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Stephen Kurzban
 
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Default Facing rectangular stock in a lathe


See the line from MASH where Clinger said his parents put a violin in the
crib, hoping to make him a musician? He replied something to the effect
"what did I know from violins - I started sucking on the frets...".

Clinger knew more about violins as a child than I do about what I am about
to tell you ;-) so take it for what it is worth.

On a MILL (what's a lathe?), I read a given cutter NEEDS a certain cutting
pressure (feed rate?) to cut or it will just generate heat and
self-destruct. Balance this with a need that the given pressure must not
cause deflection of the work piece for an accurate cut, and the solution
becomes either reduce deflection (make your "setup" more rigid if the
deflection is not the workpiece itself), or you *must* use a cutter with
less surface area requiring less pressure/feed rate.

It's been said two or three times in a matter of offering a (correct)
solution - but I offer this a the reason for the problem's existence (sure
hope I ain't steering you askew!).

Basically what I hope I said correctly is, you GOTTA push to cut - and
smaller cutting surface areas require less pushing (causing less problems
concerning deflection, resonance, chatter, or ?).

I probably should have hit the delete key at this point vbg so please
re-read my above "disclaimer". I better re-enter lurk mode...

Best,

SBK

Greg Menke wrote:

Hi,

I have a 6" Atlas- nice old iron, lightweight but it works fine for
me. The project was to face the cut ends of several pieces of 1x1"
12L14 bar stock down to make 1x1x1" cubes, leaving a reasonable finish
in place of the burrs. The stock was aligned by chucking it in a 4
jaw chuck, with the jaws against the factory faces, the theory being
this makes the face pretty well perpendicular to the factory sides.
Since I was only facing only, centering wasn't critical.

It seemed to work pretty well, but being a newbie at this sort of
thing, there are (in this case) some not unattractive tool marks left.

I'm more interested in the 4 corners of the face- instead of the
uniform spiral pattern, the leading edge of each corner has a somewhat
"smeared" look. I think its caused by the tool deflecting when it
hits the edge of the stock. I tried a variety of speeds, depths and
cutting fluid quantities without affecting the "smears" very much.

At this point, I imagine the tool edge might well be a significant
issue (I'm not very good at grinding tools at present), but I was also
wondering how smooth a finish I'd be able to achieve with this
technique on this hardware given more experience.

Thanks,

Gregm