soffee83 wrote:
>--- In Homebrew_PCBs@yahoogroups.com, "Mike Young" <mikewhy@s...>
>wrote:
>
>
>>After squaring the axis to the table, you can swing a bent wire in
>>the spindle to square it to the table. The height of the free end
>>above the table should be the same through a full circle.
>>
>>
>
>That sounds good (and easy)! It sounds just like the procedure in my
>radial saw manual, where you rotate the arm with the arbor lightly
>scraping the table.
>
>
It sounds good only if you want to see if your drill is perpendicular
to the table. I don't generally care if it's exactly perp. to the table
or not, I want it true to the motion so it doesn't snap bits.
Set your axis to 85 degrees instead of 90. Set your tool back 5
degrees to the 90. You're back to perpendicular to the table. Get this
to zero, then go up and down and see that it's still zero, even though
you move over quite a bit for any change in depth. This measurement
doesn't begin to take out any error in axis motion alignment, it left
that back at the initial setup for the axis.
Errors either add, or worse than that, multiply. All measurements
have error. You don't align the axis, let that have error, then only
align the tool to flat to the table, let that have error, and then let
the two errors add up. You measure what you want correct directly, only
having one source of measurement error, and minimize that error. The
off angle motion that that bent wire test can't even detect is way more
important than whether the tool and axis are exactly 90 degrees to the
table or not.
Yes, almost all machinists use dial indicators a lot. But there are
still many classes of machinist, most notably the average ones, and
those that can do truly exceptional things. I seriously doubt any of
that higher class would settle for the double error of the indirect
measures mentioned, I know I don't, and I have barely scratched the
surface of machining. What I outlined gives a direct measure of the
true path of the bit, trying to add up any other couple of measurements
to get that is going to be a second class measurement. Lots of people
like to measure lots of things with lots of numbers and say they're
highly accurate, but it isn't the case at all if they aren't using the
best methods and looking through the data to select only the most useful
and get the best answers. The alarming thing is just how many of those
machinists out there with 10x the tools I have can barely beat what I
can get done with very little, when they should be able to do at least
10x more easily. And I find those who insist that all their tools be
super accurate are often the least accurate themselves, not the most.
They generally need that super accuracy of everything else to make up
for the slop in what they do with the tools, it's why they insist on it
so much.
I generally don't care if the drill is at 90, or 88, or 75, or 103
degrees to the table. The only thing that matters to breaking the bits
is whether the shaft follows the hole cut by the tip exactly down the
hole or not. The best way to measure that is directly. After you get
that right, then it's easy to get the whole axis very near 90 degrees,
and you don't even have to care much if there is error in that
measurement or not, it has no bearing on snapping bits. Doesn't matter
if you do that part first, but checking the tool path directly better be
done somewhere along the line if you expect to have any sort of high
accuracy.
Most machinists would laugh at my setup. But chuck up a #80 bit, and
start drilling lots of little holes without breaking bits, and I'm sure
I can get most of them quiet without much problem. Especially after I
stop drilling, wiggle the chuck back and forth probably .010" or .020"
total with my fingers, then start drilling again and still not breaking
bits. Parallel motion is key, basically nothing else matters much. But
I'll put some videos up once things are going soon so you can see what
it'll do for yourselves..
>I've saved Alan's posts for later. They're a bit over my head for now,
>but I understand most of it. I figure if the pivoting presses are good
>enough for most work, this thing should be able to get straight
>enough. I'm considering incorporating some type of screws or shims in
>the tool holder to make it easier to tweak the alignment if need be.
>
>
>
Well the pivot type press works because come out a bit and it's only
a tiny fraction off from a line, and it's easy to take nearly all the
play out of hinges. If what you're doing will have much off axis travel
or notable play it can easily end up not being as good as the simple
hinge.. Everything is different, but simple is very good because there
is less to go wrong.
With $5 or $10 per 50 or 100 bits, it really won't matter that much if
things break a bit more than they should. Even a little sub-optimal is
still fine for general use if you're not using the very smallest bits..
.025 or .030 etc bits won't like the flexing and will break more
quickly, but they don't just snap when you breathe wrong like .016 and
smaller tend to do. I've snapped the 80s a few times in my hands or
while holding what they were in, and you can barely even feel them break..
>PS - If Alan reads this- The camera technique is out of my league, but
>I got a "forbidden" error when going to look at those pictures. Not
>sure if others can see them. I'm on Opera 8.51 for Windows.
>
> -Much Thanks as Usual!
>George
>
>
Suspect Opera for that. Hotlinking is disabled on my web space, and
some browsers mask the referring URL. If your referring URL given by
the browser is anything besides direct URL entry or link from my site,
you won't get the file.. Could of course be several other problems
since I haven't tested it from away lately, but that is the most likely,
I think it's in the privacy settings of some browsers, seem to have read
it somewhere a while back.
Alan
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