thanks all
I will avoid the glue  & imbalance problem  by using  optical  reflector.
Interesting, the epoxy  putty toroid flew apart leaving a  section
that included the  magnet.
i concluded the bond to the steel  was  not  uniform  despite  prep..
Now looking  for opto and matte black  paint.
Thx  TomP

On Sat, Nov 7, 2020 at 12:12 AM <[email protected]> wrote:
>
> How about *NOT* securing a magnet to the shaft? A magnet rotating at high
> speed will probably cause a balance problem even if you can secure it. Use a
> gear tooth sensor and mount a small steel gear on the shaft. Search Digikey
> for "gear tooth sensor" (no quotation marks) for lots of sensors.
>
> -----Original Message-----
> From: Thomas J Powderly <[email protected]>
> Sent: November 6, 2020 11:50 AM
> To: [email protected]
> Subject: [Emc-developers] spindle speed hall sensor magnet
>
> I'm having trouble securing a magnet onto a trim router spindle shaft for
> hall sensor rpm.
>
> I tried a 3m 2 part glue and a loctite kneadble epoxy putty,
>
> both blew up as i approached the 35000 rpm of the trim router.
>
> The control scheme works ( arduino with pid, pyvcp speed set and rpm meter,
> zero cross detector opto triac ... )
>
> Does anyone have suggestion for securing the magnet on the shaft?
>
> Is glue a solution?
>
> This is all manual work, no machine available.
>
> Magnet is 5mm dia x 3mm high neodynium on a 10 mm shaft, between end bearing
> and brush.
>
> tia
>
> thx tomp
>
>
>
>
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