The A3 project hasn't been at the top of my "hot list" for awhile. If you have been reading other sections of this site you'll have seen my comments about the Texas summer temperatures. The shop is not air conditioned, so sometimes the weather has a strong influence on how much time I spend with the machine tools. A lot of other duties have also kept me away from my "hobby" shop. Of course, I sometimes go out and talk to my tools. Just once in awhile. (Honest Doc... Honest... Honest... I am perfectly normal... Honest Doc...)
I admit I have kind of gone into "overkill" mode in this presentation on such a small part. This is because I want to illustrate that even the smallest of parts will have a lot of moves and setups before they are properly finished. On top of that, the process must be repeated eight (or more) times to get eight good bearings. Yep, I flubbed the first one when I forgot to take only HALF the remaining depth on a lathe cut.
I have also begun to use "back side" photo's of the machining action. It is much easier to keep the cameras set up, and it is out of the way of my work. I hope you can adjust to the new viewing angle.
The tender wheel bearings are made from bearing bronze. The wheel axles do not ride directly on the brass in the journal boxes. That means I have to make eight identical tiny little bushing bearings. Here I am using my trusty power saw to cut off a 3/4 inch chunk of the bronze rod stock. |
The accuracy of the three jaw is perfectly adequate, as everything except the back side facing (to length) cuts are made in one chucking. You'll see how that is handled further down the page. |
This is the initial facing cut on the end of the material. All you have to do is clear off the saw cuts. Note: Very little swarf here. |
This is a center drill operation... |
followed by drilling through with a letter "D" drill. I thought of selling those chips as fake gold, but they will eventually oxidize. Rats... |
The 1/4" reamer gets the hole perfectly round and smooth. |
Kozo suggests using a boring bar to chamfer the inside edge of the hole, but that seemed a lot of fuss to me for a non-critical cut. Here I am using a 90 degree countersink to cut a slight chamfer. |
I am just starting to turn down the diameter to the proper value. This is the move I admit I missed by overshooting. (Uh... let's see... I need .008 more... remember, crank in .004) That means I had to do all of the above all over again. |
The bearings taper 3 degrees from each end on the outside. This is to allow some "rocking" movement in the journal boxes. And more work in making the part! |
I am using the Mark I eyeball (Navy jargon) to set the compound. This taper is non critical so no need to bust your... uh...er... eyeballs to get it perfect. |
This is the second side of the taper being cut toward the chuck. One of the reasons I love machining is is the "thinking through the process" of exactly how to make each cut. Also getting to know your tools and machines and how to best use them. |
I set the auto timer on the camera and started the cut-off. I have an Alan er... hex wrench in my right hand to catch the part. |
This is the second chucking to trim the bearing to length as well as face off the cut-off. The reamer is used to position the part in the chuck. Since only facing cuts will be made, the part does not have to be concentric with the rotation. This is plenty accurate for this part. |
This is the second side facing cut being made. Many of these shots were made with the machine running. |
It's hard to see what I am doing here. I have the dial caliper in there measuring the length after I squared the end. Note the "dent" in my thumb from just having pushed on the jaw roller. (It goes away in about two seconds!) Amazing what you can see in a picture you never notice otherwise. |
Another chamfer for this end of the bearing. |
And a light file touch to slightly radius the sharp outer edge. |
Here are the eight finished journal bearings. Them shore be looking pretty! |
Here is my standard left hand to provide a size reference. (Yes, it is good for other things as well...) Not much left of that 3/4 inch piece of bronze bar stock. A lot of work in such a tiny part. This article has also shown that it is not difficult to make small parts on a machine (8x14 lathe) like mine. This size is nothing compared to the micro parts I have seen others make on smaller machines. However, everything you see in this page is the machine tool finish. I used no abrasives to get the nice shinny finishes. |
Perfect fit on the end of an axle (The wheels will be in the machined area under my thumb.) |
The bearings then insert into the journal boxes. |
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The next step will be to fabricate the bolster columns! |
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