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  1. #1
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    I need a unit similar to a electric motor armature but all steel. Tolerance is not critical.

    I need a 1" shaft 6" long which will slide through bearings so it can spin but not a pressed fit.
    Onto that shaft I need a 3"Dia 3"long steel part pressed.

    The 3"dia part can be solid round bar stock with just a hole in the center, or it could be built up as thick pipe/tubing with solid ends and hole in center to press onto the shaft. If built up it must be about 3/8-1/2" thick wall.

    Needs to be true, straight, and reasonably in balance. May spin about 1,500RPM rarely, 600-900rpm often.

    That's it, nothing real major or critical. I need a few for prototype units I am building and later may need alot more of them.

    Thanks

  2. #2
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    I think you need to revisit the "tolerance not critical" bit. If you want it to go through bearings and be concentric and have the inner race rotate with it then a tolerance will be needed.

    You also ask that it be "true, straight and reasonably in balance". These requirements say that you have to put limits on them to be assured that you get what you want.

    Think of a drawing as a contract. Do you want the steel to be rusty before or after they ship it to you.

    Unless it's on the drawing you will not get what you want guaranteed.

    Chris P

  3. #3
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    Sent e-mail

  4. #4
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    bcstractor,
    Thanks you have good points there.

    This part will have changes made as needed here and just a starting point till I figure exactly what I need. I am busy with other areas of the project like making molds for rough casting the aluminum parts that will be needed also.

    Basically a 3"dia round bar stock 3" long, center bored for the shaft, press in the shaft and true it on the lathe with a straight cut (no taper) and turn the shaft to the correct size for the bearing. I don't know the exact bearing size yet.
    I plan for 1" shaft and bearings but may actually turn it down later to around 3/4" anyway.

    That should get me pretty close to exactly what I want for now.
    6" long shaft? Could be 6 1/4" or 5 3/4"?
    How far onto the shaft the 3"dia part is pressed I have to measure still but could be off 1/4" either way no problem really.
    3"dia should be close enough to look like 3" using a 4th grade school kids plastic ruler.

    So really untill I fine tune exactly what I what for the final production product this would almost be a good project for a beginer with a new lathe and maybe drill press.
    Later when I have decided exactly what I want consistantly I will want every part the same and have far better measurements for everything.

    Was asked in an e-mail if turning the shaft on one end a bit smaller to make a shoulder could be done.
    Yes, I had not thought of it myself and not really needed, but that could also provide an acurate stop when pressing together the parts so that I have the same shaft length on the back side each time. I will have to figure now how far that should be as I would want the front side of the shaft to be the thickest as it takes all the stress. Side loads and torque is worse on the front shaft and bearing.

  5. #5
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    Hi, I also sent an email, which may or may not have worked out.

    My questions were...what materials (mild steel?) and which size of bearings will you be using?

    Are you asking the machine shop to spec and buy the bearings, assign the fits as above, or will you supply the bearings?

    One final question I just thought of...with a slip-fit on the inner shaft, you will need some way to control end thrust, even if it is very mild, otherwise the roller will "walk" axially on the shaft. Snap-ring grooves or simple bolted-on shaft collars come to mind as easy solutions.

  6. #6
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    matt_isserstedt,

    I got the e-mail and sent a reply also now.

    I think mild steel will be fine, at least to begin with, after testing I may decide the shaft needs to be harder but maybe not.

    Bearings are optional, if a shop can get me a good price on them or I can get them myself. I am looking at several options. But I'll need a bearing source of my own if/when this goes into production later. Bearings are the only part with much wear or to fail and need replaced under warauntee perhaps. This is the reason I don't really want pressed bearings, I beleave in user servicable parts inside
    I'd rather ship 2lbs of bearings than a 50lb unit.
    Most "NORMAL" people don't have a shop press but would have a screwdriver or $10 cheapy socket set at least.

    Yes I have thought about end thrust. Not sure what I will do about that for the prototype yet. Probably a collar for now. Later I might go a little larger shaft or smaller bearings so the shaft could have a shoulder on each end, it could actually walk forward or back.
    Before I can have shoulders on the shaft though I have to get the case built and measure it for length and know where the bearings sit etc..
    I am working on the molds for casting the case now but it will be awhile. Far too many parts to make on this project and too little time.

  7. #7
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    I sent you a e-mail with a link to our shops site. Please take a look and see if we can be of service. Thanks Rodney C


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