Turning Cast Iron with HHS

outsider347

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By now, you probably figured out the question

Tool bit dulling in about 15 rev of the work. every HHS tool that I have dulled

So got the books out & re ground to the following spec
8 deg F clearance
10 deg side

5 deg Pos top rake

80 deg tool included angle
speed at 50 ft /min


Im attempting to machine a back plate for my new 4jaw All purchased from Shars

Suggestions appreciated
 
I've never had a problem cutting cast iron with hss. Is it Chinese hss? That could be a problem.

Chuck
 
I've never had a problem cutting cast iron with hss. Is it Chinese hss? That could be a problem.

Chuck

don t think so. The tool bits all came with the lathe and the are quite old USA stuff

I have turned some other Cast iron & everything worked pretty well
 
Rough Turning CI Machine Speed 800-1000 SFM --- Feed .014-.020 ipr -------- Finish Turning Machine Speed 1400 to 1800 SFM Feed .004-.020 ipr. These numbers are from the DuraBar web site. ------ "Billy GT"
 
No idea what type CI
The Shars site doesn't say

Looks like I'll to start taking a look at carbide

Suggestions please
Holder
inserts

My lathe is a 10" Atlas with a AXA QC tool post

thanks Gents
 
I think those numbers are for carbide, though their machining doc is not very clear. They reference HSS in one place, and carbide in two others, and don't specify either in most places...
 
I think I would look closely at the grind on your tool. It sounds like it's rubbing instead of cutting. I've cut shars plates with hss before...that's not to say they couldn't have changed suppliers since I bought mine.
 
Sometimes CI has a glass-like coating on it which is a remnant from the casting process. Although I'm not 100% certain, I believe it's melted sand left-over from the casting process. I've encountered this many times. If that's what it is, it's silicon (not silicone) which is darn hard stuff! Once you get past that layer of glass, things improve. I'm hoping one of the folks who really know CI will chime-in here but, it's my understanding this is why CI gets "pickled" in muriatic (i.e hydrochloric acid, HCL). It breaks down that glass. Again, I could be wrong about that.

In any event, I usually use the cheap Harbor Freight carbide bits to get that stuff off. I too have problems with HSS on CI on the lathe and I always use carbide now. I've had better luck on the mill and a couple guys here once gave me some good starting points for SFM and told me not to "play around" while cutting. Be firm with it. It worked-out very well.

Good luck

Ray
 
Cast iron has a hard shell on the outside that is real hard on HSS tools - I personally ground my HSS cutter trying to face a back plate. the trick is to take the first few passes deeper than you think to remove that hard shell - the inside of the CI is fairly soft albeit abrasive to some degree. after I ground my HSS bit I turned to carbide to complete the process which cut it properly.
 
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