Inexpensive Touchless Tach

[rake60]

I've seen these non-contact tachometers online for anywhere from $15 to $30UDS.
You are all aware of my frugality.
I bought this one from an eBay vendor for $15.49 with free shipping.

It's pretty much idiot proof.
It comes with several feet of reflective tape that you cut and stick a small piece on whatever
it is you are checking the speed of. I'm sure any reflective tape would do.

With the belts positioned as they are on the lathe, the decal says the speed should be 600 RPM.

[ame]http://www.youtube.com/watch?v=I2rlXXpcvB8[/ame]

678 to 679 RPM is quite a difference from 600 RPM.
I re-checked it with a good old fashioned contact tach and discovered a difference in the results.
The mechanical tach showed a speed of only 677 RPM.

Nice tool for a very low cost!

Rick

 

[Deanofid]

I have that exact same one, Rick. Got it a couple of years ago from ebay, at about the same price as
yours. For an hour or so, I went around checking everything that turned. : )
Found my 618 was a little slow, and my Taig with a variable speed was going quite a bit faster than I
usually estimated. Now I know! Fun gadget.

 

[hopeless]

they read closer than you think Rick. the belt speed is calculated at the spindle diam. you need to allow for the chuck size I would think. It was on mine anyhow ;D
Pete

 

[Deanofid]

...the belt speed is calculated at the spindle diam. you need to allow for the chuck size I would think. It was on mine anyhow ;D
Pete

Well, RPM is RPM, whether it's on something one inch in diameter, or one mile in diameter,
so chuck size won't make a difference to the gadget measuring it.

 

[terrywerm]

I think Pete was thinking about Surface Feet per Minute without really thinking about it consciously, such as one would consider for proper speed for the cutting tool in use and the size of the stock being worked.

 

[Ken I]

They generally work without the reflecting tape - if there is a sufficiently large contrast on the rotating object.

On my levitating motor (with 4 photocell sides) it reads 4 times the actual speed. Reading off the tips of the 3 jaw it reads x3 etc. etc.

Even a white typex spot on a dark background works.

FYI

en

 

[Jack]

I also just recently purchased one of the tachs online for a ridiculous low price of like $12.00 and $2.99 shipping. The more expensive one do come with a 9 volt battery this one didn't so I just took the battery out of the smoke detecter.
I have wanted one for some time but I found them ranging from 10 dollars up to $40.00 but I always hesitated but several weeks ago I found it as cheap as I had ever seen so I bought it. It was like the old days when you would send a dollar and two box tops and sit back and wait.
I too measured everything around here that moved including my 3 speed ceiling fan. Its fun to play with but I actually use it to check my spindle speed on my CNC mill after issuing a S command in Mach3.

Most things show speed a little faster than advertised but I'm happy its usually in the ballpark.

Jack

 

[John Rudd]

I also just recently purchased one of the tachs online for a ridiculous low price of like $12.00 and $2.99 shipping. The more expensive one do come with a 9 volt battery this one didn't so I just took the battery out of the smoke detecter.


Jack

Nice idea....Hope your shop doesnt catch fire......

 

[TroyO]

Nice idea....Hope your shop doesnt catch fire......

No worries... I'm sure he took the one out of the carbon monoxide detector to replace the one in the smoke detector.... ;-P (Well, I would have...

 

[hopeless]

yep got me again......talk about hopeless ;D
was the work speed I was thinkin of and confussed me agin :-[
Pete

 

[rake60]

yep got me again......talk about hopeless ;D
was the work speed I was thinkin of and confussed me agin :-[
Pete

No worries Pete.
I thought exactly the same thing when I first saw the difference.

Some of us have become programmed to see what a cutting tool sees.

Rick