Machining cast iron- need advise

[Metal Butcher]

I decided to start my build of "Chucks Single" today by making the cylinder.

The only material I have on hand for the cylinder is a 1-1/2" bar of cast iron from Enco.

I'm trying to machine it down to 1.250 inch and having a problem. It looks grooved like an old 78 rpm record.

Is this normal?

Tried many different styles and shapes of carbide and HSS cutters. Even tried brown cutting oil.

I know this is a tough question but I have never had a problem with the finish on brass or aluminum.

Help!

-MB

 

[bentprop]

The standard way of machining cast iron is with sharp hss.Slow speed and feed ,and machine dry.
That should give a smooth surface.If that doesn't work,it must be some odd sort of stock.

 

[tel]

I"m with Hans - all the CI stock I get machines beautifully dry. Messy tho'.

 

[rake60]

Most grades of gray cast it will cut like chalk but but are very abrasive to the tooling.
Light feeds and slower speeds usually help delay the cutting edge erosion.
If the material is ductile cast light feeds might work harden the piece.
If you happen to have a piece of chilled cast stock you might as well
throw it away and try to find a piece of gray or ductile stock to replace it.

Cast actually fractures away from the parent material ahead of the cutting edge
of the tool so getting a good finish can be little tough at times.

Rick

 

[Metal Butcher]

I"m with Hans - all the CI stock I get machines beautifully dry. Messy tho'.

I have read "machines like butter" And other very positive remarks.

I'm just about ready to pull it out the chuck and make the cylinder out of aluminum!

I get a better finish on 1018 cold rolled. Its making a tearing and raspy type sound while I machine it . I'm down to the last cut of .010, should I just try to finish it with a file?

-MB

 

[Maryak]

MB,

When you get to the end of the cut, try reversing the feed and see if that improves the finish.

Speed around 150 rpm, feed as slow as you can.

Hope this helps ???

Best Regards
Bob

 

[GailInNM]

MB,
Double check you tool height. CI does not like it at all if the tool is above center. I have used a lot of CI from Enco (Can't beat the shipping) and have not had a problem. I use a C2 grade insert with a 1/32 tip radius.
Rigidity is important. If you are trying to machine on the end of a 12 inch length it may chatter even with a center.
Gail in NM,USA

 

[Metal Butcher]

I took a look at the carbide cutter. It was on center but the cutting edge looked odd. I removed it and walked it over to my magnifier and the cutting edge looked rounded. I installed another carbide with a small radius edge that looked good and sharp. With about .010 to go I took a .005 cut and the lines started to disappear! the next cut was .002 and all the evidence was gone! Another .001 did not make any more improvement but the finish is very acceptable.
Its not the CD disc look I get on AL or brass, but when I run my finger over it feels silky smooth.
The gloss improved but it has a bit of a dull streaked look about it. The diameter is 1.254 or .004 over size but I think I'll leave it as is and go on to the drilling and boring. I think fins would add a little complexity but that part has got me a little worried since I will be using a cut-off blade. My cut-offs attempts on Steel always end badly.

I really need to get a new eye glass prescription. Its funny that I can see a lousy finish buy missed the dull cutters (I tried more than one cutter). Maybe all my cutters are dull!

Cutting cast iron is new to me and I appreciate all your advice.

Thanks for all the help. :bow:

-MB

 

[Metal Butcher]

I forgot to mention that with over .250 to remove I was taking cuts of .040.

Could this have been a contributing factor?

I usually take larger cuts on AL and brass (.050 to .100) with good resulting finishes.

-MB