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Drilling a spoke hub correctly

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  • Drilling a spoke hub correctly

    I'm trying to make a wheel hub that will hold spokes out to a rim. The hub is aluminum, about 3" dia and 1" thick. The spokes are 1/2" rod and 8" long.

    The problem I am having is that I can't seem to get the spoke holes in the hub perpendicular to the bore hole, ie parralel to the ends. When I sit the hub down on the end and insert the spokes, some are level, some point up a bit, and some point down. This is my fourth try and still no luck.

    I machined the hub on the lathe. Faced and bored accurately. I mounted the hub in a vise on the drill press to drill the spoke holes. Everything looked OK. But the holes don't come out right. What am I doing wrong? Is it just not possible to accurately drill these holes with a drill press? (Cheap POS chinese press BTW, Palmgren vise)

  • #2
    Very difficult to do that way. What you need is a spin idex or dividing head.





    BTW did you use a center drill to start the holes?
    To invent, you need a good imagination - and a pile of junk. Thomas A. Edison

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    • #3
      From experience.

      Even a rigid ram, a 14" indexer, the best chuck available, a poor sharpened drill bit will go where ever. I never realized that before I started trying to do Precision machining. Pilot holes help, but do not fix the problem.

      Drilling a very deep hole will tell immediately. Even new sharp bits can be trash, throwing curls off one side is a sure indication, One side should be offset the depth of the cut on the first side per rev.

      I have this beautiful octagon barrel, the bore is off center. My only thing to do with it is make a pistol, not what I started out to do. It was purchased , not drilled here.

      breaks my heart and postpones another project.

      EDM, now ain't that cool? perfect and where you want it.


      OHH>>>> a real neat trick I learned.. A Uni-bit is rigid, using it to start center holes in things in my lathe it don't wiggle very much at all. It has one cutting edge usually. Sometimes it is better/quicker then center punching.

      David

      [This message has been edited by ibewgypsie (edited 02-21-2004).]

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      • #4
        Thanks guys.

        Unfortunately, I don't have a dividing head, or a milling machine for that matter. I didn't realize that this apparently simple job is actually a rather precision opperation when I began.

        I understand that the geometry of the spoke and hub spoke hole will accentuate any error in the spoke hole. For example, the hole I'm drilling is 1" deep. If the hole is angled by .003' over its length, then by using similar triangles, an 8" spoke will have the end displaced by 8 x .003" or .024". Quite noticeable in this case.

        I did find a way to produce the hub I needed using the equipment I have on hand. I have a milling attachement for my lathe. I mounted the hub in the milling attachement so the hole could be made in the lathe. After aligning the work, I center drilled a pilot hole to locate the hole accurately. Next I drilled the hole to 31/64th. I then bored the hole useing a 1/2" end mill to the required depth. The spokes are now withing a few thou at the ends when installed in the hub.

        As for the drilling using the drill press, I think the major problem was the slop in the quill of my POS machine. The table is accurately squared up to the quill, but the quill itself can move around radially 11 - 17 thou.

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        • #5
          Another way to do that without a milling attachment is to use a faceplate. Sandwich the hub between two pieces of angle iron, using a bolt where the unthreaded portion is long enough to pass through both angles and the hub. Bolt the angles to the faceplate, being careful to get the axis of rotation centered. This is two adjustments, one to get the hub on axis (now at 90 degrees to the spindle axis) and the other to have the holes centered within the thickness of the hub. The rest of the operation is center drilling, enlarging, and possibly boring to final size, if that much accuracy is required. You'll have to loosen the bolt and rotate the hub between the angles to drill the successive spoke holes. Obviously, you'll have to index the hub somehow. This could be done before mounting it by marking out one face, and have an index mark on one of the angle pieces.
          I find that holes drilled in the lathe using a chuck in the tailstock are more accurate than those drilled in a press, since the workpiece is rotating. That tends to self-center the bit to the axis of rotation, as opposed to the bit having to follow it's own axis of rotation, and probably going off center. And if you bore to final diameter, you'll be correcting any offsets.
          If your hub disc is 3 inches across, then 2 inch angle would do the job. That will allow for up to a 7/16 diameter through bolt, though that's cutting it close. If the hole in the hub is much larger, you could machine a short section of shaft to fit it, and drill through it so a smaller diameter bolt can be used to mount the hub for drilling. It should only take a short time to cobble up these angles, and then you have them for future jobs.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #6
            I only meant that even with the best equipment, a poor drill bit will screw up the results. Poorer equipment only adds to the problem.

            It makes me mad to make silly mistakes like not looking at a drill bit really close.

            David

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            • #7
              Instead of center drills, I've been using 90 deg cobalt spotting drills. THey go Where you tell it to go. The little bit cost me 9$, it was worth it.

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              • #8
                One mistake many make is to start a center drill or spoting drill then use progressively larger drills up to the size you want - DON'T do this! From the center drill or spotting drill use the correct sized bit to drill the hole - you get a more accurate sized hole this way. If it is critical then finish ream it or use a boring head to finish the bore for the larger holes.

                If you don's have any way to accurately set the drill point on a round surface you can use a crotch point (upside down v block with a hardened drill bushing installed in a drilled through hole) block clamped on the work to guide the drill bit and prevent it from wandering.

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                • #9
                  on my wheels, I was going from a 1/4 step drill to a X bit. I figured as much, thinking, you know.. I Think I should have a larger spotting drill for this. DOnt matter though, I then bored he hole, then reamed it.

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                  • #10
                    While we are on drill bits, has anyone saw a decent cheap silohette loupe for inspecting drills? they have the angles and the sidebars.

                    I want one, not saw one in about ten years thou. I am growing a set of middle 40 eyes and need all the magnifiers I can get.

                    Perhaps a old webcam into visual basic? Microscope? what? Help a old blind man out.

                    David

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                    • #11
                      Did you check that pos china drill press table for square,you know they tilt left and right and the one we have at work is constantly off.
                      I just need one more tool,just one!

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                      • #12
                        Weird's got it, I betcha.

                        You won't find the POS to be square, count on it. I acraped mine in until I got tired of scraping, then shimmed the X-Y table to finish the job.

                        I scraped the face of the arm where it contacts the carrier running on the column. They didn't allow enough relief, and I couldn't hold it in the lathe to face it, or I would have scraped it all the way.

                        I am holding out for a nice old Buffalo Forge DP, with a LOOOOONG quill travel. Then the POS is history.
                        1601

                        Keep eye on ball.
                        Hashim Khan

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                        • #13
                          I have a POS drill press (Not the Strand). Upon applying any amount of force the table deflects down a couple or more degrees from the column. This can't be good for accuracy. I use it mainly for countersinking.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            Yep, been there done that on the Ching-Chang DP.

                            Great tip Thrud!
                            I've got an orphin V-block I've been wondering what to make out of it. I was about to cut it length wise so I'd have two. Your idea is better.

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