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Options for D-shaft slot in handwheel

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  • Options for D-shaft slot in handwheel

    Hi everyone,
    I got some good deals last week and picked up a bunch of stuff from a guy on eBay (Interapid indicator, a couple different size surface gages, and a height gage). When I got the package the postal system had beaten it black and blue, but fortunately due to the good packaging the only thing broken was a plastic handwheel. I figure I'll probably machine a new one out of some 7075-T6 that I've got on hand, but what I'm unsure about is what to do for the slot for the D-shaft.

    I glued the larger bits and pieces back together for the sake of a couple pictures, so this will give you an idea of what I'm dealing with:



    As you can see the handwheel slides on to a D-shaft on the height gage, with a nut & washer holding it in place. The problem is how to machine the D-shaft slot. I don't have access to a shaper, only a CNC mill & lathe and other general shop equipment (50T press, mig & arc welders [no tig, unfortunately], etc.). I don't have access to a rotary broach either.

    Here's a couple ideas I had thus far:
    1. Drill or rough out the hole to remove as much material as possible, then use as small an endmill as reasonable (probably about 3/32" due to spindle speed limitations) to remove material at the corners of the flat to allow the shaft to fit. My biggest concern with this method is introducing slop, either initially or over time as things wear a bit, due to the unsupported spaces at both ends of the flat.
    2. Machine the hole as though there were no flat, then machine a slot to hole a key so the long side of the key forms the flat. My concern, again, would be slop, though I think if I carefully machined the key myself I could eliminate that issue. There's also the fact that it looks kludgey.
    3. Remove as much material from the hole as possible, form a broach from drill rod and use the press to finish the hole. I'm thinking the press because I don't know how much force is required to push the boach, having never used one before. I'm thinking a fair bit, though. Also, this would be the most "experimental" due to my lack of experience broaching.
    4. Just make the hole round, make a "hub" that extends up past the surface a decent amount, drill an angled hole (as there wouldn't be room to get a drill in 90 degrees to the shaft) and install a set screw. Probably the most complicated option.

    What do you guys think? Is there a simpler/easier way? Or would one of these methods work? If you've got any ideas/suggestions I'd appreciate them. I'm also open to the idea of just buying a replacement handle to fit (the dia of the shaft is .250" btw) if I could find one and the price was right, or a hub with the proper hole that I could insert into the handle. But I haven't been able to find either.

  • #2
    I vote for #4, but depending on how thick the web would be, it may be possible to drill into the central bore from the rim. A bit tricky, but IMHO, no worse than drilling and threading an angled hole.
    Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

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    • #3
      I think #2 is the best solution. You can measure the edge of the slot that forms the flat to get it's position right. The backside doesn't matter because you can make the key thickness to fit. You say there's a washer so it will trap the key without further effort, or some Loctite would keep it there. This was done a lot in moldmaking with a former employer to fix the position of a round pin that had to be oriented correctly. Only the head of the pin needed a flat so the key intersected the counterbore on the back.
      .
      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

      Comment


      • #4
        I'd suggest an amended #2: instead of a key, use a piece of flat steel spring across the flat section. Curve it a bit towards the flat. If done right, this will eliminate slop.
        This is done on knobs for stoves etc.

        Benta.

        Comment


        • #5
          I don't see a problem. You have a cnc mill and a 3/32 end mill. Drill a starter hole and program the mill to cut the "D". At the intersection of the flat aand the circle cut a relief just large enough to remove the radius and allow the shaft to pass. The washer will cover it.

          Comment


          • #6
            Originally posted by tdmidget
            I don't see a problem. You have a cnc mill and a 3/32 end mill. Drill a starter hole and program the mill to cut the "D". At the intersection of the flat aand the circle cut a relief just large enough to remove the radius and allow the shaft to pass. The washer will cover it.
            That was my option #1. My biggest problem with it was that after darwing it & looking at the amount of unoccupied space left by the relief cuts, even with a 3/32" cutter, I was afraid it might be able to rotate off the flat, especially given that the pocket/hole is just over 1/2" deep(about 6x the cutter's dia). Although, thinking about it, it really wouldn't take much to hold it on as it's just a handwheel with light pressure required ( even just a bit of sleeve retainer and a drilled hole would probably hold). I may try it on some scrap, along with some of the other suggestions, to see what holds up.

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            • #7
              +1 for #2

              I think the keystock option is best.

              Drill the hole to shaft size.
              Use a broach to cut for an oversize key - up to the width of the shaft flat.
              Thin a key to fit - mill or grinder
              Silversolder or braze the key in place.
              Face both sides to clean it up.

              Comment


              • #8
                What I'd first try, is bore the hole out to about double the size of the round part of the D.
                Then turn and knurl two pieces of brass suitable for press fit into that hole, with the correct size hole drilled/bored/reamed into one of those.
                Then slice away the portion of the thru-holed piece where the flat is needed, and substitute in its place the right sized chunk taken from the other knurled piece.
                And then... press the two pieces in simultaneously, as a unit.
                ...Viola!

                Then after that didn't work ....

                Kidding aside, I don't think it would be too difficult to get a pretty nice, neat appearance by doing that.
                And you could leave a little flange on one end, and leave the length long enough to stand slightly proud when pressed in. Then when sandwiched between washers above and below, all should be locked firmly in place.

                Of course there are plenty of places to buy such plastic knobs and wheels, e.g. Reidsupplyl.com, and Rockler Woodworking supply (I recently bought some from them), as well as McMaster Carr, etc. That'd be the most efficient solution, but where's the fun in that? ...eh?
                Last edited by lynnl; 12-21-2010, 02:08 PM.
                Lynn (Huntsville, AL)

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                • #9
                  Why not just make a one time use broach? Jut take a piece of drill rod, concave the cutting end, grind or mill the flat, harden and ten sharpen the end up. Ram it through. Might have to make a bushing to make it go straight.

                  Comment


                  • #10
                    How about a set screw? Either on its own, Or along with the 'key' to keep the slop out.
                    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                    • #11
                      You've got the original hub which appears undamaged.

                      One possibility would be to make a stub arbor to fit this hub and machine the hub round (to remove the remaining broken pieces) . Then make a replacement handwheel with a hole to accept this hub and epoxy it in place. Make a nice large washer to hide the hub with a pocket to go over the hub and hide it completely.

                      John
                      Location: Newtown, CT USA

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                      • #12
                        You could look through a variety of knobs from appliances and electronic equipment to find a metal insert to fit and press fit it into your new knob.

                        Comment


                        • #13
                          Originally posted by macona
                          Why not just make a one time use broach? Jut take a piece of drill rod, concave the cutting end, grind or mill the flat, harden and ten sharpen the end up. Ram it through. Might have to make a bushing to make it go straight.
                          I was thinking of this but how much pressure do you think would be needed to push the broach through assuming most of the material was removed via the CNC (ie. there should basically only be the 2 corners to work with)?

                          Comment


                          • #14
                            Originally posted by GadgetBuilder
                            You've got the original hub which appears undamaged.
                            It looks OK in the picture, but the whole thing was actually shattered into pieces. It was basically snapped in half like a cookie, then one half was smashed into smaller bits. It's kind of holding together, but very lightly. It took a full 5 minutes of being clamped with superglue before it held at all.

                            Thanks everyone for your suggestions thus far, they've been some really helpful suggestions. I won't be going at this for about a week or so and am in the planning stage right now. These ideas sound really promising.

                            Comment


                            • #15
                              Originally posted by lynnl
                              What I'd first try, is bore the hole out to about double the size of the round part of the D.
                              Then turn and knurl two pieces of brass suitable for press fit into that hole, with the correct size hole drilled/bored/reamed into one of those.
                              Then slice away the portion of the thru-holed piece where the flat is needed, and substitute in its place the right sized chunk taken from the other knurled piece.
                              And then... press the two pieces in simultaneously, as a unit.
                              ...Viola!

                              Then after that didn't work ....

                              Kidding aside, I don't think it would be too difficult to get a pretty nice, neat appearance by doing that.
                              And you could leave a little flange on one end, and leave the length long enough to stand slightly proud when pressed in. Then when sandwiched between washers above and below, all should be locked firmly in place.

                              Of course there are plenty of places to buy such plastic knobs and wheels, e.g. Reidsupplyl.com, and Rockler Woodworking supply (I recently bought some from them), as well as McMaster Carr, etc. That'd be the most efficient solution, but where's the fun in that? ...eh?
                              That's an interesting idea - basically a split hub. I'll put that on my trial/experimental list to see how it works out.

                              I tried McMaster as I was fairly certain I'd seen some similar items before but despite them having a search entry for "hand wheels" there were no results. So I'm guessing my search term must be wrong. I'll give knob a try, as well as the other companies. Thanks!

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