First Boring Bar Purchase - Evaluating Options

[mattthemuppet2]

starting out I'd recommend getting a set of cheap SCLCR boring bars (8-12mm), a pack of CCMT and a pack of CCGT inserts and run with that (about $50). Then as you figure out what sizes you use/ need the most, replace as necessary with solid carbide indexable boring bars (about $30-40). You can use the same inserts with turning tools, which keeps things simple.

The above is what I did about 5 years ago or so and I've been very happy with the results on an Atlas 618 lathe. I'll be passing on some of the spares when I sell it and using the rest on my SB9 when it's up and running.

 

[Janderso]

The Micro 100 tools are nice but very delicate

+1-ask me how I know.

 

[mikey]

The Micro 100 tools are nice but very delicate. Any mistake on moving the dials or kissing the bottom of a hole will cause an instant "snap".
Don't ask how I know this...

All carbide bars, including Micro 100 or other solid carbide bars, can snap if you contact the bottom of a blind bore with a rapid feed.

The most common setting when a bar breaks is the initial cuts. The hole we drilled has a cone at the bottom and if you try to enlarge the hole without flattening the bottom first, the bar has a huge amount of material to take off and it snaps. What is happening is that all three cutting forces - axial, tangential and radial - spike all at the same time and the bar bends and then snaps when it reaches its deformation limit.

For all blind bores, try to use a carriage stop and set it to the final depth of your bore. Then flatten the bottom of your drilled hole before trying to enlarge the ID. It is wise to flatten that bottom in stages if it is a big hole. Set your carriage stop first, then take small bites and feed towards the center until the bottom is flat. Then you can enlarge the ID. Done this way, you will not snap bars.