What causes this behavior, and how to correct it? PM 728 VT

[MLab]

78+

78

Very helpful replies, thank you all!

Will try conventional milling next, and reserve climb for the finish pass (although it does seem to work with aluminum). I never lock the table as I am using CNC, so can't use that trick; my quill is always locked maybe try it there.

I think 7milesup has it figured out. You're re-cutting swarf, or more precisely, swarf is following your cutter around and acting as an occasional wedge between your cutter and work piece. You might try air ( https://www.amazon.com/dp/B0BRYYY5LX?psc=1&ref=ppx_yo2ov_dt_b_product_details ) to clear swarf off your cutter as it exits your cut.

 

[a smile]

I was milling some mild steel for the t-nut of my QCTP when I noticed a certain skipping noise. so I grabbed several short videos that i spliced together a 20-second video to show it. See for example at 2 seconds, 10s, 13s (this is the most pronounced, the whole spindle seems to jerk quite prominently), and 19s.

Is this only chatter, or is there something wring with the spindle? Thank you all for your help.

I think the small machine tool will not be rigid enough, the most important thing is that you choose the smooth milling, but your screw gap is a little big, if you choose the reverse walking will solve this problem, but the finish will be reduced!

 

[Janderso]

Thank you, will change the milling direction to do conventional. Seems like my mill doesn't tolerate climb in steel. As you see in the video, I took very light, 0.02" passes.
Is the table jumping a measure of the x axis double nut having backlash or what?
Also I am concerned about the spindle deflecting like at 13seconds.

.020" passes climb milling is an aggressive bite. imho

 

[verbotenwhisky]

You are climb cutting and the table is jumping . Mill conventional .

I do not think he is climb milling in both directions, only in the front, the back appears to be conventional. You might check your gib, it appears the table jumped.

 

[mmcmdl]

He's climbing in both directions in the video .

 

[verbotenwhisky]

He's climbing in both directions in the video .

Yup, your correct, I had to look at it again....

 

[verbotenwhisky]

He's climbing in both directions in the video .

I still think he needs to check his Gib...

 

[mmcmdl]

I still think he needs to check his Gib...

I agree 100% . He may have a worn out leadscrew also .

 

[verbotenwhisky]

I agree 100% . He may have a worn out leadscrew also .

Just talking out loud here, not throwing rocks to be argumentative...

The machine he has is a Taiwanese machine as opposed to my Chinese machine; but I'll bet the gibs are setup very similar and mine have required adjustment in the short time I have owned the machine. Mine's twitch was not as pronounced as his was (I suspect because it has more mass) but it did get a bit crunchy and tightening the gib took care of the issue on mine. From the sounds of B2's comment (he has the gear head CNC version of my mill) has had similar issues.