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Thread: R.P.M Lathe meter mod.

  1. #1
    Captainleeward's Avatar
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    R.P.M Lathe meter mod.

    R.P.M Lathe meter mod. New blue meter mod.
    R.P.M Lathe meter mod.-013.jpgR.P.M Lathe meter mod.-014.jpgR.P.M Lathe meter mod.-015.jpg

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    I like tachometers in lathes, even more on a varispeed mill. My lathe is geared, RPM is assured with voltage. Does the tach monitor spindle or motor, and indicate when cuts bog down?
    Sincerely,
    Toolmaker51
    ...we'll learn more by wandering than searching...

  4. #3

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    I purchased a Thai made bicycle speedometer for my band saw several years ago and mounted that on the top wheel. Using a formula I found somewhere like this forum I set it to read blade speed in metres per second tho it could also be set to read rpm or fpm. I may still have the setup instructions and formula if you need them.

    I should have been smart and kept it when I replaced that bandsaw.

    I think you could probably find a suitable location for the small magnet that provided the pulse AND the peanut sized sensor so that it would read chuck rpm

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    So much TO LEARN! Apparently, I need to add electronics to curriculum. That a speedometer could interpret as FPM is like made to order. I'd recommend posting the setup and formula an individual thread. Sure to be appreciated by many.
    Sincerely,
    Toolmaker51
    ...we'll learn more by wandering than searching...

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    Yes they do indicate when the spindle bogs down. shows lower rpm.
    I drilled a hole in the pulley and put a magnet with a hole in the middle (ebay) and screwed it on work real good.
    however the magnent had to be flipped over for it to work.
    Last edited by Captainleeward; 02-12-2019 at 02:22 AM.

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    [email protected] tonyfoale's Avatar
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    Quote Originally Posted by Toolmaker51 View Post
    I like tachometers in lathes, even more on a varispeed mill. My lathe is geared, RPM is assured with voltage. Does the tach monitor spindle or motor, and indicate when cuts bog down?
    Here is one that I got, UK eBay but I am sure that the US eBay has them too. I was going to make my own but at that price that would have been folly beyond imagination. ebay tacho

    Here is a pic from the listing Name:  tacho.jpg
Views: 1645
Size:  11.9 KB

    You need no knowledge of electronics, it will measure the rpm of whatever device you put the pickup on.

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    mklotz mklotz's Avatar
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    Quote Originally Posted by Toolmaker51 View Post
    So much TO LEARN! Apparently, I need to add electronics to curriculum. That a speedometer could interpret as FPM is like made to order. I'd recommend posting the setup and formula an individual thread. Sure to be appreciated by many.
    I'm assuming "FPM" is a typo and you meant RPM.

    Firm proof that one can find the answer to anything on the web. (Well, at least stuff that has an answer. "Meaning of life" and such questions are referred to the religious shamans.)

    https://www.instructables.com/id/Tac...ometer-cycloc/
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    Regards, Marv


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    Yes, in a roundabout way. Response [post #3] led me believe the 'program' functioned in conversion RPM & wheel diameter to FPM. To date, all the bandsaw FPM gauges I've seen are cable driven analog
    Sincerely,
    Toolmaker51
    ...we'll learn more by wandering than searching...

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    [email protected] tonyfoale's Avatar
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    Quote Originally Posted by Toolmaker51 View Post
    Yes, in a roundabout way. Response [post #3] led me believe the 'program' functioned in conversion RPM & wheel diameter to FPM. To date, all the bandsaw FPM gauges I've seen are cable driven analog
    Your first interpretation of that post was correct. The bicycle speedos allow the input of the bicycle wheel diameter, so by adjusting the input diameter you can alter the displayed reading for a given RPM of the thing being measured (within the range of acceptable input values). As the m/s value (or FPM) is directly proportional to the RPM of the bandsaw wheel it is only necessary to fudge the input wheel diameter for the readout to be in appropriate linear units. That is a trivial calculation. If the calculated fudged diameter is below what the bicycle speedo accepts then you can fudge the reading by integer multiples by the simple expedient of getting multiple pulses from each rev of the band saw wheel.

    The above only applies to the use of the bicycle speedos (mentioned in post 3) or other tachos which allow for a method of calibration. IT DOES NOT APPLY to the type of tacho shown in the first post. These have no calibration or adjustment features, they are made to display RPM based on a single pulse per rev.

    However, it would be a simple project to put an Arduino or similar micro between the pickup and display, programmed to convert the pulse rate into a linear measure which could be made m/s or FPM at the press of a button or flick of a switch. The programme (confusingly called a sketch in Arduino speak) could have the bandsaw wheel diameter hard coded before being downloaded from a PC. That would keep the programming simple but would mean that minor software changes would be needed for each wheel diameter or there are various ways to set it up to accept the diameter data via controls on the device itself, like programming a VFD or setting the time on a digital clock. The Arduino programming would be more complex in that case.

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    Thanks Captainleeward! We've added your Lathe Tachometer to our Measuring and Marking category,
    as well as to your builder page: Captainleeward's Homemade Tools. Your receipt:





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