I work at a small company that sells and assembles various styles of pumps. The main type that we deal with are centrifugal. Part of the process involves trimming the impeller to meet gpm and tdh requirements. All of the impellers I've dealt with so far have been bronze wich is pretty easy to work with. About 10% of what we deal with is stainless steel or cast iron wich brings me to my question. I need to trim one thats cast iron either Monday or Tuesday and I dont have any experience with the material (about 45 days on the job, automotive background). Can anyone give a little advice on working with this material? Cutting speed, feed speed or cutting tool?

 

run it probably close to the same speed as stainless, or a little slower... lots of coolant and if you don't have carbide meant for cast, try a hss bit. you will find it doesn't really chip anything at all like the ss or bronze... it almost crumbles or makes like a fine dust. just make sure you keep it nice and cool because it will get pretty warm.

 

the cutting "bit" that i use is carbide (triangle shape), i wasnt aware there is a specific carbide for cast iron. i dont have any problems with chipping when working with bronze, it actually comes off in long smooth shavings. unfortunately we dont run coolant because of the contamination factor. many of the pumps are used in large waterparks or bottled water companies, cold water and hot water supplies, so no petrolium products. im going to look for an old cast impeller and experiment i guess. any other feedback is appreciated

 

When I turn cast iron, I usually keep a slow speed, deep cuts, with medium feed. Seems to work pretty good without coolant. I've used carbide and HSS with success. If you use HSS, make sure your bit is nice and sharp. You can also use air cooling for cast iron, works great and is the preferred method for things like what your doing. And I never post on here, but this site has an awesome fab section.

 

thanks for the tip on air cooling, i didnt think of that. can you tell me what the material (shavings) "should" look like as its removed.

 

It's like weir described, just croubles. Little bits of metal. It's not like turning steel where you get a curly wire. Also keep everything as rigid as possible. Well, that's always a good idea. Don't let your tool post hang out any further than necessary, lock the compound if your not using it, stuff like that.

 

sounds good, thanks again. i hope i can find a scrap cast impeller to play with before the real deal, it would cost about 800 bones to replace if i somehow screw it up.