Drunken Threads

A while back I was making some BA screws using my tailstock dieholder. I was surprised to find that the resultant threads were deformed having lots of space between the undersized metal bits. Just what I was expecting to avoid.

On examination I could see that the die was not sitting squarely in its holder.Tthis seemed to be caused by the relative positioning of the tapped adjusting screw holes in the holder and the dimples on the OD of the die. Tightening the adjusting screws just pulled the die out of alignment.

Since then I have resorted to mounting the die in a hand held holder kept square to the work by the inner part of the tailstock dieholder bearing on the face of the die itself, not the holder. It's all rather awkward but produces satisfactory threads. Anybody else had similar problems ?

Chris, put a spacer washer behind the die. To check the screws line up with the divots just go around the OD with a magic marker painting it black, put it in the holder with just the screw tip protruding and turn the die so the screw tip scrapes a line in the black coating. Adjust the spacer to suit.

Was it the die or the holder that was wrong? One of my small handheld diestocks is definitely wrong, and I line up the die square by using the front faces of the tailstock Jacobs chuck jaws against the rear face of the die. I'm aware this may not be truly kosher, but it's good enough for all fastener threads I've had to do so far.

I have a cheap tailstock dieholder too, and no quibbles with that except that it can be time-consuming to set up and clean afterwards. It's best employed when there are several piece-parts with the same thread to be made.

When using a Tap or Died in the Tailstock, I ensure that the holder is a loose fit on the arbor. In that way, the Tap or Die will float and self align on the workpiece to avoid drunken threads.

One instance where a precision fit is a disadvantage.

Howard