On Dec 21, 8:25*pm, "Michael Koblic" wrote:
On Dec 21, 8:25 pm, "Michael Koblic" wrote:
Jim Wilkins wrote:
...
Since you have a mill now, you can cut one surface down to a polygon
centered on another cylindrical part quite easily. ...
I *think* I got that.
Normally you would do this on an R/T?
Here is a dummy setup for roughing out a curve concentric to a hole:
http://picasaweb.google.com/KB1DAL/T...75471032901730
The part is a clamp to hold an indicator on the Clausing mill's
spindle. I bored the hole first and then cut away the rest. As you can
see this aluminum part was finished on a rotary table, a lightweight
no-name one that wouldn't handle this job in a similar piece of steel.
The vise setup is much quicker than centering and clamping the part on
an R/T, and safer when the curve ends in straight tangents where the
end mill can grab, rotate the table by its free play and dig in
badly.
When I blend a curve to a flat this way, I set the end mill to the
height of the flat and then lower the table (you'd raise the spindle)
about 0.005". The line of tangency won't be exactly radial but that is
invisible, whereas cutting too deep leaves an obvious step at the end
of the curve.
A trick that's claimed to work is to drill a slightly undersized hole
between two hardwood clamp blocks and sprinkle in powdered rosin, like
baseball players use for grip. Or scrape some off a tree.
I use it for soldering. Maybe that is the answer. That would mean having the
gnomon stationary and some sort of die-holder chucked in the drill press.
I usually clamp the shaft horizontally in the bench vise with the end
protruding slightly and align the die parallel to the jaw end by eye.
A square end on the blocks would let you do the same. This is for
large coarse threads, for small ones I square the die with a drill
arbor or female center in the lathe's tailstock.
Alignment would be easier in a drill press vise. Push the shaft toward
the jaw with the die and tighten just before it makes contact.
Once the die starts to bite you can control the whole assembly with
one hand, slide the shaft out a little to give the die some clearance,
and use the other hand to retighten the vise.
Or if you put the starting stub on the gnomon you can align it in the
drill press and then cut the full thread in clamp blocks.
...well-documented crafts with good tricks that can be used
elsewhere. ...
Knife-making. Most of my early learning came from there.
I have the Hrisoulas video but not the artistic ability. My best
effort has been compared to a prison shiv.
The most useful watchmaking idea was the button / disk technique for
accurate hole layout on their manufacturing jigs. ...
I shall have to read this a few more times...:-)
Here is an example:
http://picasaweb.google.com/KB1DAL/T...90941151914594
The disks are the black hardened cylinders on the upper left jaw, with
dowel pins protruding. The upper right jaw shows the hole pattern that
matches the pins and tapped hole on the chuck. The pin spacing appears
to be 1-5/32" but they are too short and rounded to mike directly.
The chuck is like one from the old Holtzapffel drawings. Rotating the
outer knurled ring cams the pin plates about 0.050" in and out. It's
used to turn delicate rings such as lens retainers, by closing it half
way (I think) and cutting a step to clamp the part securely all the
way around. I didn't waste large enough stock to reach the center
because I use 5C collets for smaller tubing.
I turned all three disks down until they fit in line on the chuck
pins. The middle one pushes through with slight resistance, less than
its weight, so tilting the chuck until it slips through is a very
sensitive way to test the fit.
I didn't drill through them, but drilled and reamed the first hole at
a punch mark and then used them with dowel pins to center the mill
spindle for the other two. Since only the outer holes are really
critical, I put a dowel pin in a collet, lowered it into a disk and
adjusted the mill table to get the same feel when sliding the center
disk between them as on the chuck pins.
I guess my 10-ft scarf is right out, then... :-)
Isadora Duncan
Jim Wilkins