I'm not a mechanical eng, but my Dad is.  He used to do a similar thing with
brass rings and a steel insert.  He used to heat the brass up in our oven
(much to the delight of my mother!), take them out and pop in the steel
inserts.  You never get them out afterwards though, so you have to get this
right first time, or you scrap the job.  It was quite easy after you got the
hang of it, as the brass expanded quite allot.  Of course you need to get
all the hole sizes right, I think he did this mathematically.

Brian.

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Mike Hord
> Sent: 23 January 2004 14:52
> 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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