kurtak
Well-known member
I added pictures
In the post with the 2 pictures the contact point upper righthand side of pic is absolutely without question a tungsten/silver contact point
The absolute dead giveaway that it is tungsten/silver is the rough surface (lines) on the "back" side of the point
ALL tungsten/silver contact points (& ONLY tungsten/silver contact points) have some sort of rough surface on the "back" side of the points commonly referred to as a "waffle pattern" --- that rough surface can ether be an actual waffle like pattern - or lines - or small dots
That is because tungsten does not make a good strong solder/braze adhesion to the point when they solder/braze the points to the bus bar --- so when they sinter/press the points they do it to create that waffle pattern on the back side of the point which gives the points a rough surface for the solder/braze to better grip/bond/adhere the points to bus bar
Because (unlike most other metals) solder/braze does not bond well with tungsten the points would fail (break free from the bus bar) as a result of the conductive heat generated by the electrical current running though them when closed so the waffle pattern on the back side of the points gives the solder/braze something to better grip/bond the points & prevent that failure
These tungsten/silver contact points come (almost) exclusively out of "hand thrown" circuit breakers (as opposed it magnetic "disconnects" &/or relays) whether they are the circuit breakers you find in you house electric panel or LARGE industrial circuit breakers --- you may (or not) also find them in other "hand thrown" switches
So any time you see that waffle pattern on the back side of the point you can be absolutely sure they are the tungsten/sliver points --- you may not always see the waffle pattern on the back when you de-solder/braze the points from the bus bar as the solder/braze may (or not) cover up the waffle pattern
So - if they come out of hand thrown circuit beakers they will "absolutely" be tungsten/silver - if they have a waffle pattern on the back they will "absolutely" be tungsten/silver
Also - tungsten is "very" brittle (as well as it is a sintered product & not an actual alloy) so if you put them in a vice & hit them with a hammer they will break (may bend "a little" before breaking) --- whereas actual silver contacts will bend a lot before breaking
Kurt
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