Index Model 645 Mill

The gear came in and it fits the worm perfectly. Here's a comparison between new and old:
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I could use some advise on how to secure the new gear to the old hub once I get them mated together. I was thinking two or three #10 socket head cap screws through the face of the gear into the large portion of the hub. Then I got to wondering if it would be a good idea to use something that would shear in the event of a crash (not that I would ever let that happen :cool:). What do ya'll think?
 
That is super! I think it's going to take more than three 10# socket head cap screws. I would figure at least 4 just to make sure. Have a way to cut a matching hex in the gear? Doing that, three screws should be plenty. Red Loctite gear to the other piece and blue Loctite on the socket head cap screws.
 
Here is a sketch of my plan:
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I was doing it this way to avoid having to cut the hex shaped bore into the gear. One dimension not on the drawing is the corner to corner distance on the hex is about 0.825". I was figuring on placing the screws adjacent to the flats on the hex, to give me a little more room. If you don't think three is enough, I may just go ahead and put in six.
 
Put in six screws. Do you have a way to cut two small keyways in the gear and shaft? This item can see a lot of torque at times. Try six screws for now. If they get sheared off or loosen, you'll need to put a couple of keys in there. How about putting two H & G dowel pins in place of two of the screws. That should keep the gear from loosening the screws.
 
The dowel pins should work. There's not going to be enough meat on the 'shaft' part to put in a keyway.
 
The gear came in and it fits the worm perfectly. Here's a comparison between new and old...... What do ya'll think?

I think the centre hole in the new one is all wrong......it needs to be some kind of wallowed out daisy-shape to match the old one. :D

But seriously.......
I like the idea of dowel pins.....but the "old hub" seems a little worn on the OD:
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We don't have measurements of this:
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versus this:
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It _looks_ like the old hub is bigger than the new hub......but it's hard to tell from here........

-brino
 
That portion of the old hub you have circled is unmachined casting. That section is just a spacer between the gear and the bearing journal to the left.

It _looks_ like the old hub is bigger than the new hub......but it's hard to tell from here..

You are correct, but the hub of the new gear will be removed.
 
I might be a little late. I found a 3/4" hex broach in my toybox that I had forgotten all about. Your more than welcome to borrow it if you like.

Ken
 
You're not too late, as I haven't started on it yet. I really appreciate the offer, but I think I'll go a different route. As you can see from the photos, the bore is not a true hex. As Brino said, "daisy-shaped" might be more accurate. I don't think this is wear. I think it was purposely cut this way so that it bears on the flats of the driveshaft rather than on the corners.

I've been thinking a lot about how to go about this project. One thing that occurred to me last night, is that I could try to cut the hex in the new gear, and if it didn't work, I could go back to my original plan. I would start by drilling holes for the 6 corners, then hog out the middle with an end mill. The final shaping would be done with a file.
 
That "daisy-shape" is wear, but that's ok. Still has lots of life. It'll last your lifetime since it don't have to work for a living anymore. Mine is more a true hex with some wear from what I remember. Too much crap to remove to get to that gear on my mill to look at it again.
 
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