Equipment: New Neck Turner From Italy

This article was sent to us by Mario Favaron, a record holding Benchrest shooter who has a real dedication to finding every possible bit of accuracy from his equipment.  Mario describes his reasoning and design for a neck turning tool and expander die that incorporate several innovative features.  I'm not much of a translator; to do that one must have a mastery of the languages involved and, in the case of a technical subject, also of that area of expertise.  Although I speak a few languages, Italian isn't one of them, so I used some computer translation, my knowledge of the subject and a bit of my Spanish and Portuguese to get past the rough spots.  I think this translation adequately conveys Mario's message and any flaws are strictly due to my inadequate mastery of Italian.  - GAS -

New Developments in Neck Turning Equipment

Friends, I hope that this article expands our knowledge and satisfies our curiosity about improving some aspects of our reloading practices.  The tools shown here are not available for sale and in fact, exist only through the dedicated effort of our friends who have the equipment and expertise to bring these designs into existence.  The EDM machine shown at the right was essential to creating these tools.

I would like to express my sincere thanks to J.C. Braconi, whose innovative ideas and insights are as valuable as the advice he always shares.  Also, my friends Alessandro and Lucio who are the real experts with the machine work and computer modeling.  To all of them, my sincere thanks and my apologies for all that I have troubled them!


We come now to the point of this article and the presentation of what I believe is at least partly a completely innovative approach to the design of a neck turning tool.




As you know, the neck of a .220 Russian case must be expanded and the shoulder set back slightly as part of the process of converting it to a 6 PPC.  In this article, we will illustrate a modified Redding Type S full length sizing die which both expands the neck and sets the shoulder back in a single operation. The photos show the expander (1) which is ground to an initial diameter of 5.6 mm for the length of the case neck, then expands with a tapers of 0.5 ° to reach a diameter of 6.14 mm.  This diameter is not a random choice, it is designed to match the pilot of the neck turner.

The die's retaining cap, which normally locks the bushing down and holds the decapping stem, was drilled and tapped from the sides (2) in order to retain the new expander (no bushing is used).  The expander's position is adjusted so that it is about 1 mm from the bottom of the case when the case is all the way in the die. Expanding and setting the shoulder back in a single step not only saves a step, but the expander holds the case neck in line with the body to limit runout induced by the sizing/expanding operation.









The new expander die was specially designed to be used in conjunction with the new neck turner which also incorporates several new concepts.  We wanted to create a high precision tool with very fine adjustment and innovative cutting characteristics.  It was designed using CAD and produced with EDM machinery and ground on all appropriate surfaces.


It was thus decided to make the cutter blade and pilot from carbide. In particular, the blade is rectangular with a corner angle matching the shoulder angle with a rounded edge offset 2/100 mm from the centerline of the pilot in order to create optimal conditions for good turning. The cutter is then placed parallel to the pilot with a cutting angle of 1/100 mm. between the front (closest to neck) and back (closer to the shoulder). The blade is held in a slot with a tolerance of 2 microns and can be adjusted by a screw that fits an incline milled into the side of the blade.



I must say that the turner body, which is all EDM cut is a true jewel. A rectangular section slot was also EDM cut to hold the blade and then another hole was EDM cut to allow placement of a dial indicator. The indicator's tip rests on the blade and allows you to measure the blade's movement as you adjust the side mounted set screw that controls the blade's position.

To calibrate the cutter depth, begin by placing the blade in contact with the pilot, zero the dial indicator and adjust the blade with the set screw until the indicator reads the desired neck thickness. Once the desired setting is reached, lock the blade using the two locking set screws positioned opposite each other on the side of the tool body. I think the photos are clearer than my words, but even a minimal description seemed appropriate.





The pilot of the neck turner deserves a separate description because although seemingly simple, it is an important element of the tool's improved performance.  The pilot is made from carbide, from an old mill.  The first objective is to allow turning the neck to the shoulder consistently, without have to trim the case necks beforehand, since the case will shrink in length during the fireforming process.  With the traditional pilot design such as the Sinclair, which uses the case neck for a stop, you must trim prior to turning and then the case shrinks further on fireforming.


With this pilot, instead of using the case neck for a stop, we sought to use the bottom of the cartridge case for a stop, which allows turning the necks to a consistent stop point regardless of the length of the necks.   The necks can be trimmed after being fired at least three times. This translates into the ability to have longer necks which can reach 38 to 38.2 mm. That was virtually impossible with a traditional pilot design.

The cutter pilot has an initial diameter of 6.12 mm then grows on a taper of 0.5 ° up to a diameter of 6.14 mm. This creates a close fit of the neck to the pilot.  The pilot being carbide can be cleaned frequently with 1000 grit sandpaper to remove any traces of metal (brass) deposited on it during the turning operations without altering its diameter. This phenomenon, known as galling, occurs when turning at too high a speed, or with inadequate lubrication. The recommended speed for turning is roughly 60 RPM.

The steps needed to turn necks with thickness tolerance reduced to 1 micron (the mere warmth of the hand on the cartridge case to change the measurement by several microns) can be summarized as follows:

1. Lubricate the case prior to inserting into the expander/sizer die.

2. Lubricate the inside of the neck with a nylon brush and moly grease.

3. Run the case into the die, turning the expander holder 1/4 turn and reinserting the case 4 times.

4. Let the cases stand for at least 24 hours.

5. Turn the necks down, removing 80% of the desired total amount to be removed.

6. Let the cases stand for at least 24 hours.

7. Size the necks down with a full length die using the appropriate bushing.

8. Run the case through expander die as in step 3 to bring the neck ID back to 6.14 mm, thus re-creating the proper tension on the neck of the neck turner pilot.

9. Let the cases stand for at least 24 hours.

10. Turn the necks again to the final thickness.

You should also lubricate the blade while cutting the neck, thus avoiding problems of galling on the blade and increasing the smoothness of cut.

I am sure many of you will wonder if all this effort is worthwhile, but I must say that the search for an ever increasing level of precision carries with it a duty to experiment, to seek new solutions.  Although the results themselves are comforting, the satisfaction of having contributed to the sport amply rewards the effort and expense involved.

A final thanks to my friend J.C. who always encourages me to measure everything I do, to take notes and thus to be able to replicate my experiments in the future

Top view of the tool showing hole for dial indicator.


Side vew showing the blade locking set screw and the stepped pilot.


Sinclair tool with traditional stype pilot, using the case mouth for a stop.


Sinclair tool modified with Mario's long pilot using the case base for a stop and with Mario's carbide cutter blade with a radiused corner.

Front view shows  set screw that regulates the cutter height, the cutter itself and the pilot shaft hole.


Side view showing set screw used to retain the dial indicator.


Alessandro in the shop.

Lucio on the grinder.




 

All contents Copyright 2012 The Rifleman's Journal