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Parting off chatter problem with one speed

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gerritv:
My experience with a King KC1022ML is that the cross slide moves unless you over tighten the gib screws, then back the off a 1/8th turn. The way I check this is to pull up on the tool post while placing a finger across the cross slide/carriage joint. If I feel any movement then I over tighten the gib again etc.
Lubrication and feed in speed also impact chatter. I have learned to feed faster if chatter develops.
Variable spindle speed is my next step, looking for a treadmill to butcher.

Gerrit

PekkaNF:
Sparky....you are right on this one. No matter what I do to that lathe it's still small chinese lathe with all of it's limitations. However, half decent second hand machines are rare here. I don't have space for 3-5 metre lathes - those are cheap here.

Think it would be whole lot more nice to use with 0,75 kW three phase motor with VFD and good belt drive. I checked it this evening. It's not only belts, the pulleys are out of round too and the drive system is way too weak. And anyway, I like re-building and/or improving machines.

Gerit, I can conform all that. Today I was parting off happily with no problem at all. It was that one speed that was giving all the resonance and chatter.

Pekka

PekkaNF:
MGEHR1616-2 & MGMN200-G vs. SGTHR 20-2 & GTN2.

GTN wins.

Pekka

sparky961:
So, which of the two shown side-by-side is the winner?  I've never been great with all of the number/letter designations for holders.  Which criteria are you using to determine your winner?

In your last picture, just looking at the chips below (small short curled chips lower left, which may or may not be from the active parting cut), it looks like you're getting a lot of heat.  It would help to get some soluble oil coolant in there via a squirt bottle or more fancy delivery system, or straight cutting oil - which will do the same job with probably a lot more nasty smoke. ;)

What feed/speed are you using?  Or are you feeding by hand?

PekkaNF:
GTN is in the second picture on the left. One ended insert, friction seating no clampping screw to hold it.

It winns because no chatter and cuts cleanly. Probably much of the reason the inser holder that has less overhang. Also difficult material chip was formed better on the Iscar GTN inser than on the two sided cheap chinese one. Although I must say that the one chinese I got was surpricingly well made and the tool holder is about 1/4 of the price  paid for iscar. Inserts are 10 times cheaper tha iscar. I got one box of the chinese iserts that are next to uselees: they cut bright drawn shaft, but chip formation is bad and they break often. These on the picture were much much better. Still no markings on the box but these insers actually work.

I have pictures of the two sided grooving system (MGEHR1616-2 & MGMN200-G ) at the end. Last picture of the cheap but surpricingly good insert after the I cut two cuts on MOC, four cuts on drill rold (silver steel) and whole evening of general parting off (maybe dozen of cut outs) on structural steel. If I can find aluminium inser for it I would dedicate that holder for aluminium parting off. However, on more difficult materials and deeper cuts than parting of maybe 35 mm dia I will be using GTN2 system.

The material that gives most trouble is pretty hard tempering steel, known here as 34CrNiMo6 to me, these are other names for same stuff (or close) 4340, 817M40, En24 the one I got is tempered to pretty high hardness. Produces very long swarf and seems to cut best when run hot. Cip formation takes a whole lot from chip breaker.

Pekka

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