Well... I decided to start the index plates. They will be a long and tedious process, especially drilling all those holes. I will make the first set of holes in one plate and the dividing head will make its own hole circles in the plates after that. By doing this, they will be extremely accurate. In fact , i read that if you drill the first set of holes and use them for the head to make the rest from it, the new holes will be 30 times more accurate than the first one you make. So if I take great care to make an accurate set of start holes, the plates resulting will be more accurate than I have the ability to measure. Anyway... on to the work for today.
I stacked four 5" round plates 1/4" thick on a 1/2" bolt. After checking several bolts, I found one that spun fairly true, So I center drilled the end and stacked the plates on after drilling a 1/2" hole as close to the center of each as possible. In the photo, my tool is HSS and it wiped out immediately when it hit the torched edges of the plates. I switched to a carbide tool with a fairly large radius and it cut the scale of, then I finished with the HSS tool. The 5 inch plate stack finished a 4.900" diameter. I could have used 6 inch plates and would have but these were available and they will be just fine.
After the plates were trued up, each one was put on the same bolt and the edges smoothed and polished to a nice shiny finish ( I like shiny things
). I was going to polish to a mirror finish but figured they are going to scratch up handling and using so i quit at an almost mirror finish ( or very shiny). This head is nice looking, but it ain't a show piece. It WILL get used.
The next step was to mount the hub from the dividing head into the lathe and using my drilling jig I made , drill the three mounting holes in one plate and the hub at the same time. You will notice I put a tight fitting drill in the first finished hole before drilling the second hole. then i put another drill in the second hole before drilling the third hole. This keeps everything aligned. I setup my degree wheel on the back of the lathe to index the 120 degree intervals. I also drilled a 1/8" pin hole, for an alignment pin, between two of the mounting screw holes. This was because no matter how hard I try the holes will not be perfect enough to line up at any position. So the alignment pin will tell where to orient the plate for mounting. I made extremely close tolerance holes. If I oversize the holes I could get them to align in ant position, but I never like doing that, even though the close tolerance hub keeps the plate centered.
I stacked the plates , in my 4 jaw chuck to hold them on the drill press with the drilled plate on top. If you look close you can see a close fitting sleeve in the center hole to keep all the plates exactly aligned because everything here is very close tolerance and there is no room for errors. The drill follows the hole in the first plate and they will all match and be interchangeable. ( I know this because I tried each one when I finished.
The photo below is the shaft and the first half with the offset and hub which is lock-tited together forever were complicated and took many hours to machine and have all the surfaces a perfect fit. The last thin you want to do is MESS THIS UP. The largest shiny part on the right end is the hub I just drill the three mounting holes in.
The three holes needed to be tapped 10-24. The first one tapped fairly easy until I got in a ways and it wouldn't go any more. So, I moved to the next hole and it is even harder to tap. So, I try two more new taps and they won't go either. THEN IT HAPPENED! ..... that little "snap"....... the freaking tap broke
. and It won't come out. I was envisioning having to make this assembly all over again and I also did not have any material to make it with.
. I spent the next two hours beating the tap with a punch and hammer and now the hub is all beat and dinged up. Looks like a total loss...
... I sat down and thought a bit and with nothing to lose, I put it in the lathe and started hacking at it with a carbide cutter, as I knew it was the only thing I have that will cut a tap. It is a good thing the hub was thick as I had to cut .150: off it to get the tap out. after re machining the banged up areas and some polishing it is as good as new ...
...... I so lucky!
Here is the head with the direct indexing plate and an index plate mounted on the hub. I have three index plates. I plan to mark degree graduations on the outside edge of the direct index plate, but there is no room for the numbers as it is 1/4" thick. I am thinking the numbers , if I put them on could go on the back side at the outer edge .
There was one more thing that was still bugging me. That .009" end play in the worm shaft. I had a piece of brass with a 1/2" hole in it so..... If you want something difficult... try machining a .008" thick washer for a shim. I took a couple tries, but I finally was able to part of a .010" thick one and stuck it to a piece of tape to hold it while I rubbed it on a file until it was .008" thick.
If you look close, you can see my little shim washer behind the e-clip. Now there is virtually no end play in the shaft. With the worm adjusted right this head is really tight, no detectable play and it still turns very smooth. That is what paying close attention too tolerances will do.
The next thing to address probably should be the spindle brake as it will be needed to use the head to make the index plates.