Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Machining

SFT Search:   
Reply
 
Thread Tools Display Modes
  #1  
Old 09-19-2006, 01:46 AM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 6,903
Default Repairing a Broken Shaft

Broken shaft on a small induction motor. This is the first time I came across a rotor shaft that was hardened.
It snapped right on a radius transition line from one diameter to a smaller diameter

======
The broken shaft is semi-hard so I'm going to use a carbide drill and carbide reamer.
I centered the rotor in my mill and also checked that it was vertical, then drilled and reamed a hole down the center of the shaft about a 1/2" deep.

I got some chatter in the hole from the reamer that I did not like. I had suspicions about the reamer before I used it, it was way to sharp and to much back relief. I reamed a lot of holes over time but this is the first time I got vertical chatter lines that look like they were broached straight down.
It didn't matter how the hole came out because, I will turn down the shaft and that will correct any problems.
Otherwise I would have made a test hole with the reamer for size and finish.

New shaft,
I had some O1 drill rod that was laying around, that's oil Hardening tool steel about $ 7.00 for a 3 ft piece.
I not going to harden the new shaft.
The shaft pressed in nicely and is ready for welding.
Attached Thumbnails
Click image for larger version

Name:	1R.JPG
Views:	1048
Size:	34.7 KB
ID:	15921   Click image for larger version

Name:	2R.JPG
Views:	989
Size:	41.0 KB
ID:	15922   Click image for larger version

Name:	3R Chatter.JPG
Views:	993
Size:	39.2 KB
ID:	15923   Click image for larger version

Name:	4R new shaft.JPG
Views:	944
Size:	43.8 KB
ID:	15924  
Reply With Quote
  #2  
Old 09-19-2006, 01:49 AM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 6,903
Default

Welding:

Wrapped the rotor with some fireproof material and soaked it in water.

Welding it with my MIG was challenging, without having something to rotate it, I had to weld, stop, rotate 1/4 turn and keep doing that for two passes.
Note to self. Make electric rotary platform.

After welding, I let it cool off slowly.
Unwrapped the fireproof material. I was surprised to see the shaft below the weld was shiny and the upper portion of the shaft changed colors.
Attached Thumbnails
Click image for larger version

Name:	5R weld.JPG
Views:	903
Size:	39.8 KB
ID:	15925   Click image for larger version

Name:	6R weld.JPG
Views:	943
Size:	43.4 KB
ID:	15926  
Reply With Quote
  #3  
Old 09-19-2006, 01:54 AM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 6,903
Default

Center.

Placed the rotor back in the mill and centered it so I could drill a new center for the lathe.
After checking it with my indicator I was surprised that the new shaft was parallel and concentric within .002 to the rotor.
If I known it would come out so good after welding, I would have machined the shaft to size and welded the joint lower.
=====
Lathe:

The plan is to rough cut the shaft down and leave 0.030 stock for the finish. then mount the rotor between centers and finish it to size.

Ran into a problem roughing the shaft, a small portion of the shaft where the bearing seats has hard spots following the welding pattern I used with the MIG.
The carbide lathe tool will not cut the hard spots, the tool just rubs and polishes the area.
You can see in the picture 10R, the shiny hard area.
I had to use my 90ยบ hand grinder to get the area down. A strange thing the deeper I ground, the wider the hard spot got (smaller image).
=====
I have several options.
Take it down and have someone grind it for me.( maybe $25.00 and two days)
Cut off the shaft and start over not using O1 material.( I'm slow maybe one week $5.00 for materials)
Make a tool post grinder for my small lathe.(maybe one month $ ??.00)

Call me something, I'm going to make a tool post grinder.

Seeing that a tool post grinder is a new project. I will start it in a new Post and add the link to this Post.
After I get the toolpost grinder made I will continue with this Post.

http://www.shopfloortalk.com/forums/...ead.php?t=8702
Attached Thumbnails
Click image for larger version

Name:	7R.JPG
Views:	966
Size:	46.0 KB
ID:	15927   Click image for larger version

Name:	8R center drilling.JPG
Views:	811
Size:	40.5 KB
ID:	15928   Click image for larger version

Name:	9R.JPG
Views:	826
Size:	40.0 KB
ID:	15929   Click image for larger version

Name:	10R Hard spots.JPG
Views:	954
Size:	60.4 KB
ID:	15930  

Last edited by GWIZ; 09-19-2006 at 02:14 AM. Reason: added Link
Reply With Quote
  #4  
Old 09-19-2006, 07:46 AM
moe1942's Avatar
moe1942 moe1942 is offline
Voice of Experience
 
Join Date: Jun 2004
Location: Alexandria, Louisiana
Posts: 10,997
Default

GWIZ, is there a reason you didn't chuck up the armature in the lathe to drill the center? That three jaw might have had acceptable runout..

Just never seen it done that way.
__________________
Don't pick a fight with an old man. If he is too old to fight, he'll just kill you... John Steinbeck

"If we ever forget that we're one nation under God, then we will
be a nation gone under". ~Ronald Reagan

We should have picked our own cotton...

I love my women hot and my beer ice cold..
Reply With Quote
  #5  
Old 09-19-2006, 02:43 PM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 6,903
Default

Quote:
Originally Posted by moe1942
GWIZ, is there a reason you didn't chuck up the armature in the lathe to drill the center? That three jaw might have had acceptable runout..

Just never seen it done that way.
Your right, the runout my have been acceptable, I did not check it.
I'm just not happy with my tailstock chuck. It may be the ENCO arbor I'm using.
The mill was already setup from the drilling and reaming operation, so it didn't take any effort drilling the center in the mill.
Reply With Quote
  #6  
Old 09-19-2006, 09:31 PM
digr's Avatar
digr digr is offline
The Real Deal
 
Join Date: Apr 2005
Location: Duluth MN
Posts: 8,234
Default

GWIZ This is probably a stupid question but couldn't you have pressed out the broken shaft and made a new one.
__________________
Drawing by Smartdraw
Reply With Quote
  #7  
Old 09-20-2006, 12:17 AM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 6,903
Default

digr,
Its not a stupid question.
I was thinking about pressing out the shaft. That's something I haven't done and want to try, but I did not want to take the risk with this motor.
Its a non stock foreign motor from France or Italy, without any other markings on the motor and appears to be a custom fit.
It may be difficult to find a new motor if things went wrong. pressing out the shaft would have been the last option.

I also felt repairing one end was safer and it would have been faster, if I didn't get the hard spots.
I didn't think the tool steel would harden without quenching it.
I have hardened O1 tool steel before and if its not quenched very well, it doesn't harden to the point you cant cut it.
I guess I learned something new, welding the O1 tool steel all bets are off.
Reply With Quote
  #8  
Old 09-20-2006, 01:56 AM
Ed ke6bnl Ed ke6bnl is offline
Member
 
Join Date: Feb 2006
Location: Agua Dulce, So. Calif.
Posts: 84
Default

just a thought could you have silver soldiered the new slip in fitting less heat and seems it would be strong Ed ke6bnl
Reply With Quote
  #9  
Old 09-20-2006, 04:07 AM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 6,903
Default

All thoughts are welcome.

Ed,
If the remaining shaft was further away from the rotor maybe.
The way I see it. Heat transfer (Time) would be the problem.

I would need to get the shaft red hot, heating it longer with my gas welding setup.
Aluminum is casted into the rotor. If the heat gets to the aluminum it will expand and separate from the steel laminate's when it cooled.

With arc welding the heat is more concentrated so the bond is immediate, that equals less heat transfer time (within reason).
I didn't time my self, but I would say it took me less then 30 seconds of weld time to make two passes.
That thermal wrap soaked in water more then likely prevented any heat to get transferred to the aluminum for that short weld time.

I estimate It would take about three minutes to get the area red hot for soldering.
The thermal wrap I used would be ineffective on removing heat after the water evaporated, it was slightly moist when finish MIG welding.
Reply With Quote
  #10  
Old 09-20-2006, 05:47 PM
Cavalry's Avatar
Cavalry Cavalry is offline
Below Wholesale
 
Join Date: Jul 2005
Location: Evil Empire State
Posts: 9,022
Default

what do you have between the chuck jaws and the armature?

great write-up!
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 05:08 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.