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thoughts on ccmt 32.52 boring inserts

twodog35

Plastic
Joined
Jan 17, 2016
I am looking for suggestions/recommendations on ccmt 32.52 boring inserts.
I do a lot of 8620 turning and I am trying to find a good roughing insert
for a 5/8 boring bar. boring hole from 1.312 up to 1.814. can someone
suggest a brand/insert for roughing and one for finishing? I use 2 5/8 boring
bars( 1 roughing/ 1 finishing)
thanks
 
These work great in low and medium carbon steels, up to 46Rc.
The 31.52 has a .031 nose radius, that's a fair amount of tool pressure for that little insert.
Might try the 31.51 version here. It's a little more free cutting:

ccmt lathe insert
 
I'd be using a larger bar to rough with, probably a 1" bar, with a TNMG (with medium roughing geometry) insert in it. The first pass would open the hole to 1.5" or so, so no clearance issues making the bar fit. This should give a nice chip break at a moderate feed of .010 to .012"

The Sandvik literature seemed to give the best coding system I could understand, that describes what kind of feed you should use with a given insert geometry. If you follow their guidelines, you'll get good chipbreaking, which is what roughing is all about. Unfortunately, you need to stock maybe three different geometries in any given insert in order to have sort of a starter toolkit to handle any job halfways efficiently.

Use your preferred insert as a finisher. C inserts generally have issues with chips getting wedged between the bar and the bore, and honestly, I don't know why everyone seems to prefer making those sets of boring bars. They're just barely serviceable for shallow bores only, IMO.
 
Always had good luck with KM KC850. We use them in 5/8- 1" bars in 8620 quite a bit. There is probably a more high tech insert grade out there, but how much real "roughing" are you going to do in a small bore like that? Blow the material out with an insert drill and give the boring bar a break. Assuming of course you are using a CNC lathe.
 








 
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