Hi All, Made this up this morning on "another site" and then work happened before I could post it over here
So, here we go....
A while ago I needed to get a nice finish on a cylinder I was making... I hadn't got a boring tool small enough for my application.
So, I came up with this. I used it again the other day and thought it might be of interest to others?
A little show and tell....
First a sacrificial piece of aluminium drilled out at 5mm. (this will work on 3mm upwards.)

Then the tool... A carbide 1/8th burr held in a piece of steel hex by a pair of grub screws.

A slight kick over to prevent fouling as the shaft is slightly larger then the head of the burr.

Add a very fine cut and a quick squirt of WD40 and send it down the bore under a slow power feed... the result is a mass on very fine swarf shavings.

And a nice smooth bore



Well, that's it.
Other than to let you know that the spiral flutes on the burr are the design needed... The cross cut burrs don't give a good finish

Ralph.