JB weld for cast iron repair

Glenn Brooks

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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.
 
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:
 
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?
 
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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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.
 
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
 
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
 
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.
 
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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