In article ,
"Harold and Susan Vordos" wrote:
"B.B." u wrote in message
news
In article ,
"Harold and Susan Vordos" wrote:
snip--
So what does the C2/C5 rating refer to? Grain size? Carbide vs.
"other" content? Is there some sort of system to choose which grade
where, or is it just down to C2 for some stuff, C5 for others, all other
grades not made anymore?
Searching on google got me a whole lot of marketing, but not much
else.
I've been out of the shop so long that I am no longer knowledgeable where
carbides are concerned. It's particularly bad considering they've made
great strides with carbide, too, so I can only assume that it may not be as
critical as it once was. I'm not convinced you'd find many machinists
that really understood the differences in how they're put together, though.
When you go back to my time in the shop (primarily brazed carbides),
constituents of the carbide were altered to accomplish the performance
required. Carbide went from hard to strong, and from edge wear resistant
to crater resistant. As you moved from one feature towards another, you
gained certain qualities, but lost others. It could be that today it's
just not as important. Dunno.
I'll do some more digging on carbides and grades. If I find anything
juicy I'll post it in RCM. Seems like something that would be nice to
know.
These inserts get used on any damn thing that finds its way onto the
lathes. Poor things probably had to cut stone at some point. In fact,
I had to put a steel center into the chuck and take a light cut off of
it so the mandrel would run true immediately before I machined the
wheel. So, yeah, it got "steeled" first.
Your chance of accomplishing good cuts is way down. It would be especially
true if the carbide is intended for machining steel, which I would imagine
it is.
I'm sure it is too. Would an aluminum-cutting setup involve only a
different insert, or also a different insert holder. IIRC, the holders
out there have a negative rake (angles down towards the work, which I
believe is called negative) and a negative side-rake. (down towards the
headstock) Are the rake angles a function of the holders, or are all
holders angles this way, expecting the lip on the edge of the carbide to
determine back/side rake?
Would the steel or aluminum--not both rule also apply to HSS bits, or
are they OK with it since they can be sharpened?
HSS is not as critical as to how it's applied, but when it is a concern, one
selects tool steel high in cobalt, which offers tougher conditions at
elevated temperatures. Any HSS will work for aluminum, especially if you
understand chip breakers and rake angles. You can create tools that will
peel it off faster than you can imagine. Lubrication is very important,
however. It doesn't take much, something as simple as brush application
works fine. Kerosene is the lubricant of choice for aluminum, but almost
anything is better than nothing. I've used Stoddard solvent that isn't real
clean with great success, but if you'd like things to smell nice, consider a
small can of WD-40. It appears to be nothing more than solvent with a
little wax dissolved in it, along with a perfume. It works fine for
aluminum.
Rake angles I think I've got a handle on. At least enough to get
started. As I understand it a chip breaker is just a little groove some
ways back from the cutting edge, correct?
It was common practice to have a small can on the machine with an acid brush
in it. To keep the can from getting blown about by the air hose (they're
use extensively in production shops, believe it or not) you'd place a piece
of stock in the bottom. I've always had a can of kerosene and sulfur based
oil at my lathe and mill.
Is diesel close enough to kerosene to work? I can get a little
container of diesel easy, but kerosene will be a hassle. I'm in texas,
so our diesel is as sulphury as law allows. (:
I wound up leaving the outside of my flywheel .003" oversize (we have
a tolerance of .005" over/under) so I could file/sand off the uglyness.
Alas, there is no lubricant. I did try painting my wheel with a film
of oil for one cut, but it didn't appear to help any, so I didn't mess
with it any more. Got a bit stinky anyhow.
My lathe actually had two carbides sitting at it. One was undamaged,
but the other had an impressive little heap of metal welded firmly to
the cutting edge.
With the inserts you described, it's no wonder. Once you find chip
welding on an insert, for all practical purposes, it's no longer a good
insert. The welding generally occurs because of tip flaking or cratering,
with the chips welding into the rough edge or surface. There's usually no
way in hell it will cut well once that happens.
Good to know. Thanks.
But that's really nothing compared to the guy who took a .050" pass
using a carbide insert cutter in the mill, but ran it backwards and way
too fast. It took off .050, but as a smear instead of as chips. Ah,
school.
Carbide is so weak in tensile that a tool that backs up ever so slightly is
usually ruined. Running a cutter backwards is a sure recipe for
destruction. You must have witnessed a hell of a lot of sparking unless he
was machining aluminum.
It was aluminum. Now I can't wait for someone to do it with a steel
piece so I can watch the sparks! (: Before I ever use a cutter out of
the "studentized" cabinet I always check it first. I think I know which
one he used because it's covered in rubbing marks and two of the three
inserts are missing the tips. The teacher says he's going to leave it
in the cabinet for the rest of the semester so people will learn to look
at their tools before using them.
You'll come to realize that not everyone in your class will have the same
dedication to learning as you may have. I took a welding class several
years ago. One of the students was a druggie, and wasn't interested in the
least in learning anything. He took advantage of circumstances for reasons
best known to him. Didn't make sense to me, but it apparently did to him.
Sigh! He finally quit showing up-----
Heh, over in my welding class two weeks back some guy showed up for
the first time since the beginning of the semester. The teacher simply
told him up-front that he hasn't been there, his excuse (broke down
truck) was bull****, and he would do nothing more than waste his and the
teacher's time and a whole bunch of electricity. Kicked him out on the
spot. I like that teacher!
In my machining class we've gone from 12 down to seven or six
students. Probably going to be five by the end of the semester.
Welding is worse, started with 11, down to six who show up at all, and
it'll likely be three of us by the end. OTOH, my other classes are
grad-level and our flaky guys are the ones who've missed as many as
three days. (:
--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/