Lathe Indexable Boring Bar Angle and Inserts

tonydi

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I'm looking to move away from the brazed carbide boring bars and get an indexable bar. But I see them listed with different angles like 91 and 95 deg and I don't know what the difference is (yeah funny guy, I know, it's 4 deg) and what I should look for to meet my particular needs.

I mainly machine aluminum and delrin with an occasional foray into mild steel. I've seen discussions revolve around thru holes or blind holes but I do both types.

Also, what type of insert would work for the boring bar on my mini-lathe? I use TCGT inserts on my regular turning tooling and it works great for all of the materials I use.
 

mattthemuppet2

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TCGT inserts are really nice to use, same with CCGT, but you get an extra tip. STUCR bars will work really nicely on the lathe as they have decent end and side clearance, so facing the bottom of the hole is easy. Same with SCLCR bars that use CC*T inserts. STFCR bars have less end clearance, so although they'll work fine for boring, they might not be as good for facing the bottom of holes. However they are what you want for a boring head on a mill as they leave a much smoother bottom.
 

Janderso

Jeff Anderson
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Interesting, I’ve recently discovered the brazed carbide tooling.
I’m able to get a razor sharp edge with the slow speed lapping machine.
As I’ve learned more about the geometry needed to make a cut I can create a capable lathe tool.

Boring bars with the brazed carbide is something I’ve struggled with as well.
Maybe I should try again.
Matt maybe on to something.
Tony, let us know what you end up with and how it works. Delving and aluminum like sharp edges.
On the other hand, inserts made for aluminum are incredible.
 

mattthemuppet2

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I tried brazed carbide for a bit. Found it worked great and then chipped = a great deal of work to grind it back into shape. Might have also been due to using it on a light duty lathe.

The sharp ground inserts for alu on the otherhand have been fabulous. This is the finish I got with one last night using powerfeed (first time!)
IMG_0167.JPG
 

tonydi

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TCGT inserts are really nice to use, same with CCGT, but you get an extra tip. STUCR bars will work really nicely on the lathe as they have decent end and side clearance, so facing the bottom of the hole is easy. Same with SCLCR bars that use CC*T inserts. STFCR bars have less end clearance, so although they'll work fine for boring, they might not be as good for facing the bottom of holes. However they are what you want for a boring head on a mill as they leave a much smoother bottom.

Based on this I was looking for STUCR bars with a 1/2" shank but couldn't find any that worked in a bore smaller than 5/8". Then it dawned on me that index insert size determines boring head min size. DOH! Still, the ability to use the same in inserts as I already have is a plus for when I need larger bore.

About the angle callouts, can anyone enlighten me on the significance or the different styles?
 

Ianagos

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I’d say go for ccmt inserts and enjoy the chips.

You can use them in turning and boring tools.

I have 5mm boring bar that can bore in a 1/4 hole that uses tiny little ccmt inserts.

I also have 1” stick tools and 1.25” solid carbide boring bars that take ccmt inserts.

Ccmt is very versatile and can take a decent beating without chipping.

This part was turned and bored with ccmt tools.

Used a 3/8 boring bar for most of the boring just taking .03” per pass

f85b8e026683125ee3412d44b5100c71.jpg
 

tonydi

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I've also got a 2" boring head for my mini-mill. I'm thinking it would accept the same 1/2" boring bars that work on a lathe or is there something I'm missing about the geometry?
 
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