Stroboscopic effects on lathe

Perceived wisdom seems to be that you should avoid fluorescent lighting in case you fool yourself into thinking the chuck is actually stopped and the
noise of the lathe running at 1000rpm is coming from next door. I've tried winding the lathe spindle speed up and down from 40 - 2000 rpm and I can't get this to happen, almost at around 300 rpm, certainly not at 50 rpm.
Wouldn't it actually be a good thing to be able to strobe the work piece so you could see the finish as it happened, particularly when facing off ?
The ramblings of a muddle engineer...
Steve
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100Hz is 6000 rpm so a 3 jaw chuck will sync at 2000 (or 4000 or 6000) rpm and a 4 jaw at 1500 (or 3000, 4500 or 6000).
--
Boo

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wrote:

Some years ago we bought a large industrial strobe unit with remote lamp to shine onto a grinding wheel doing 3,000 rpm to 'stop' it so the operator could see better to freehand grind some small drills. It worked very well. Later we bought a Christian drill grinder and the strobe was redundant.
I 'obtained ' it with the idea of shining it down inside some skeletal housings on the lathe with loads if internal fins to 'stop the housing so i could see better to pick up an existing feature and make it deeper. At 15 " which is as close as I could get it it hardly worked.
I have tried many times with VFD controlled equipment to get a chuck to stop under florry essence lighting but have never managed it.
In theory it should work but I personally have never met anyone who has experienced this phenomenon and tend to regard it as an unproven old wives tale.
JS.
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==Fluoro tubs have a fluorescent powder coating internally specially designed to retain a glow between cycles to minimise what is an annoyance to most users.
For true stroboscopic effect a neon tube is flashed electronically, illuminating the field momentarily, leaving no glow between cycles.
JWฒ
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On Fri, 23 Jan 2009 14:26:39 +0900, JW?

If you want a good stroboscopic effect take a LED torch , remove the batteries and feed it from a 4 to 6V AC source.
Strictly speaking a series diode should be used to avoid exceeding the normal -5V reverse rating. However this rating is an extremely conservative manufacturers figure for a parameter that is not normally important to the user. Checks on a few white LEDs showed reverse tolerance greater than 20V. If you've got a spare diode - use it. Otherwise don't bother
Jim
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On Thu, 22 Jan 2009 16:42:55 -0800 (PST), John S

The most pronounced effect I have seen is a very blurred slight 'banding' or 'shadowing' of the surface, but the suggestion that the chuck had 'stopped' is fantasy.
Just a week ago I put some white sticky tape stripe across the end of a (1500 RPM) motor shaft to check it was running at the proper speed. We were just about able to distinguish a fuzzy cross of less dimness. This was a background no natural light at all (10 PM) and all light from florries. It served out purpose, but in no way did the shaft 'stop'.
Richard
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`Fraid it`s not John.It was common in the shop where I served my time.Ancient flourescents and large chucks never doing over 400 rpm. I can get it on my Ikegai with 400w metal hallide low bay lights also. Mark.
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On Fri, 23 Jan 2009 03:50:27 -0800 (PST), " snipped-for-privacy@ems-fife.co.uk"

Methinks you're both right.
It _is_ an old wives tale and it _did_ happen.
Modern fluorescent light phosphors have a longer persistence than ones in use in the sixties and earlier, so don't show the effect. Some metal halide and all low pressure sodium lights will show the effect to an extent. No one will ever be so confused by a mains generate stroboscopic effect on a machine tool as to think it's stopped.
Mark Rand RTFM
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Steve wrote:

If you want to avoid this then you could use high frequency ballasts. That will operate at some wierd frequency in the order of 10's of kHz. In this case the odd of getting a strobe are slim to nil.
RPM's on a lathe are whole numbers? As in a round integer?
Rob.
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Steve wrote:

I think this is done. It's certainly done in the print industry, where strobing is used to freeze multiple copies of a printed page on a (rather fast) converyor.
BugBear
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