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WASTED CORNER BORING BAR

edwin dirnbeck

Hot Rolled
Joined
Oct 24, 2013
Location
st,louis mo
I am looking for a 3/4 or 7/8 or 1 inch lathe boring bar that will use the 100 degree corner of a cnmg insert. I will use this for THRU boring some very tough steel.I have hundreds of perfectly good corners. Does such a thing exist? Thanks in advance. Edwin Dirnbeck
 
Edwin, assuming CN.. inserts and right-hand turning, shop for an SCKNR boring bar. Or if you want a different clamping style, substitute the appropriate first letter like PCKNR or MCKNR.
 
And then chatter like a big dog. In a boring bar will need a lot of lead angle, say 45 degrees.
 
Inclined to agree with gebnt that the one linked to by MrWhoopee is likely to chatter. Not a lot of metal between pocket and shank.

I'd start with a lathe tool and do a minimum metal removal operation to get enough clearance for boring. Be a darn sight stronger than that one. Maybe I'm misunderstanding the situation but a tool of that style presenting the insert at that angle is hardly the thing for itty bitty holes. More ahfty tool for a hefty hole taking a hefty cut with a good shove behind it.

Clive
 
I use up the 100deg corners of a CNMG with an outside turning holder. Not too bad for roughing. Wouldn’t try for boring.
 
We used a lot of those insert where I worked in the 90s.
They bought a turning holder to use the 'wasted' corners.
There were some large rollers for a steel mill.
20" od x 8 ft long that got welded with sub-arc and turned down.
With that much tool pressure in the large lathes, it worked great.
It ripped the crust and give a 125??????? finish that they wanted
It would seem to me that as mentioned above, that you couldn't get enough pressure with that small dia bar to avoid chatter.
 
I've used them on both OD turning and boring. Decent for roughing but mega tool pressure. Definitely want a stout bar and a rigid, powerful machine to use them to much advantage. Most of these inserts are edge prepped so as to be able to take a beating, so they aren't very free cutting. Probably do a lot better if you have very sharp edged ones.
 
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I've made my own custom boring bars on a B'port for cnmg inserts. Use them for turning banjo rims on a patternmakers lathe. The obtuse corner of the polished, high rake inserts for aluminum work great for wood.

Wasn't that hard to do, just need a tapered endmill and metric tap for the screw. And some math.
 
Seems to me, Edwin asked for leads to a boring bar.

Not to repair an existing one he has, not to machine a pocket, not to weld anything…just a boring bar to hold CNMG inserts “sideways” and make use of the commonly unused edges.
 
Seems to me, Edwin asked for leads to a boring bar.

Not to repair an existing one he has, not to machine a pocket, not to weld anything…just a boring bar to hold CNMG inserts “sideways” and make use of the commonly unused edges.
Holy shit man. The guys doing some hack roughing bullshit and wants a bar just for roughing with inserts from his carbide scrap bucket.

You think he should spend $1000 on a special CNMG bar that probably won't work for beans?

I suggest he take a CNMG tool, whatever it may be, OD, boring, whatever, cut the end off of it and glue it with his welder to the end of whatever size bar he likes at whatever angles he needs.

That's how us silly machinists do it so we get the job done without spending $1000 every time a job comes in the door.
 








 
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