert

running speed - 400rpm

hydraulic feed is 0.2 mm

we are getting on chatter marks inside the bore in above process .

how to rectify problem ?
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PWSlack
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#1

Re: chatter mark on bore inside

09/13/2013 7:08 AM

Either make the tool-holder stiffer, or make shallower cuts, or reduce the feed rate, or some combination of them.?

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Mike W
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#2

Re: Chatter Mark on Bore Inside

09/13/2013 10:45 AM

Also, be sure that the insert is correct for the material/cutting rate.

An insert for roughing may chatter on a finish cut.

You can try an insert with a larger nose radius as that puts more pressure on the tool which may relieve the chattering.

Sometimes I have had good results by cutting on the back stroke when taking a fine cut like that.

On the other hand, you may need to back off and take a larger finish cut to keep the tool from bouncing around.

Try another cutting fluid.

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lyn
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Join Date: Oct 2008
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#3

Re: Chatter Mark on Bore Inside

09/13/2013 7:27 PM

It might help to know what material you are trying to run, and the actual feed rate.

Depth of cut may be an issue, but not knowing the material renders all opinions moot.
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GW
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Location: Surrey BC Canada
Posts: 1571
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#4

Re: Chatter Mark on Bore Inside

09/14/2013 1:28 AM

You gave no description of the part being machined, size of machine, material being cut etc.

I have sometimes eliminated chatter by actually cutting much faster. Chatter is partially a resonant phenomenon, along with metal properties.

Keeping the tooling and supports rigid always seems to help.
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Munster
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Join Date: Nov 2011
Location: New Hampshire
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#5

Re: Chatter Mark on Bore Inside

09/14/2013 6:11 AM

Presently working for a weapons factory, I have known the speed of the drill in rpm's has an effect. The first thing I would do is increase the speed of the drill at least 5 times. The drills at my company has drill speeds in excess of 10,000 rpm.
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evaluator
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#6

Re: Chatter Mark on Bore Inside

09/15/2013 8:26 PM

Need more info. A sketch or photo of part and how it is held would greatly help.
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Master of Naught
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Join Date: Sep 2012
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#7

Re: Chatter Mark on Bore Inside

09/16/2013 12:30 AM

Hi

1. Vary the revs you might not have the right cutting speed but you will get away from the resonance (you might have to go slow to get under the chatter and then increase for finish).

2. Change the length and or increase the diameter of the boring bar (can you provide another support for the bar eg a backing strap) You can also clamp mass of the bar to absorb vibrations, also a rubbing block attached to the bar will change the amplitude.

3. Change cutting compound

4. Change the tip material, rake and radius (smaller will take less resistance and may overcome chatter)

5. Try a heavier finishing cut and increase/decrease feed (will stop the tip from springing)

These are not in actual order (depending on how much material you have left) try what is the easiest first step
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lyn
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#8

Re: Chatter Mark on Bore Inside

09/16/2013 9:50 AM

Looks like another waste of our time on someone who doesn't have the courtesy to respond to the help offered.

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Harvey Patterson
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Join Date: Jun 2011
Location: Southern CA
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#9

Re: Chatter Mark on Bore Inside

09/16/2013 10:01 AM

Depending on the material you are cutting the speed may be correct. If the feed is .2mm per minute, I am guessing, then the feed rate is way too slow. If you are using a coated insert the hone on the cutting edge is likely to be greater than the feed. When the feed is less than the hone then you are not cutting, you are pushing the metal which creates alot more pressure. I would try a higher feed rate.

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Govind Rao
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India - Member - New Member

Join Date: Jan 2009
Posts: 114
#10

Re: Chatter Mark on Bore Inside

12/04/2013 12:07 AM

You need to have a sturdy boring bar with the right length. Try to manufacture a boring bar with slight taper towards the cutting tip. Make sure that the hydraulic feed is smooth and and does not work intermittently.
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Users who posted comments:

evaluator (1); Govind Rao (1); GW (1); Harvey Patterson (1); lyn (2); Master of Naught (1); Mike W (1); Munster (1); PWSlack (1)

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