Machining Full-hard Hss

I can't recall a lot of screeching when turning full hard steel,or HSS. Maybe your speeds has something to do with it.
 
roadie33 said:
I had to turn down the shank on a 3/4" drill to 5/8 to fit my chuck last night, it destroyed 5 of my cheap Chinese made brazed carbides before I was done.
No great loss as I got them free and they did the job.
But that was the hardest turning and loudest screeching I have ever done.
The chips coming off it were a kind of Blue, almost Turquoise in color.
Dogs were going crazy barking and whining.
Wife was too. (she was Whining that is, no barking) LOL
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Normally a drill shank is relatively soft, and turns easily with carbide. Low speed is in order, on 3/4 < 200 RPM would be about right. It's been my experience that the cheap brazed carbide bits won't cut right out of the box, they need to be ground for clearance before using. I normally buy the AR-6 junk bits from HF for utility turning, and never found one that would cut without grinding into an actual cutting tool shape.
 
Cheap,brazed carbide bits really are NOT meant to be ready out of the box.
 
I use those cheap tools from time to time. I use them to remove rusty pitted scale or when something is to hard for HSS. They do the job if I can get the tool post rotated just right. Small diameter stuff I set the tool just below center.

I decide to rework done the other day so I ground the soft metal out of the way & used a diamond hone to work the carbide. It really didn't take to long. I had ordered a cheap diamond wheel from China to use to make a to grinder so I put a piece of stock in the lathe & turned a arbor for it to use in the lathe. It worked week but I was going very slow with the concern I'd break the stone so it probably took longer to do two on there then it took to do the ones on the hone.

After I got done I was really impressed with how well the worked. All 4 that I had done had bad tips to start with so nothing was lost if things went bad. I now have 4 more tools that are better then when they were new. :)
 
w9jbc said:
I made a set of headspace gages for a 30m1 carbine out of dowel pins using carbide tools in the lathe. the carbide tools turned the dowel pins ok wasn't easy but got it done!
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There is a wide band of different grades of carbide; some won't even hardly touch hard steels, but others will cut hard steel freely; the best I have used is the Kennametal K-6 grade, renamed to another equivalent grade in later years. It is recommended for cast iron and non ferrous work, but is very good for hard part turning as well. Also of note for this sort of work are ceramic inserts and CBN (cubic boron nitride) these are the analog to diamond cutting tools for machining hard steels where diamond tools are not advised due their interaction with the carbon in the steels and subsequent degradation. Also note that there is a wide world of difference in the hardness of HSS tools; some that are made for heavy roughing operations are significantly softer than those intended for fine finish work on harder materials.
 
gooogle "hard turn lathe". Couple of Youtube videos on it too. A place I worked at in the late 90's had several of the machines.
 
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