HSS or Carbide Insert

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alandarkdale

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Inexperienced newbie question alert:

I'm working on a "Boring and Transfer Block" from Metal Lathe in Pa. http://www.statecollegecentral.com/metallathe/U-12.html

The suggestion is to turn the 4-jaw chuck into a fly cutter to rough things out and reduce the casting to where it will just fit the 9" ENCO lathe I've got.

The 1/4" HSS tool ground to a Vee will make about three passes over the face of the cast iron block and then dulls to the point (or lack thereof) where is just skates over the CI. I reground it with the same result. Then I ground the surface of the CI block off with an angle grinder to get through the skin that I've read about. Remounted block on crossfeed and tried again, same result. Grind new cutter just in case I ruined the temper in the other one. Same result.

Running the lathe fairly slow. Slowest speed in regular gearing. Tried it fast once and that was really dumb! See, I can learn.

Bad HSS bit? Buy and 1/4" shank replaceable carbide bit set and shorten one shank so I don't have too much tool sticking out?

Ideas please.

Thanks, Dale (the 56 year old new guy that wants to learn machining.)
 
If it is an interrupted cut, HSS will probably be your best bet, although some grades of carbide do OK with it. If you go with a brazed bit, use C-2, it's tough enough for interrupted cuts and good on most CI. There are a few types, and some are more likely to have hard spots. Slow speed is probably going to help. Neutral to slightly positive rake and 10° lead angle.
 
Thanks Tony. I do not know where this tool blank came from. It will not hold an edge. Will try a different one.
 
Dale,

High speed steel is definitely better suited for your application than carbide, but it must be run at the proper speed. It sounds like you may be running it way too fast. What is the effective diameter of your cutter, with the bit mounted in the four jaw? If it's 6" for instance, the rpm should be around 100 for cast iron (4 x 150/6), where 150 is the cutting speed of cast iron for HSS and 6 is the diameter.

Tom
 
Cast iron is generally machined dry, AFAIK. Make sure to cover all exposed parts of your lathe, to keep dust from getting into places where it shouldn't oughta' be.
 
Thanks guys. The next opportunity I get (Friday evening?) I will run it as slow as I can get it to go with a new tool of HSS. The local hardware place actually had the M4 .70 set screw I needed to replace on the cross slide. Will wonders never cease?

At this point I would be happy to have to clean CI chips off of everything.
Dale
 
Whenever I got a cast iron casting from the museum's foundry,I found that I had to soak it in muriatic acid for hours. It is amazing how much trapped sand will fall out of an untreated cast iron casting. The skin of your casting MAY,or may not be full of trapped sand. Unless you are running the HSS too fast,that could certainly dull it in a hurry.

I always have to use carbide on any cast iron of significant size,like taking a truing cut off of an already surfaced lathe face plate. Otherwise,a HSS cutter would not make it all the way across. The surface would not be consistent where I had to change the cutter. So,like Tony,I recommend C2 carbide,and go slow speed. Make sure your casting's surface isn't dirty from the mold.
 
Cast iron should be machined dry, especially when drilling. A little oil when tapping will help but not to much. Cast iron dust will stick together and pack up in the flutes of the drill if you use coolant.

Sandro Di Filippo
 
I was just cleaning up two handles( from the Cattail foundry) for my jointer on the lathe. I used carbide to make the first cleaning pass on the rough cast iron but could only get a smooth finish cut with HSS. And definitely cut dry.
 
Sharp HSS cutter, 120 rpm equals clean cutting.

Trashed v-belt equals waiting for the mail man to visit.

Lesson to be learned: Cast Iron means go slow.

Thanks guys.:think1: Dale
 
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