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Carbide insert boring bar recommendations

beckerkumm

Hot Rolled
Joined
Aug 5, 2014
Location
Wisconsin Rapids WI
I have a couple of Criterion and import boring heads that take .75" bars and some brazed tip bars that came with them as part of the machine deals. My Smart Brown 1024 can also use the same size. What are good choices for insert bars? I'm a hobby guy but willing to watch for decent stuff. Thanks, Dave
 
I got a Critter some years ago and the brazed carbide tip bars that I have came with that purchase. Made in India. Not so good.
 
If you buy sets of boring tools with brazed carbide expect to grind them all to establish proper clearance angles. I suspect these bars are left as brazed with no attempt establish proper tool geometry. Once properly ground they work pretty well.
 
If you buy sets of boring tools with brazed carbide expect to grind them all to establish proper clearance angles. I suspect these bars are left as brazed with no attempt establish proper tool geometry. Once properly ground they work pretty well.

Some of those bits are brazed in a position off from center. Means more grinding practice.
 
Not familiar with your lathe, but if you would consider it a light duty machine, you probably want to go with positive rake inserts (for example, TPxx instead of TNxx).

If your lathe is heavier, you can use negative rake tooling and get twice the tool life because you can use the other side.

Look at what the inserts cost - you will buy the boring bar once and inserts a bunch of times. I once picked up a boring bar cheap and the inserts were like $30 each.

T inserts are popular (probably the most plentiful on places such as ebay), as are C. C is stronger because the angle is 80 degrees instead of 60.

Go here for the secret decoder ring of inserts and toolholders:
Carbide Depot Technical Resources

The W insert I think makes the most sense, as you get three corners but they are 80 degrees, but they are quite a bit more expensive.

For my shop, I've settled on three inserts:
T - because I can get them cheap
C - I inherited a bunch of boxes, bought some toolholders and they work pretty well
V - for when I need to get into a really tight space.

I'm going to get one tooholder for square inserts so I can have a 45 degree chamfer tool.

Also, when looking for inserts, look at the grade as well as the size. Some are better for steel, some for cast iron, some for alloys. Carbide depot has a grade lookup. When you get the box, write on it what it is for, as you don't want to go looking up which is for stainless when it's time to start turning.

Steve
 
After having steel shank insert boring bars in my lathe for forever ... and always being frusturated boring ... I finally got a solid carbide boring bar (Ultradex) and it is night and day difference from steel. Doesn't chatter and actually cuts nicely. On my Mazak CNC lathe I used to put in the biggest steel shank insert boring bar I could fit in the hole to be able to take decent cuts. Now I am pretty happy with a 3/8" shank boring bar for most everything under 2" deep. Over that depth I switch to a 3/4" solid carbide bar and the sky is the limit, as far as what I can actually fit in my lathe.

Ultra-Dex boring bar example

I am not sure if any of that is relevant to what you want to do.
 
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