Greetings all;

I am trying to carve the curve/arc in the toolpost base that replaces the 
bad compound in this Sheldon.  Currently mounted about 3/4" off center 
so I am basically cutting away anything on the front of the base that a 
workpiece could hit. I did this in 1/4 size, for TLM, and that, plus the 
tapered gibs almost make TLM a decent but smallish lathe. Any remaining 
tendency to chatter seems to be in the flexing of the spindle itself.

My code at the instant starts out with a huge radii in order to start 
with a light enough cut TLM can power thru it. The start and end points 
are fixed, and this of course is hard on the tool insert as it dulls and 
starts skidding before it starts cutting at both ends.  Next pass 
reduces the radii, but I cannot get a straight line increase in the 
belly of the curve, which is about a 60 degree arc section.

Is there a math function that would give me a uniform increase in the 
belly of the center of the arc?, which I am now convinced was a error in 
my concept of how to do it.

So, should I just give up and use a fixed radii curve, but move its xz 
anchor radii point? That would get me a constant depth of cut, and would 
likely be easier on the tool insert too. I haven't a clue whats in this 
cast, intended for large car wheel hubs, but its tough, and abrasive 
stuff. You could call it found iron I guess.

H&K casting where I got it, probably considers that proprietary info 
since its a contract that specifies the alloy's ingredients.

I think the reason I didn't originally was that I was running out of out 
x motion to use a fixed offset for cutting the starter angle.

What say you folks, how would you do it? Keeping in mind TLM cannot pull 
more that about a .4mm cut at this nearly 4" working diameter, at about 
150 rpms.

I need to take about 1/4" off the top of this yet, so while the "hive 
mind" is cogitating, I'll go do that, with a nominal 2 thou dish in the 
center so that big Phase-II toolpost is sitting on its outside corners 
and much more capable of resisting turning forces in the middle of a 
boring bar job.  I did a 1 thou dish on the smaller post I made for TLM 
and that little QC holder hasn't moved on the post since.

Thanks for any advice everybody.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <>

Emc-users mailing list

Reply via email to