WARNING: I am not a ME so take this AS IS.

1. Look into the Coefficients of expansion for the two materials, can
you heat or cool one and get it to expand or contract to fit?

2. Could you possibly cut a key into the bit and use a tiny taper key?



Charles K Roberts II
ORNL-SNS Project


-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Mike Hord
Sent: Friday, January 23, 2004 9:52 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: [OT:] Securing a steel pin in brass

Okay, this is tricky to explain, but I'll try.  The important bit is the
fourth paragraph, so you can skip the first bit if it's too poorly
explained to make sense.

Imagine two brass cylinders, 4mm in diameter, one 2mm in height
and the other 10mm in height.  Now stack them vertically, aligned
along their central axis.  Drill a hole in the center, and pass a small
screw through the hole in the 2mm piece and thread it into the
hole on the 10mm piece.

Now drill three holes spaced equally around the screw, and put a
steel drill bit with the flutes removed in two of them.  The result
is that when you turn the screw, it pulls the 2mm piece towards
the 10mm piece a little at a time, with the drill bits sliding down
into the 10mm piece and affixed to the 2mm piece.

Here's the problem:  how do you join the steel bits to the brass?
Right now we use super glue, which is okay, but since they really
need to be sterile, it would be nice to autoclave them, which
means temperatures up to 150-170 degrees C, and superglue
doesn't generally like that.

Solder won't join to the steel.  Any other ideas?

Mike H.

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