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JB weld for cast iron repair

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Glenn Brooks

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#1
Well, I think I know the answer already, but looking for the voice of experience on this one.

Iam trying to reattach a 1" x 1" x 2" cast iron foot to the body of an old, very large electric motor body casting off my Van Norman 12 horizontal mill. This little piece holds one of four 3/8" motor mounting bolts, that secure the motor to the top of the machine. Alas, This little foot broke off the base of the motor body when the mill tipped over during a move.

I have drilled and tapped two holes to bolt the piece back onto the body. Using 1/4x 20 bolts, the piece seems to attach strong and stable. Yet, I would like to have a permanent bond along the fracture for added strength. (The motor mounting bolts apply shearing force to the bolted together part when then are torqued down.)

I don't want to braze this part back onto the casting as I don't want to risk damaging or melting the copper wiring and old insulation affixed inside the motor. So thinking about using JB weld to glue the edges together, and then hold with the two set screws into the holes I made.

Wondering if using JB weld is a wasted effort? (It only has 1000# shear strength)

Anybody have a similar experience?

Thanks
Glenn B.
 

RandyM

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#2
Glenn, you already mention that the bolts are taking the shear. I'd think that the added strength of the glue would only be a bonus. I say glue away. :encourage:
 

gwade

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#4
I've had pretty good luck with JB weld (for cosmetic purposes) IF nothing moves or is stressed during bolting. Otherwise the joint will likely fail. Can you get everything bolted in-place then apply the JB weld?
 

markba633csi

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#5
Agree with Randy: It'll be strong as heck, with the bolts to reinforce you can't lose- it's all in the prep- with enough surface area you can get
extremely strong repairs.
Try to squeeze out equal portions, mix well. Cure it at about 100 degrees F. for about 4 hours.
Mark
ps Silverbullet is right, clean it well with solvent/degreaser beforehand
 
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Silverbullet

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#6
You'd have to take the bell housing off to braze it safely. Try the epoxy metal it won't hurt anything . Clean it real good to get good adhesion.
 

dgehricke

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#7
Glenn,
Forget the JB weld and replace it with DEVCON I used this stuff to repair a blown head gasket on a 6-71 ( high block is compression rings) diesel engine in the Amazon river and it held for 2.5 months And deacon comes is Alum mix and steel mix and I believe cast iron mix.
And its on Amazon < https://www.amazon.com/Devcon-10240...ie=UTF8&qid=1510701666&sr=8-4&keywords=devcon > a bit pricy but good stuff.
Good luck
regards
dgehricke
 

rock_breaker

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#8
Have used J B Weld on a small pump shaft rebuild with good results. Have wondered about Devcon and according to dgehrike it is an excellent product. Believe either will work, somewhere I got the idea J B Weld was good for 3500 PSI in tension and better in compression, not arguing about the 1000 psi shear strength. With the two 1/4-20 bolts I am assuming some torgue along with the shear, so anything to fill the small spaces to avoid movement.
Have a good day
Ray
 

Dave Paine

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#9
Believe either will work, somewhere I got the idea J B Weld was good for 3500 PSI in tension and better in compression, not arguing about the 1000 psi shear strength. With the two 1/4-20 bolts I am assuming some torgue along with the shear, so anything to fill the small spaces to avoid movement.
I mixed some JB Weld today. The package states "Strength 3960 psi" no mention of tension or compression.

I agree with two 1/4-20 bolts it should be more than strong enough for the foot of a motor.
 

Glenn Brooks

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#10
Ray, you are correct, the JB weld manufacture says approx 3960 PSI in compression, but only around 1050"PSI,or so in tensile shear. The shear stress imparted on the foot, by the motor mount bolts, is the principle factor Iam worried about. I'll look into Devcon. Might be a higher strength formula.

Also maybe I can apply the glue and bolt the motor in one operation. Letting the epoxy cure up after imposing the additional mounting bolt compression force on the horizontal foot.

Just don't want to apply this stuff, then have it crack and worsen the bearing surface/ gap between the parts when grinding off the broken epoxy.

Glenn
 
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woodchucker

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#11
if you apply any glue to the bolt, make sure you have a hole somewhere to let the glue out and air out. you don't want a hyrdaulic seal preventing you from tighening it. You can even drill a hole in the bolt to let the shmooo out.:)
 

Aukai

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#12
Loctite also had a commercial on TV for metal bonding. 2 plates with adhesive connecting a locomotive to a stack of RR cars.

 

Mr Mike

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#14
You may want to look at this product too, Low temp weld - says it creates a joint stronger then the original cast iron.

Castaloy
 

magu

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#15
Devcon is great stuff. Loctite also makes great products. In a past life we used Loctite to hold carbide "teeth" on a crusher that applied over 6 million pounds of cyclic force. That being said all these products are designed for certain situations. some require a gap, some don't. Some thrive under pre-load, some don't. They will all make you do a lot of swearing if you need to remove them because you need to braze or solder the joint.

A question to ask first though, is why is the foot broken? If it got wacked or something happened that's one thing, but if there is a vibration or mounting issue you're going to continue having issues.
 

RandyM

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#16
Well, I think I know the answer already, but looking for the voice of experience on this one.

Iam trying to reattach a 1" x 1" x 2" cast iron foot to the body of an old, very large electric motor body casting off my Van Norman 12 horizontal mill. This little piece holds one of four 3/8" motor mounting bolts, that secure the motor to the top of the machine. Alas, This little foot broke off the base of the motor body when the mill tipped over during a move.

I have drilled and tapped two holes to bolt the piece back onto the body. Using 1/4x 20 bolts, the piece seems to attach strong and stable. Yet, I would like to have a permanent bond along the fracture for added strength. (The motor mounting bolts apply shearing force to the bolted together part when then are torqued down.)

I don't want to braze this part back onto the casting as I don't want to risk damaging or melting the copper wiring and old insulation affixed inside the motor. So thinking about using JB weld to glue the edges together, and then hold with the two set screws into the holes I made.

Wondering if using JB weld is a wasted effort? (It only has 1000# shear strength)

Anybody have a similar experience?

Thanks
Glenn B.
Devcon is great stuff. Loctite also makes great products. In a past life we used Loctite to hold carbide "teeth" on a crusher that applied over 6 million pounds of cyclic force. That being said all these products are designed for certain situations. some require a gap, some don't. Some thrive under pre-load, some don't. They will all make you do a lot of swearing if you need to remove them because you need to braze or solder the joint.

A question to ask first though, is why is the foot broken? If it got wacked or something happened that's one thing, but if there is a vibration or mounting issue you're going to continue having issues.
It was a moving issue.
 

Groundhog

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#17
We used JB Weld to fabricate a new carburetor flange on the head of a welders gas motor when it broke off as a result of falling off a truck. Welder saw rough field work at the ski area for several years before we replaced the welder. Carb stayed bolted to the JB Weld flanges (with heli-coil threads) and the flanges never cracked.
If you would have bet me on this before hand you could have won a lot of money!
 

Downunder Bob

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#19
Generally agree with all of the above. I have never used JB weld, but I've heard a lot of good things about it. I have had great success with Devcon, I've even repaired a large flame gouge in the mating face of cylinder liner and head on a large marine diesel engine. was quite succesful. I would think any good quality epoxy would work, especially if you apply the adhesive and then bolt it up tight, the bolts will be a bit like putting reo rods in concrete, Depending on the contact area available you may have room to drill some small holes to act as an extra key. Also follow the rules good prep, and very clean surfaces. Should be a great success.
 

Glenn Brooks

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#20
Went out looking for Devcon today. Of course none to be found. Any chain stores on the west coast known to stock it?
 

Aukai

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#21
Devcon epoxy where to buy, showed Walmart, Lowes, Ace. It was using my computer location though.
 

rock_breaker

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#23
Also maybe I can apply the glue and bolt the motor in one operation. Letting the epoxy cure up after imposing the additional mounting bolt compression force on the horizontal foot.

Would certainly be in final alignment. Just thinking, (dangerous) would the broken foot be the last one to do the final tightening on? This is probably ONE OF THOSE CHICKEN OR EGG QUESTIONS.
Have a good day
Ray
 

Downunder Bob

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#24
Went out looking for Devcon today. Of course none to be found. Any chain stores on the west coast known to stock it?
Google devcon they are a USA company and should ahve a supplier locator. I tried it but only got suppliers in Australia, but included major hardware , tool and engineering supplies. Or asa last ditch effort give them a call.

If you are concerned about the join pulling apart, you could wrap the leg either side of the join with wire mesh and trowel epoxy all over it, just make sure that youve thoroughly cleaned the area first. I';m sure it will be a great success.
 

EmilioG

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#25
LocTite makes a new metal/epoxy that looks promising.
JB Weld just doesn't adhere very well to metal, metal to metal, even after sanding & degreasing.
 

Nogoingback

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#26
Glenn, one thing to consider is that some epoxies don't perform well if you bolt/clamp the part too tightly: they require some thickness between the parts. Before you purchase you might want to check the manufacterer's recommendations
on clamping.

I'm not all that familiar with epoxies like JB weld, but I've worked with woodworking epoxies. I know that when overclamped, joint failure can occur.
 
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NortonDommi

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#29
Belzona gets AAA+ rating. Any good Epoxy should work just to stop fretting if the bolts are taking the load. One thing I've foung worth taking a close look at it the alignment of all contact points,(all the feet together), as often when bolting or pinning if the broken bit is not mounted in place with some sort of glue before drilling it usually ends up not exactly square with the world which puts strain on the joint when bolted down that can lead to failure or stress transfer.
 

FLguy

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#30
At the areo space company I worked for 10 years we used nothing but Devcon. It's cool to make small ??? for the kids too.
 
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