# Plunge countersink for cast iron.  Need tool suggestion.



## Ray C (Jan 13, 2013)

All,

I need to make a 5/8 dia. flat countersink into CI about 3/8" deep.  A HSS 5/8 endmill would work fine if I were working with steel but CI will kill it in a heartbeat.  All the carbide endmills I have will not face cut.  Looked around at the usual sources and can't find the right tool...  Any suggestions?

Thanks

Ray


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## OldMachinist (Jan 13, 2013)

*Re: Plunge countersinke for cast iron.  Need tool suggestion.*

Unless it's a piece of junk cast iron with lots of sand in it a high speed end mill should work fine as long it run the right surface speed.  I've put many counterbores in lathe chuck backing plates with a end mill.


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## Ray C (Jan 13, 2013)

*Re: Plunge countersinke for cast iron.  Need tool suggestion.*

Hmmm...  It's good quality CI -very clean.  I tried 2 & 4 flute endmills in good condition and it didn't feel right.  Tried a couple speeds too and quit before I end-up with a dead bit.  Any ideas on speed?  BTW:  I'm cutting dry.


Ray



OldMachinist said:


> Unless it's a piece of junk cast iron with lots of sand in it a high speed end mill should work fine as long it run the right surface speed.  I've put many counterbores in lathe chuck backing plates with a end mill.


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## OldMachinist (Jan 13, 2013)

60-80 fpm is about right for most cast iron so (12 times 60) divided by (3.1415 times .625) equals 366 rpm's or for 80 fpm it would be 488 rpm's. I always cut cast iron dry.


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## Jeff in Pa (Jan 13, 2013)

OldMachinist said:


> 60-80 fpm is about right for most cast iron so (12 times 60) divided by (3.1415 times .625) equals 366 rpm's or for 80 fpm it would be 488 rpm's. I always cut cast iron dry.



 I work with castings a lot at work and I run a bit slower ( 40-60 sfm) but our castings are a bit complex and can have hard spots. 

 I agree with cutting dry.


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## Ray C (Jan 13, 2013)

OK guys, thanks.  I'll try later this evening.   BTW:  I converted a couple threaded chuck backs to D1-4.  Nailed the geometry on the head, knocked-out the studs, drilled/tapped all the holes in the plates and when came time to countersink to fit the studs, it just seemed weird.  -Not too experienced with milling CI so I hung it up till after dinner.

I'll let you know how it goes...

Thanks
Ray


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## Jeff in Pa (Jan 13, 2013)

No "lolly gagging" in the hole ( don't dwell/rub, _*cut*_).  Don't jam it in but a controlled cut should work best.


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## Ray C (Jan 13, 2013)

No lolly-gag'n here boss -despite the 20min nap after dinner...

Perfect!  Just finished the 1st hole at 540RPM.  Nice, easy, clean -firm & steady.

Thanks to both you guys...  Appreciate it.

Will post a few follow-up pics in the thread about D1 Measurement when I'm done.


Ray


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