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Spin Indexer

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  • Spin Indexer

    I've been wanting one for quite awhile. Finally bought one from Shars. Knowing it is a Chinese tool, the first thing I did was take it apart and clean out lots of grinding grit. The fit of the spindle to the casting was pretty good, some slop but tolerable. I clamped it to the mill table and put a pretty accurately machined test rod in a collet. The runout near the collet was .0015". I was using a Chinese collet so don't know which was causing the runout. But for my rather crude level of machining and the source, acceptable. Using the test rod and rotating it to the least runout position I aligned the test rod to the table travel and locked the casting to the mill. I wanted to machine the sides of the casting paralleling the bore to the mill travel. I machined as much of the length of one side as I could. The large end of the casting sticks out more than the base on the one end. I then mounted the casting in the vice and trued the freshly milled edge to the table so I could finish out the machining of the first edge. Did the second edge referencing the first. I had checked the test rod against the machined face and found they were not perpendicular to each other or to the newly machined edges. That made for a more complicated mounting in the vice for the 2nd edge. Not a big deal since I would most likely never be using the front & back faces to set the indexer up.
    Time to test run my new toy. I machined a piece of 3" cast aluminum with a 15/16" stub sticking out to hold in the collet. I turned it around and put the stub into the collet chuck and machine the large diameter to look like a nice knob. The plan was to use the indexer to make a series of radius recesses on the edge of the practice knob. So, using the same collet as I had used on the lathe I chucked up the part on the indexer. Tightened the collet as tight as I could manage and proceeded to spin the work in the collet as soon as the 3/4" ball end mill made contact. Turns out I could spin the work in the collet by hand! A little research and I found that the length of the tube that tightens the collet was so long that the collet couldn't be pulled all the way home. Took the handle off the end of that tube so I could machine off about 1/8" on the lathe. That's when I found that the fit of the crank handle was pretty sloppy and that it was held to the tube with 3 very small set screws that just pressed on the diameter of the tube. No flats, or dimples. When I put the handle back on the tube I used the set screws to position it and a Can't Twist clamp to hold it while I removed each screw in succession and drilled a dimple into the tube. Not the ideal solution but it will have to do until I can make a new handle scheme.
    Back to my test part, now smaller in diameter after cleaning up the mess from spinning it. I machined 9 recesses to .075 deep in several passes (40 degrees apart.) It worked! Indexing was very easy but I found I needed to make sure I locked the spindle each time with the aluminum knurled knob provided or it would move too much in the slop of the casting. I found it difficult to tighten the indexing plate nut tight enough to make sure it didn't slip. The nut has two small drilled spots that look like they are intended for a spanner wrench, so I made one.
    I'm now reasonably happy with what it can be used for. A fine tool its not but good enough for my use. The bottom was nicely ground and parallel to the bore. It can swing 5" while bolted to the mill table (I should probably drill the casting for bolting to the table rather than using step clamps, later) or 13" while mounted in my vice. With a fairly accurate 1 degree indexing it will do most of what I think I will be using it for. I've considered buying a 5" 3 jaw for it but that will wait until I actually need it.

  • #2

    Glad it's working out for you. But spindexers aren't really made for milling radial features. They simply aren't design for that kind of work. They do work a treat for milling flats and drilling holes around a part. But as you found out, not so good for milling a radius. Rotary tables are best for that.
    If you think you understand what is going on, you haven't been paying attention.


    • #3
      Originally posted by Larry42 View Post
      I found it difficult to tighten the indexing plate nut tight enough to make sure it didn't slip.
      Key the plate.
      I simply drilled between the edge of the plate and shaft, ground up a little taper pin, tapped it in and made it flush.
      Mine hasn't been a problem since - and I was using the spindex well beyond its design parameters, drilling and milling features in S-7 on a production run.