"D Murphy" wrote in message
...
"Harold and Susan Vordos" wrote in
:

Hi Dan,

Surface grinding:

My mentor had vast experience and was gracious enough to not only
teach me all methods, but wise enough to point out the pitfalls of
using each one. I have him to thank for what little knowledge I carry
with me today.

I've read acouple of posts where you gave out good advice on surface
grinding and offhand tool grinding. We had similar teachers.


It's been a very revealing experience to find that so many grind by
methods different form the one you and I prefer. I can say with
total honesty that grinding by my recommended procedure is the best
way, hands down, assuming finish is important. That would apply to
even small, dry grinders.

The company I work for imported a surface grinder from Taiwan for a time.
We used to gring hardened 52100 steel to a mirror finish at the machine
tool shows for a demo. All you need is the right wheel, balance it, dress
it properly, and grind using the method you describe. Worked every time.
These weren't great machines either. They were better quality than I
expected but they weren't Mitsui's by any stretch.

I've been away from machining since '83, so I'm painfully behind in what's
happening today, including knowing anything about a Mitsui, but a friend
that is working as a mold maker was talking about one of them recently.
They're apparently a super nice grinder. Your comments on procedure
should be very enlightening for those that don't subscribe to what I call
*proper* grinding, verifying that which I've been espousing.



Sorry to say I've never touched a double disk grinder, although I have
seen one. If by chance you manage to corner some information about
one, I'd be keenly interested in hearing what you discover. We had
no need for one at the missile facility, otherwise we'd have had one.

Actually we sell one. We have had some issues with the wheel we are using
and the manufacturer hasn't been a lot of help. It's a CBN wheel and it
has been chipping out on the edges during cycle. The trouble seems to be
on parts where we are grinding single sided rather than double disk. I've
got some other projects where customers are wanting us to run a part and
I'm not comfortable buying another wheel from the current supplier at the
moment. I need to hold .0001" parallelism and .0001" flatness. Thickness
is wide open at .0003" total. I have to hold a 1.67 Cpk running these off
so there is no room for variation. When the wheel chips on the current
job the chip gets dragged across the wheel and my dimensions will jump
about .00006". sixty millionths may not seem like much but it's enough to
fail the run off. To say nothing about a very expensive wheel falling
apart. If you want to see the machine it's he
http://www.tsugami.co.jp/product/lapping/TVG4/TVG4.html
Unfortunately it's not in English, and we haven't added it to our web
site yet. http://www.remsales.com/
Dan

Wow! Very impressive looking machine, and a total surprise. The one I'd
seen had horizontal spindles with a carrier for the part which oscillated
back and forth between the two wheels. Very old technology, to be sure.
One of the jobs the shop was running with is was the slide portion of a
pistol.

I'm not familiar in the least with CBN wheels, considering they were not in
use when I retired from (commercial) machining. I gather that such a wheel
is more or less a necessity for the work at hand, but I'd be inclined to use
a different wheel, assuming that would be possible. You didn't mention the
material being ground.

Funny, talking about .000060" and having it be a concern. Yeah, it
doesn't sound like much to worry about, but when you have no tolerance to
speak of, it obviously spells the difference. I think it's hard for the
average machinist to grasp the concept of fine work. So much so that I've
commented more than once that it takes a special kind of guy to be
successful in the grinding department. Some guys never really make the
grade, yet may have years of shop experience.

About the chipping. I can't help but wonder if it's not being caused by
your parts chattering slightly. Your operation being a total stranger to
me, could it be that your coolant plays into the problem? For typical
grinding, the level of concentration of lubricant (in the coolant) isn't
critical, more for rust prevention than anything, but when you use machines
that rely on surfaces for support (like when grinding on one side only) it
could be you need more lubrication. We always ran a higher level of
concentration in the centerless grinder for that very reason. It's
interesting that it happens when grinding single sided, which prompts my
chatter question. My other suggestion would be feed rate, but without
understanding how the machine operates, I'm not sure I'd be in the ball
park.

I looked at the lathes offered by your firm. Sure makes me breath easier
to know that if I was really in need that there are still reasonable
machines on the market. I was particularly impressed by the one model
that offered 2,500 RPM at the spindle. I'm running a Sag 12 Graziano that
I bought new in '67, and I"m hoping it will see me through to my dying days,
but I'd not hesitate to buy something similar (new) if the need arose. I'd
rather it didn't come from Harbor Freight, if you get my drift!

Harold