Well let's start this project with the milling of the slide valve. As I said, I'm going to try to do the majority of the work on the Sherline lathe/mill. I got this piece of equipment at an auction. It came with many tools and the column to turn the lathe into a mill. It's not the standard lathe and mill but a conversion piece that will turn the lathe into a mill.
Here's the lathe.
And here's the lathe converted to a mill. I have added a sacrificial aluminum table. It has 1/4-20 threaded holes so you can bolt things down. It also has a fence on the back to place your part squarely against. The rough slide valve is sitting next to a AA battery for size comparison.
Here is a close up of the valve mounted against the fence with a finger strap. The bottom of the part was filed to get rid of the flash from the casting process. There wasn't very much of it. These casting are very clean. I also filed the flash off the sides so I could be confident that the part was close to square. I then milled the three sides to just clean up the taper of the casting. Now before anybody gets upset and tells me you shouldn't use a drill chuck to mill with and that it will fall out of the taper, I'll explain. The drill chuck is held in the taper spindle with a draw rod. If anybody is interested in seeing the draw rod let me know and I'll show a pic of it. Also the Sherline has a 0 taper spindle.
Here's a close up were you can see the aluminum table with the back fence. The part has been milled on three sides. The shiny finish is the milled off part.
This one's for Bogs. He always says that "You can make small parts in a big machine, but you can't make big parts in a small machine." Here is the part sitting on the LARGE vise. Bog's how do you expect someone to hold such a small part in that big vise?
Very simple. You make yourself a small table like this to hold the small parts in a large vise. How'd I do Bog's?
Ok enough of that big machine. Back to the small one. I have now mounted the vise and the part which has some what square sides in the small vise. I’m ready to fly cut the bottom of the valve smooth and flat. The round part with the slots is the Sherline faceplate. A cutter attached to it to makes it into a fly cutter. Works very nice. You just have to remember to turn the speed of the spindle down so the machine doesn't dance all over the table. Ask me how I know.
Again I took just a skim cut. You can see a bit of shiny surface and a matt finish surface. Looks pretty good for being square.
Once I got the bottom surface all cleaned up I marked a line in about .050". The base has a dimension of .531" square. That's the square you see marked out on the piece.
I've milled the first side that is against the solid jaw to the marked line. That's not the line you see, it's the burr the cutter raised on the side. Then I went around the part to the opposite side and milled to the .531" dimension given on the print. Then the other two sides were done.
With all four sides on the bottom of the valve square, I finished milled the top part of the valve sides. The top part will have two slots put in. One for an adjustment nut and the other for the valve rod. This will become clearer when the parts are assembled later.
Here's a little trick I learned were I worked. In order to find when the mill touches the side of the work without putting a divot in the work from the spinning cutter, use a piece of paper. Mic the paper so you know the size. Hold between two fingers very lightly and bring the cutter into the work slowly. When the cutter pulls the paper out of your hand you know you close to with in the papers thickness. Just remember to let go.
And here we have the semi finished part next to the rough casting. Rough on the left, semi finished on the right.
Well that's it for now. Next time I hope to finish up by milling in the two slots on top and the pocket in the bottom.
Here's a drawing of the valve to help you visualize what it looks like for those who are not familiar with steam engines.
Until next time,
Bernd
