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Tweezer for platinum


#1

To all the platinumsmiths out there… how can I make tungsten
tipped tweezers? Rivet or weld/plat? I think tung/carbide would
contaminate the platinum…

Eric P.


#2

The commercial tweezers I’ve seem (carbide, not tungston metal,
but would be the same) use screws to attach a thicker steel block
to existing tweezer shanks, that block being drilled in the ends
to insert a carbide rod, which then is held in by additional set
screws. I tried making a pair by silver soldering carbide rods
to tweezers. Only lasted a short time before the carbide
cracked off the solder, to my considerable surprise…’

Carbide doesn’t contaminate the platinum. Neither does tungston
metal, which I use for soldering picks for platinum.

Peter Rowe


#3

Peter,

The carbide and steel have very different thermal expansion

characteristics and if they are soldered directly together it
can fracture the carbide. The solder used to braze carbide to
tool shanks is specially formulated to reduce the stress in this
kind of joint and often a special kind of solder preform that has
a three layer composition is used it is solder then copper then
solder. This reduces the stress in the brazed joint and provides
for some shock resistance in the tool.

A good source for the pure tungsten rods for platinum work is

the welding supply They sell pure tungsten rods that range in
size from 1/16" x 6"" to 3/16" X 6" for the non-consumable
electrode in TIG welding torches.

Jim


#4
   	The carbide and steel have very different thermal
expansion characteristics and if they are soldered directly
together  it can fracture the carbide.  .... 

I figured something of the sort happened, but was still
surprised. I’d used a whole Lot of easy silver solder,
thinking that at least the carbide would be securly held/trapped
in by the solder mass. When it broke away, it seemed as though
the carbide surface had not been hardly even “wet” by the
solder, despite the flux used, so I expect that the joint failed
even in cooling with just the carbide separating again from the
solder. Was funny…

 	A good source for the pure tungsten rods for platinum work
is the welding supply They sell pure tungsten rods that range
in size from 1/16" x 6"" to 3/16" X 6" for the non-consumable
electrode in TIG welding torches. 

Good idea, thanks. I’ve gotton rather fond of tungston as a
solder pick in general, in preference ot titanium or steel…

Peter


#5

The AWS brazing book says that the carbides need to be ground
or sandblasted prior to brazing to remove any carbon enrichment
of the surface. The pure carbon is not easily wet by the brazing
filler metal. They also suggest a flux containing Borates and
Flourides to help wet the carbide.

Jim


@jbin
James Binnion Metal Arts
2916 Chapman St
Oakland, CA 94601
510-436-3552