Cracked motor mounting plate

The plate in the attached images is a motor mounting plate from a large cast-iron woodworking bandsaw I am getting back into action.

The plate is approximately 12mm thick and 24cm by 26cm. 

I know several people who will tell me they can repair it for me but none of them trained as welders. I'd like to know what might be the best approach before handing it over.

Edited By pgrbff on 28/01/2021 10:38:30

Edited By pgrbff on 28/01/2021 10:40:07

As it is cast iron, it would best be preheated and then welded by a specialist cast iron welder. Alas my best welder is not now available.

Hello,

As I understand it, welding Cast Iron requires some experience. Best take it to someone who knows what they're doing.

Have a chat with John Smith 'Doubleboost' Regards, Lynne

I had a gear wheel with a broken tooth, my friend a coded welder brazed the tooth back in place, that was several years ago and it still going strong. Perhaps a plate bolted threw, below might be an alterative. John

If I was still working then a good friend who is a skilled welder would have been the first option. Now I don’t have anyone who would do it for mates rates I would probably make a sub plate to go between the motor and the bracket and screw the plate to the bracket with countersunk screws. It may be a candidate for metal stitching but this is likely to be quite costly.

Mike

Edited By Mike Poole on 28/01/2021 10:59:52

You don't have to be a skilled welder to do a basic job

Half the farms in Britain must have skilled welders if that was the case

I have welded cast iron myself, not very pretty and not particularly weight-bearing but it has held up. I used an inverter and cast iron electrodes.

Worth trying to discover how it came to be broken , what you don't want to do, is build the problem back

into the repair.

As the cast iron has an old crack judging by the rust, I would reinforce the flat side with steel strip bolted to the casting, at least 3mm thick and packing the other end of the motor bracket with the same.

Cast iron rods need less current than normal steel ones being mostly Nickel and the ones I got for a cracked exhaust manifold struck really well. Preheat was easy - run the engine after grinding a vee along the crack. The job couldn't wriggle as it was still bolted to the head. The weld out lived the car. Use decent 95% or better nickel rods.

I would span that crack with a piece of mild stel plate and some screws or bolts. If I was absolutely hell-bent on welding it rather than plating it with a doubler I would either silver solder or tig braze it.

The danger of distortion should be kept in mind.

+1 for brazing. Pre-heat it first and make sure it's really clean. After that, a reinforcing plate probably wouldn't hurt either.

Rob

As has been said, being able to weld with some proficiency is a good plan. V out, then the use of cast iron rods which being high nickel are expensive but should run like butter with preheat and slow cooling. If the above is not possible then if the job is worth it get it done by a professional. Noel

Depends what final result you want,appearance wise? To my mind a bolted on plate as mentiioned, L shaped of you want, with a deep vee either side, heated and filled in by someone who can run a rod would be a succesfull repair.

I am thinking this a not a highly stress part, but as someone mentioned why did it crack?

Pete

As it is a crack you can cut a V on the outside but how do you clean the insides of the crack you can't see?

I live in a very rural area, there are many local businesses that take in old agricultural machines for repair. Let's hope I pick the right one.

If it is difficult to get the job done, or it is expensive, Dave H and Pete R have the easier/cheaper solution. Even another 5mm added to the thickness would likely make not a jot of difference to the machine’s operation. Farmers do not usually just weld up broken machinery - they reinforce it at the same time.

As the overall mounting plate is flat I would just get a 3mm steel sheet the same size as the whole plate an bolt it on. Redrill the holes for the motor mounts and it's done. If you wanted a belt and braces job you could put some JB weld or similar between the steel and cast iron.

John

I'd suggest the steel sub-plate bolt on as well, if you do not have oxy acetylene equipment or a friend skilled in welding.

If it were my bracket, I would grind out the crack to an open vee shape, clean off all adjacent paint, and pre-heat to dull red heat. Then bronze weld / braze with bronze rod the vee'd area with oxy acetylene. Good solid repair.