Zee, thanks again for your comments.
Some aluminum is kind of gooey, or mushy, and will smear over small openings. Thinking about the kind of aluminum that plugs small end mills, here. Sometimes your tool may just need a little touch up, or something like a spritz of WD 40 will help. Sometimes, nothing will help much.
Arnold and Mike, thanks a lot for continuing to check in on the build.
Always appreciate that!
Hi Artie;
The cut was .060" deep with a 1/16" end mill. It probably looks like more because of the close shot and the lighting/shadows. Sorry, I don't know much about your medicating. I hope you get over it soon...
Today.. Boring.
Cylinder boring!
I chose to align bore this piece. It is easier just to chuck it up in a four jaw and run a reamer
through it, but I don't have a reamer larger than 1/2". The bore is .625". Anyway, I don't
mind doing the needed set up for an align boring job, (some folks call it line-boring). I've used
this method for a lot of projects, and it works well.
First thing to do is find the center of the cylinder. I don't have a surface plate, but the finished
surface of my bench is quite flat. I used a surface gauge to mark out square lines on the end
of the work piece, then reset the gauge to mark out another smaller square.
Doing it this way gives you a neat little grid. You could just mark out one square for the
same result as in the picture above, but marking a second smaller square gives you a kind
of bullseye target and you can easily see if you've got something off center. Laying out
the "X" that marks center is just a matter of running a line through the corners of the squares.
Then the piece is center punched using a magnifying glass, and put into a vise on the lathe
cross slide. Shims are used to bring the piece to the right height to match the punch mark
to the head stock center. The cross slide centers it fore and aft.
The same thing can be done without a vise. You'd just have to make a cross bar with a
couple of holes in it to bolt down across the top of the work piece.
At this point, the cross slide gib is locked.
For a final check before making any chips, I ran a DI over the top and side of the piece, just
to make sure it wasn't caddywhumpus in some direction. When everything looks good, a
hole is drilled through the center of the piece. Biggest drill bit I have is 1/2", so that what
I used. The bit was honed for cutting brass, of course.
This is the setup for align boring. After the hole through the center of the piece has been
drilled, a boring bar that has a center hole drilled in each end is passed through the piece
and mounted between centers.
The boring bar is cross drilled to take a bit made from small drill rod. A set screw holds the
bit tight in the hole.
Here, I've taken the start of the cut. For each cut, the set screw is loosened and the cutting
bit extended out of the hole a little. The bit is short enough that only one end sticks out of
the cross hole that goes through the bar.
To set the tool for a certain cut, I divide the bore size I want by two, then add one half the
diameter of the boring bar. Set the tool to that measurement, and the tool will cut the diameter needed.
For instance, the bore I want here is .625". The diameter of the boring bar is .375".
.625" / 2 = .3125"
.3125" + .1875" (half the dia of the boring bar) = .500". Nice round number in this case.
By measuring the distance from the tool tip to the back side of the boring bar OD, you can
set the tool to cut just what you want.
The shot above shows the recess that will take the inner boss on one of the end caps.
The same tool is used to cut both end recesses, and the bore. The tool is ground to a sort
of wedge shape, and will cut in either directing just by rotating it 180 deg. (It has a similar
cutting edge whether going to the right or left, right side up, or upside down.)
To measure the bore, the boring bar can be removed at any time, and since it is run between
centers, I know it will go back into the same cutting position each time I remove it and return
it to its place between the centers.
I use simple telescoping bore snap gauges for this kind of stuff. They take a little practice to
get used to, but they work pretty well, for me.
This shot shows where the end cap recess just broke through to the end of the threaded hole
for one of the condensation drains. It's supposed to be like that!
And this one shows the steam passage after the recess has been bored.
I got the piston and rod done too. I'll put pics up for that tomorrow.
Dean
