How long was the hole. Better to use 3 or 4 flute core drills to open holes out as 2 flute will wander.

Not sure from your description if the 3" piece was internal to the chuck jaws or outside. If outside the jaws, your error would suggest that you did not clock both ends of the visible piece.

You could make a mandrel on which to mount your 3" piece, then turn the outside to be parallel to your reamed hole.

It seems like you started off with a fairly small drill which would be very prone to wander over 3" the next drills would just follow the first. you might have got a better result drilling with the 31/64" drill only. For best results drill 15/32", bore out to 31/64" or .490" also not easy over 3", then ream.

Chris Gunn

Indian made 'budget' 4 jaw by any chance?…..checked the jaws for parallel internal surfaces?

Trying to drill, starting with a flimsy, flexible, drill is flawed. One must start with a rigid cutter such as a lathe centre drill. Further, the tail stock will never be perfectly centred vertically and horizontally (even if well within the machine specs). Starting the hole from an off-centre point will invariably cause some misalighnment of the hole. It may well be straight, but not necessarily parallel over the distance the OP expecting.

One of the reasons why model engineers bore cylinders. One of those very good reasons is to achieve parallelism.

Another ploy by those same people is to straighten pilot holes by drilling with a stiff/rigid end mill and not a twist drill (which will tend to follow the pilot hole).

'Nuff said?

To be able to drill straight and true through shafts this useful publication
from Camden books is worth looking at. "Making rifle barrels",it is about
drilling long straight holes ,some of it is about using gun drilling which would
probably be beyond the capability of most model engineers workshops but
there are sections giving advice on conventional drilling which result in
drilling straight holes.

I have used these methods for some of the examples shown here in the second photo.
The shaft seen here in the lathe is 8 5/8 inches long and drilled through
at 14 mm (.551 in) .Using 2 extended drills a smaller diameter pilot drill
has a bored hole formed to be a close fit at least 5x drill diameter and the hole
drilled at least another 8 to 10 x drill diameter ,the 14 mm drill size is also
bored a close fit and drilled to open the hole leaving at least 5 x depth
of the smaller diameter so the hole depth can be advanced.By changing drills
the hole is drilled right through.As can be seen in the photo a good supply of
neat cutting oil helps by cooling and lubricating and washing the drill and hole
of all swarf ,the drills should be withdrawn often to to clear the swarf and avoid
crowding the flutes.Two similar shafts were made one came out on centre the
other disappointingly was .002 inch off centre but probably within the accuracy
of the 3 jaw chuck. At full depth the hole is only 16 x the drill diameter.Using the
hole as the reference the shafts were re-centred and the finished from there.

The third photo shows one of 3 internal grinding spindles at 6 5/8 inches long
and drilled through at 7.3mm dia ,the hole depth is 22 x diameter .As can be seen
the shaft is held in the 4 jaw and supported by the fixed steady using a similar
sequence as previously the holes were drilled ,one as before was on true centre
the other .002 inch off ,the photo shows the last part of the sequence the shafts
having been referenced from the hole re-centred and rough turned to true up
to turn the 1 morse taper in the nose as in the photo .
The drills are sharpened as 4 facet drills ensuring the cutting edges are the same
each side.
The moral of the tale is if you start off with true hole the drill will most likely
follow it through.

John

What sort of boring tool would you be using for this type of procedure?

… and yet, said tailstock will form the reference axis for the tool when its finished and being used to cut threads.

I have serious doubts about the emphasis in this thread on perfection of the hole size/straightness for something as prosaic as a die-holder. For everyday threading, a tiny amount of wobble isn't going to be noticeable (look at the average tap wrench). If significant accuracy of a thread is required on occasion, then cut it.

+1 on this, but I grind the tool something like a D bit but for a 1/2" hole I would probbly use a piece of 3/8" or maybe 5/16" round HSS. It is then held so the shank is at an angle of say 5 or 10 degrees from parallel with the lathe main axis. Thus it is cutting as a boring tool on the front lefthand corner (as viewed from the tailstock) rather than drilling as a D bit.

Probably with a 1/2" hole almost 3" deep there will be a bit of chattering going on. Just take light cuts at teh finish, running the tool through job at the same setting several times until no more cutting is taking place. The reamer will take care of any chatter marks. All that matters at the boring stage is that the hole is basically concentric and straight; surface finish not important.

Peter, glad you got it done, but not cheating at all, just following the advice of many who advised boring the hole prior to reaming.

Chris Gunn