Previously I have written that I was contemplating the use of a double “Vee”-notched shape for piano-wire boring bits, in lieu of the single-flat “D” bits that were giving bent and offcentre bores in Pear wood. The billets were some 15" long, turned down to about 1.5"                      diameter and bored at 5/32" diameter.

Since then [ have bored six billets of Plum wood and one of Pear wood using different combinations of revolving speed /“D” bit and “Vee”-notch bit / a counter-rotating bit in a hand-drill and a non-rotating bit in a tail-stock chuck.

Conclusions: The non-rotating feed of the tail-stock chuck is IN , the rotating feed of the hand-drill is OUT: low speed rotation of the billet (850rpm) is OUT, a higher speed (2160rpm) is LN; the double-flat “Vee”-notch bit is IN, the “D” bit is OUT.

Of the seven test pieces, those with the IN feature were either on-centre or within 1/16", but most importantly, all were dead straight in the bore.

The tools used: A flat-bed wood lathe with #2 Morse, 38" between centres, pulley speeds of 850/1375/2160/3500rpm, and a graduated tail stock spindle with 2" travel. A 1/2" Jacob’s chuck and arbour. A grinder. An auger-bit file. A bench-vice. Several lengths of 5/32"                       diameter piano wire. A jam-chuck for the head stock. A steady-bearing to hold the tail end of the billet.

Both SAE 30 engine-oil and spray-on silicon were used for lubrication, with a preference for the former: cheaper, no smoke, no smell!

The jam-chuck can be made from a square piece of 2" x 4" lumber, screw-fixed to a 3” face-plate, turned down to 3.25" diameter, bored for a depth of 1" at about 1.375" to suit the diameter of the billet and through-bored at 1/2” to give outlet clearance to the 5/32" boring bit.

A thin bead of glue round and 1/4" from the end of the billet will secure the driven end and afford easy removal of the billet on completion of the boring operation.

NOTE:  

If the central part of the bit, between the two flats is thicker than 1/16", the bit will rapidly over-heat. Slightly less and with a shallow “Vee”, the bit will cut several times before                       becoming hot.

Care must be taken when inserting the longer bits, that the bit is centred truly. There are two corners, and if one catches on the end-face of the wood the bit will gyrate frantically.

Several bits of increasing length, from the starter at 3" to the last at 17", were used to give maximum rigidity per group of cuts and to afford a cool and sharp cutting edge.

No annealing of the cutting edge of the bit was necessary, even though the metal was “blued” in the grinding process and the conclusion is that metal will cut wood quite differently. But don’t overdo it.

Finally, this dissertation is in no way a denigration of other methods of wood boring, particularly that of Malcolm McLaren which gave me a start. it is offered as a possible improvement to all makers of pipe chanters and discussion is invited.