Hi Delw,
Do you use coolant when turning with ceramics? Also, what kind of doc were you taking and do you remember your speeds and feeds? One thing that also makes the inconel 625 we work with so tough is that it is a raw forging. I really would like to get the ceramics to work though. We are a father/son business, and my dad always said that the round button inserts always chattered way more than the other inserts because of the larger radius. Did you have that problem?
We almost always use carbide wnmg no 2 radius and cnmg no 2 radius for roughing.
Thanks,
Chris
Chris if you have a stout lathe heavier the better you shouldnt have any issues. the smallest machine I used them on was a 1990 hitachi seiki 20sII 8 inch chuck.
That machine was pushing it it had liner ways and a no gearbox motor . Rarely got chatter but stalled it quite a few times, just work around it.
box ways is the best. our other machines were big H.E.S. and a few big manual machines.
surface feed what we ran was around 800-1100. cuts anywhere from .035 -.150 feed rates were .008- .015 sometimes higher
we primary used 1/2" rounds flat greenleafs the whisker ones, I liked the old black Mitsubishi inserts I cant remember the number on those.
we also reground our 1/2 rounds on the surface grinders and used carbide shims and we didnt put a land on the regrinds they worked just as well.
always used flood coolant with 1/2" lines on the tool. we tried them with out coolant but found we could get more tool life with coolant on the regrinds.
again the key is your entry the part must not have a sharp entry edge, we used SNMG inserts to put angles on all out entry areas. also as all of our parts had holes in them we drilled them 1st so not to have the insert goto center line and break.
all our parts were garret aviation aka allied signal rotors, housings, seals etc etc.
for smaller fetures we used the 1/4 " round inserts with the v groove for location. those sucked for regrind and useage as you only were able to rotate once. it was more cost effective to use carbide on those features most of the time.
if I recall we went through about 50-75 ceramic inserts a week running 2 10 hour shifts on 4 machines. if you dont run your ceramic till it breaks you can get 8-10 edges on the top of the insert and the same on the bottom when you flip it. that obviously depends on your depth of cut. your chips will tell you when its time to rotate them. we had a few guys that were lazy on the 30 min-1.5 hour rough cycle and would not watch the machine breaking the inserts with out rotating it.
if I recall we would get about 15 mins before we had to rotate the insert running .050-.075 doc. everything that had a contour we roughed in contour form they would keep the inserts from breaking as well.
if we were just facing or cutting a od we always rad on the end of each pass so not to ruin the inserts. sometimes it was a toss up on those just to use a 5 or 6 series(big ones) snmg at a 45 degree angle to take off stock you could get about .150 .200 DOC. yeah it was slow but we didnt break inserts on break outs.
if I recall carboly 883 885(cant remember exact grade)? grade was best for our high nickle/cobalt alloys at that times. if we didnt have those it was h13a nothing beat them as we tried all the grades avail. back then and most werent cost justifiable.
hope that helps as I dont know what they have out now for inserts.