Tachometer

[Dave Lehnert]

Is there such a thing as an usable inexpensive tachometer? I would like to have one to check the speed of a Shopsmith among other things.
Anything like a dial type that you can hook to a shaft, Kinda like a speedometer we had as kids hooked to our bikes?
How does an auto tach work? can one be rigged to a tool like a lathe or the like?

[Lee Schierer]

It depends upon what you call cheap. You can get a tachometer (contact or non-contact type) for between $200 and $500. ou might also be able to get a bycycle speedometer like my cateye micro (about 10 years old) that records pedal rpm based on a magnet passing by the pickup head. It may not have enough digits for what you need though. McMaster Carr has several regular tachometers, but I am sure there are other sources.

[Josiah Bartlett]

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41727

How about $49.95? Seems cheap enough to me. Probably accurate enough for your use.

[Dave Lehnert]

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41727

How about $49.95? Seems cheap enough to me. Probably accurate enough for your use.
Thats more like it $$$$ Any experience with this unit?

[Wes Bischel]

Dave,
You could go old school with a speed indicator:
http://www.gilai.com/scripts/more/tog681-tools_misc-Misc.-yes.html
This tool and a watch with a second hand. Simple, reliable, and can be had inexpensively on eBay.

FWIW,
Wes

[Wilbur Pan]

I got a cheap laser tachometer off of eBay for about $30. It's pretty easy to find -- just search for "laser tachometer" on eBay. I used it to figure out the true speeds on my lathe.

[Dave Lehnert]

Dave,
You could go old school with a speed indicator:
http://www.gilai.com/scripts/more/tog681-tools_misc-Misc.-yes.html
This tool and a watch with a second hand. Simple, reliable, and can be had inexpensively on eBay.

FWIW,
Wes

Wow! That is interesting. How does it work?

[Michael Faurot]

Wow! That is interesting. How does it work?

I've not used one myself, but a friend had one similar to that. From the way my friend explained it, the idea is to touch/connect the shaft of the speed indicator to the spinning thing you want to measure, and then run it for sixty seconds (i.e., one minute). After one minute look at the dial on the speed indicator and that will tell you the RPM.

[Steve Rozmiarek]

Wow! That is interesting. How does it work?

Dave, I'll strongly second the Starrett tach. They are such a simple little thing, and accurate. Really is a rotation counter, count the revs in 60 sec, and you have rpm. As machines don't change rpm once set, this is a really cheap and accurate way to set up your tools. I've bought a few off ebay and at farm auctions, never paid more then $10.

[Wes Bischel]

Michael and Steve explained it well. I have an ancient Craftsman that you have to multiply the readings by 100 to get the RPMs. I hold my finger over the 0/100 mark to feel each time the dimple goes by. That lets me keep my eye on the watch.
I like it because it's "anvil technology" (a phrase used often by a friend) stupid simple and unpretentious.

There are always a few on eBay.

Wes

[james gerus]

The laser tach uses the light reflecting off the rotating shaft to measure RPM. You tape off part of shaft surface so the tach gets a "pulse" of light to count. Jim Gerus

[Frank Townend]

As with Wilbur I bought one from eBay. It came with a fair amount of reflective tape. I measure my lathe, drill press, portable drill, band saw, my cats; you name it.

[Steve Rozmiarek]

As with Wilbur I bought one from eBay. It came with a fair amount of reflective tape. I measure my lathe, drill press, portable drill, band saw, my cats; you name it.


Your cats?! Thats funny!

[Frank Townend]

Thanks Steve. Fast little suckers come dinner time.

[Karl Brogger]

Check a hobby store. A long time ago when I was into RC airplanes I remember seeing a tach of some sort that worked optically.

[Marcus Isaacson]

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPT31&P=ML

This is one that is a little cheaper with maybe less features. It is normally used for telling rpm of model plane props. You can adapt it to equipment by putting a black stripe down one side of the rotating device. Sometimes though, you have to use it without interior lighting as the "flickering" of the lights will give you the same rpm reading for whatever speed. Daylight or a flashlight work well.

[Alan Schaffter]

I built one into my drill press:

http://www.ncwoodworker.net/pp/data/500/DP-7.JPG

and lathe

http://www.ncwoodworker.net/pp/data/500/Lathe-7.JPG

Since I equipped both with VFD's

Here is the basic unit. You just put a stripe pattern on a rotating part:

http://mkctools.com/mvc-539s.jpg

Which costs $64.95 from MKC Tools (http://www.mkctools.com/tachoptions.htm). By the way he restores Shopsmiths too.

[Brad Townsend]

Alan, that installation is great. Is there a thread or link that gives more detail as to how you did it?

[Alan Schaffter]

Alan, that installation is great. Is there a thread or link that gives more detail as to how you did it?

I assume you are talking about the tach installation, and not the VFD.

I've probably posted some details on the The WoodWorks or NCWW but not sure. If you follow the link to the MKC site it shows various installations.

Both of my tach installations are different than standard, the DP more so.

For the lathe I wanted a low profile so remounted the display on the edge instead of the face of the circuit board.

For the drill press, I asked them to send me a unit with the display unmounted. I mounted the sensor and circuit board in the pulley housing and ran a multi-strand cable down to the display.

Below is one more pic showing the parts (this was a special order with display unmounted). The sensor will work with a variety of heavy contrast patterns (Xerox of supplied pattern, painted, polished/dull, etc.). The board has dip switches where you select 1 - 16 marks per revolution. I am thinking of adding one to my router table, but will need to trick the unit. I will set it for 10 marks, but just use 1 mark so I can display router's higher RPMs (20,000 max) since the tach only measures up to 9999 RPM. I will lose the "one's" resolution and the display will have an implied last digit- 20,000 RPM router speed will display as 2000 RPM, 15,118 will read 1512.

Here is a pic of the temporary installation on my DP- the tach CB is in the plastic bag, the orange cable goes to the sensor which is mounted out of view on the aluminum bracket, and just visible is the paper sensor pattern I glued on the lower pulley sheave.

http://www.ncwoodworker.net/pp/data/500/DP-10.JPG

The parts:

http://www.ncwoodworker.net/pp/data/500/Lathe-1.JPG