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Author Topic: I don’t have a Tach  (Read 2524 times)

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Offline kolias

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I don’t have a Tach
« on: January 08, 2014, 02:55:02 PM »
I don’t have a tach or anything similar to measure the spindle RPM to calibrate my VFD

Is there anything else to estimate the RPM besides listening to the sound of the spindle and guessing?
Nicolas

Offline Hood

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Re: I don’t have a Tach
« Reply #1 on: January 08, 2014, 02:59:16 PM »
Fit a slotted disc and an optical sensor to your spindle and set it up in Mach as the index input.
Even if you do not have any way to permanently mount it you could set one up in the actual spindles collet just for your calibration.
Hood

Offline kolias

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Re: I don’t have a Tach
« Reply #2 on: January 08, 2014, 03:11:56 PM »
I kind of figured that I may have to buy something, but sounds good what you say. Any idea of suggested optical sensor besides searching the web?
Nicolas

Offline Hood

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Re: I don’t have a Tach
« Reply #3 on: January 08, 2014, 03:34:39 PM »
I used to use an Optek OPB 916B or 917B.
You will also need a resistor to limit the current to the LED in the Opto, I used the OPB and a 220 ohm resistor on the recommendation of John Prentice many years ago and I never had a problem.
For a slotted disc, if it was a temporary setup a CD would likely be  fine.
Hood

Offline Vogavt

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Re: I don’t have a Tach
« Reply #4 on: January 11, 2014, 09:20:23 AM »
Look here.

You should be able to modify it for the mill.
Print it on a disk and mount it in your spindle. Using the Fixed Ring Indicator you should be able to at least calibrate relatively close.  Or at least get you in the ballpark.

I enlarged both the images equally in size and found it to be fairly useful.

YMMV,
Vogavt
« Last Edit: January 11, 2014, 09:28:48 AM by Vogavt »

Offline kolias

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Re: I don’t have a Tach
« Reply #5 on: January 11, 2014, 10:25:05 AM »
Thanks for your time Vogavt, pretty neat idea this gauge but for my needs I ordered a handheld digital tach ($13) which I hope it will give me what I want. I watched a video on youtube and the guy was testing this tach on a mill with some pulleys and according to him the tach was accurate
Nicolas