Monday, March 20, 2017

Salvaging Off-Cuts

With the price of virgin material being what it is, I've found it worthwhile to go to considerable lengths to make good use of off-cuts wherever and whenever I can. By means of lamination and biscuit joinery, one can make very good use of odd bits of material. A recent example is a 'floor' I made for an open-framed dolly. Here's a view of the dolly doing its job under a saw stand.

That void in the middle of the dolly is just begging for a floor. A piece of 1/2" plywood would be ideal, but I don't have any of that on hand. What I did have on hand was --
  • A piece of 7mm firply.
  • A piece of 1/4" poplar flooring underlay plywood.
  • A length of 1"x2" clear pine.
Thickness plane the 1"x2" as required, put those items together with glue and biscuits, and you get a large enough panel, like this.

Here's a closeup view of one corner.

And now the dolly has a floor.

Not a bad outcome from six biscuits, some glue and some 'waste' material.

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Thursday, March 2, 2017

Ridgid's Oscillating Edge Belt/Spindle Sander Model No. EB4424

I finally got one of these for a reasonable price.

It appears that if you have your eye on a piece of machinery from the Home Depot, it pays to be patient, and check often for price changes.

Some weeks ago, this sander was on for $229.00. Then, the price jumped up to $259.00 and stayed there for weeks. I was in the local store yesterday for some odds and ends, and I went over to the tools section for a look-see -- the sander was on for $199.00! I figured that's likely the best price I'll ever see it at, so I got one.

I'll get around to unpacking it soon, and seeing if the machine is as good as I hope it is.

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Wednesday, March 1, 2017

HDE Digital Photo Tachometer DT-2234C+

A photo tachometer is a thing that I don't truly, absolutely need, but it's something I've wanted to have for a long time. Sometimes, I'd just like to know the actual speed of a piece of rotating workshop machinery for no other reason than 'just because'. So, when I found this item on Amazon for a very reasonable price ($14.95 CDN + shipping), I couldn't resist. I ordered one up and it arrived yesterday, one day earlier than Amazon said it would. Here's a view of the thing.

It comes without a battery. A single 9V rectangular battery is all that's needed. The strips down in front are adhesive reflective tape strips. There's about a 24-inch supply there.

I read the little manual, stuck a piece of tape on the spindle of my wood lathe and tried the device out. It works as advertised; I'm delighted with it.

Setting Up For A Measurement

Any rotating device to be tested must have a target adhered to it that the instrument can get a light reflection from -- that's where the reflective tape comes in. Stick a bit of the tape onto your rotating shaft or whatever, like so.

The pressure-sensitive tape adheres quite well to clean, smooth surfaces.

Set the shaft to rotating, aim the tachometer at the target and press and hold the TEST button and you'll begin to get your reading, like so.

A highly visible red light beam floods the target area, making it very easy to see that you're holding the tachometer correctly aimed. When the instrument is getting a signal, there's a 'MONITOR INDICATOR' symbol that comes on in the display directly above the least significant digit. (It looks like three sets of parentheses around a dot.) If you're not seeing the MONITOR INDICATOR in the display, you're not getting a reading.

And that's about it. As long as you keep the TEST button depressed, and you have a MONITOR INDICATOR in the display, you'll continue to get a live reading of the target shaft's rotational speed.

Following a reading, the MEM button lets you retrieve the lowest, highest and last speeds that the instrument observed. I'm not sure how useful that information is, but it's there for whatever it's worth.

An Alternative To The Reflective Tape

Don't worry about running out of tape; Liquid Paper or Wite-Out work fine. This splotch of Wite-Out on a table saw motor's shaft yielded an acceptable target for the tachometer to read from.

If you get an erratic reading, or a reading that's not credible, wrap the shaft to be tested with black friction tape and apply a Wite-Out splotch to the tape, like so.

Black electrical tape is too glossy to work reliably.

An Operational Test Method

There's a quick-and-dirty way to check the tachometer's functionality that doesn't involve any machinery. Just aim the unit at a nearby conventionally-ballasted fluorescent light, and you should get a reading of 7,200 rpm, or very close to it.

Our eyes' persistence-of-vision doesn't allow us to see it, but fluorescent lights actually extinguish and relight 120 times per second. Multiply 120 times per second by 60 seconds per minute, and you get 7,200, so 7,200 rpm is what the tachometer 'observes' when it's given a fluorescent light's output for an input. Fluorescent lights with solid-state ballasts operate at a different rate entirely. I tried getting a reading off of one, and obtained nothing sensible.

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Further To Wite-Out Splotch Markers -- SUNDAY, May 28, 2017

I tried the Wite-Out splotch method on a lawnmower engine's flywheel and it worked fine. Here's a view of the splotch peeking out from under the engine's shroud.

The contrast between the white splotch and the metallic substrate is sufficient for the instrument to obtain a reading.

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