Hi shild,
I thought it might help if I show how I do things on my mill.
A long time ago, I inherited the frame and wheels for Jeannie Deans, a 3 1/2" scale model of an English Webb compound designed by L.B.S.C. the guy who started all this stuff in England over a hundred years ago.
Jeanie Deans is not a beginner's locomotive, but it is interesting because its a compound with the two outside high pressure cylinders driving the rear axle and the center low pressure cylinder driving the front main axle. There are also a pair of front pilot wheels for guidance. There are no coupling rods between the driving axles. Recently, I decided to work on "Jeannie" so I got the castings (except for the wheels which I had) and drawings from Reeves in England. As you can see in the last two pictures, I have made the rear axle and the crank axle is partly done.
- Milling final axlebox down to finished thickness
This first picture shows the final axlebox held in the vice and supported by two parallels so that the vice grips the part by the lower 3/16" only. This gives plenty of exposure for the cutter to work on the part. By the way, in the picture you can see I'm using a 3/4" dia. end mill in two parallel passes to face off the surface. Since the head has been "trammed in" (truly perpendicular to the table) you can hardly see where the passes overlap.
- Same setup but showing the entire vice.
This second picture shows the entire vice, including the handle. When tightening the vice, I push down on the part against the parallels as I hand tighten the handle, and then I use a wooden mallet on the handle to make sure the vice is really tight. Cutting forces are high, so it is important to make sure that nothing can move. If you look carefully, you will see that the vice jaws are smooth with no grooves of any kind. Whenever I remove the vice, when I put it back, I always use a dial indicator in the spindle on the fixed jaw to make sure the vice is aligned with the ways to a thousandth of an inch over the 5" length of the jaw.
- This picture shows all 4 axleboxes.
This picture shows all four of the partly finished axleboxes. I cut them from a piece of 1 1/2" dia. bronze bar stock that I had. The slices were 5/8" thick (you can see the center drill in one).
I used the lathe tool to cut a series of grooves at 5/8" spacing and then used a hacksaw to cut through the grooves while the lathe was running. I prefer this method to using a parting off tool (because the forces are less) and it gave slices that weren't wedge shaped. I first used a smaller parallel to flatten the sides of each part and then I used the pictured setup to "face" one side of each part. When doing this, its important to run all the pieces through the same setup one part at a time. It is just one of the many steps you need to take to make all the parts interchangeable. Since I have a 3 axis readout on the mill which is set to read to two tenths of a thou, it is easy to work to close tolerances. The readout can go to one micron (a thousandth of a millimeter) but the mill isn't that accurate.
Once they have all been brought to the 1/2" thickness, the next step is to align each part in the vice so it is flush with the side face and then locate the center of the axlebox in both X and Y directions. Next, lock the table and then use center drills and end mills to open out the hole and finally use an 11/16" dia. machine reamer to put the hole on size in each axlebox (I'm using 11/16" because that is the size I need to press in the needle bearing I'm using, otherwise the hole would be 1/2").
Next, without moving the table, run all the other axleboxes through the same setup so each one has a 11/16" reamed hole. After that, go through the steps to make all the axleboxes 1" square, then cut the 3/8" wide slots so each one will fit in the frame. They should slide easily and tip a bit, but they shouldn't rattle. I have measured the frame sides and on one side, both holes are .875" but on the other, the openings are .880" so I'll file the .875" openings to make them .880" like the other side. This way, all the axleboxes can be the same.
- bottom view of the frame
This picture shows an upside down view of the frame. You can also see the rear wheels in the top left corner of the picture. You can see that the workmanship on the frame is pretty good and the wheels are nice too.
- side view of frame
Finally, this picture shows a side view of the frame.
This explanation and series of pictures shows how I approach a project. It is meant as a guide to learn from, it does not mean you have to follow it completely. It also shows that speed is not the most important factor, but while you may not have to do precision work all the time, it is important to be able to do so and you should learn and know how. For me, because of the equipment I have, it is just as easy to be precise all the time.
You will also need to be able to measure to 1/1000" of an inch, so you will need a zero to one inch micrometer as well as a 1" to 2" micrometer (they come in 1" increments). You will also need a 5" or 6" vernier caliper and a 6" dial caliper. These should all be new and of good quality. Most important, they should only be out of the case when they are actually being used to make a measurement. You will also need a dial indicator that shows .001" graduations. While not essential, sometimes it is handy to also have one that can read to .0001"
I hope this helps. Welcome to the club. Once you get into actually making a locomotive, a lot of your questions will be answered.
Richard Trounce.