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What end mill to use machining through a weld?

rickseeman

Cast Iron
Joined
Oct 7, 2014
I had crack repair done on a cast iron part. Now I have to machine it down. My HSS end mills won't think about cutting it. The last one I tried was a good Niagara 3/8" end mill with TiCN coating. I don't know what kind of rod he used on this but it is hard stuff. I guess I should have asked him to braze. If I get a solid carbide end mill would it cut it? Thank you for the help.
 
You may wish to carefully freehand grind to remove as much material as your are comfortable your skills will allow. A carbide end mill, at about 50 surface feet, should clean it up. If the surface geometry allows consider a carbide tipped fly cutter. Not thats its better, just easily resharpened. If the rigidity isn't good, expect the heat affected zone to be proud of the rest of the surface.
 
I had crack repair done on a cast iron part. Now I have to machine it down. My HSS end mills won't think about cutting it. The last one I tried was a good Niagara 3/8" end mill with TiCN coating. I don't know what kind of rod he used on this but it is hard stuff. I guess I should have asked him to braze. If I get a solid carbide end mill would it cut it? Thank you for the help.

My first reaction to hitting any HAZ* is a fly cutter with a carbide tipped lathe tool mounted. I've got hundreds of them, and they are easy to dust off when dull.

* After using abrasive machining as others have mentioned.

But, as there is no description of the geometry that needs cleaning up. I can only offer the idea. 'can't say if it will work for your needs.
 
One of the welds is down in a .300" wide square groove machined for a seal. It would be a nightmare to grind that part out. (Not within my capabilities.) The part is around 12" ID. We can get a new part from Taiwan for $577 plus the wait/freight but I want to save this one. And nobody wants to wait a month. The part goes on a Peerless 30" x 60" bandsaw for structural steel.
 
I got a carbide end mill and tried it. It worked great. Now I have put the setup all back together because I tore it down when I gave up. Thank you for all your help.
 
What magpie said. Nickel welds are soft and machinable, but the adjoining iron is now white iron, slick, incredibly hard, and brittle as glass. That's why arc welded repairs on cold cast iron are not a real good idea.
 
I just pull out a worn carbide end mill from the drawer. That's what they are here for so says the sarge from Full Metal Jacket when addressing troops at graduation:

Most of you end mills will go to machine the weld.
Some of you will not come back.
But remember this: The end mill core lives forever, so that means you live forever.
 
Try a Kyocera endmill with cermet inserts. Any of the TN grades will cut white cast iron and are the low-cost equal of Greenleaf whisker-reinforced ceramic. You can take a cut off a 3/4 inch HSS tool bit. Throws sparks 20 feet but it will definitely do it—quicker than grinding too. Once you've adopted that tooling you won't bother with carbide, let alone HSS.

Caveat: no other cermet will do the above, not worth trying.
 
I wouldn't waste money on new carbide end mills or inserts for this. The times I had to clean up welds, the end mill got red hot. Better to use something that has already been used up.
 
I've had a lot of success using ferro-nickel rods on cast iron. Pure nickel is known to be hot-short, which is the exact opposite property to what you want when welding a crack prone material. But ferro-nickel is fully machinable as nickel. but deposits very quickly and peens well. I use a mild preheat to try to eliminate shocking the HAZ too much. The HAZ is very minimal. Still not something I'd want to have to tap threads through.
 








 
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