Thread: Gunmetal !

Hi Guys,

I have a gunmetal die holder where the threads have stripped out of the single screw.

For the life of me I cannot drill the hole out to re-tap it, nor drill a new hole in the other side !

I've tried altering the cutting angles on the 3 mm drill ( the original was threaded M4 ) but all that seems to happen is material just builds up on the cutting edge and the drill just spins.

Anyone have any suggestions please. I do have another die holder I can use though it is the same gunmetal material.

Thanks.

Hello young fellow.
I would use a hand stone to alter the drill flute angle to close to zero rake. This will also give you a sharp edge. Use kero as a lube and 300 rpm. Similar to copper. You only need to remove 10 thou from the drill.
Regards
BC

Originally Posted by steamloco1954

Hello young fellow.
I would use a hand stone to alter the drill flute angle to close to zero rake. This will also give you a sharp edge. Use kero as a lube and 300 rpm. Similar to copper. You only need to remove 10 thou from the drill.
Regards
BC

Hi BC,

Thank you for the complement I like the "Young Fellow" !

This stuff, what ever it is barely marks ! But you are right, I've gone the wrong direction making the drill bit very sharp, backing it off well. I'll make and try a spade bit !

I am always been intrigued by "gunmetal" I think I must have seen 50 different metals described as such.

Originally Posted by China

I am always been intrigued by "gunmetal" I think I must have seen 50 different metals described as such.

And colours described as gunmetal...

Michael

Hi Guys, Thanks for the replies

This stuff is a bright silvery colour, a bit like bright lead, its quite heavy as well !

Hello again.
Gun metal is usually coppery/bronze in colour. Nickle bronze is often called silver bronze by mistake because of it's silver colour. I am thinking cupro/nickle or monel. Used long ago for corrosion resistance. A sharp drill and high feed pressure. This metal work hardens big time. When I came to industry it was out of favour due to cost but it is tough stuff. Centre punch with a pyramid point punch to let the drill bite.
Regards
BC
Next you have to tap it. Or braze in an insert.

Thanks BC,

I'm rapidly coming to the conclusion that "A" I'm wasting my time and "B" its more trouble than its worth, particularly because I do have another and a new one is only £10.00p

So into the scrap bin with it !

PS. I'll salvage the steel handles though