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[4]

How to chuck up a gear?

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Bob V

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#1
Hi everyone,
I'm working on the transmission from my 100hp tractor because it was "popping" out of gear.
The main problems I've found have been worn bushings in the gear bores, and a totally destroyed needle bearing that was between two gears.
The teeth of the gears are fine and so are the bores (once the bushings are replaced.
However when the needle bearing between two gears blew up, it badly scored the mating surfaces between two gears. I need to get these scored areas flat again, then I think I can use shims to make up for the lost material and put a new needle bearing on the shaft between the two damaged gears.
I haven't done that much machining and I have two questions about this project:
1) What is the best way to "chuck up" the gear in my lathe to clean up the scored areas on the side of the gears?
2) How hard are transmission gears? Will I be able to remove this material? ?HSS ?carbide cutters.
Thanks in advance for the help.
Bob
 

Ulma Doctor

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#2
Hi Bob
if you can use a 4 jaw chuck on the outside diameter, you'll have the best luck.
you can use soft stock to cushion the teeth from the jaws
indicate the bore to desired precision.
if the bore will cut with a file, HSS will be sufficient to perform the boring operation

as a point of information, your transmission gears may not be hardened all the way through, they may have surface hardening
if the gears are very hard, you may get lucky and the gear may be able to be bored with carbide, otherwise the bore may need to be ground to dimension.

you could possibly construct a sleeve to be press fit into the gear bore to take up for the excessive clearance the boring operation will create, if you were so inclined.
you could make the slug, press it home and then bore to accept the original bearing.

i wish you the very best of luck!
 

f350ca

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#3
If you have two piece jaws on a three jaw chuck you can make soft jaws out of aluminum or mild steel and bore them to the dia of the gear. The back shoulder on the jaw will have no runout as well so the surface you need to machine should be plumb. As for hardness you'll have to try it.


Greg
 

GoceKU

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#4
Your best chance is to use a tool post grinder, it will give you very smooth finish and it can cut no matter how hard it is
 

Bob V

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#6
Thank you, Mike and Greg.
I really like both methods you have given me to hold the gear. I've used heavy copper wire before with a 4 jaw chuck to center a stainless rod in my lathe before--don't know why I didn't think of that!

The gears are hard-- won't cut with a file.

I should have mentioned that one of the gears that needs work is a shifting collar which has a grove maybe 1/2" wide around the outside for the shifting fork to ride in, and the inside "bore" is actually a cut gear that rides on a hub gear and locks on to the adjacent gears on either side when shifting. The collar has very tiny (maybe a couple thou) burrs on the gear teeth that are cut on the inside of the bore.
All I have to do is take off a few thousands of material, tiny burrs around the inside of the shifting collar gear.
The collar alone costs $614. --so I'm determined to fix it instead of buying new. This particular collar is for shifting between 1st and reverse gears, so it is only used for short periods of time and almost always under very little load, so I don't think a couple thou off the "corners" of this collar will cause any problems.
---So maybe I have a good excuse to get a tool post grinder! I'd love to go this route, but I need to get the tractor back together to use on my small farm--

I know this sounds kind of "bush league" but since I only need to remove a couple thou from the inside "corner" of the collar-- do you think I could get away with spinning the collar in the lathe and using some emery paper on a wood dowel to take this tiny burr off?
 

GoceKU

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#7
You should be able to do it with sandpaper or a fine machinist file, just be careful not to hurt yourself, if is not working try using a long piece of sandpaper and dragging it in long strokes, that always works for me.
 

f350ca

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#8
Emery paper and a dowel should remove the burr but it will also remove material all around the inside creating a somewhat oval hole. If you have a dremel tool or die grinder a simple mount for it should do a better, more controlled job.

Greg
 

tq60

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#9
Do not use the lathe for the inside work.

Many options here depending on how much work but will give 2.

Get a Dowell or other small hardwood and shape it so it fits in the tooth of gear.

Fold wet dry paper or use rolled abrasixe and place gear in vice and with the paper in strips hold wood in place to guide sandpaper as you pull it through the hole.

Second is get a glass or tile cutting blade for jigsaw and if needed use a grinder to form it a bit so it can get where needed.

Either place it in a handle and do it be hand or use saw and go slow.

Soda cans make great soft shim stock.

Cut strips with scissors and place in chuck.

You will be making lite cuts so little clamping force.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 

whitmore

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#10
You should be able to do it with sandpaper or a fine machinist file, just be careful not to hurt yourself, if is not working try using a long piece of sandpaper and dragging it in long strokes, that always works for me.
Yeah, for random damage, sometimes handwork is better than accurate machines...
I'd also consider a Dremel with felt buff and emery compound, if it's just a surface scratches issue
(you'll get rid of high spots and any material that could come loose later).
 

Silverbullet

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#11
You can still grind it while in the lathe with a good indicating job. The gear will be flat and squared to the bore. With a dremel strapped to your tool post you can grind and polish the faces and then your bore if needed. You can even do the key way by turning the lathe handle moving the compound in and out with the head locked in back gear and motor off. Keep old towels dampened with light oil the sparks and metal will stick and not get in the lathe. It will take time to set up face and bore to grind but it can be done.
 

Bob V

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#12
Thanks very much for all the tips-- there are lots of ways to skin this cat! I will definitely remember the dremel ideas and the soda can and other ideas for the future!

Anyways, I came up with a "poor mans tool post grinder" setup as in the pic. I wouldn't have come around to this setup without all your help. The ring indicated as being round on the inside after chucking it up. It's just a 10" piece of stainless bar about 2" in diameter wrapped with medium emery cloth. I held it in the grove that the tool post usually slides into and with firm down pressure from my hand, I used the lathe controls to run it into the chucked up gear ring and it worked great. It chattered just a little bit but worked fine. I took off about 4 thou off the top of the teeth inside the ring and the new gear now slides through the ring as it should. --saved me $614. I'm posting the pics just because it might be useful to someone else. IMG_0841.jpg IMG_0842.jpg
Thanks again for all the advice.
I still plan to look for a tool post grinder!

Bob
 
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