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  1. #841
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    I have such an idea for stand by, but I wouldn't drill the casting, I'd remove the bushing to get greater access and then drill, and I'd put the force not against the casting but the center hole of the shaft itself, so the casting would not receive any stress at all, would all be between the gears and shaft.


    But I am proceeding with the current plan now and I have ground a groove on the shaft and exposed the key.

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  3. #842
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    Well that tears it. Broke off the tip of the dril in the key slot. I was worried it would happen. I don't know, feels I am back to square one now.

    I am contemplating sacrificing the shaft, I've removed too much of the keys under the first shaft to think of just putting everything back together as well so those solutions are out. I took a good look and I think maybe it could be cut with a reciprocating saw behind the 3rd gear, and then again between the 3rd and 2nd gear, then that might be enough to get the gears out the side. If nothing else I would have more room to excert a lot more pressure on the shaft and press it out. Or I might make things worse.

  4. #843
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    You have already built a gear press to push the gears back on, now build one to push them off. You can do it. Use a flat piece of steel that reaches in there behind gear 3, weld it to a square tube to reach around to the front of the shaft with a bolt to push it out. Just like your other press but shorter.

    If you destroy the shaft with a drill, you run the risk of NEVER getting it back up and running again. There is very little motivation to work on a machine that CAN't run.

    Just do it, if you start now you can have it done in one evening.

    I am sure that I speak for all of your fans when I say "you can do it" and we will be so disappointed if we don't see you making chips soon.

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  6. #844
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    If you could get a drill in the slot you can get a fine grinding point in there. It may require a bit of fiddling to make the proper extension, but once you have that it is simply an exercise in patience. I have had to do that on a couple of special castings other people have broken drills in. In one case it took the better part on an afternoon , but the salvage operation was completely successful.

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    maxspongebob I am not sure that the thickness of plate I could get in behind the gear would be stiff enough.

    At any rate I don't see how I could possibly destroy it beyond repair, even if the shaft was completely destroyed, making a new one is only a matter of money (I pay a machine shop to make one in that case), not skill or ability.

    But I believe I can salvage the rear half of the shaft even if I were to drill or cut it using a reciprocating saw. I have thought about that for many days and have a workable plan of action lined up if that becomes neccessary.

    Code:
    1. The shaft is cut right in front of the center bearing seat
    
    2. The rear of the shaft is chucked up in the lathe, centered and supported with a steady rest.
    
    3. The cut face is faced off for a clean surface and a hole drilled and then turned to a suitable diameter.
    
    4. The hole is threaded with a thread that runs counter to rotation so it will naturally tighten under operation.
    
    5. An over sized part of a suitable material is turned and threaded so it will fit the female threaded hole I made. The two parts are mated, perhaps loctited. 
    
    6. This assembly is chucked up in the lathe as one whole part and the new front of this shaft is faced and centered. Then I turn the part between centers until it is the right size (nominally 25mm).
    
    7. I have a local machine shop mill two new slots for 4x4mm keys in the repaired shaft and also add another slot to the gears.
    
    8. Reassembly.
    That is how I have thought to go about it if I need to sacrifice the shaft.


    But maybe I will try and grind the drill bit out first as mnl says. And maybe I will try and build a press like you suggest before resorting to this action. But I think it's doable as a last resort.

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    Sorry to hear that the drill bit broke off.

    In your shoes I would also try to make a press. How thick could you make the fingers behind gear 3? If these are too thin, could you push gear 3 against the casting and have the press bear on the other side of the casting? This would only work if gear 3 hits the casting squarely, or could be supported so that it did that.

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    The thickest steel I could get behind the 3rd gear is 6mm, if I where to remove the front bushing though I think I could increase it by quite a lot, maybe I could get 12mm steel in there. I could increase the support and stiffness by welding diagonal supports behind the fingers to go as far in as the cat iron rib would allow. Hard to say if it would be enough, with 12mm I think it would be enough.

    The 3rd gear hits the casting pretty square on too, though there is a casting seam in the middle that protrudes a little bit. That could perhaps be alleviated with some steel shims.

    I will go and buy some fine threaded rod and nuts, M16 or M18 perhaps or some higher grade steel for this pusher.

    EDIT:

    I am thinking my next step is to remove the front bushing to increase my access, it will also give more space axially. If I am really lucky it will free up enough space that using my small pushers I can plop off the first gear of the shaft, though I wouldn't bet on it.

    I am also thinking, maybe it would be better to not make this complicated U-shaped press that might not even work. Maybe it is better I remove the front bushing, rent a magnetic drill and drill through the gears instead (I think two holes for M10 rods will be enough). If I get the bushing out I should have enough space to put washers and nuts behind the 3rd gear, then I could truly push on it without worrying about the casting.

    I have also ordered some pink 4mm dremel grinding points to see if I can grind the drill bit out, might help to have it gone.
    Last edited by DennisCA; 08-20-2019 at 12:38 AM.

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    Quote Originally Posted by DennisCA View Post
    The 3rd gear hits the casting pretty square on too, though there is a casting seam in the middle that protrudes a little bit. That could perhaps be alleviated with some steel shims.
    I would rather use hardwood shims, oak or beech. These will crush slightly under pressure, deforming a bit to conform to imperfections and support the surface better.

    I would worry about drilling gear 3 with a 10mm hole and then pushing hard. If the gear is cast iron then it might crack by the stress points around the 10mm hole. If the gear is steel then you might deform it. The nut and washer on the back side of the gear will not sit flat, and will also tend to twist the M10 threaded rod. So my preference would still be for the welded up pusher.

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    Well, I think the bushing is the first order of business. Depending on how much more axial space it allows me, that can alter how to best proceed. I assume it will slide hammer out after the set screw is removed.

    I thought the gears were steel since apparently the teeth were hardened. I also think that a big "washer" custom made from steel that covers most of the area of the gear could be made, much in the same vein one would make the pushing "fingers" for the other design. That would spread out the force over the gear as much as any pusher design would.

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    Gears would be steel and carburized (case hardened) Likely made form something analogous to 8620...
    Surface hardness around 58-60 RCH with a core at around 30 Rockwell C.

    The gears will resist bending. To deform those gears one must apply enough force to first fracture the outer case...They are quite tough and i would have doubts that you could bend them using anything
    that you could get in the limited space available. 50 ton hydraulic press, sure no problem...but using glue and bailing wire, and match sticks not likely.

    Is it still possible to rotate the #3 gear on the shaft after the broken drill incident?

    Cheers Ross

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    Yes the drill never got that far before it broke, nowhere near even.

    I purchased an M16 rod today, fine thread pitch and some nuts, to make a pusher. I also removed the set screw holding the bushing in place. It was not difficult to get out, it was just buried under so much dirt that had to be gotten rid of first. I determined the thread pitch to be 1.0 mm and the diameter is just under 50mm so I will turn a plug to screw into the bushing so I can slide hammer it out.

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    Any chance that you could work some lapping compound into the #3 gear/shaft interface.....
    I would try to work the gear with abrasive to see if i could get things to loosen up....
    Some fine abrasive (400 grit or finer) thinned with light oil of WD40....work the gear back and fourth while applying some pressure
    on the gear forward and backward....parallel to the shaft axis.....

    Just might make a difference with a little time spent.....Its low impact and won't cost much to do.....Could inject the slurry down the key way...then rotate the shaft to point the key slot to the bottom so the slurry
    gets into the space between the gear and shaft.....Small hypodermic is good for this sort of work
    Cheers Ross

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    Worth a try I suppose, once I get the bushing off I should be able to separate the gears further and have better access. I have some 320 grit "E-Z bore" lapping compound already, maybe that could work.

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    Quote Originally Posted by AlfaGTA View Post
    Any chance that you could work some lapping compound into the #3 gear/shaft interface.....
    Ross, some time ago, following your advice, I got four small tins of "time-saver lapping compound". Great stuff, in part because after use it breaks down and does not contaminate the works with lapping paste. I can post some of this to Dennis, which grit(s) would you suggest?

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    Bruce:
    Think i would start with something fine...because using too coarse a grit might jam up the clearances and make rotating the gear difficult....
    If the fine grit works at all, it will increase the clearance and then you could go a bit coarser to speed up the process....
    Sorry i can't give you a number as i don't have my "kit" here , so i am not sure of the grit numbers that are possible...


    Yes "TimeSaver" is great stuff....Like the fact that it is supplied as a powder and you can mix to the viscosity you desire.

    Cheers Ross

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  21. #856
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    That seems like an interesting compound, I did some research and apparently the key to it's claims is due to the abrasive which is made from garnet.

    It seems very expensive, but I have been able to find garnet based lapping compounds of other brands.

    Triumph Lapping Compound

    EDIT, turned a plug last night and threaded it, but I am going to have to do some welding to make a compatible interface with the slide hammer.

    More edits,
    I have also found that Brownells sells garnet lapping compound, and also pure garnet lapping powder in various grits, 15 dollars for a 1/4lbs can that you can mix with water or oil base:
    SUPPLIES BRASS - Flutes, Wind Instruments, Repairs, Supplies
    Last edited by DennisCA; 08-22-2019 at 03:26 AM.

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    I removed the bushing tonight but it seemed this was a waste of time, no more space was gained as the first gear also stops against the bushing of the lower axle. I would have to remove that too in order to get more axial space. Not sure that is worth it. I will wait now for the supplies I ordered.

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    I've been working on a pusher this weekend, it started as a simple U shape but I kept adding on bits to increase the stiffness but nothing, it won't move a millimeter. I've got the fine threaded M16 rod through two nuts and I have put so much force on it now that the two wrenches I use are becoming insufficient leverage.




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    Hey Dennis, hold on tight...

    No suggestions here, a few comments:
    - a shorter screw might help, will reduce flexing, easier to feel if/when something moves
    - some hits with a hammer might help
    - heat on the gear could help
    - you might want to remove your table, don't need it right now. You only risk damaging it and it also gets in the way...

    Good luck

    Thanos

    (Can you see the pusher flex? Where is all this force directed to?)

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    That's quite a construction! Be sure to grease the screw. Also would be good to lay a piece of plywood or carpeting over the table to protect it when the shaft finally does move, since the pusher might fall.

    Is there a gap between the third gear and the first two gears? So you can be sure it is gear 3 that is stuck? Do you think the problem is the (remains of the) shaft key hanging up on the key slot?


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