Need Help!- add-on to a prev.

[gene rhodes]

Previously, I talked of SFM's and such but I don't know that my direct problem has been resolved. Is there no way to accomplish a face-off maneuver with a ceramic insert?? My problem lied in the fact that the ends of our material was being hardened on the cutting operation (using a savage saw....just a large scale chop saw) and they (we) are trying to resolve this problem without a large-scale tear down/rebuild of this saw. It cuts approx. a 15 deg. angle on the end of the part (2.5" rod as an example) and the angle combined with the downforce is hardening the material beyond the cutting capabilities of our roughng inserts. We have tried slowing/speeding the spindle, the feedrate, adding more passes...almost at wits end!!
Any input would be greatly appreciated.......

[Geof]

You say the material is being hardened during the cutting. This suggests you start with annealed material, or at least not fully hard, and the rapid extreme heat of the chop saw cut is being 'quenched' by the bulk of material on either side of the cut acting as a big heat sink.

One possible way to prevent this is to preheat the bar before cutting. Nowhere near hot enough to be near heat treating temperatures, more like up to the lower range of tempering temperatures. With this the bulk of material adjacent to the cut does not act as such a good heat sink so the extreme heat right at the cut is not quenched. It may still finish up a bit harder than it started but certainly not fully hard.

[little bubba]

Gene, went back to other thread you had, Hardened Chromed rod. Trying to face it, 15 degree angle, so an interrupted cut, ceramics.

So, back to basics again, how do ceramics work???? Heat, they don't cut, they melt and push. They literally create a huge butt load of heat, and plasticize (hot and gooey) the metal in front of the cutter and wipe it away. So you are in an interrupted cut due to the angle, that gives the insert time to cool off while its not in the cut, so GO FASTER. Totally bass ackwards from conventional cutting tools.

So... how does this heat get built up? you have a cool insert and a cool part, you have to ease into it gently, and then go hog wild once you have the heat built up, and stay in the cut, I'd say 90% of all damage to ceramic inserts is in entering the cut. A facing canned cycle isn't going to work. You are going to have to ramp, keep the speed up as high as you can, max out the RPMs coming to center, and then ramp back out, keeping the tool in the cut.

I think it can be done, you are going to have to be a bit creative, and have a good understanding of what your ceramics are doing, and why.

Another thing is you can build up too much heat with ceramics, turning everything into a big pile of molten goo, which you very well may run up against, since you are going from an interrupted cut into a continuous cut. You may have to run her really hard and fast through the interrupted cut, and then slow her down as you are getting into a continuous cut. Its going to be a trial and error thing.

Ceramics are a strange breed, if you take everything you know about carbide and HSS, and do the exact opposite, you'll be pretty close. A chipped or trashed insert means you are going too slow or entering the cut too aggressively.

[gene rhodes]

ok then....Am kinda limited on the amount of time I have to be creative. It sounds like I could end up going through alot of inserts before I even get close....and those things ain't cheap!! SO, aside from spending $100 a piece or more on some fancy Polycrys. type insert, does anyone have some good trick-of-the-trade advice to attempt here or should I just give up? Don't know if I mentioned it before or not, but the savage saw DOES use coolant that also has a mix of rust-lick in it as well ( no idea of strength of mixture )
the sprayer is approx. 2" from the blade and it floods it pretty good.....
but coolant or not, if it's not straight it's gonna burn, right? I don't know of a feed/speed chart or scale to this machine off of, nor do the people who run it on a daily basis...so they pretty much run it by ear. I do know it does cut fairly slowly through a 2.5" part (about 8-12 sec. complete cut)
any ideas would be great..............