Lathe RPMs

[Tim Boger]

I just had the Head Stock off my Jet 14 42 rebuild, new bearings, 2 sheaves (one on each pulley) and a new belt .... it runs silky smooth.

My concern is the RPMs don't seem to be reaching the top speed of 3000 RPMs like it used to, how can I test this?

Thanks,
Tim

[Bill White]

I have seen (somewhere) a plan for a poster board disc marked so as to read rpms when used in fluorescent lighting.
Ya might wanna Google lathe speed indicators.
Bill

[John K Jordan]

You can buy a digital optical tachometer for almost nothing:
http://www.amazon.com/gp/product/B004Q8L894
I bought this model about three years ago and it works fine. I used it to calibrate the speed knob on my milling machine.

You simply put some reflective tape on something that turns, press the button, and aim the light at the tape. It comes with the reflective tape.

JKJ

[Tim Boger]

You can buy a digital optical tachometer for almost nothing:
http://www.amazon.com/gp/product/B004Q8L894
I bought this model about three years ago and it works fine. I used it to calibrate the speed knob on my milling machine.

You simply put some reflective tape on something that turns, press the button, and aim the light at the tape. It comes with the reflective tape.

JKJ

Thanks John,
I had no idea such a simple device existed. Appreciate the link.
Tim

[John K Jordan]

I hope it helps! It is actually cheaper now than when I bought one. You might check around but this one has pretty good ratings.

The disk mentioned also works, although I haven't used one in probably 40 years. You simply print the downloaded disk, glue it onto cardboard, then turn off all lights except for a single (standard) fluorescent bulb. The strobing effect of the 60 hz light flicker highlights certain bars and let you read the RPM. I suspect it won't work with a CFL light (they are high frequency) and maybe even some bulbs with high-persistent phosphors.

A few years ago I started accumulating various test instruments and devices just to have them around. I have been surprised at how many uses I find for some of these. I bought that tachometer, a sound meter, a good light meter, a dual-thermocouple reader, a non-contact IR thermometer, precision scales, UV lights, and a laser particulate air quality monitor. Added to a collection of microscopes, moisture meters, laser distance meter, oscilloscope, and other electronics I can almost always find a way to measure something!

JKJ

[Russell Neyman]

You replaced only half of each pulley? I was under the impression that Jet only sold them in sets.

Regarding the perceived top speed, this could be caused by two variables. A new belt is likely to be thicker, which causes it to ride at a higher point on the drive pulley. Or, you might simply have tightened the upper pulleys too close or too far from each other.

[Tim Boger]

Hey Russell,

I could be wrong about the pulley replacement, I had the work done at a local tool store ... I expect they have access to one or both pieces of the pulley sets.

It's interesting, my lowest speed setting which is indicated as 450 RPMs now seems lower (which may be a good thing) This morning will be my first opportunity to use the tool since having the repairs done on it. I did turn it on last night to hear it run but have not had any wood attached as yet.

Thanks for your feedback,
Tim
You replaced only half of each pulley? I was under the impression that Jet only sold them in sets.

Regarding the perceived top speed, this could be caused by two variables. A new belt is likely to be thicker, which causes it to ride at a higher point on the drive pulley. Or, you might simply have tightened the upper pulleys too close or too far from each other.

[Jason Edwards]

It's probably running the same speed, just quieter, making you think it's slower.

[Tim Boger]

An interesting thought .... thanks.


It's probably running the same speed, just quieter, making you think it's slower.