rpm counter

[Paul.]

Interesting, I had one of those digital meters for use when installing machinery such as conveyors etc to match and fine tune belt speeds, it gave me loads of erroneous readings so i gave up on it and went back to a contact analog version, I assumed that reflections (mostly stainless machinery) may have been the problem, but reading through this thread I wonder now if the fluorescent lighting may have been the problem.

This is what I use, its showing my polisher spindle running at just under 3000 rpm, it also has a wheel attachment, for peripheral or conveyor belt speed, you just hold it on the belt and then read 10% of the indicated value as metres per minute, of course you need to be comfortable working with moving machinery to use these, so a digital is safer

 

[breezer]

he he he.

My dog's got no nose
How does he smell?

etc etc

Through a weeping infected gash on the front of it's face?

 

[chunkolini]

Good grief!!
A simple question leads to a load of consciousness raising, yet again.
Chunko'.

 

[syborg]

forgive me as ive just skimmed this thread,

it seems that surface speed and rpm are gettin confused.

like someone said, say the earth is spinning at 120000rpm, imagine turning down the earth to 10mm diameter, it would still be spinning at 120000rpm but the surface speed will be lower. thus how gears work.

there is a mathematical formula for working out rpm,torque and surface speed. its buried somewhere in my assignments from engineering college. cant remember it of the top of my head.

peace

syborg

 

[Weldingartisan]

But don't forget it's the peripheral speed that counts for cutting tools not RPM. W/A

 

[MrFluffy]

Just to add, Ive got a digital rpm counter I built for my lathe, but it uses a slotted interrupter thats read by a diode/ir transistor pair rather than the shiney spot method (although the kits come with both, I figured the interrupter would be more repeatable). Backed up against a analog tacho I have like Paul's it seems fairly consistant.
LS Caine has the kits in varying levels of componentry :-
http://medw.co.uk/wiki/index.php?page=Tachometer