Troubles Parting

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jason30809

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for the last few weeks I have had trouble parting off through round stock that's anywhere between 1-2in OD. I am using an atlas 10f and positioning the work mybe an inch from the chuck.i have only owned one steel blade and have never had problems with it until the last few weeks. horrible chatter like I have never heard before followed by the feeling that it was digging in. I have raised the tool, lowered the tool, adjusted stickout of the tool and the work, and tried every speed setting I can think of. I also decided to try to use an indexable cutoff blade which is my knext problem. from the world go it is chattering bumpy and small sparks can be seen inside the 304ss cut. I have checked different hight and speed settings. any advice for me would be appreciated very much because im about to go nuts!
 
I've not got that much experience but have managed to part off 1 in ss on my minilathe. The things I found made a big difference were 1) the tool has got to be sharp (chatter and dig-ins wreck the cutting edge so it might need resharpening), 2) lubrication (a constant dribble of cutting oil into the slot throughout the parting operation) and 3) part off close to the chuck (on my setup even 1 in away will result in chatter).

You'll need a good feed rate too, esp with stainless. Go at it too timidly and it'll harden making all your problems worse.

Rob
 
SS can be difficult, and that's a pretty big piece. I'd cut it off in a saw and then face it.
 
jason30809 said:
for the last few weeks I have had trouble parting off...... i have only owned one steel blade and have never had problems with it until the last few weeks.
Click to expand...

The answer is proabaly in your sentences above. What has changed? I'm guessing something has gotten loose. Gibs? Spindle bearings? Maybe it's time to go through and check a few things.
 
gibs are tight and as far as bearings go I only have about a year of formal schooling as a machinist and that was 10 years ago so the best I have been able to do is check spindle run out and to apply a little force left, right and up and down while the indicator is on it and I see nothing abnormal. between .0025-.0005. only thing different is a new 6 in 4 jaw chuck and I always indicate the work to less than half a thou when chucking. is there another way to check the headstock bearings? thanks for the answers
 
In general, when troubleshooting any problem, one of the first questions I ask myself, or the machine operator, is "what was different before the problem started happening?" You look for a logical progression to the current condition.

I'm going to defer to others on checking the spindle bearings on your lathe because I'm not familiar with your particular machine. I run my Jet pretty tight (over tight maybe). Also, the only parting tool I own is a hacksaw.:)
 
Something I learned from this site was the saying "304 she's a whore, 303 she's for me" Has to do with the machinability of those alloys.
Try sharpening your cutoff tool and parting some friendly steel. Might give you an idea if the 304 is the whole problem.
 
I had horrendous problems when I first parted off in my asian 9x20.
I could physically see the tool post flex very badly.
Since then I've made a bunch of alterations to improve this including removing the compound and replacing it with a solid post.
I also snug up the gibbs when parting as I found you could feel the join in the cross slide vibrating.
With a very sharp HSS tool it works a treat and most metals can now be parted easily.
As Rob stated constant dribble of cutting oil, very sharp, constant feed and seek out any possible flex and remove it.
I could never have parted this chunk before the alterations but now I dont even think about it.
http://www.hobby-machinist.com/thre...in-your-shop-today.14637/page-260#post-410776
 
Slow the speed way down and don't be afraid to feed right through the chatter. Just my $.02
 
'Sparks in the cut......' doesn't sound like your cutting lube is getting to the bottom of the cut.
 
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