# Photo Tachometers & Spindle RPM



## elecbob (May 12, 2013)

I am wondering what opinions the membership has about the many photo tachometers that are available. Also if there is a quick cross index of spindle RPM versus Cutting Speeds in FPM? I know that it depends on diameter of the work piece and of the material being turned. I have a South Bend 9 lathe. Once I get the various RPM's I think it should be easy to develop a chart for cutting speeds. Like to hear some input. This forum is such a vast knowledge base. Thanks, 
Bob


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## Old Iron (May 12, 2013)

Bob


I have a 13" South bend and this is the tack I use, I think it has the functions your looking for.

Paul

http://mkctools.com/tachulator.htm


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## itsme_Bernie (May 12, 2013)

Hey Bob

Here is the array of RPM measuring tools I have gone through.

All worked, but I am now using the tool on the left is the most useful now, the Monarch Pocket Tach 100.
I got that on Craigslist for $25.  Snap!  Uses this special reflective tape, $3.00 a roll.  Little 3/8 inch square pieces on any spindle, in an pit of the way place.  

The second is the Westward mechanical tach which has a rubber tip that you just stick onto a rotating shaft.  I made a brass fitting to stick into a chuck or collet and measure from there.  I got this for $40 on EBay once, like new.  

http://www.grainger.com/Grainger/WESTWARD-Dial-Tachometer-3BY11?Pid=search

The last is a Starrett 104 "Tach", really a counter.  It counts turns, and you watch your second hand on your watch.  These can go for $5 to $50 on EBay, depending on what tips come in it, and who is watching!

The digital tach is nice because one little piece of the $3 roll of tape on every spindle in the shop and I am all set to take a two second reading!  

Bernie


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## itsme_Bernie (May 12, 2013)

Wow Paul

That Tachulator looks pretty cool!  SFM too?


Bernie


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## franklin (May 12, 2013)

Bernie,
where do you get the reflective tape for the optical tachometers from?
Have a tacho but no tape.
thanks
Frank


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## hman (May 13, 2013)

There's another electronic tach/SFM calculator similar to the Tachulator.  It's the MachTach.
http://www.machtach.com

There are two disadvantages to the MachTach.  First off, it's only available as a kit. (-BUT- there's an offsetting advantage.  The kit is only $56 (less power supply and enclosure), with free shipping to the US, $14 international.  Tachulator is ~$120, assembled)  Secondly, it's a one-man show, and there have been times when the kits have been unavailable.

The Mach Tach allows using/entering any number of "slots" (light/dark transitions) on the shaft between 1 and 60, allows entering diameters from .01" to 99.99" (or 1 to 000mm), displays RPM from 0 to 9999, displays SFM from 0-9999 (or surface meters/minute from 0 to 9999).  You specify inch or metric mode when you order.

Several sensors are available form MachTach - IR reflective, slot-type optical sensor, and Hall effect sensor.

For further info, check their website or the MachTach Yahoo group.

Bottom line:  The MachTach has pretty much the same specs as the Tachulator, and you can save some money if you DIY.


Disclaimer:  Other than having bought one, I have no connection to MachTach.

Best wishes!


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## itsme_Bernie (May 13, 2013)

franklin said:


> Bernie,
> where do you get the reflective tape for the optical tachometers from?
> Have a tacho but no tape.
> thanks
> Frank



Hey Frank

Whoops - it was $9.59 at Grainger.  I have one ten minutes away.  You only use a tiny piece on every machine, so it is a lifetime supply!  Hah hah

http://www.grainger.com/Grainger/TIF-Reflective-Tape-1T982?Pid=search


Bernie


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## Uncle Buck (May 13, 2013)

Bernie, you lost me with this comment *"The second is the Westward mechanical tach which has a rubber tip that you just stick onto a rotating shaft.  I made a brass fitting to stick into a chuck or collet and measure from there.  I got this for $40 on EBay once, like new."        
*The Westward comment lost me. I have a tach just like that one. Yours just like mine has the SW logo on it's face. Those tachs were made by Stewart Warner. I have no knowledge of any link to a Westward???


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## Old Iron (May 13, 2013)

itsme_Bernie said:


> Wow Paul
> 
> That Tachulator looks pretty cool! SFM too?
> 
> ...




Yes it has SFM.

Paul


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## Hawkeye (May 13, 2013)

I have three MachTachs on two mills (one of them CNC) and on the shared VFD installation on the third mill and lathe. When you switch between machines, the tach shifts to the active machine. I really like these tachs.


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## itsme_Bernie (May 13, 2013)

Uncle Buck said:


> Bernie, you lost me with this comment *"The second is the Westward mechanical tach which has a rubber tip that you just stick onto a rotating shaft.  I made a brass fitting to stick into a chuck or collet and measure from there.  I got this for $40 on EBay once, like new."
> *The Westward comment lost me. I have a tach just like that one. Yours just like mine has the SW logo on it's face. Those tachs were made by Stewart Warner. I have no knowledge of any link to a Westward???



Thanks Buck

I got mixed up there.  I think I Stewart Warner sells them through Grainger as well, and when I googled it, Grainger popped up, and listed it as Westward.

Even though I OWN it, I let Google tell me what it was!!!  Aye yay yay

It's pretty nice though, right?  


Bernie


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## Uncle Buck (May 13, 2013)

itsme_Bernie said:


> Thanks Buck
> 
> I got mixed up there.  I think I Stewart Warner sells them through Grainger as well, and when I googled it, Grainger popped up, and listed it as Westward.
> 
> ...


  Those old SW tach's are nice. I thought them relatively rare when I found mine complete with instructions tips and tin can pre internet. I have since figured out they seem to be fairly common. For all I know they might still be available new. WOW, just checked Grainger, $117 for the SW!


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## Tony Wells (May 14, 2013)

Westward is just Grainger's house brand name, not the manufacturer.


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## bonehead (May 14, 2013)

I looked into tachometers and found out that they cost quite a bit more than i expected so i made my own. It works exceptionally well and im refitting it for a laser range finder to make it easier to set the part surface height. The instructions for making the tachometer is here: http://www.floridaame.org/Plans/Kamran Nili/rpm/tachometer.html . I didnt write this but i found it useful. it cost me around $50 for everything even the material for the case(which is a plastic cutting board i used for cheap plastic $1). I think i can go without using the microcontroller but im not sure yet if linuxcnc can accept the raw data or if it needs a different format. Dont tell my wife where the new unused cutting board went.


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## bedwards (May 14, 2013)

franklin said:


> Bernie,
> where do you get the reflective tape for the optical tachometers from?
> Have a tacho but no tape.
> thanks
> Frank



I use shiny finger nail polish I swipe from my wife and seems to do well with the Harbor Freight optical tachometer.


bedwards


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## Starlight Tools (May 14, 2013)

I picked up a Monarch Phaser-Laser Portable Tachometer a few years back on ebay, it was from a company that rebuilds and re-certifies them, so came marked with the calibration sticker on it.

Got a 5 foot x 1/2" roll of reflective tape from KBC Tools

see http://www.kbctools.com  page 925 in their catalogue.

To check that a photo Tach is working properly aim them at a Flourescent light bulb (,bulb must be on, LOL) and they should read 7200 RPM  ( 60 Cycles / Second x 60 Seconds / Minute x 2 Pulses / Cycle = 7200 Pulses / Minute)

This works great for measuring the RPM and or confirming that the item is turning at the "proper" RPM.

With a bit of math it is easy to determine what the proper calculated RPM should be.  R1xD1=R2xD2, so as long as we can determine at least three points we can calculate the missing one.  IE  Motor is 3400 RPM, and we measure the two pulleys and determine that on is 1" diameter and the other is 2" diameter.  Then do our calculations based on that to find what the expected output RPM should be.  Or if we know that we want a certain RPM on the output and we are starting with a known RPM at the input we can then determine the needed diameters of the pulleys or the gears.  

I went through this with the Logan 9x28 and used the tach to verify that the spindle speeds were within a few RPM of the calculated values for each pulley combination both in and out of back gear.

As for cutting speed, that is easy to calculate,  RPM=CSx4/dia   CS comes from the tables in books like the Machinery Handbook and is in Feet /Minute, and the 4 factors out Pi at 3.14159 and that there are 12 inches/foot.  After a few times, the CS becomes ingrained in our head, and the rest is easy calculations.

Here is a basic graphical chart for SFM.

Walter


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## Kennyd (May 14, 2013)

The aluminum tape that HVAC guys use on ductwork will work fine as well if you know someone in the business.


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## Starlight Tools (May 14, 2013)

Basicaly, anything reflective that is different, ie contrasts from the surface being scanned will work.  If there is no reflective surface, then it will try to find a spot on the surface that is different, and sometimes that works, but often it gives miss readings.  If you put on two patches you will read double the readings.

Walter


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## Old Iron (May 14, 2013)

I use black tape on half of my spindle and left the other spot bear metal.

Paul


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## E.MARQUEZ (May 14, 2013)

Hawkeye said:


> I have three MachTachs on two mills (one of them CNC) and on the shared VFD installation on the third mill and lathe. When you switch between machines, the tach shifts to the active machine. I really like these tachs.


Same here, very much like my MachTachs for my lathe.


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## elecbob (May 18, 2013)

Thanks for the many inputs. I ended up getting a Nieko (Asian) photo tach off ebay. I had noticed that the guy on Hoss Machine was using one. It was only $24.95 and free shipping. Comes with a good quantity of reflective tape and a nice fabric case. Seems to be accurate enough. I made a chart of all the different spindle RPM's using the different pulley and back gear combos. Thanks for all the info.
Bob


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## lens42 (Jun 5, 2013)

Yes, it's "pretty much" that simple. I don't know if it was this exact tachometer, but I bought one of the Asian cheapy tachs off eBay for about $8 with shipping, and built it into my Maximat lathe. I used a QRD1114 photo transmitter/receiver (Digikey) for the sensor. I also added a comparator to square up the sensor output for the tach input. I'm not sure if that is absolutely needed, but it makes a nice squarewave that I figured would be less susceptible to noise. I hacked up some copper clad with a hobby knife, wired up the the sensor and comparator IC, covered it with heat-shrink tubing and mounted it over my spindle. There's an inch of reflective tape on the spindle. This works very nicely.

One other thing I did is modify the Tach to run off 5V so I could power it from a spare 5V phone wall wart. It's spec'd at 12V, but the whole board runs off a 12V to 5V linear regulator, so I bypassed that and hooked 5V to the regulator output. That also makes the board run cooler, which I cared about since I have it in a closed-up box.

(unrelated - If anyone knows why I can't get rid of that last photo (the 2nd control box picture), I'd like to know. When I try to edit the post, it's not there, but when I preview or save, it shows up. I thought I deleted it)









RCW said:


> Has anyone tried one of these?
> 
> It sounds as though you hook up a sensor, hook up a power supply and off to the races.  Surely it cannot be that simple?
> 
> ...


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## lens42 (Jun 5, 2013)

nine4gmc said:


> Thanks for posting^. I was just looking at that model and wondered if it would work decent or not. I have a drill press and lathe I would like to hook up.



One thing I forgot to mention is if you plan on panel-mounting the tach without their cheap plastic case, be sure you get one with a circuit board that has mounting holes in the corner. Not all the Chinese eBay tachs have the holes, but some show pictures that do. It only matters if you plan on NOT using their snap-in case and mounting it like it like I did.


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