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MichaelG.

No need to overthink things, carbide is much better at resisting deflection and in a boring bar that is a valuable property.

Tony

These tiny ones are great, not too expensive, and they last for ages:

https://www.shop-apt.co.uk/mtr-miniature-carbide-boring-bars.html

They also have lower natural vibration characteristics due to their density. One point to mention is that solid carbide boring bars have brazed on steel ends to hold the inserts, probably because of the difficulty of forming the small threads for the screw. I used to make them from carbide rod stock with the cut off ends from same size steel bars silver soldered on. They needed special holders as I couldn’t put a flat on the shanks. Some did break at the joint, the commercial ones often have shaped joints with more surface area. I haven’t made any since getting my stock of Densimet tungsten rod which can be machined and which is almost as stiff as carbide. Like most things, the price has gone up for solid carbide boring bars, I bought as many as I could get my hands on while they were cheap, sizes running from 6mm to 20mm. Gary got us a stock of micro boring bars together with holders and included were micro threading and grooving bars, hole sizes from 3mm upwards.