Harold Hall

Manufacture

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.

Body

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.

Bushes

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 component.

In use

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.

Drawings

First Page

Sheet One

Sheet Two

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.

Metalworking

Workshop Projects