As construction is not difficult I will keep explanations to a minimum relying on
the drawings to provide the information required. The essential requirements are
concentricity of the die holder and the guide bushes. Providing this is taken care
of there is little in the way of complication.
Cut a length of material for the body and place in the three-jaw and bore the three
diameters. This ensures concentricity of the larger for the die with the smaller
for the guide bush. The intermediate bore is only to provide space for cleaning and
visibility of the thread being made. Cut away (mill or saw) the two sides as per
drawing to provide visual access to the part being threaded and using a file open
up the aperture for easy access to the part. Drill holes for handles and fit these
using a two-part resin adhesive. Drill and tap holes for die setting screws.
Ensure concentricity by turning the outer and inner diameters without removing the
part from the chuck. Make the outer diameter a close fit in the body but the inner
bore a little over the thread size, say 10.05 for an M10 thread. The reason for this
is, as I know to my cost, that if made a very close fit and subsequently it is attempted
to thread a piece of material that is slightly oversize then the bush will not go
on. A little clearance will have negligible effect on the accuracy of the threaded
Fit the die in the holder, leading side toward the bush, together with its appropriate
bush and placing the bush over the part to be threaded proceed to thread as is the
normal practice with a hand operated diestock. The forward movement will keep the
bush in the diestock and, if when removing it for cleaning, a bur exists on the inner
end of the thread the bush will remain on the thread, but still allowing the diestock
to be easily removed. A clamp screw for the bush as proposed in some designs in the
past would seem superfluous.
The photograph shows the completed item. This makes producing long threads an easy
operation with even very long threads being produced without any tendency to wander.
When threading to a shoulder, the die can be reversed in the diestock and finished
off with a trailing bush.
Having made and used he item I am sure you will say, why have I not made one previously.
Model Engineers' Workshop Projects
This project is one, of sixteen, from the above book, the others being simple, as
this one, or more complex, such as a tapping stand having an automatic feed facility.
For more details regarding the book see my page elsewhere on the site.