Help identify 5C grinding fixture (dividing head indexing)
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  1. #1
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    Default Help identify 5C grinding fixture (dividing head indexing)

    I got this 5C dividing head type indexing grinding fixture the other day and would like to find the manufacturer and more info on it, especially what exactly was broken off. I imagine it was some sort of locking mechanism. There are threads in the hole where the break is. I assume this is a grinding fixture because it's not as sturdy as a milling type dividing head and the spindle centerline is offset from the base center. There are no markings on it. The base is just over 3.5" wide but it looks like one side has been cut down. The slot in the base is .625" wide. The center height is just under 3.5" and since it looks like there has been machining on the vertical part, maybe the base bottom has been cut down slightly also. It has marking for 0 to 90 degrees vertical rotation. The worm ratio is 40 and the indexing plate is double sided with one side having holes of 18, 24, 30, 33, 42, 45, 49, 56, 58 and the other side of 28, 34, 37, 39, 41, 43, 47, 54, 62 so it can cover a nice range of indexing numbers.

    Thanks in advance for any info!

    Irby

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    Attached Thumbnails Attached Thumbnails img_4254.jpg   img_4251.jpg   img_4249.jpg   img_4252.jpg  

  2. #2
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    Does it really matter who made it? It seem pretty obvious that a locking knob with a dog point that pressed into the groove when tightened must have been used in the threaded hole.

    My guess is it broke because someone either grossly over-tightened it or more likely struck the knob by dropping something.

    Biggest question is how to repair it, especially if cosmetics are important. A threaded screw with a brass dog point and a knurled head would probably be close to the original one after the broken out section was replaced. If it were mine I'd probably just make a semi-circular "splint" fastened with small screws and epoxy and do a little epoxy putty sculpting for looks before painting.

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    I've been known to fix breaks like that with JB Weld. My usual tricks for repairs like that are to make a wall in the cavity by using sheet metal with parchment paper taped over it, and to use some kind of mold release on a male thread clamped into the female thread remnants. When the JB Weld dries, with luck you can just unscrew the fastener and wa la your threaded hole is back.

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    Looking at that again, it strongly brings Hardinge to mind. You might send that pic to one of their product support guys.

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    Hi Irby,

    Nice score! Sorry, I can't identify it, but I do find a few things about it interesting that may give some clues.

    1- It tilts, but doesn't rotate. Seems to me this would be uncommon for a standard grinding fixture. The ones I'm familiar with, if they only pivot on one axis, they will rotate, but not tilt. Not tilt with no rotation...???

    2- There are internal threads on the back side of the spindle. I would think that just a draw bar would go into this end to tighten the collet. What would those threads be for???

    3- What's the smaller, chamfered hole for? Is it nicely machined for a precision fit? Is it tapered? Looks like there might be a knock out hole on the back side???

    I agree with your thought that the missing/broken section was for a position locking screw.

    Good luck Sherlock! I know you'll get it figured out!

    Ted

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    I figured out how the locking mechanism worked on the unit. The split ring at the back acts like a spring to push the spindle forward in the housing, keeping it in place normally. The ring is stationary and has a thin bearing material between it and the spindle. It rests in a relieved area of the housing with a tapered landing on the very back edge of the housing. The back edge of the ring is tapered also. These tapers are shown in the first photo. The tapered part of the ring rides along the tapered part of the housing, pushing the ring forward against the spindle by the force of the ring trying to expand. Where the ring is split, it has a taper on each side, as shown in the second photo. It turns out if I spread the ring apart even slightly it locks up the spindle. And I bet the wedge shaped split is a clue. So the part that is broken off held some mechanism that when turned pushed a wedge into the tapered split of the ring, spreading it apart a little more, and locking up the spindle. I could make a piece that completes the threaded hole and reinforces it well. Then make a fitting that screws into the hole that has fine threads on the outside and has a plunger inside that has a taper on the end that fits into the tapered split in the ring and sticks slightly above the top end of the fitting. Then a knurled cap that screws onto the fitting can be used to push the plunger down and lock the spindle, as shown in the third photo.








    I also figured out how to take it apart! When I looked at the diameters of the spindle at the rear, the spindle in the front and the worm gear inside. The spindle diameter at the front was smaller than the worm diameter and the spindle diameter at the rear, so I figured the spindle must come out through the rear. And I figured the split ring must be small enough an OD when fully compressed to fit through the ID of the housing at the rear. Sure enough it started pushing on a collet inserted into the front the ring started to compress and eventually started to come out of the end of the housing. I stopped when it was out just past the taper and made a ring out of a piece of pipe with an ID a few thousandths smaller than the ring diameter at that time, and set it against the ring to support the housing and to capture the ring. Then continued to push out the ring. It came out fine and when completely out, the spindle came out freely. I say freely, it is a very close fit into the housing.

    So now if I wanted I could braze in a new piece to the housing but I don't think I want the heat on it so I'll try the reinforcing ring and screws bit to attach a new part to it. Here are the pieces. The collet nut runs on a set of ball bearings. And under the paint is a nice coating of black filler, so this isn't a cheap unit. It has a quality paint job, which I've messed up now looking for pins holding the spindle in place, so now I have to redo. The fit of the spindle into the housing is very, very fine! There's a taper at the front inside of the housing and the spindle to center it and align it. That also makes it lock up easier when the split ring pushes it forward. Since the spindle is held in position by the spring force of the split ring, it's definitely a light duty unit. The ring at the lower left corner of the last photo is what I made to capture the split ring.





    Irby
    Attached Thumbnails Attached Thumbnails img_4278_1a.jpg   img_4275_1.jpg   missing-fitting.jpg   img_4290_1.jpg   img_4283_1.jpg  


  7. Likes Technical Ted liked this post
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    With that hole below the spindle I would say that is the base for a reamer grinding attachment. The rod projecting from that hole would have mounted a dead center. As to the fix of the broken casting: can you TIG braze or weld in a piece? The tapped hole will need to be outside the HAZ because welding will harden the CI.

  9. #8
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    Rode hard and put away wet. I noticed what looks like chisel marks in the first picture. Then the broken piece in the second picture. Wow. The previous owner either had anger issues or no clue.


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