"Sunworshiper" wrote in message
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snip---
Experience answer is ok with me , but I was hoping you were going to
come back with something about the under magnification grains, how
they break, and the "glue" holding the wheels together.
While I understand wheels enough to know which one may be better suited to a
particular job, I would not be a candidate for explaining the complexities
of wheel construction theory. I'd gladly leave that to one that is properly
trained and educated.
Maybe, I'm
just missing it or think too much. Tell more , I dressed wheels a
couple of times a day and just don't see how a diamond dressed wheel
can get any better,
I agree, but not for offhand grinding. Don't confuse the two. Diamond
dressing is almost mandatory on precision grinders, especially in today's
environment where demands of superior finishes and precision are required.
except the loading problem, and trying to
visualize it being too smooth. When and after I use to grind aircraft
and huge Cat cranks I was thinking how the coolant oil and the steel
doesn't load up the wheel fast... What are you suppose to think about
when machining. 
)
Wheel loading is avoided by the proper selection of wheel abrasive grain
size, friability of the wheel, and the degree of openness of the bond,
generally a vitrified wheel for crank grinding.
After the 60 other different things your not to
forget. I see now after D just posted pic.s from you how I got lost?
I don't have a cut off tool holder and never used one , but I've made
them from 1/2" HSS cause I was desperate.
Nor do I. I have always hand ground parting tools. I can't even mount a
commercial holding tool on my lathe due to the tool block I choose to run.
It won't accommodate one. I can readily hand grind parting tools that are
adequate for the work I do and see no reason to do anything else.
I don't enjoy the thought
of cutting work right off the lathe and catching it , ya'll say its
easy, but I need to see it done once to feel comfortable about doing
it myself. That or have a real need for going in 2".
I've parted 2" stock with no trouble, including stainless steel. It
requires considerable attention, plenty of lubrication and a little luck.
303 stainless is much easier. One of the toughest to part is actually mild
steel, due to it's eagerness to tear, jamming the tool and breaking it.
Regardless of what's being parted, it's no big deal when it comes off the
machine, you just have to make sure it doesn't end up in the jaws when it
finally lets go. If you're parting a long item, you can actually hold it
as it gets near coming off and lightly push it towards the rear of the lathe
so it won't bind. The degree of flexibility at that point is so great that
it moves easily. At that point it hasn't enough strength to do any damage,
it just comes off in your hand when it's ready.
See, I was
thinking and still missed I guess that you were talking about cutting
the HSS lengthways kinda , but you talking about parting tools made
under 1/2 deep /downward wise when in use.
Envision a 1/2" square tool that has a narrow blade (the parting tool
portion) that is an inch long along its length. The limiting factor with
the hand ground tools is height. Commercial tools often have much more
strength vertically than these tools, therefore are much harder to break.
That is the only benefit I can see to using them, aside from the savings of
time in grinding them.
I wonder if the wheel was loaded on this one crank I was doing that
the machine that took a number of steps to the other end started
chattering. I'm sure you know what a headache chatter means when your
in the middle of something you can't reset. They didn't have a dresser
that would do it under the work you have on the machine and can't
move.
Chatter has many sources. It's not always evident if a wheel is loaded or
dull. The only solution, in either case, is to dress the wheel. If the
wheel is glazing prematurely, a softer wheel may be in order.
I use to try to calculate in my head where best to stand and
cringe when pushing the start button. 11.25 degrees or 22.5 , 30 + was
out of the question , you have to be right there close and if it let
go I'm with ya on the funeral part. All for just above minimum wage.
What a wise person does is hit the button and get the hell away from the
wheel as far as possible. There is no need to stand in front of a wheel
when starting it up. On a crank grinder, the wheel should spool up slow
enough to allow you time to retreat before it's running at top speed. If
nothing else, I'd step to the tailstock side of the grinding head. A wheel
is much less likely to deflect that direction than towards the headstock if
for no other reason, the mass of the wheel head. My policy is to start a
wheel and give it a minute of time to see if it's going to hold.
No one told me how to sharpen or make metal cutting tools , I just
read and mathematical pictures of how the metal fractures and did it.
I still am stumped on how the bit will load/pile up where I can't see
the edge (even closely examined with it off the machine) and its
cutting just fine. Maybe that isn't suppose to happen , but on some
material I can't seem to stop it.
That's where learning about chip breakers and how to grind them gets
important. What you do is provide a better rake angle for the chip, and a
reason for it to do something it isn't already doing. It's called chip
flow. If you're getting tip welding, it's usually a function of a poor
combination of speeds and feeds and related rake angles. It can be
avoided. There's no substitute for experience in this situation. Once you
see it done and understand what to do about it, it's much easier. One
of the big problems with tip welding is in grinding unreasonable chip
breakers, where the chip can't flow. I've seen pretty much any material
perform poorly under that condition. Once the chip starts stacking up, it's
all over. The only exception in metals might be magnesium and free machining
copper alloys. . It's hard to get them to not cut well.
My mom made me go to school for architecture and I took as many math
and mechanical engineering classes as I could get away with. It was
way more interesting and I had planed to live in Florida and continue
flight lessons to be a corp. pilot. I blindly bought a lathe and had
no real idea how to use it 20 yrs. after school and grinding cranks. I
just got sick of paying machinist to make me stuff. I can't even
recall how I know what is happening , but just have a nak at it. I
really get lost on alot of posts cause I don't know the jargon of
shoulder here and what ever there in the printed work , but pictures
are clear as day. Oh, send me pictures of the grinder you built, even
though I'm not sure if the small upgrade will let me see pictures from
email. I'll just keep it if I can't open it.
I don't have any pictures at the moment, but I'll try to take them today
some time and get them to you via email. I'll send them as an attachment.
Feel free to query me if you have any questions.
I finally got to see
the drawings of the holder to grind blanks that wouldn't open from the
drop box. BTW my planer would make those easy. What would be cool is
cast iron blanks to bolt it down on the surface grinder and cut
different angles with the planer to accept the blanks.
Yep, that's the only negative about the design. The idea is good, but you
often have need for different angles. That's plenty easy to overcome by
having a few holders with the desired angles. Very nice idea, that one.
Harold