# question on turning/facing



## Steven57 (Dec 23, 2014)

Just starting out, again after 30 year lapse.

Put a 1/2"od piece of 6061 in the 3 jaw protruding out about 4". Did some light turning cuts.002-.004 and a couple .010"
RPM around 650. half looked smooth closer to 3 jaw and the extended half looked rougher (galled?)

Went to face and after entering the cut maybe .020" in the piece would "tink" like it was jumping off the cutter. Tried a couple times and got same result and the piece visibly looked out of balance.



I have it sticking too far out unsupported, don't I?

Assuming yes, Do I push the piece in, face it, bring it back out?
Or am I to keep it locked it place and do steady rest/moving rest?


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## Karl_T (Dec 23, 2014)

Steven57 said:


> I have it sticking too far out unsupported, don't I?
> ?


learn to think in diameters   4/.5=8

8 diameters is marginal but doable with sharp HSS tooling set up exactly on center.

I suspect you have issues with your tool set up


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## f350ca (Dec 23, 2014)

As Karl said 8 times the dia out is pushing the envelope but should be doable with light cuts if the chuck is in good shape. Is the part now bent or can you physically move it side ways. If the chuck jaws are at all sprung the tips may not be holding the work and allowing it to twist. You would see this as a taper on your dia, but that could also be due to flex in the part but on facing it would probably shift sideways and stay there.
I just turned 2 inches of 7/32 cold roll down to 3/16 and single point threaded it for the end of a control rod and got away with it while holding it in a collet.

Greg


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## tmarks11 (Dec 23, 2014)

[COLOR=#3E3E3E said:
			
		

> Steven57[/COLOR]]half looked smooth closer to 3 jaw and the extended half looked rougher




general guidance is use a center when your ratio of length to diameter exceeds 3 or 4.  I think you are a bit over, and the finish you get confirms that.  You will have more problems with that kind of hangout with carbide than with HSS.

So what were you using? Carbide or HSS?

The rest of your story makes it sound like you have a chuck issue.  Yes, the part will deflect if it is hanging out to far.  But it will spring back, and the result is that you will get a cone shaped part.  From your explanation, it sounds like it is shifting in the chuck.


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## xalky (Dec 24, 2014)

The way I'd do that part is to Chuck it up tight to the Chuck first, then face it and center drill it. Then extend it out of the Chuck to a little over your required finished length. Bring a live/dead center in from the tail stock to support it. Cut the diameter to required size. Then back out the center . Cut the part to length using a parting tool, leaving enough material so that you can face it. Flip the part around, face it to length. Done.

Marcel


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## zmotorsports (Dec 24, 2014)

xalky said:


> The way I'd do that part is to Chuck it up tight to the Chuck first, then face it and center drill it. Then extend it out of the Chuck to a little over your required finished length. Bring a live/dead center in from the tail stock to support it. Cut the diameter to required size. Then back out the center . Cut the part to length using a parting tool, leaving enough material so that you can face it. Flip the part around, face it to length. Done.
> 
> Marcel



^^Bingo, that is exactly how I would do it. 

Leave the part just long enough so you can machine off the center drill afterwards. I try to keep my parts within about 3-4 times the diameter of stickout.


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## Steven57 (Dec 25, 2014)

Using HSS. Not bent just springing out of the way. Needed to raise the cutter .024 and that helped alot.


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## tmarks11 (Dec 25, 2014)

Steven57 said:


> Using HSS. Not bent just springing out of the way. Needed to raise the cutter .024 and that helped alot.


Since it has been awhile, maybe your forgot the trick of putting a machinist steel rule between the edge of the lathe bit and the workpiece, and looking at the slope?  Then raise or lower the tool bit until the ruler is vertical?  Quick to find the vertical center of the part. 

Than face it, and adjust again to get rid of the little nib that you leave.


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## Karl_T (Dec 26, 2014)

Steven57 said:


> Using HSS. Not bent just springing out of the way. Needed to raise the cutter .024 and that helped alot.



You've made one big step. 

Assuming you're new to all this, grinding an HSS tool perfectly takes practice. Why don't you read up on procedure here and grind another? Then hone it on a stone and try yet again.

After you have these two steps optimized, start playing with speeds 'n' feeds.

Then next time you have a long L/D part, you'll do it perfectly the first time. You don't become expert at this craft by reading a book.


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## tmarks11 (Dec 26, 2014)

Karl_T said:


> ...grinding an HSS tool perfectly takes practice. Why don't you read up on procedure here and grind another? Then hone it on a stone and try yet again.


Here is a great video on grinding HSS bits (first of three parts, RH, LH, and threading):

https://www.youtube.com/watch?v=qCpIxq0kHzo&spfreload=10


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