Hello Dell, what method were you using to thread the rod? i.e. hand held die, die held in tailstock?

David

The extreme ends of silver steel rods can be very hard depending on how it is cut

Roy

Not impossible the material was faulty, but unlikely! I've noticed most of the 'poor materials' reported on the web are found in hobby workshops, not on production lines churning out thousands of identical items!

I suspect trapped swarf wedging into the die. As the die cuts down the rod, we hope the swarf escapes through the slots provided, but they aren't very big and there's always a risk swarf is going to get minced and pulled into the cutting edges. Enough of that will cause the die to blunt and jamb, and – because the screw thread provides a massive mechanical advantage – the turning force is enough to gouge the rod as it enters the die.

Not enough to be conclusive, but in my workshop:

• Brass never mangles.
• Soft Aluminium often strips,
• EN1A-Pb rarely strips
• Ordinary mild steel sometimes jambs and strips
• Some stainless steels are vile!
• Much more likely to happen cutting by hand when nothing apart from me is keeping the die straight. I put this down to the wobbly operator skewing the die into the rod.
• Power cutting with a die on the lathe rarely strips. I think this is all to do with steadiness; the die goes straight down the rod at a steady speed with no jerks or twists. I suspect the swarf comes off cleanly with enough energy to eject away from the cutting edges.

Assuming the rod is the correct diameter and the die in good condition, I think the answer is plenty of lube, periodically winding back the die to clear swarf, maintaining a steady cut-rate, and keeping the die absolutely straight.

Dave

Turn the die by hand with very frequent reversal and use plenty of cutting oil. Turning too fast and too far without backing off will twist the part. As the swarf length builds up it will create a higher force on the part. Frequent backing off keeps the chips small and lowers the resultant force on the part. When cutting small threads I back off at least each half turn often less. Chips will also build up between the die cutting edges and can jam into the die causing stripping of the treads.

I have to agree that it’s likely that it’s dwarf in the die and as it’s silver steel the swarf is slightly hardened causing your damage. I just wonder why you use silver steel to make screws?. From my own perspective it’s a horrible material for that sort of work. Most of the small screws that you buy are from an easily machined steel and if really necessary machine from a material that readily hardened EN8 , EN 16 etc. The other possibility is to use 303 or 304 st st.

It looks to me that the die was run into the shoulder. Sometimes this can cause the thread to be stripped or be damaged enough that when the die is reversed , it unwinds and the damaged section comes out. The damaged section looks to be the length of a die. Should always stop before a shoulder, and then very carefully come up to the shoulder if it does require the full length to be threaded. Often designs can be modified is such a way that the thread is only required to be within 1 pitch away from a shoulder. Allows room for a nice radius transition at the shoulder and for an easier part to make. Silver steel can actually be quite tough on dies, especially if the dies is a High Carbon Steel die. HSS dies will last a lot longer cutting threads on Silver steel stock. An advantage to threading and then backing off, and then threading again, is that it forces the swarf to be broken, and not become a long spiral. It also allows for you see the progress of the thread and if anything is going not right can be detected very early on. Tool life can be greatly improved with proper cutting fluids as well.