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Why do my cermet boring head inserts break down so quickly?

Finegrain

Diamond
Joined
Sep 6, 2007
Location
Seattle, Washington
1018 steel
1" thick
.7504" thru bore
Rough it out to .748" with an endmill

Brother Speedio S700X1
Stanny micron boring head
16mm x 60mm bar
TPGH09020L TN60 insert (Kyocera cermet)
2,000 RPM
.0015 IPR
Flood coolant

I get good results for 4 or 5 parts, then I have to start bringing the cutter out a couple tenths between parts, then after 7 or 8 parts the surface finish suffers and I have to rotate the insert.

Why so poor tool life?

Thanks, and regards.

Mike
 
Quick guess - too flexy a setup and too soft a material. Chatter results, the bouncing damages the tool edge and the bore starts degrading.

For your needs, I'd look at a twin (balanced) boring head with tougher inserts, maybe with coatings and geometry to suit soft steels.

Just my ramblings, may be totally off...
 
Quick guess - too flexy a setup and too soft a material. Chatter results, the bouncing damages the tool edge and the bore starts degrading.

For your needs, I'd look at a twin (balanced) boring head with tougher inserts, maybe with coatings and geometry to suit soft steels.

Just my ramblings, may be totally off...

The head is a Taiwanese clone of the D'Andrea Testarossa which is a very rigid system with pretty good balance characteristics when used close to centreline. If it's a well made item, that should be no problem - I run my D'Andreas at much higher speeds than that, although I don't have any 30 taper machines....
 
Surface speed is way too low, which is probably not helping. You're more in carbide territory there. Any particular reason for cermet?

These are the inserts that are supplied by the place I bought the boring head kit from. These are the only insert I have yet found, that fits these bars. I'm fine to try a carbide insert, but am having trouble finding carbide inserts that would interchange with TPGH0902L.

Regards.

Mike
 
The head is a Taiwanese clone of the D'Andrea Testarossa which is a very rigid system with pretty good balance characteristics when used close to centreline. If it's a well made item, that should be no problem - I run my D'Andreas at much higher speeds than that, although I don't have any 30 taper machines....

Hi Gregor,
It's not so much the boring head itself, it's the system of head, spindle (30T), machine, fixturing, etc. Not a knock on the Brothers, it's just that with a single boring bar there is an offset force path, which I think a good 40 taper machine will handle better than a 30.

So my suggestion of a twin bar (balanced) head style to even-out the cutting loads and reduce the offset loading.

Again, just my guesses on the dynamics, so I could be quite wrong on what's happening. But my thoughts on a tougher insert stand...
 
Whisper quiet and a mirror finish, until the edge starts to break down.

Regards.

Damn.

1018 needs wickedly sharp tool with small cuts and low speed.
My best GUESS would be that you wear the cutting edge just enough to make your life miserable.
 
Not what you asked but I would be tempted to modify one TPGT11 boring bar to your head. TPGT11 size would have infinite number of suppliers, grades and chip breaker options compared to your current insert.
 
Early flank wear or chipping?
3 parts and what is seen?
Side rub or chipout? Be careful here no side contact, this will also make chipout but different shape.
Speed seems way slow but I suspect other as you are way under tool life.
Bob
 
These are the inserts that are supplied by the place I bought the boring head kit from. These are the only insert I have yet found, that fits these bars. I'm fine to try a carbide insert, but am having trouble finding carbide inserts that would interchange with TPGH0902L.

Regards.

Mike

You can get those from Tungaloy.

TUNGALOY United Kingdom | Turning > External Turning > Turning Indexable Inserts > TPGHR/L-W10 | TUN6997998

Just one example, not the only insert available there.

The D'Andrea heads also use some slightly odd size inserts, I buy them all from Tungaloy these days.
 
Early flank wear or chipping?
3 parts and what is seen?
Side rub or chipout? Be careful here no side contact, this will also make chipout but different shape.
Speed seems way slow but I suspect other as you are way under tool life.
Bob

1. I suspect flank wear at first, then chipping once things start going sideways. I don't have a microscope so do not know specifically.
2. Bore size starts going small, then after a couple boring head adjustments, the bore's surface finish degrades

Regards.

Mike
 
1. I suspect flank wear at first, then chipping once things start going sideways. I don't have a microscope so do not know specifically.
2. Bore size starts going small, then after a couple boring head adjustments, the bore's surface finish degrades

Regards.

Mike

See if you can put a small chamfer at the start of the hole. we had problems like this using them years ago. if the bore has a sharp edge it tends to break down the tip of the insert pretty fast.
BTW I love those cermet inserts, I use them on my citizen from time to time on o.d. parts when I need slow rpm and good finishes in soft materials. (ccmt styles with .004 rad)
 
See if you can put a small chamfer at the start of the hole. we had problems like this using them years ago. if the bore has a sharp edge it tends to break down the tip of the insert pretty fast.
BTW I love those cermet inserts, I use them on my citizen from time to time on o.d. parts when I need slow rpm and good finishes in soft materials. (ccmt styles with .004 rad)

Yes, I cut a chamfer after roughing and before finishing so the boring head should have a gentle entry.

Regards.

Mike
 








 
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