Transposing gears, the crazy way

[brino]

Great thread, I am really enjoy it.
Thanks to all the contributors!
-brino

 

[Ulma Doctor]

Maybe 47/37 tooth gears for transposition instead of 120/127?

 

[RandyWilson]

I talked about the 37/47 earlier. There are two reasons I don't go that route. First is it just isn't the way the lathe was meant to work. The other is the working diameter of a 37/47 12dp (half of each) is about 3.5". There is a sign inside my gear cover that says you must be at least 5.25" tall to ride this banjo. It won't fit. At least it won't fit without adding a second idler.

@Lo-Fi Somehow I missed your post. Yes, this antique has the capability to do relative indexing. But alas I only got the dividing head. No spare plates, no tailstock, no gear train support. I really think that making and setting up a 127 dividing plate will be the easiest part of this job. the DRO will handle it. The head has the capacity for such a large plate. Tedious for sure, but so will be cutting 247 teeth. I ordered a 9" x 3/8 HRS plate off ebay. For the price I couldn't drive around the few suppliers that will talk to us hobbyists, find the scrap, and then make it round.

Right now I'm more concerned with holding things. Holding the blank. The head has a keyed 1 1/16 hole at one end, a #10 B&S taper at the other, and a 5" three jaw over the taper. I'm thinking I will attempt to just the taper first. If that fails, choose one of the others. Holding the cutter at the needed height will also require making something. Remember "normal" would be able to use the gillion R8 arbors on ebay. Not this Cinci.

I have two dividing head apps on my phone. One you program in all the the plate counts you have. then it tells you which combinations work for your target pattern. The other you give the target pattern and the worm ratio, and it gives all results that work from 10 to 99. I'm going to ping the author and see if he can make the upper limit adjustable.

Tonight I set up the chainfall and hoisted the head up onto the mill table. The spindle center is exactly 5.25 above the table. I will have to shim it I single 1/8", such as a parallel, will give me 10 3/4 swing. I need 10 9/16+. Tomorrow I will do some indicator work to check runout and parallelism.

 

[Bi11Hudson]

For what it's worth ~~~ Just to throw my two cents in. I normally use a Craftsman 12X36 but have a Grizzly G1550-9X19 as a back-up machine. The Griz has Modulus 1 gears(25.4 DP), the Craftsman has 16 DP. The few gears I make for the Craftsman are both with the indexing head and the spin indexer.

I have the spin indexer modified to accept the metric gears from the Griz. Including the 127 tooth metric transposing gear. I don't have any plans, just cobbled something together to take the metric sized gears. I haven't made a 127 yet. I haven't found a piece of aluminium big enough as scrap. I'm allergic to sales reciepts. . . It will requite riser blocks, no big deal. When I need 'em, I'll make 'em.

The key being the Grizzly 127 tooth gear and the spin indexer. Cheating??? Well, yeah. What the hey?

.

 

[silverhawk]

I think both options should work. If you can use the bolt circle function on the dro, that will make it easier. Use that to make a new index plate.

If you can't get the dividing head onto the mill, though, that's a problem. In that case, the 127 tooth MGB flywheel will work if you can key your blank to the flywheel and lock them together. Then just lock a vertical shaft to the mill table and a way to index off of the flywheel. You would need an adapter for the flywheel-to-blank. It should work well enough.

joe

Just to revisit the thought of direct drive using a gear to index, if you are using a vertical mill, you probably can't arrange it vertically. You would need to possibly arrange the gear hanging off the side of the table, keyed to a shaft with the blank and run it horizontally.

joe

 

[RandyWilson]

I gained a few experience points today. The first time using the taper attachment. And the first time cutting 4142 in earnest.





Last to first. Top is the gear cutter arbor. Right side is turned to 1", as it's a convenient size for the Cinci mill and the largest 5C collet I have for the lathe.The cutter end is cut down to 22.1mm and a random depth. It will be finished off when the Chicom cutters arrive. I was finally getting the hang of cutting the 4142, speeds and feeds. .010 made birds nests. .020 made very long stiff tight spirals.... maybe .200 diameter by 3-4 feet long. Still more controllable than the birds nesting. .025 started making decent chips. And .030 was more than the 5C collet could hold against.... shoved the work right back into the headstock, it did.

Middle is the dividing head arbor to hold the gear blanks. Right side is cut to a B&S #10 and drilled and tapped for a draw bar. This was the first time using the taper attachment, and at a really odd setting. 1.232 degrees / 0.5161 in/ft. The taper blued up... okay first try. The left end is cut to 7/8" by .950 with a 3/16 keyway. It's done. I cut the taper on the lather, and roughed in the gear end. Then I installed it in the dividing head, and spun it against an endmill to finish. It took a few tries to get it to cut square. The divisions on the Dividing head are about a 1/4 degree off, it seems. We'll see how well it's trammed in when there is a 10" gear blank chucked up.

Next up will be one little arbor to hold the gear blanks in the lathe for initial sizing and truing. Then it's wait until they frisbee in my 9" steel plate so I can drill a few dozen holes...

 

[RandyWilson]

My frisbee arrived. I learned something, again. A36 is not the most friendly stuff to machine. Stringy, gummy, with chunks of glass tossed in. I eventually got it cut down to size and trued up. then I proceeded to drill the 127 hole pattern. And I learned something there, too. When you instruction this DRO to put 127 holes on a 360 circle, it does exactly that. Hole #1 at 0 degrees, hole #127 at 360 degrees. Grumble.

So I redrilled the 127, then moved my clamping so I could drill a few patterns on the inner part, and also to final bore the center to 1.750. I need 42 holes, which is on plate 2 for my dividing head, I don't have plate 2. So I started drilling the circles until I was getting close to my clamps and blocks again. 38, 42, 47, and 49.




Final score, Harbor Freight 1/8" drill bit, 429, plate 0. I bought a 5 pack, and am shocked that the first bit is still going strong after all of that.

 

[RandyWilson]

And mounted with arbor installed. The dividing head is ready. That's a 9" OD plate, and I have room for bigger still.




I hit it with a scotchbrite scruffy, looks like I used 10 grit in the pic.


The cutters aren't here yet, of course. But there is still lots to do. Next up is one of two projects. I've been pondering how to cut the 3/16 keyways in the stud gears. I had resigned to cutting a start with a 3/16 end mill and then hand-filing square. But I had vague memories of a keyway broach coming in a lot of used endmills I bought at auction a year or two ago. What are the odds it's 3/16? Turns out, 100%. And it's brand friggin new. So I need to make a 7/8" guide bush for the broach. And ponder what material to use. I have aluminum bar, which might be good enough since I'm cutting aluminum. I also have more of the 4142, but.... whine.

The other objective is to cut the blanks to size. I mis-mathed above. I gave pitch diameter rather than OD. OD is 10.75. So I need to turn these roughly 14.5" to 11" and 10.5 for the 127 and 120, then bring them to final size in the lathe. I made an arbor to hold them that fits the biggest collet the lathe has, a 1" 5C. I've tried a wood bandsaw. A jigsaw. A cutoff saw. None showed much progress, and most didn't have enough control. I'm trying not to waste stock as I will be needing a 3.5" piece for the 40 tooth stud gear later on. Yes, I could just chuck them up in the lathe and chip-ize 160 cubic inches of aluminum. But that would be too easy. An wasteful. And I'd have to buy more stock to make the 40 and 28.

So then I look at that old rotary table. It's a 12" table, and I"m working with 14.5" blanks. And I want to offset the cut. So no. But... wait. What size taper is the center hole? It's full of crud and goo. A bit of clean up, and I find it's not tapered. It's 1". Exactly 1.000 inch. My lathe arbor from above is a light press into it. Bingo. Hold it on the table with that arbor, get some jacks under the perimeter (may have to make some short enough) And then just play merry-go-round. Uggh. How many passes, 2? 3? 5? 90:1 worm in the table. Add fabricating a way to drive the table crank with my drill to the list.


But first, I need to clean up all the swarf from that hideous A36.

 

[RandyWilson]

Today I cleaned up.


Then made an even bigger mess. OMG

 

[RandyWilson]

The two big blanks are cut. I still have to do the two little ones.


But the cutters arrived!!!


Question. How much TIR is acceptable? Right now, on 6 inches of arbor stickout, I have .002. Part of me is panicked, the other part is Meh, it's likely the least of my precision issues.