Today was snow tire day at my house, which took up much of the afternoon, so only this little bit got done.
This will become the top of the cross head slipper. The slipper has two pieces, steel where
the con rod and the piston rod connect, and a brass foot that slips inside the cross head
guides. The two will be soldered together.
In the shot above, I have a piece of left over something in CRS. It looks like a mouse has
been gnawing on it! I'm taking an .050 d.o.c. about half the width of the 1/4" end mill to
square an end. That end mill is just about worn out, and I ended up replacing it after getting
this piece cut to shape. It still cuts well enough, but the finish was showing a lot of marks.
I'll use it only for roughing after this.
After the piece is cut to its rectangular shape, I replaced the end mill with a new one. I'm
just about to cut the center slot in the piece, but first, a skim cut was taken off the top.
It is probably not necessary for this particular piece, but it's a good machining practice.
When cutting slots and such, and especially when cutting things like dovetails, it's important
to have surfaces parallel. So, I usually skim anything like this right before cutting then next
parallel surface, just out of habit.
After the top cut, the piece was centered and the slot cut, seen in the next picture.
Here, the slot has been cut, and it's being center drilled for a hole that will be tapped. I just
made sure to drill the hole deep enough that it would go clear through after I had finished the
bottom of the piece.
This is all that can be done in the mill, for now.
A cross hole has to be drilled through the sloted part for the piston rod pin. If I had started with
a piece that was a stock size of material, I would have drilled this hole first. Since it had to be
made from oversized stock, that couldn't be done.
The location for the hole is laid out, and a piece of wood and some shims are put between the
two "ears" so they will not be deformed while drilling. The shims are just to keep the wooden
piece nice and tight in the slot.
Then the piece is center punched and spot drilled. The wood piece serves a second purpose here,
which is to keep the piece flat on the top of the vise jaws. The piece is clamped on the larger
waste material, so I don't have to worry about scarring the "good" part. Then the piece is drilled
through and reamed.
Another use for the wooden piece. I used a file to clean up what will be the finished slipper.
In this picture, the wood piece is wedged between the ears to keep them from vibrating while
I'm filing across the narrow dimensions of them. Vibrations in a thin piece will cause the file
to skip over the part, and the finish suffers.
Still using the waste piece for work holding, the top corners of the ears are filed to a radius that
suits me.
The diagonal marks you see are from using a fast cutting file. I started the radius with an eight
inch double cut mill bastard. That's a good size for removing a lot of material from a small work
piece. As file sizes go up, (in length), the the tooth size on the file changes, even though the
name of the cut is the same. In other words, a 4" mill cut file will be much finer than a 12" mill
cut file.
Filing is a whole 'nuther aspect to machine work, and is a subject in itself. If a few folks would
like to know more about it, I can write more...
Back to this little part. After I had roughed out the radius with the double cut, I finished it up with
a finer file.
When I had done most of the filing, the waste piece was cut off. I left it on as long as possible,
mainly for something to grab in the vise. The threads that were on the end were from a test
thread done some time back, for some forgotten project.
Now it's back to the mill to get rid of the nasty end.
Then the previously drilled hole is wiggled in, and the hole is tapped 5-40.
And that's the whole days work. Well, only a few hours, really. Spent most of the day chasing
around town. Didn't even get to work on the new/old lathe today!
Next time, the slipper foot. Sounds like a Cinderella story...
Dean
