[woodnthings]

That makes no sense to me

Hi Steve,

I'm long hole boring through square stock(approx 16" long)
Starting with 5/16" (using a d-bit), then plan on stepping from 1/4" to 1/2", then reaming smooth to achieve a conical bore.


Rich

To get a conical bore you would need a very long tapered reamer, and you'd have to make that. The hole must progress from largest at the tail stock to smallest nearest the headstock. You can't drill the larger hole at the end.
I don't know why you would need a conical and "smooth" hole on the inside of a square stock. No one will ever see it. What is going inside this object?
:vs_cool:

 

[woodnthings]

making a tapered reamer

Indeed... I'll be making my own reamers: most who undertake this particular work do.
Nothing going inside except air...
This is a musical instrument.
I only said square, because the bore is made before turning down to round.


rich

I would look closely at a 1/2" rat tail file which is hardened steel and has a taper of approximately the correct dimensions. Grind a groove down the length with a cut off wheel leaving a sharp edge which will cut wood and leave a path for the saw dust to travel out. The files are brittle and won't take much torque, but as close to ready made as anything I can think of.