# 9a Idler Gear Wobble



## sbx (Jun 2, 2015)

Hello,

So, I am finally nearing completion of my 9A rehab. But, after getting everything running, there is a ton of noise coming from the gear train. After checking everything I have narrowed it down to the 80Tooth Idler gear on the Banjo.

With the gear mounted firmly on the bushing and in place in the gear train, there is a significant amount of wobble of the gear on the bushing. Checking the bore of the gear, there is some wear, mostly on one side, which I think is a major part. You can visibly and by feel rock the gear a little back and forth on the bushing shaft. It is much more pronounced when the gear is mounted and in place but still noticeable when just checking the gear to bushing. I'd guess maybe an extra thousandth than would be normal.

The other issue is about .011" gap between the hardened bushing and the gear which allows some side to side slippage.

I've read up on some cures to this, including boring out the gear for an Oilite bushing, and have seen a few replacement gears on ebay. But, I don't yet have a 4 jaw chuck, which I think is needed to zero out the run out on the gear bore.

So, my question to you guys is really about a question of "What would you do?" and also what to do about the .011" play on the bushing front to back? Have any of you folks measured yours? What is considered acceptable? I am unsure if this is a case of mixed/matched parts from a previous owner, or wear to the bushing? Or if its just the wobble induced in by the bad bore of the gear itself that is the sole  issue.

Any thoughts appreciated.


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## sbx (Jun 2, 2015)

Adding a pic of the gear bore.


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## Kernbigo (Jun 2, 2015)

chuck it up bore it out and rebush it


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## Brain Coral (Jun 2, 2015)

Hello SBX,

I agree with you, in that, you must turn the gear concentric to the bore... hence, the need for a 4-jaw chuck. How large is the diameter of this gear ? At 80 teeth, it must be considerable. I had to replace some gears on a lathe, and they needed to be bored, bronze bushed and keyed. Like yourself, I had no 4-jaw chuck. It was proposed to me to make a "pot" chuck....








If you have something large enough to hold the gear, yet, small enough to chuck in your 3-jaw, if you bore this material to the gear size, it will run concentric with the bore.  You should also check to see if the shaft has not been worn out of round.


Brian


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## Andre (Jun 2, 2015)

Make a thin bushing, maybe .050" wall thickness with (not worn) bore diameter of the gear. Mount the gear in the lathe, bore to the OD of your bushing, then press the new bushing into the gear.


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## sbx (Jun 2, 2015)

Thanks for the suggestions so far. Sucked it up and put a bid in on a 4 Jaw on ebay. We'll see how that goes.

I'm not quite sure how you would bore in place on a bushing in the 3 Jaw. I am also not sure I have material large enough at the moment for the "pot" chuck idea, but it is interesting.

Any other ideas on the front to back slop? Even if I get a concentric bore trued up with a bushing, I am not sure how I should deal with that.

Thanks,
sbx


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## Brain Coral (Jun 3, 2015)

Without a photo of the situation, it's difficult to give you an answer in regards to the for and aft slop.... but, I would think that you could remedy that with the oilite bushing, by leaving some of it sticking out of the gear bore, either on one side or both, depending on what you need...

Brian


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## sbx (Jun 3, 2015)

4 Jaw Secured (well, auction was won). So, it looks like I'll be able to do the boring operation.

Brian - Good thought with the oversizing the bushing. I will try that, and worse case I can face it off after pressing in.

Thanks!


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