Extending a 5/16 (5mm) shell auger

[Lazurus]

OK I have a need to extend a long hole boring auger for use on my wood lathe. It has a specific end which allows it to follow the centre line of the lathe and prevents wandering like a spiral drill bit might. Anyways I need to extend it by around 12" it is currently around 30" long or so. How can I acheive this whist retaining the concentricity of the long bit. How to weld an extension and keep it all in line - thread the old and new? Any suggestions

 

[frank horton]

pick ur new extension bar........I'd go for ground finish........turn one end to a point and do the same on the Auger.....
Tack weld the points, use some V blocks if u have em or some angle.....then turn and tack again in 3 places....
check its concentric and weld som more.......
with all the heat u still may have to give it a tweek but it will be quite close.....

I used to do the same on 6m lengths of 25mm bars...these went thru the wall's on stone houses.....
not quite as accurate but very close....

 

[Maker]

Don't know about extending the bit but 5/16" is closer to 8mm than 5.

 

[Lazurus]

Thank you