Repair Worn Shaft with Stick Welding - Advice Requested

[BlackMelon]

TL;DR Summary

I have a motor, whose shaft is worn-out. Please comment on my repair method.

Hello everyone,

I have a fan's induction motor, whose shaft is worn-out. I would like to use Shielded Metal Arc Welding (a.k.a. Stick Welding) to fill some metal into the worn-out area. Then, I will do machining to cut the excessive metal out. However, somebody told me that if the temperature of the shaft is too hot, it will deform and not be able to fit in my fan. I then Google about the forging temperature of a Carbon steel - 0.50% carbon content. Wiki said it is 1230 celcius. I should not go over 70% of 1230 celcius, which is 861. So, I would like to use some substance as an indicator that smokes at 861 celcius. Could you please suggest the substance that is cheap, available on marketplace, and easy to use?

Thank You

 

[Lnewqban]

...I have a fan's induction motor, whose shaft is worn-out. I would like to use Shielded Metal Arc Welding (a.k.a. Stick Welding) to fill some metal into the worn-out area. Then, I will do machining to cut the excessive metal out. However, somebody told me that if the temperature of the shaft is too hot, it will deform and not be able to fit in my fan.

Could you post a picture of the damaged shaft?

 

[The Fez]

SMAW, or any other traditional welding technique will not work, because you are depositing molten metal in a localized area, which will cause distortion in the Heat Affected Zone. You are also unlikely to achieve the required shaft hardness to withstand further wear. However, there are many shops that can perform a spray metal deposition, which slowly deposits metal on the shaft while it rotates. This can then be machined to the final dimensions. You will also be able to better control the metal composition and hardness of the finished product. There are some interesting videos online about the process if you would like to know more.

 

[Tom.G]

Hmm. I wrote tthis last night and forgot to click the 'Post reply' button... so here it is in support of the post by @The Fez.

In industrial-sized equipment, the usual fix is plasma spraying filler metal onto the damaged area, then machining to size. For small stuff it's probably cheaper to just replace it.

For medium sized, slower speed usage, like a 3 foot diameter centrifugal blower with a 1 inch shaft, there are slip-on ball bearings that attach to the worn shaft using a collar with three set screws. This allows precise, but tedious, centering at
very low cash outlay.

Cheers,
Tom

 

[Baluncore]

I have a fan's induction motor, whose shaft is worn-out.

Until we know what part is worn out it is difficult to comment.
Will the armature survive the welding operation or will you have to press the shaft out of the armature?
Is this an industrial fan or a domestic fan?
Is the fan loose on the shaft?
How was the fan attached to the shaft, with a keyway or spline?
What type of shaft bearings, bush or ball, are they worn?
Are there dust seals that have worn the shaft?

 

[Averagesupernova]

I would never say something like this is out of the question since I have done it successfully. However, without any more details than we have been given, I can't say it is a guaranteed success either. Original shaft hardness may not be relevant if the damage was caused by another parts failure. The main issue will be preventing warpage of the shaft close to the weld but not where the weld will be machined. I have had this happen. It takes patience, a good press and a dial indicator to bring it back in.
-
As already mentioned, some pix would be nice.

 

[BlackMelon]

I'm sorry for the late reply. Here are more details about my questions

Could you post a picture of the damaged shaft?

Here is the picture with dimensions and the worn-out area marked.

SMAW, or any other traditional welding technique will not work, because you are depositing molten metal in a localized area, which will cause distortion in the Heat Affected Zone... However, there are many shops that can perform a spray metal deposition, which slowly deposits metal on the shaft while it rotates.

First, if I use a current limitable inverter welder and do SMAW at the worn-out area in the picture at the lowest current limit (20A). How severe would the heat affect the rest of the shaft? Second, I have heard about the cold forging cream named Belzona for fixing this issue. However, the price is expensive. If there is no other way, then I have to buy it.

For medium sized, slower speed usage, like a 3 foot diameter centrifugal blower with a 1 inch shaft, there are slip-on ball bearings that attach to the worn shaft using a collar with three set screws. This allows precise, but tedious, centering at
very low cash outlay.

Cheers,
Tom

I would like to read more about this technique. Could you please give me links or keywords to search on Google?

Will the armature survive the welding operation or will you have to press the shaft out of the armature?
Is this an industrial fan or a domestic fan?
Is the fan loose on the shaft?
How was the fan attached to the shaft, with a keyway or spline?
What type of shaft bearings, bush or ball, are they worn?
Are there dust seals that have worn the shaft?

Thank you for these good questions.
1. I will press the shaft out of the armature.
2. This is a domestic fan.
3. No, the fan does not loose. The worn-out area on the shaft was inserted into a bush.
4. Just a pin. Not keyway nor spline. See the second picture below
5. Shaft bearings are bushes.
6. I will check this out.

As already mentioned, some pix would be nice.

Thank you. Please see the pictures below

 

[Averagesupernova]

So let me guess. That worn part of the shaft goes into a brass bushing. And the fan squeals when it is run correct? Do you know how much the shaft is worn? Chances are not much and if my above assumptions are correct, you need to replace the bushing, that's it. It is likely an oil impregnated bushing and in my experience when they squeal, the only option is to replace. If there is a little play between the new bushing and worn part of the shaft it will likely run quiet.

 

[Tom.G]

Since that is a small motor, [ USER 455902 ]@anorlunda[ /USER ] Oops! @Averagesupernova in the above post has the most practical approach.

Another possibility:
Remove the sleeve and thoroughly soak and clean it in some warm lacquer thinner. You want to get the old oxidized and hardened oil out of it.
Then soak it in hot 50W motor oil, should be good for a few more years at least.

there are slip-on ball bearings that attach to the worn shaft using a collar with three set screws. This allows precise, but tedious, centering at
very low cash outlay.

I would like to read more about this technique. Could you please give me links or keywords to search on Google?

I can't find the specific ones I used, it was over 50 years ago! However here is a somewhat similar one that will give you the general idea. The difference being the one I used had 3 set screws on the collar spaced 120° apart. That way you could get the centering correct regardless of uneven wear. I just walked into an industrial hardware store, told them the problem, and they brought the bearings out!

https://bearingsdirect.com/insert-b...urce=google&utm_medium=cpc&utm_campaign=Smart Shopping&gclid=EAIaIQobChMI6P3FiYzj7QIVqj6tBh20BAFmEAQYBCABEgKKJPD_BwE

Cheers,
Tom

 

[OCR]

I have heard about the cold forging cream named Belzona for fixing this issue. However, the price is expensive.

JB Weld. . . maybe ?JB Weld - Practical Machinist

.

 

[Baluncore]

That is an easy problem to solve, once you know how.

I have used stainless steel sleeves to repair worn shafts on several occasions. There are sleeves available to fix shaft wear caused by lip seals that may work for your application. You may also be able to buy a stock shim sleeve to fit that shaft. Some hobby shops sell thin wall tube in various materials and sizes.
Google 'Shaft Repair Sleeve'

If the shaft wear is significant you can fill the cavity with a metal loaded epoxy as you press the sleeve into place.

A steel shaft wears when particles of hard grit becomes embedded in the softer bush material, so you will need to replace the bush, clean, and lubricate the bearing surfaces. The bush may need to be made slightly over-size to fit a repair sleeve.

 

[anorlunda]

Since that is a small motor, @anorlunda in the above post has the most practical approach

Don't you mean @Averagesupernova ?

 

[Tom.G]

Yup.
Thanks!