There are 8 tender wheels that need to be machined, but knowing me, I machined 10 just to be on the safe side. The material used is 2.375" cold
rolled round 12L14 Carbon Steel. The "L" means that fine Lead particles have
been dispersed throughout the alloy which makes for easier machining.
Here I'm cutting the 1st of the 10 disks. Each one needs to be at least .500" so that there is plenty of material on both sides to end up with a
wheel thickness of .4375" (or as Kozo puts it ... 7/16"). My 1st
disk had a
thickness of .530" a bit too thick; so after measuring the flatness I changed
it to .480", that way I don't have to take off a lot of material. I'm using the Harbor Freight band saw with a bi-metal
blade ... it cut through the 12L14 like soft butter (well ... almost!).
Each wheel requires chucking 3 times. All machining needs to be completed before removing them from the chuck otherwise you will lose concentricity.
The 1st chucking is to face one side, then machine the wheel plate.
The 2nd chucking faces the other side and sets the thickness, then machine the wheel plate and drill out the axle hole. The 3rd chucking requires an arbor to machine the flange diameter, the flange, taper thread and the tapered flange. A lot of work! The photo on the right shows my 1st chucking ... facing. Notice the hot oil burning off the curly swarf ... yes the chuck is moving. Can you tell which way the swarf is moving? This is a real "stationary action" shot!
This is still the 1st chucking ... I'm doing all 10 wheels before moving on to the next chucking ... saves time! After facing and applying blue layout ink I set the tool bit at the center of the wheel, set the indicated to zero and the moved out .312" and scribe a line by manually rotating the chuck. Repeated at a distance of .875". Now all I had to do was remove the material between these two scribed lines at .125" depth. Click on the thumbnail and see the dial indicator reads .875" (be sure to "arrow back"). This would complete the machining of the wheel plate for one side. Notice the tool bit ... a Kozo special. This is one thing I would change ... I used 1/2" tool stock then ground down the point ... I should have used 1/4" tool stock. My 1/2" was too big to fit on the edge so I had to grind down a lot of extra material to get it to fit. A smaller one would have been much easier!
Finished with the 1st chucking!
The 2nd chucking was done the same way as the first: However, when placing the wheel in the chuck make sure that the "faced" side is firmly against the jaw face, otherwise the faces will not be parallel. Machined the thickness to .4375", then drilled the axle hole and finally reamed to .3125". No pictures for that but a note on what I did. I didn't like the way the axle hole was going, the boring to .308" was not working very well, so I looked up the spec for the reamer and found that it could remove .010" without a problem. So I went from the countersink to a 6.0mm drill bit (what I have on hand), then to a N (.302"), finally the reamer (.3125"). A little more work but they look great ... nice and smooth! I had to scrap out one wheel due to a dull tool and probably feeding it too fast ... took out a large chunk of material. So I repeated the process for a new disk. I wanted 10 good wheels going into the 3rd chucking.
The picture to the right shows the set up for the 3rd chucking. An arbor is made that must stay in the chuck until all wheels are completed ... again to keep concentricity. This set up accomplished 3 things ... cuts the flange diameter (2.25"), cuts the tread diameter (2.125") and the 3° tapered tread. Since I made a 4 hole plate as one of my modification to the lathe I can no longer read the compound degree setting. So I made a tool that sets the angle for me with very good repeatability. I have another that reads a negative 3°. It makes for easy switching from the 10° back to 3°.
After machining the flange and tread diameter, I changed back to Kozo's tool bit. You can see the tip of the tool that is required to give the 3/64" radius between the tread and the flange. Per Kozo (he has great ideas and suggestions!) you start at the corner and machine outwards to get the taper (left to right). The red ink provides a high contrast for easy seeing, take a little off at a time until there is small red line (you can see that I have a little more to cut). Your done. Set the compound for the 10° to taper the flange, then reverse the wheel and make the final 10° cut. A little filing on the flange rim gives a good smooth curve and your done. I did all 10 tender wheels using this method with great results, now I can remove the arbor! The rest is polishing. Painting will come later, as I haven't decided on the color or the method yet.
Now that I'm finished machining all ten Tender Wheels I picked 8, as some of them I know I didn't make to "print". So here are my best 8 measurement results:
There are certainly other measurements that can be made but these are the ones I decided to take. The important one is Tread Diameter which was very good at 2.0625 ± 0.0025". The others are okay, I see that I am removing more material than I should in most cases. Something for me to work on for the other parts. The axle hole I really can't measure very well ... as I don't have any plug gages. Since it was done with a reamer it will have to do.
As Patrick would say "What happened!". Well I didn't paint them, I just placed them on a shelve stacked on top of each other. There they stayed for over 6 months ... out of sight and out of mind. Big mistake, I should have oiled them up and placed them in an oil soaked bag or container. Are they ruined? Do I have to remake them? Fortunately .... NO on both counts!! I just re-chucked them on the arbor and polished then using 400 and 600 grit paper. I bet you can tell which wheel was on top of the pile!
Well here they are, in my special made paint booth (also known as a big cardboard box!) all nice and ready for paint. After trying to tape them using pieces of masking tape, I did the following which made the process much easier: Use a 2 1/2 inch wide single strip masking tape placed on one side of the wheel, using a sharp knife cut out the tape along the edge (see photo on left). Fold the excess tape over the flange and tread. Repeat for the other side. I sprayed two coats black flat enamel. Came out great! This time I oiled them real good and placed them in a closed container. Axles (update 1/27/06) Now to the axles ... these should be easy. After all we only have 5 lengths, 4 diameters to cut and we are done. As usual the axles turned out to be a bit more of a job then I thought!
I used 3/8" 303 Stainless Steel rod from McMaster Carr as with most of
the material. I used my 3 jaw chuck to get to the overall length to 4.75" for the 4 axles, but since my 3 jaw has a TIR of .002" plus (Kozo says it needs to be .002" max) I set up my 4 jaw to turn them down for the tender wheel and bushing diameters. The only issue here is that it takes about 2-5 minutes for me to get the TIR <.001" for each end. Not bad ... then I scrapped out 3 of the 4 axles due to my blunders ... now the set up time has significantly increased because I needed to remake 3 axles for the correct length using my 4 jaw! And I thought these would be easy!! Finally done ... only to find out that my last axle is not quite to print. The diameter for the tender wheel should between .3120" and .3125" .. oops mine are .31175". Oh well, I am not remaking it. The Lockite will have to make up that little difference of .00025"!! And the bearing diameter is just outside the specification ... again I not redoing it for the .00025"!! Since I like to take measurements to see how I'm doing and what I need to correct here are the results for the 4 axles:
As can be seen from the table above I'm still taking too much material off ... must be more careful otherwise I will have enough parts for 3 steam engines.
Well here are my results so far ......... The axle at the top (with the tape on it) didn't meet the specification, but is good for show and tell!
This completes section 2.0 ... now on to Section 3 (Journal Boxes and Bearings etc.) maybe they will be easier! |
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