|Ian Parkin||15/09/2020 18:22:14|
972 forum posts
I need to fit a tachometer on a machine in the morning
how do i fit the small button magnet to a shaft?
if i glue it to a mild steel shaft does the steel sap the magnetism ?
21307 forum posts
Araldite worked OK on mine
2225 forum posts
No it will be fine.
|Brian Sweeting||16/09/2020 00:10:24|
|453 forum posts|
Make sure that you stick the magnet the right way around, you just know that it will happen.
|Neil Wyatt||16/09/2020 15:57:27|
18727 forum posts
I found the small neodymium magnets are so strong that popping one in a keyway or spanner notch has always worked for me without adhesive.
|1719 forum posts|
... which probably makes Brian's admonition even more important
|Ron Laden||17/09/2020 06:59:34|
2236 forum posts
I have fitted one to my mill and one to the lathe ( dry with no adhesive) and neither have budged yet.
Edited By Ron Laden on 17/09/2020 07:07:17
7476 forum posts
My lathe's magnet sits in a slight recess, which I guess gives it more grip on a machined flat surface and stops it sliding on a smooth round shaft.
Sliding may be a problem - although I can't imagine a strong magnet coming off, it might move sideways. Sideways movement may not show up in practice. Provided the magnet's close enough right-left to activate the hall sensor, rpm will still be measured. Even if a magnet gradually walks around the circumference, the effect on rpm readings will be small.
A spot of glue would also stop sideways movement and be less trouble to apply at home Another guess; it's cheaper for the manufacturer to machine a flat recess on a lathe spindle than it is to clean it carefully and apply a glue resistant to oil and heat. Also easier to fix an unglued magnet if untrained labour puts it on upside down.
|Ian Parkin||17/09/2020 16:30:57|
972 forum posts
I did the job today just ground a flat on a 20mm silver steel shaft and placed the magnet and it stays there even at 1000rpm
its been running an hour or so now
I had it in my head that a magnet would have need putting in a non ferrous collar to work adequately
thanks for all the help with this
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