I'd suggest a 4 1/2" angle grinder with a cutoff disk of 80 or so grit. You may be a long long time and go through many expensive Dremel grindstones doing the vee out with a Dremel.

"don't bring a knife to a gun fight" as they say in the movies.

Sorry to nit-pick … but surely the choice between Dremel and 4 1/2” angle grinder depends upon the physical size of the job.

The title mentions “a small crack” and the text mentions “a cast iron plate”

… any advance on a 6mm long crack in a 50mm square plate, 4mm thick

MichaelG.

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I agree, George … my point being that we don’t know what the OP meant by small.

MichaelG.

Carbide burr gets my vote – not so much because of removal rates, but anything abrasive may (will?) leave contamination embedded in the metal. May or may not be important depending on what you plan to do after forming your V…

Rob

My input at post no 11 to try to solve this, small or big, problem, lol.

Cast iron and plate sort of tells me its an angle grinder job without much doubt, could be wrong often am, as the wife she will confrim that for sure, again without much doubt !

I go with The Bear, on both of his points. lol

Pete

Edited By Pete White on 13/02/2021 08:56:29

The OP has not stated that he intends to weld this, but it's a fair assumption. I would think that a dremel will struggle to do the job. A 4.5" grinder or an air driven die grinder might be better. The success of a burr will depend on the hardness of the iron, and a disc or wheel will soon shatter or wear very quickly if allowed to bounce on the work. To weld or braze, a slow heat up and a long cooling will aid the chances of success. If welding try to buy a rod for cast iron, it will be high nickle and not cheap. Good luck Noel.

'If I can find someone to do it I hope to have it brazed rather than welded'

Try getting in touch with 'Doubleboost' he has brazed CI before with his TIG set, shown on one of his videos.

George.

Hi pgrbff, if it were mine, I would cut along where I've drawn the yellow line first, with a thin in a 4-1/2" angle grinder, aiming aim the best I could judge, to the bottom of the crack and then along the red line as best I could. Don't worry about trying to get into that little corner and you can build the shape back up with weld or brazing.

Regards Nick.

P.S. You can always tidy the V up and take any dirty bits out with a small stone or burr in your Dremel.

Edited By Nicholas Farr on 13/02/2021 15:47:37