Author Topic: Gear running eccentric  (Read 473 times)

Carpenter84

  • Hero Member
  • *****
  • Posts: 965
  • Total likes: 6
  • Karma: +10/-3
  • Bowmanville, Ontario. Hobbies, hobbies, hobbies.
Gear running eccentric
« on: July 30, 2018, 07:45:27 AM »
For the duration of time I've had my lathe, there's always been a "clunk" in the gear box. I've torn the gear box apart twice before to try and find it but never found anything. I had suspected a single gear in the past but couldn't find any issues with the teeth that would be causing issues. Until I noticed it was not turning true on its shaft. It is the gear on the selector handle.
I pulled it off and did my best to replace the brass bushing inside but it's the gear itself that's running untrue. At the time I had absolutely no idea how I set the gear up in the chuck and put an indicator on it to center it to return the bore. I believe I tried to indicate on the tip of the teeth but the gear is somewhat worn, so that was tricky at best. Not being able to indicate where the jaws were holding, I gave up for the fear of ruining the gear and rendering my gear box useless until I managed to find a replacement. Well that fear is still present even tho im a year further along with that much more knowledge, I'm still unsure how to approach this issue.

The only thing that comes to mind currently is to attach some kind of mount to the gear and hold that in the chuck, then indicate as best I can on the teeth, and clean out the bore.
The tips of the teeth aren't badly worn, but there are irregularities.
There are no other witness shoulders or rings on the gear I can indicate to. The gear was cast or pressed then the teeth made, so any shoulders do not run true.

I'm throwing my hat in the ring for ideas...
The lathe runs fine, but the more I work with it, the more I have a desire to fix up the issues that always irritated me. At some point, there's a pulley belt change needed. The bent must be lumpy and causes additional bumping/clunking. That's a spindle removal job..... Unless I get those build-a-belt... Can those take the same kind of torque a normal v-belt can?
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

4GSR

Re: Gear running eccentric
« Reply #1 on: July 30, 2018, 08:21:50 AM »
First thing, Study the gear teeth carefully.  Look for dull spots on the tooth flanks on each gear involved.  All it takes is one small spot.  Or even large spot. when found, work with needle files to remove any positive metal from the tooth surface.  Using High Spot Blue can help you too, if you want to wear it too.

Ken
Ken

Carpenter84

  • Hero Member
  • *****
  • Posts: 965
  • Total likes: 6
  • Karma: +10/-3
  • Bowmanville, Ontario. Hobbies, hobbies, hobbies.
Re: Gear running eccentric
« Reply #2 on: July 30, 2018, 09:28:39 AM »
It's definitely due to the eccentric turning. The last time I took it out I did exactly what you just mentioned. I could not find any suspect tooth. I spent a few days on it. Come to the conclusion the brass bushing was worn but realized the gear had a brass bushing pressed in because the gear wasn't round fron manufacturing or a previous owner. The gear is visibly wobbly and runs untrue.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

4GSR

Re: Gear running eccentric
« Reply #3 on: July 30, 2018, 09:59:53 AM »
Make you a new bronze bushing and bore it to size after it is pressed into the gear.
Ken

Carpenter84

  • Hero Member
  • *****
  • Posts: 965
  • Total likes: 6
  • Karma: +10/-3
  • Bowmanville, Ontario. Hobbies, hobbies, hobbies.
Re: Gear running eccentric
« Reply #4 on: July 30, 2018, 11:11:21 AM »
Yup...

The problem is how to chuck up the gear and dial it in true?
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

4GSR

Re: Gear running eccentric
« Reply #5 on: July 30, 2018, 11:13:26 AM »
It's easy to do if you have a 4-jaw.  Use some pieces of aluminum under the jaws and get after it.  Yeah, it's havoc on the dial indicator, but with patients you'll get the hand of it.

Ken
Ken

Carpenter84

  • Hero Member
  • *****
  • Posts: 965
  • Total likes: 6
  • Karma: +10/-3
  • Bowmanville, Ontario. Hobbies, hobbies, hobbies.
Re: Gear running eccentric
« Reply #6 on: July 30, 2018, 01:56:23 PM »
Huh, so just, "head down, grit your teeth, get it done" sort of true it up? No fancy schmancy tricks?

If the outside of the teeth are worn, maybe I'll use the small tipped needle of my dti and use the root of the tooth to center?
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

4GSR

Re: Gear running eccentric
« Reply #7 on: July 30, 2018, 02:03:39 PM »
What for?  If the teeth are worn that much, you need a new gear.  File off the burr or raised part on top of the teeth. Get it within a couple of thousandths.  Then dial in the gear. Any closer than that, your chasing your tail.   The other way would be to set up a set of soft jaws on your 3-jaw, if you have two piece jaws. Bore them out to hold the gear.  Still have to deburr the top of the gear before chucking on it.
Ken

Carpenter84

  • Hero Member
  • *****
  • Posts: 965
  • Total likes: 6
  • Karma: +10/-3
  • Bowmanville, Ontario. Hobbies, hobbies, hobbies.
Re: Gear running eccentric
« Reply #8 on: July 30, 2018, 02:08:18 PM »
I suppose I'm making mountain out of a molehill.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

Bill Gruby

Re: Gear running eccentric
« Reply #9 on: July 30, 2018, 03:52:51 PM »
 Make a ring with the ID same as the gear OD. (light friction fit) OD of the ring to fit your chuck. Split the ring in one place. Push the gear into the split ring and chuck up in the 4 jaw. Center it and bore the gear and rebush it. Piece of cake.

 "Billy G"
« Last Edit: July 30, 2018, 04:16:46 PM by Bill Gruby »

chips and more

Re: Gear running eccentric
« Reply #10 on: July 30, 2018, 05:34:10 PM »
Don’t know how good your 3 jaw is? On my 3 jaw, I could turn the jaws around, hold the gear that way and call it good. On your chuck maybe hold a test round first and see what the indicator says…Dave

Jake Parker

Re: Gear running eccentric
« Reply #11 on: July 30, 2018, 06:36:41 PM »
I bored a sprocket once. I lucked out that the jaws of the 4jaw all fell in a valley, and I dialed it in via the back side of the jaws.

woodchucker

Re: Gear running eccentric
« Reply #12 on: July 30, 2018, 08:28:10 PM »
Yup...

The problem is how to chuck up the gear and dial it in true?

one other way to to take a piece of aluminum and turn it true, then bore it out undersize to hold the gear. Heat it up and put the gear in it... you can also cool the gear in a plastic bag in the ice box. put the gear into the bore.. you now have a nice holder that should average out the teeth. Bore oversize hole. Press  a piece of brass into the bore. Rebore to correct size. I think that should give you a close enough fit. better than what you have.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://woodchucker.imgur.com

Carpenter84

  • Hero Member
  • *****
  • Posts: 965
  • Total likes: 6
  • Karma: +10/-3
  • Bowmanville, Ontario. Hobbies, hobbies, hobbies.
Re: Gear running eccentric
« Reply #13 on: July 30, 2018, 10:05:31 PM »
K thanks guys.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

f350ca

Re: Gear running eccentric
« Reply #14 on: August 18, 2018, 11:39:48 PM »
Chiming in late but may be of help. If you have a 3 jaw with two piece jaws, you can make or buy soft machinable jaws. Put something at the back of the jaws to clamp on, then bore the soft jaws to the diameter of the gear. You get zero runout after boring the jaws and the wide face of the jaws won't mark the gear teeth.

Greg